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A TREATISE 
 
 ON 
 
 NAVAL ARCHITECTURE. 
 
 COMPILED FEOM VAEIOUS STANDAED AUTHORITIES. 
 
 By It. Commander E. W. MEADE, U. S. N. 
 
 FOB THE USE OF THE STTJDEH'TS OF THE U. S. WAVAL ACADEMY. 
 
 ANNAPOLIS, MD. 
 
 EGBERT r. BONSALL, Peinter. 
 1868. 
 
Vice-Admiral DAVID D. PORTER, U. S. N., 
 
 UNDER WHOSE AUSPICES AS 
 
 SUPERINTENDENT OF THE NAVAL ACADEMY. 
 
 THE IMFOKTANT STUDY OF NAVA.li OONSTKtrCTIOJST 
 WAS REGULARLY TAKEN UP AT THAT INSTITUTION, 
 
 This Work is respectfully dedicated, by 
 
 THE COMPILER. 
 
PREFACE 
 
 The matter contained in this book, has been mainly gathered from such 
 standard works as those of Russell and Knowles, with some assistance 
 from Creuze, Marrett and Peake. 
 
 A Naval Officer of fair m-athematical ability, can readily make himself 
 familiar with all the essential principles governing the design of a ship, as 
 well as the mode of making the calculations; though to become a Naval Con- 
 structor may need the apprenticeship of the "mould loft" and ship yard. 
 
 In fact, there is no more mystery abopt the subject of Naval Construction 
 than there is about the subject of Steam Enginery, and any intelligent 
 officer may easily make himself perfectly conversant vvith both, while the 
 importance of acquiring such knowledge, is self evident. 
 
 In accordance with these views, the first portion of the work, entitled 
 "Naval Architecture," has been put together for the ]ise of the Students at 
 the TJ. S. Naval Academy. 
 
 A short treatise on "Ship-byilding" will be added tp the next edition. 
 
TAB Lb: OF CONTENTS. 
 
 Chapter. Page. 
 
 The Science of Naval Archilecture I. 3. 
 
 The Art of Ship-Building II. 4. 
 
 The IVtethods of Propelling Ships, III. 7. 
 
 Different classes of Ships for Peace or War IV. 10. 
 
 Displacenjent — How to make a Ship Swim and Carry, V. 13. 
 
 Buoyancy-^Power of water to float bodies heavier than itself, VI. 18. 
 
 Stability — Power of water to make a Ship stand upright VII. 22. 
 
 Powers of shoulder and under- water body VIII. 25. 
 
 On the proportions which make a stable or unstable ship, IX. 30. 
 
 The method of measuring stability, X. 33. 
 
 The powers and properties of the "shoulders," XI. 36. 
 
 How to give a Ship stability without great breadth of "shoulder" , XII. 38. 
 
 How to make a Ship dry and easy XIII. 41. 
 
 On.longitudinal stab.lity XIV, 47- 
 
 On the quality of weatherliness, and how to give it, XV. 40. 
 
 How to make a Ship handy and easy to steer, XVI. 55. 
 
 Of balance of body and balance of sail, XVII. 5S, 
 
 Of the proportion, balance, division and distribution of sail XVIII. 63. 
 
 Of symmetry, fashion and handiness of sail, XIX. 76. 
 
 General conditions of the problem of Naval Architecture XX. 81. 
 
 How to design the lines of a Ship by the "wave system," XXI. 85. 
 
 On the first approximate calculation of a design, - XXII. 101, 
 
 Ships for War, including list of the iron clad ships of the United States 
 
 and those of England XXIH. 113, 
 
 How to make a Ship drawing, XXIV. 123, 
 
 Construction — various systems — construction of a yacht by "parabolic" 
 
 system XXV. 127, 
 
 Mode of making calculations, XXVI. 135. 
 
 How to set about the design of a man-of-war XXVII. 144. 
 
 APPENDIX.— Vocabulary of terms used in Ship-building. 
 
CHAPTER I. 
 
 THE SCIENCE OF NAVAL ARCHITECTUBE. 
 
 The Science of Naval Architecture treats of several great The chief prob- 
 
 problemS. ArehUecmref' 
 
 1st. How to make- a ship swim. 
 
 2d. How to make her carry heavy weights. 
 
 3d. How to make her. stand upright, when the waves or the 
 winds try to upset her. 
 
 4th. How to make her obey the will of her Commander. 
 5th. How, in addition to all these, to make her go easily 
 through the water at high speed. 
 
 Subordinate to the above, are the following; 
 
 6th. How to give a ship a given draft of water and no more ; Minor problems, 
 first, when she is light, and second, when she is laden. 
 
 Tth. How, with the given draft of water, to prevent her over- 
 setting when she is light, and rises high out of the water; and 
 how to prevent her being overturned by the great burden laid 
 upon her when she is. heavily laden. 
 
 8th. How, when a heavy sea strikes on one side of the ship, 
 to prevent it from rolling into her, without, at the same time, 
 heeling her so far over, as to expose her to danger on the other 
 side. 
 
 9th. How to make her bow rise to the sea, so that the waves 
 may not roll over her deck, without, at the same time, making 
 her rise so far as to plunge her deeply into the succeeding hol- 
 low, and make her uneasy and slow. 
 
 10th. How to make her stern of such a form that when scud- 
 ding, the sea shall not break over her poop. 
 
 11th. How to make her so stiff on the water, that the pressure 
 of the wind on her sails shall not upset her, without, at the same 
 time, giving her so much stiffness as to endanger her masts, by 
 the jerk 'of the sea. 
 
 12th. How to make her turn quickly, and in short space, in 
 obedience to her rudder, no matter how fast she may be going; 
 and how to make her weatherly. 
 
 13th. How, in combination with the foregoing, to make her fast 
 before the wind, against the wind, across the wind, when she is 
 laden, when light, when the sea is smooth, and when the sea is 
 rough. 
 
 These are some of the undertakings with which the science 
 of the Naval Architect must qope. They are all matters the 
 principles of which belong to science. They are all matters of 
 forethought and calculation, for which exact results are to be 
 sought and ascertained, long before the ship builder can even 
 set about his work. They form the science of Naval Architec- 
 ture, as distinguished from the art of Ship Building. 
 
THE ART OF SHIP BUILDING. 
 
 CHAPTER II. 
 
 THE ART OF SHIP BUILDING. 
 
 The Art of Ship Building, consists in giving to the materials 
 of which the ship is to consist, all the forms, dimensions, shapes, 
 strengths, powers and movements necessary to make them ful- 
 fill and comply with the conditions resulting from the calcula- 
 tions of the Naval Architect. 
 Chief problems 1. To make the ship swim, she must be tight and staunch 
 
 of Ship Building. , J. i 1 ■ J. j^i ,1 
 
 every where, so as to take m no water through her seams or 
 fastenings. * 
 
 2. To make her swim so deep, and no deeper, the weights of 
 all her parts, taken together, must be equal to the measure the 
 Naval Architect has given, and which he has called her "light 
 displacement.'''' This done, it is the business of the Naval 
 Architect, and not of the builder, to see that a given load, placed 
 in the vessel, will not sink her beyond her given load draft. 
 
 3. To make the ship strong enough to carry her load without 
 straining herself, is part of the art of ship building ; the quan- 
 tity of material put into the ship being limited by the Naval 
 Architect, it belongs to the craft of the ship builder to select the 
 fittest quality of material, to put it in the most eflectual place, 
 and to unite each piece in so substantial a manner, that no piece, 
 when strained, shall part from its neighbor, but that everj- part 
 shall not only do its own work, but be able to help, in need, every 
 other part, so that all joined together, shall form one staunch 
 whole. 
 
 4. In making the ship strong enough for the work she has to 
 do, the builder must yet preserve, throughout the whole, such a 
 just distribution of the weight of the parts, as that she shall not 
 be too heavy at the bottom, nor at the top, nor at the bow, nor 
 at the stern ; but that the weights of the parts, in their places, 
 shall so accurately correspond to the nature of the design, that 
 there shall be a perfect balance of weight around the exact 
 centre, intended by the Architect. This is necessary to be so 
 exactly preserved, in order that the trim of the vessel, both at 
 the bow and the stern, and her nfiffness or power to stand up- 
 right, shall turn out to be what is meant in the plan. The best 
 designs have failed through unnecessary weights being, in the 
 execution of the work, placed where they did harm, instead of 
 where they could have done good. Disposition of weight, there- 
 fore, in the hull, is an important point in practical ship building. 
 
 Necessity tt:at 5. The geometry of ship building is one of the most inipor- 
 shouid under- tani branches of the ship builder's art, and the exact fitting and 
 we"!*^ •'''""*"'' execution of parts truly shaped, is one of the best points in 
 which he can show hia skill. The design to be executed having 
 been put into his hand, the ship builder has first to lay it down 
 on the mould loft floor, ,to its full size, next he has to divide and 
 show on this drawing, in its full size, every part of which the 
 ship is to" consist; of each of these parts a separate and indepen- 
 dent drawing has now to be made, and a shape or mould made 
 from this in .paper, in wood, or in iron. To this mould the ma- 
 
THE ART OP SHIP BUILDING. 5 
 
 terial of the sMp, whether pieces of iron or wood, have to be 
 exactly shaped ; and these independent drawings or moulds 
 must show every face and every dimension of each part. When 
 it is remembered that, in every ship, consisting probably of sev- 
 eral thousand parts, generally speaking, no two are alike, and 
 only two, at most, resemble each other, namely, the counter- 
 part pieces on the two opposite sides, and that every one of those 
 pieces has probably four sides, each with a different curve from 
 the other, and containing possibly one hundred perforations, 
 (Iron Ship building,) which must have precise positions with 
 reference to these curves, it will be seen that making the meas- 
 urements and drawings, is a labor which must be performed 
 with the utmost precision and intelligence, in order to have good, 
 honest and reliable work, "and requires no small amount of goo- , 
 
 metrical skill from the builder. 
 
 6. The art of the ship builder frequently extends, not only outline of tiie 
 to the mere construction of the ship's hull, but also to the. con- snip Builder, 
 struction, or fitting in, of all those separate things which are 
 not parts of the ship proper, and yet without which she cannot 
 be sent to sea. There are parts which, if not made by the ship 
 builder himself, must be so provided and fitted as if he had him- 
 self made them. A ship cannot be a ship without a rudder, 
 without steering mechanism, without" compasses and their bin- 
 nacles, without anchors and their cables, without capstans and 
 windlasses to raise and lower the anchor, without boats and 
 davits, and the tackle to raise and lower them, without masts 
 and yards, and standing rigging and running rigging, and sails 
 and blocks, and all the means of placing them, and fastening, 
 supporting and working them. There must be, also, pumps to 
 work in case of accident, besides a large inventory of smaller 
 things, all to be found, before a ship is a ship, or fit to go to sea. 
 All these, for the most part, the ship builder has to find, and, 
 while it is a matter of doubt, of opinion, of custom, or of 
 special contract, how many, and which of them, are parts of the 
 hull, or parts merely of the equipment of the hull, or of stores 
 for her voyage, yet it is always in the ship builder's province to 
 consider fully all these things, and so to arrange for them, that 
 no unnecessary difficulties may be interposed in the way of 
 those who have to supply and to fit them. Generally speaking, 
 the rudder and steering-gear, the mechanism for fixing and 
 working the anchors and cables, the masts and spars, and the 
 means of attaching the rigging and working the sails, and boats 
 and the ship's pumps, are reckoned part of the ship proper, and 
 they a^e generally done in the ship builder's yard, while the rig- 
 ging itself, the sails, the anchors, the cables, the compasses, 
 and all the minor inventory are reckoned as "Equipment" only. 
 It is part, therefore, of the craft of the ship builder to under- 
 stand thoroughly, as well as to execute, that part of the equip- 
 ment and the fitting which aje reckoned as part of the hull. 
 
 "I. But it is the finishing stroke of the ship-builder to place 
 his vessel safely in the water. To this part of his skill belong 
 all the traditions of launching. In this the traditional ship 
 builder excels ; for science has taught him nothing. The know- 
 ledge of launching has grown, and, with the odd variations in 
 form, there is a wonderfial unity in substance, even in different 
 
6 THE ART OF SHIP BUILDING. 
 
 sh?p"Bunder "'^ Countries. The construction of the cradle in which the infant 
 ship is conamitted to the deep, of the ways which carry her 
 from the shore into the water, of the slope on which she glides 
 so smoothly down, even to the very mixture of soap and grease 
 which lubricates her passage ; all is known by fixed tradition, 
 and so skilled has the long progress of practice rendered this 
 finishing stroke of art, that constructors, when ordered to lengthen 
 a ship already built, have been known to cut her in two, and to 
 give to the after part so gentle a launch, that it stopped exactly 
 when it had reached the point of distance from the fore part, 
 to which the lengthening was meant to extend. So, also, 
 when an attempt was made, as in the launch of the "Great Eas- 
 tern," to bring in other than ship building skill, the result 
 was a miserable and extravagant failure. This, therefore, is 
 one of the points in which the ship builder cannot do better than 
 adhere to his traditions. But along with these general principles of 
 matured experience, there is enough variety of practice to leave 
 the ship builder a wide choice. Some nations launch with the 
 bow, some with the stern foremost, some broadside on. Some 
 launch with the keel resting on the ways, the bilges clear ; oth- 
 ers launch with the bilges on the ways, and the keel clear; but 
 in all these different modes a tolerable attention to the precepts 
 of tradition will enable the ship builder to execute this "tour de 
 force" with a fair cerlrainty of success. In England, some have 
 even ventured to carry this so far as to launch steamers with 
 masts up, rigging fitted, and sails bent, their equipment on 
 board, their engine and boilers fitted in them, their fires lighted 
 and steam up ; and they have left the ship-yard from the launch- 
 ways in perfect safety, propelled by their own steam. 
 
 So ends the ship builder's duty. 
 
THE METHODS OF PROPELLING SHIPS. 
 
 CHAPTER III. 
 
 TEE METHODS OF PROPELLING SHIPS. 
 
 The Naval Architect, the ship builder, and the marine engi- ti'c \mh\em or 
 neer, represent three classes of professional skill, all of which gounn.'"" ^'^'^^' 
 to the achievement of a perfect steamship. The duties of all 
 must be successfully performed, in order that the duty of the 
 steam-ship may also be performed successfully. It is not neces- 
 sary that the three duties should be performed by three sepa- 
 rate men, but all are essential. They may even be all performed 
 by one man, and he may first form the design of the whole, then 
 build the ship, and, lastly, construct the engines :* but, in theory, 
 it is better to keep these parts separate, although, in practice, they 
 cannot be too closely united. 
 
 Steam Navigation, or the propelling of a ship by steam, is ef- The Bmier. 
 fected by means of three great instruments. The source of the 
 entire steam-power of a ship resides ia the boiler, and it is the 
 power of this boiler to produce steam, which ultimately deter- 
 mines the entire question of the power and speed of the ship. 
 Boilers, therefore, are the first consideration ia marine engineer- 
 ing. The second part, is that which applies the steam made in 
 the boiler to the purpose of producing mechanical motion, and 
 forms what is called the machinery, or steam-engine. It is by The Engine, 
 the engine that the steam is turned to use and worked ; but en- 
 gines accomplish their purpose better and worse ; they all 
 waste some steam in moving themselves, and not in moving the 
 ship, some waste much steam, and do little work, others waste 
 less steam, and do more work. It is very difficult to know how 
 much is wasted, even by the best marine engines, and some 
 of great reputation waste more than others of less. It is the 
 business of the marine engineer to see that he effects the least 
 possible waste, and gets out of his engines the maximum pos- 
 sible effect : but this result he can only know by taking careful 
 measures, not merely of the work done by the steam in the en- 
 gine, but also of the work given out by the engine after work- 
 ing itself It is the duty of the marine engineer, thoroughly, to 
 master all these points. 
 
 . The third instrument of steam navigation, is that by which The Propeiier. 
 the ship is made to move. The boiler makes the steam, and 
 the steam moves the engine merely, but not the ship. The en- 
 gine has to move something which has to move the water, and 
 which by moving the water, shall compel the ship to move. 
 Though all three instruments move the ship, or tend to move 
 it, it is only this last which directly touches the water, and which 
 moves it and the ship : it is called the motor or propeller. The 
 steam propeller is, therefore, the third instrument employed in 
 steam navigation. The kinds of propellers are many and va- 
 rious ; some being a single instrument, as a screw propeller ; and ti?s"'of'''B t\"'m 
 the paddle wheel propeller, when used singly in the stern of a Propciiere. 
 steamer, or in the centre of a double or twin vessel. There are 
 also double propellers, as where two screws are used in one 
 
 * This ia tlic case in the French Navy, where the chief constructor is also the construct- 
 ing engineer. 
 
8 THE METHODS OP PROPELLING SHIPS. 
 
 vessel, or where two paddle wheels are used on a vessel. 
 There is also the jet propeller, (both steam and water,) the chain 
 propeller, the stern propeller, and a host of others not now in 
 practical use, but which it is good to know of, in order to avoid 
 inventing them over again. There are propellers out of the wa- 
 ter, and under water, at the sides and the bottoms of ships, at 
 the bow as well as at the stern, and almost every place that can be 
 named, has been selected by somebody for a propeller. It is the 
 business of the practical marine engineer to devote his atten- 
 tion to those modes of propelling which are in general use. . He 
 must examine the laws which govern all steam propulsion ; he 
 must learn to measure the degree in which it can be made per- 
 fect, and the degree in which, in the nature of things, it must 
 remain imperfect, aiming continually to get as near to perfection 
 as possible. He must never forget, however, that it is absolute- 
 siip. ly impossible to attain this perfection ; he must remember thsit 
 
 water slips away from the propeller, and that in escaping from 
 the propeller, it carries off power in the very act of motion. 
 This power, said to be so lost, is called loss by slip. A 
 scientific knowledge of the laws of propulsion enables him to 
 judge when this slip runs to waste merely, and when, on the other 
 hand, it is no more in quantity than is necessary to produce the 
 propulsion of the vessel. In order to propel the vessel, the pro- 
 peller must take hold of the water, and must push the water ; the 
 water will slip away from its hold, but in the very act of slip- 
 ping, the propeller must dexterously lay hold of the water in 
 just so many instants of time as to take out of it the greatest 
 push with the least slip ; no slip is nonsense ; much slip is fol- 
 ly ; as little slip as is practicable, may be fairly demanded of the 
 competent Naval Engineer.* 
 Sails. Besides propulsion by steam, there is another method of pro- 
 
 pulsion, the subject of an entirely distinct profession from 
 that of the engineer and architect; that is, driving ships by 
 sails, instead of steam. This is properly the business of the 
 Naval officer. It is the Naval officer's business to know how 
 he would best like all arrangements of the masts, sails and 
 yards, so that he and his crew can best handle and manage 
 them. But there is one part which the Naval Architect should 
 do: he should thoroughly study the balance of sail, as every 
 ship, according to the qualities of her design, will carry her 
 ' sails badly, if they have not been perfectly balanced, in conformi- 
 ty with the peculiar properties, proportions and dimensions of 
 each ship. It is the Naval Architect's business to provide the 
 Naval officer with a perfect balance of sail ; and it is the latter's 
 business to know how to use it, and handle his ship properly 
 when he has got it. Balance of sail, therefore, must be studied 
 along with balance of body, draft of water, trim, and the other 
 original mathematical elements of the design of a ship, 
 stowage and There is, finsilly, another point in which the professions of the 
 
 edUe 'thiit'Ts're- Naval officer and Naval Architect touch each other very closely. 
 
 qu'site in a Na- ijijis is, the trim and stowage of the ship; and the reason why the 
 business of the sailor here touches so closely upon that of the 
 
 * Th« term Engineer is liere used to denote the builder of an engine — not the mere "en- 
 gine ihii'cr" of the naval scrviec. 
 
THE METHODS OP PROPELLING SHIPS. 9 
 
 Architect is, that a little ignorance or folly, on the part of a Na- ^^^^"''''^^'^ " ""^ 
 val Officer, can neutralize and undo all that the Naval Architect 
 and ship builder have done for the good qualities of the ship. 
 
 If he has not knowledge enough of the place where the cen- 
 tre of balance of weight of the ship is put, and does not con- 
 trive to keep it where it ought to be, but fills the ship with im- 
 proper weights at improper places, he will ruin the performance, 
 and mar the reputation, of the finest ship in the world. 
 
 But few Captains know these things thoroughly, and thereby 
 acquire the reputation of good sailors, both for themselves and 
 their ships. With an ignorant officer, it is impossible to know 
 whether the ship be a good or a bad one. 
 
 Although it may not always be possible for a sailor to be also a 
 thorough Naval Architect, inasmuch as each profession demands 
 the study of a lifetime to learn it, yet a sailor should know 
 enough of the architectural points of a ship to turn them to 
 the best account; and it will be necessary, therefore, farther on, 
 to inves'tigate some of these points common to the Naval Officer, 
 and Naval Architect. 
 
10 ' DIFFERENT CLASSES OF SHIPS, 
 
 CHAPTER IV. 
 
 DIFFEEENT CLASSES OF SHIPS FOB PEACE 
 OB WAB. 
 
 DiffiTcnt ciaa- Although the principles which guide the Naval Architect in 
 session Pe;u^e or ^j^g construction of ships, and' govern their behavior in the sea, 
 are fixed and invariable, it will be the use the ship is to be put 
 to, which" must govern the Naval Architect in the application of 
 those principles to practical ukc. Ships employed for purposes 
 of commerce, for mere pleasure, or for purposes of war, must be 
 as different in their construction as in the-ir objects, and accor- 
 dingly, the different classes of ships designed for such different 
 uses, give rise to distinct departments of Naval Architecture. 
 
 For the .purposes of war, the conditions which the Naval 
 Architect has to fulfill, are widely different from those he has to 
 meet in the design of a merchant vessel. The principles which 
 guide him are the same ; yet the points of practice are in some 
 respects easier, in others more difficult. The merchant shjp, in 
 its voyages around the world, in search of freight, has to under- 
 go all sorts of conditions of emptiness and fullness, of lightness 
 and deepness of draft, and has to stow all sorts of cargoes, with 
 every, variety of bulk and of specific gravity; sometimes she 
 has to' carry a heavy deck load with little in her hold, and at 
 other times, so much weight, so deep in her bottom, that it 
 would seem to be almost impossible to re-unite two such oppo- 
 site uses in the same ship. 
 The shjpnr- Thc man-of-war has but one duty: to convey a known weight- 
 " "''■ of gufts and of men to a known place ; and this kind of work, be- 
 
 ing so exactly known, ought to be infallibly and exactly done. 
 That a ship-of-war, under such known c'onditions, should ever 
 rc'Iu'itifsiiouwbe have a mistake made, or an inaccuracy found, in her draft of wa- 
 at-iiirate. tcr, her stability or her speed, might seem therefore disgraceful, 
 
 if it were not, unhappily, too common. The explanation which 
 is sometimes given, is: that the people whose business it is to 
 order these ships, are unable to settle, beforehand, what they are 
 intended to do, and that they are generally afterwards ordered 
 to do exactly that for which they were not originally designed.* 
 Here it is clearly the duty of the competent Architect to refuse 
 to construct the design of a ship until the essential elements for 
 her construction have been authoritatively settled: for by so do- 
 ing, he brings upon the profession of Naval Architecture, that 
 disgrace which ought to fall on the shoulders of those who have 
 the power and the ignorance to order him to make bricks with- 
 Spi'ci. out straw. 
 
 There is one peculiarity which belongs equally to both kinds 
 of vessels; that, whatever her load may be, she must, above all 
 things, be fast. In commerce — time is money; in war — time is 
 victory: and victory, the sole object of war, is entirely in the 
 hands of the man who has the choice when and where to meet 
 his enemy. This is an axiom, and needs no argument. 
 
 'This was the case with the "Double endera" during the late war— they were designed 
 for river service, but were employer! at sea, on blockade. 
 
DIFFERENT CLASSES OP SHIPS. 11 
 
 moju. 
 
 To have easy movements in bad weather, is also the indis- Rase of move 
 
 pensafile requisite of a good ship of both sorts; but the quality" 
 
 which constitutes a good sea-going vessel, may have to be 
 given to them in different ways. 
 
 In a merchant ship, the lading of the ship being variable, 
 and its arrangement entirely under the disposition of the Cap- 
 tain and owner, the internal adjustment of weights may be so 
 made, as to give her every variety of quality. In the ship-of- 
 war, on the contrary, the disposition of weights being both in- 
 variable and inevitable, and fixed by the indispensable purpose 
 of the vessel, the sea-going qualities must be given by the Na- 
 val Architect alone, in his original design; and the subsequent 
 adjustment of the qualities of the ship, by disposition of weight, 
 can be carried out only within narrow limits. It may happen, 
 and it does happen, that the necessary disposition of the great- 
 est weights of the ship-of-war, are hostile to the soa^going quali- 
 ties of the vessel, and to the desire of the Naval Architect. The 
 battery of the ship may be a great weight, acting high out of 
 the water; and that will be a great difficulty, acting with great 
 power against him. 
 
 It may be that he h'as to carry heavy loads of iron armor at 
 great distances from those centres of his ship around which he 
 is anxious to have the most complete repose, even at the time 
 when the efforts of the sea are greatest to put those weights 
 into violent motion ; yet these very causes of bad qualities for 
 the sea^going vessel, may form a specific virtue for the fighting 
 vessel. Th6 successful reconciliation of such antagonism, is the 
 highest triumph of the skill of the Xaval Architect, in the de- 
 sign of a ship-of-war. 
 
 A third condition of both kinds of vessel, differently carried 
 out, according to the diversity of use, is what it will be neces- 
 sary to call "capacity of endurance." In a merchant ship, sail- 
 ing or steamship, this means ability to carry a large freight, to ' 
 carry it at small cost, within an assigned time. To do this, a 
 merchant ship should maintain her given speed with regularity, 
 independently of weather, should do so at moderate wear and tear, 
 'in all the elements of her first cost, and should effect, at the 
 same time, great economy in all the usable and consumable 
 stores which form a great part of her floating equipment and pro- 
 visions, and on which, in great measure, the profits or loss of 
 a voyage depends. It is by these means that the Xaval Archi- 
 tect will achieve reputation for his ship, profit for the owners, 
 and character for himself. 
 
 For a ship-of-war, the capacity of endurance must be of a na- ^ S"'''"'J"y '"'' 
 ture somewhat different. She must certainly have the power of 
 arriving with certainty at the place where she is wanted, inde- 
 pendently of weather; but her sustaining power may often con- 
 sist in her ability to keep herself in good fighting order for a 
 long time, at a great distance from home, and, without ex- 
 ercising her greatest power, to be in a condition to do so at a 
 moment's warning, without such exhaustion of her resour- 
 ces as may leave her helpless at a critical moment. This is 
 a kind of economy of a very different nature from that of a 
 merchant ship ; but must be oi'iginally conferred on the vessel 
 
 nmlitraiice for 
 .Mtrciiniitniaji. 
 
12 DIFFERENT CLASSES OF SHIPS. 
 
 by the forethought of the Naval constructor, and must be studied 
 and carried into effect by the wisdom and knowledge of the of- 
 ficer in command. 
 
 orG.inne"rv,'&c.* There is another branch of professional knowledge and skill, 
 niTcssarvVo tiic without some acquaintance with which the Naval Architect 
 .\rciiitect. cannot design a ship-of-war. A ship that cannot work and fire 
 
 her guns when wanted, may have every other good point, and 
 be worthless for want of that. The constructor must know, 
 then, what is necessary, in order that the crew may work the 
 guns to the greatest advantage, and thus aid in achieving vic- 
 tory. 
 
 Should two ships engage in a rough sea, the mere fact that 
 the guns in one could be better handled than those in the other, 
 in that state df the weather, might be the turning point of vic- 
 tory. 
 
 Ignorance of this point, therefore, on the part of the design- 
 er of the ship, would be failure, and he must have the Tinow- 
 ledge of all the points relating to the placing and working of 
 the guns before he begins his design — not as we frequently see, 
 afler the ship is built, and when it is too late. 
 
 But magnificent sailing men-of-war must be considered now 
 as finally dismissed from service. The line of battle ship, 
 fighting under canvas, is no longer a match for the little iron 
 clad gunboat. It is probable that no such vessel will ever again 
 enter into action. The production of the fleets of the future, is 
 at present a race of competition, of science, and of skill, between 
 the great Powers of the world. Who will win this race, must de- 
 pend much upon the wisdom, forethought and capacity of the 
 men who preside over the Navies of each country. 
 
 Taking this vieW of the subject, it becomes a matter of para- 
 mount necessity, that the young officers, who will eventually 
 command our ships and lead our fleets, should thoroughly un- 
 derstand the conditions which regulate and control the designs 
 of the steam fleets of modern warfare, and the methods used in 
 their practical construction, and it is hoped that this knowledge 
 may promote the advancement of the National interest, both 
 political and mercantile. 
 
HOW TO MAKE A SHIP SWIM AND CARRY. 
 
 CHAPTER V. 
 
 DISPLACEMENT.— HOW TO MAKE A SHIP SWIM 
 AND GABBY. 
 
 Archimedes, the philosopher, is the founder of the principles ^^ ^x^^^I^^^J^y^^^f^f 
 this branch of Naval Architecture. It was he who discovered the law »f Dis- 
 the law of Displacement;- or th&i jioatiiui bodies displace a p''"-"""'"'"' 
 weisrht of water exactly equal to their own weight. It is owing to 
 this discovery that we understand the principles of flotation, 
 and the best way to understand it, is to try his experiment, as 
 follows : Take a tub 6 ft. long, 2 ft. wide, and 3 ft. deep, and fill 
 it 2 ft. deep with water, mark a line where the water stands in 
 the tub, then get into it, letting yourself sink in the water until 
 nothing but a portion of your face floats above it; suppose you 
 weigh 188 lbs., you will find the water in the tub to rise ex- 
 actly 3 inches. 
 
 It need hardly be said that the rising of the water in the Dispiacemcnta 
 tub was caused by your displacing it from the lower part of the ITnTof wright" 
 tub which it previously filled, causing it to rise into the higher 
 part. In short, by so much as the bulk of your body, by so 
 much has the water been pushed out, displaced and raised. If 
 you measure the exact' bulk of your body immersed, and mea- 
 sure the exact bulk of the water raised, you will find them iden- 
 tical, bulk for bulk; but what is strange, though not obvious, is, 
 that they are also equal, weight for weight ; it was this that so 
 astonished Archimedes. 
 
 If you wish to prove this, you may do it thus: — before get- 
 ting into the tub, bore a hole just at the water's edge, and place 
 buckets under the hole, then get in, and the displaced water 
 will overflow ; remain immersed long enough for the water to have 
 flowed off through the hole, and reached the original mark. 
 All the water you have displaced, is now in the bucket, and you 
 (or rather that part of you which is immersed) occupy its for- 
 mer place; now -get out, and weigh the water in the buckets, 
 you will find it weighs 188 lbs., your own weight exactly. The 
 principle of displacement, therefore, consists of two- parts: first, .uj"'",,''",'^ "1 
 ■that a body placed under watei", displaces as much water as its DisiJiaciement. 
 own bulk ; secondly, that it floats when it weighs less than the • 
 water it displaces. 
 
 This principle, although the foundation of ship building, has usrfui appUca- 
 also a great many other useful applications. If you have any- """^ " '" '"'" 
 thing of an awkward shape, and you want to measure its bulk — 
 say a piece of wood, or a model of a boat — take a vessel of water 
 large enough to hold it; place it where it may run over, and 
 where the overflow of the water can be retained ; put the sub- 
 stance under water, and measure the overflow. That, in gallons, 
 or in cubic inches, is the exact bulk of the body. For rough and 
 ill-shaped substances, we have no better way than this. Bodies, ^^^" °^f^^ '^{J® j 
 therefore, which are designed to float in the water, must be so is necessary a- 
 designed, that when they are put into the water sufficiently far consweraiiona.^'^ 
 to swim just sp much out of the water as is intended, the part 
 in the vxtter shall he of the exact size necessary to displace 
 
14 HOW TO MAKE A SHIP SWIM AND CARRY. 
 
 the quantity of water intended, and that the body which 
 floats shall be of the exact weight of the water it is designed 
 to displace. In short, displaced bulk for immersed bulk, and 
 ■n'eip;ht for weight, the floating body and the water, whose place 
 it occupies, must be identical. 
 Should an error Let US SCO what will happen if this bo not accurately done; 
 
 happen"'^'" " '" supposo the bulk of the body has been made too small for the 
 weight which it is intended to carry, the vessel will sink deeper 
 into the water than had been intended ; and by sinking so niuch, 
 it will displace the additional quantity of water necessary to 
 make up the extra weight, and so, though it swims, will swim 
 too deep. More displacement nmst therefore be found to meet 
 the deficient weight; the vessel Avhich was intended to swim 
 light, will swim deep in the water, unless her weight be dimin- 
 ished, by lightening, until she return to her former intended 
 Carp necessary depth ; what is to be taken care Of in the calculation, therefore, 
 
 to be taken in ig^ that at whatever depth it has been decided that the ship 
 
 placemenf. '"" shall float in the water, or, which is the same thing, at what- 
 ever height the upper part is to float above the water, in that 
 position the bulk of the part in the water, and the weight of 
 the whole ship and its contents, must be so designed as to be 
 exactly equal to the bulk of the water to be displaced by the 
 ship, and the weight of the water to be so displaced. 
 How many Dis- In a ship, however, it is necessary to do more than calculate 
 
 SiiuThas!"^ " one displacement. There are two critically important displace- 
 ments to be calculated for. every vessel. 
 
 la" '^'^'t '""'*" Displacement when she is lying in the water ready to take in 
 her guns or stoves or cargo, or in the lightest stale in which she 
 will ever swim, that is, with a clean swept hold; this is called, 
 technically, "Light Displacement." The other is "Load Dis- 
 
 " Load Dis- placement," which is calculated for the heaviest wei'a'ht she will 
 
 placement," ^ ', ino iii 
 
 ever carry, and the deepest draft of water to which she will 
 ever sink under a load. These are the two important drafts or 
 depths of the ship in the water. 
 
 To calculate these, the Constructor must first ascertain the 
 exact weight of the hull of the ship. He must include, in the 
 weight of the hull, all the essential parts attached to and con- 
 nected with that hull. He must add to that the full equipment 
 necessary to fit her for sea-going use; but he must not include 
 ' those stores (water, provisions, coals, &c.) which are to be con- 
 sumed in actual service. This weight of hull and equipment 
 for service, constitute the data on which to construct the light 
 displacement of the ship. 
 
 The load displacement is next to be calculated. The data for 
 this consists, first, of the light displacement, and secondly, in ad- 
 dition to this, of all the stores, provisions, water, coals, and con- 
 sumable commodities to be used on the particular voyage or ser- 
 vice intended, together with the cargo, freight, &c., of every 
 kind which has to come on board. 
 
 To the "light displacement" corresponds what is called "the 
 light draft" (or light line) of the ship. To the load displace- 
 ment, "the load draft" (or load water line.) There is also the 
 "light trim" of the ship, and "the load trim." In some languages, 
 draft is called the "deep going" of the ship, and this phrase 
 
HOW TO MAKE A SHIP SWIM A.\D CARRY. 
 
 15 
 
 gives the exact meaning of draft. "Trim" means difference of 
 draft, or rather the difference between the depth of the after 
 part of the ship under water, and that of the fore part, (com- 
 monly called "drag.") It is usual to give a ship such trim that 
 the draft of water abaft is somewhat deeper than the draft for- 
 ward. In this case she is said to be trimmed by the stern. If 
 it were the contrary, she >\ould be said to be trimmed by the 
 head. This is what is meant when we say a ship is trimmed 
 2 ft. by the head, or -2 ft. liy the stern ; this difference of 2 ft. 
 being technically called "the trim." When a vessel trims neither 
 by the head or stern, but draws the same water forward and 
 aft, she is said to be "on an even keel." It is usual to take a 
 middle draft, half-way between the fore and after drafts, and to 
 call it 'the mean draft" of the ship, so that a ship which is 
 trimmed to 21 ft. by the stern, and 19 ft. at the bow, is said to 
 have "a mean draft" of 20 feet. In this case it is common also 
 to call this 20 ft. "the draft of the ship," and to call the greatest 
 draft of water (21 ft.) "the extreme draft;" in calculations of dis- 
 placements, it is general to use the "mean draft." 
 
 The elements to be considered in calculating displacement, 
 are as follows: 
 
 1. Dead weight when light. 
 
 2. Dead weight when laden. 
 
 3. Light draft of water. 
 
 4. Light trim. 
 
 5. Load draft of water. 
 
 6. Load trim. 
 
 These elements iDeing settled, the constructor may calculate ex- 
 actly the displacement of a ship of any given form, of which he 
 may possess a design; first, for her light draft of water; second, 
 - for her load draft. 
 
 First. — For her light draft, the constructor marks off on the 
 drawing of the ship, the exact part of the body of the vessel 
 which will be under water when she floats light. He calls this" 
 "the immersed body" of the .vessel, (light.) He then measures 
 exactly, and calculates, geometrically, the bulk of this immersed 
 body; this bulk will be expressed in so many cubic feet, say 
 18,000. He next takes the weight given for the ship and her 
 equipment, when light, say 500 tons. 
 
 Now he knows that a ship will float at a given draft of wan Light dtati 
 ter, when the quantity of water she displaces is of exactly the 
 same weight as herself, and in this case the weight is given as 500 
 tons. The question, therefore, is : — whether the volume of wa- 
 ter, namely^ 18,000 ft., which is the bulk of the immersed body, 
 (and which is therefore the quantity of water displaced,) will 
 weigh more or less than 500 tons? 
 
 S^ow, it will be found, that the bulk of 500 tons of water is 
 just 18,000 cubic feet, and the displacement of the ship, as 
 measured, is also 18,000 cubic feet; this, therefore, is the true 
 light displacement. 
 
 Secondly. — For her load draft, he marks off on the drawing of Load dtaiu 
 the ship the exact part of the body of the vessel that will be 
 
16 HOW TO MAKE A SHIP SWIM AND CARRY. 
 
 under water when she is deeply laden. He then measures exact- 
 ly, and calculates, geometrically, the bulk of that part of the ves- 
 sel which was formerly out of the water, but which has 
 now been sunk under it b}- the lading. Suppose this bulk to be 
 36,000 cubic feet. Thirty-six thousand cubic feet weigh 1000 
 tons; therefore, 1000 tons is the dead weight of cargo, which 
 the ship will carry on the given load water line. 
 
 But the total load displacement of the ship consists, first, 
 of the light displacement of 18,000 cubic feet; second, of the 
 lading displacement of 36,000 cubic feet more; so that the total 
 displacement of the ship, when laden, is the sum of the two, or 
 54r,000 cubic feet. The immersed body of the ship at the load 
 draft, has, therefore, a total displacement of .54,000 cubic feet; 
 and the ship with her cargo floats a total weight of 1500 tons. 
 
 Calculating the weight a ship will carry at a given draft of 
 water, is then a mere question of the measurement of the bulk 
 of that part of the ship which will then be under water, and 
 which is called the "immersed body." For every cubic foot of 
 that immersion, the weight of a cubic foot of water is allowed, 
 and thence is obtained the number of tons weight the water 
 will support; this is called the "floating power" of the ship, and 
 it really represents the buoyant power of the water, acting on 
 the outside of the ship. The ship, itself, has no power to carry 
 anything, or even to float; all it does is to exclude the water, and 
 enclose the cargo. The ship is merely passive ; the water car- 
 ries both the ship and her cargo ; and an iron ship will best illus- 
 trate this. Buoyancy is, therefore, the power of the water to car- 
 ry a given ship. It is proportioned exactly to the bulk of the body 
 of the ship under water, and its force is measured by the weight 
 of the water displaced, and which is called the ship's displace- 
 ment. 
 
 The floating power of a ship has nothing to do with the 
 shape of the ship, but is entirely due to its size or bulk. Prac- 
 tical ship builders, ignorant of the laws of Na.val Architecture, 
 •have imagined that they could confer surprising powers of flo- 
 tation, and ability to carry heavy weights, merely by giving cer- 
 Bunyancy de- tain "proper" shapes, imagined by 'them selves, to the immersed 
 pends upon bulk ^j^^j^g ^f ^jjpir gjjipg rp^g delusion was common at one time, 
 
 but has now passed away; yet it will take a great de&\ of 
 thought to understand, thoroughly, why no possible invention 
 of shape can give to a ship the power of greater or less buoy- 
 ancy than is measured by the exact weight of water of her dis- 
 placement. It is herein that the merit of the discovery by 
 Archimedes consists; since the existence, at one time, of an op- 
 posite opinion, tends to show that the principle of flotation is 
 by no means self-evident. 
 
sow TO MAKE A SHIP SWIM AND CARRY. 
 
 Standards of Displacement. 
 
 IT 
 
 Weights. 
 
 liuLKS. 
 
 
 Sizes. 
 
 •I ton, 
 
 *3d cubic feet fresh water. 
 
 
 2X 
 
 3X6 feet. 
 
 n " 
 
 ■fSS " " sea water, 
 
 
 2 X 2.5 X 7 " 
 
 »62.5 lbs., 
 
 *1 " foot fresh watepj 
 
 
 1 X 
 
 1X1" 
 
 tG4 lbs., 
 
 *1 " " sea water. 
 
 
 1 X 
 
 1X1 " 
 
 10 lbs., 
 
 1 gallon of fresh w.aler. 
 
 
 6 X 
 
 6 X 7.69 inch. 
 
 lb., 
 
 |27.li48 cubic inches fresh 
 
 water, . 
 
 3 X 
 
 1 X 9.216 " 
 
 1 ounce. 
 
 1.72f< cubic inches 
 
 
 
 1 X 
 
 1 X '..72ti " 
 
 0.53 ounce. 
 
 1 cubic inch 
 
 
 
 I X 
 
 1 X 1 
 
 S tons, 
 
 72 cubic feet 
 
 
 
 GX 
 
 6 X 2 feet. 
 
 5 tons, 
 
 180 cubic feet 
 
 
 
 6X 
 
 6X5" 
 
 10 totl^. 
 
 360 cubic feet 
 
 t 
 
 
 G X 
 
 6 X 10 " 
 
 100 totis. 
 
 3,1100 cubic feet 
 
 
 
 6 X 
 
 12 X 50 " 
 
 201) tons. 
 
 7.200 cubic feet 
 
 t 
 
 
 8 X 
 
 12 X 100 " 
 
 1,000 tons, 
 
 36,000 cubic feet 
 
 
 
 12 X 
 
 24 X 125 " 
 
 10,000 toils. 
 
 ;i60,000 cubic feet " 
 
 
 24 X 
 
 50 X 300 " 
 
 Standards of 
 Displacement. 
 
 * 62 5 pounds : 
 dislitltd water. 
 
 : 1-35.84 tons = )-36 tons nearly, and 1 ton = 35. a4 ft. 
 
 t 64 lbs. = 1-35 tons exactly, and 1 ton =36 cubic ft. salt water. 
 
 I The imperial gallon contains 10 ifis. of distilled water, at a temperature 
 of 62.5 Fahrenheit — and also measures 277.274 cubic inches. If ordinary 
 fresh water is taken at a lower temperature (say 40© Fahr.) as the stand- 
 ard, a cubic foot of fresh water will weigh exactly 1000 ounces, or 62. S 
 lbs. All the figures given above arecorrect, within a very small fraction. 
 In round numbers, 36 cubic feet of fresh water, and 35 feet of sea water, 
 measure 1 ton. 
 
18 POAYER OF WATER TO FLOAT HEAVY BODIES. 
 
 CHAPTER VI. 
 
 BUOYANCY.— POWEB OF WA'TER TO FLOAT BO- 
 DIES HEAVIER THAN ITSELF. 
 
 v .yi!" ''""'" "f Iron and jstccl are heavier than Avater, nevertheless out of 
 iR-livy boiiiu^."" them can be formed ships, T\-hich will not only float well above 
 the surface, but Avill carry within them Aveights much heavier 
 than themsclvcf^. Iron is nearly eight times heavier than water, 
 and sinks like stone; lead is fourteen times heavier, and gold 
 nineteen. Xcvertheless gold and lead ma)' be floated in ships 
 of iron and steel; and structures, every portion of which would, 
 if separate, sink to the bottom of the water, can be so combined 
 as to float lightly on the top. The means by Avhieh this is ac- 
 complished, is a dextrous application of the forces of i)ressure 
 of the water in such a manner, that the downward pressure of 
 the weights on a ship shall be counteracted by an equal upAvard 
 pressure from the water under the ship, and so the Aessel be 
 prevented from descending into it more than intended, 
 rower or water But this is not the only use to be made of the pressure of 
 and prevciit' up- Water. A ship, although supported from below, may roll over 
 setuug. \)j [ig QTyj^ weight, or may be overset by the force of the 
 
 AA-ind or the force of the waves ; and so it becomes necessary to 
 call in the aid of the fqrce of the water, not merely to keep the 
 ship from sinking, but to prevent it from being overset. In the 
 first case, the water gives buoyancy only; in the second case, 
 it is said to give stabilitj'" also. In the former case, it giv(>s vcrti- 
 <:al support; in the latter case, it gives lateral support. The 
 two great services required of water are, therefore, first, 
 buoyancy to support bodies much heavier than water ; second, 
 stability to be given to bodies which we unable to keep 
 themselves in an upright position, without its aid. 
 
 Thus, from an element which is light, movable, and unstable, 
 is to be draAvn support and stabilit}' by the art of Naval con- 
 struction. It is plain, therefore, that art and skill can have no 
 sure foundation, except in a complete comprehension of the na- 
 ture of water and of the laAvs Avhich govern the application of 
 its force. 
 Tiie three pro The first property of Avatcr, commonly called its liquidity, is its 
 '""""^ "*' ™^'"'" absolute indifference to shape ; that is, it presses on all'shapes 
 equally. The second quality of water is the absolute propor- 
 tion of its pressure to depth. The third property of water is the 
 jjroportion of its pressure to the extent of the surface on which 
 it presses, altogether regardless of the direction. of that surface. 
 The three elements, therefore, for the calculation of the mechan- 
 ical force of water, are weight, depth and extent of surface. 
 i,iciuidiiy or It is the liquidity of water which takes from it any tcndenev 
 
 fluidity ot water, , c i /> • -i ,■ f •' yj 
 
 m its absolute to assume hxcil iomi m its OM^n masses, (as frozen A\-ater or ice 
 
 siia'ife?"""'^ '"does,) or from exerting any force, as solid bodies do, to keep a 
 
 » ' shape in which it has been put. As a liquid, it will take the 
 
 ■exact shape of any vessel into which it is poured, as well as the 
 
 exact shape of any solid placed in, or on it. Therefore, to know 
 
 how much any vessel of curious shape Avill hold, fill it Avith wvl- 
 
POWER OF WATEE TO FLOAT HEAVY BODIES. 1!) 
 
 ter, and then empty its contents into some vessel of known 
 size, the result is the exact capacity of the vessel. 
 
 Agrain, if you wish to know the hulk of anything; of compli- 
 cated form, plunge it into water, forcing the overflow of water 
 into something that you can measure it with. The hulk of the 
 displaced water is exactly what is occupied by the body now in 
 water. This free flowing, easy running, and perfect fitting of 
 water, seems to imply that it has no force, no resistance to mov- 
 ing, no power of effort. Could it be fancied that water had no 
 weight, it might be fancied also without strength or resistance. 
 
 As liquidity allows water to be parted hither and thither, and ^'"'si"- 
 turned into any and every shape, indifferently, one must look for 
 the source of its power to sustain, to resist, and to act, in its 
 next quality, weight; which quality of matter is also indifferent 
 to shape. The weight of a piece of iron, for example, cannot be 
 altered by changing its shape. The weight uf a quantity of 
 water is the same whatever the shape of the ves.~el it may be 
 put into, or whatever shape of outline may be given to it. 
 
 The measure of the weight, or given quantity of water, is 
 as follows : 
 
 Quantity of water. Weight. 
 
 1 Cubic inch. 250 grains = .0.36 lb. 
 
 12 " inches. .^000 " = .43 " 
 
 23 " " 7000 " = 1. 
 
 1 " foot. 1000 ounces =63.5 ■' 
 36 " feet. 1 ton. 
 
 These numbers are convenient to the purpose of the Xaval Different ^ 
 Architect. In using them, however, he should remember that enc«atei5.' "^ 
 all water is not precisely alike in weight. The purer waters 
 are represented by the above figures sufficiently well for all 
 practical purjjoses. Salt water weighs more than river-water, 
 and varies in different seas. Scuu' sea-water is so heavy that 
 35 cubic feet will make a ton, instead of 36. Such salt water 
 carries ships better than fresh, in the proportion of oij to 35. 
 
 In calculations of ships in the sea. 35 feet may be conveni- 
 ently taken as a ton, and 64 lbs. as the weight of a cubic foot. 
 
 The nature of the pressure of water is this, it will flow freely Pressure of 
 into any vessel into which it is allowed to run, and will fill it 
 exactly. But if, in the bottom of the vessel, it find a hole or a 
 weak place, it will rush out there, if not stopped by force. If 
 force be applied to the hole, or the weak place, to prevent the 
 escape of the water, this force is measured exactly by the height 
 of the water above it, and by the size of the hole. 
 
 The next point in the nature of the pressure of water is, that 
 under the pressure due to its depth, the water is indifferent to 
 direction; if, at a foot deep, the pressure dowTiwards is .43 lb. on 
 an inch of surface, there is that pressm"e of .43 lb. on that inch, 
 whether that inch lie with its face downwards or upwards, back- 
 wards or forwards, to the right or to the left, or in any degree of 
 obliquity of direction. Pressure proportioned to depth, to extent 
 of surface, but alike for all shapes, and for all directions, is char- 
 acteristic of water pressure. The quantities given as the weights 
 of wat<r, enables one to measure exactly its pressure. If the 
 water be afoot deep, and the hole a square inch, the pressure of 
 
20 POWER OF WATER TO FLOAT HEANY BODIES. 
 
 the water outwards is measured (for fresh water) by the weight 
 .43 lb.; at double^ the depth, .86 lb.; and for every foot of water 
 an equal added weight. ' To stop it, requires just this weight 
 applied the contrary way. The pressure of water trying to get 
 out of a full vessel which confines it, is not different in kind or 
 quantity from the pressure of water that surrounds a vessel, try- 
 ing to get into it. If an opening be made under water in an 
 empty vessel, like a diving bell or a ship, the water around it 
 will press into it with just the same force as it would press out 
 of a full vessel, because the water is indifferent to the direction 
 of the pressure, 
 
 The pressure of the water into a vessel submerged in it is, 
 therefore, .43 lbs. for each inch. At 36 feet deep, the pressure 
 on one inch of the vessel is 15.5 lbs. 
 
 In a deep ship, loaded down in the water, the pressure of the 
 water is greatest at the bottom: the water presses into the ship 
 on every inch of "skin" with a force of .43 lb. for each foot deep 
 under water. At 1 foot deep, the water presses inwards .43 lb.; 
 at T feet deep 3 lbs. on the inch; at 28 feet deep, 12 lbs. on the 
 inch; and at 36 feet deep, 15.5 lbs. to the inch. This is- the 
 measure of the force required to prevent water leaking into a 
 ship through the seams of the sides and bottom, as well as the force 
 that crushes the ship inwards, and requires strength in the 
 hull of the ship to resist it. 
 Buoyancy. The power of water to float bodies is given by nothing more 
 
 than the pressure of water under the vessel, which is pushing it 
 upwards. To measure the buoyancy of a ship, is nothing more 
 than to measure the pressure of the water on the whole bottom 
 of the ship upwards. Let it be conceived that the ship has 
 a flat level bottom and upright sides, and floats 10 ft. deep in 
 the water : then the buoyancy and floating power of the ship, 
 will be measured by the upward pressure of the water. At 10 
 feet below the water, this pressure is 625 lbs. upon each foot of 
 water, or more than one-quarter of a ton. Reckoning the num- 
 ber of feet on the bottom to be, say 1000, the upward pressure of 
 the water, or buoyancy, will enable the ship to carry 625,000 lbs. 
 
 In this calculation of buoyancy, the upward pressure of the wa- 
 ter has been measured by the same rule as if it had been down- 
 ward pressure, because it has already been shown that it is the 
 characteristic property of water pressure, that it is proportionate 
 to depth, and is not affected by direction. It is this universality 
 of the pressure of water, with its indifference to direction, which 
 makes the calculation of buoyancy so simple and easy. This 
 principle of buoyancy, and its measurement, make it clear how 
 bodies like iron, steel and brass, so much heavier than water, 
 can be made to swim, even although, according to the law of dis- 
 placement, they weigh much more than the same quantity of 
 wat.r, 
 Hollow metal The art of making heavy bodies swim, consists then in this : 
 
 thill enoughT''^ to spread them out in a thin layer over so large a quantity of 
 water, and at such a depth, that the pressure of the water up- 
 wards, shall be greater than the pressure of weigljt downwards, 
 A cubic foot of iron weighs 448 lbs., and would sink in wa- 
 
 ' ter instantly. But take that mass and roll it out into a thin 
 
POWER OF WATER TO FLOAT HEAVY BODIES. 
 
 21 
 
 plate 8 feet long, and 8 feet wide, and turn up its edges all 
 fli'ound a foot deep; then the upward pressure of the water on 
 the 36 fieet of bottom, at the depth of one foot, will give 62.5 lbs. 
 on each foot, or one ton of 2240 lbs., on the whole piece. The 
 "buoyancy, therefore, of the water on this extent of iron, is 
 enough not only to float the original 448 lbs. forming the cubic 
 foot, but also to carry a load of 1Y92 lbs. besides. 
 
 This example shows, in a slpiking manner, how a ship may 
 not only be built of iron, which sinks by itself in water, but 
 may be so built as net merely to carry its own weight of iron, 
 but a burthen in addition four times greater than its own weight. 
 
 Such is the buoyancy of water: — and to carry any known 
 weight, it is only necessary that the surface of the bottom of 
 the ship be large enough, and placed at a sufficient depth be- 
 low the water, to produce an aggregate upward pressure equal 
 to the aggregate weights carried. 
 
 TaMe of pressure on the bottom of a Ship in Sea-iuater. 
 
 ' Table of Pres- 
 sure. 
 
 Depth 
 
 Pressure 
 
 Pressure 
 
 Depth 
 
 Pressure 
 
 Pressure 
 
 UNDEa 
 
 onaS^b-4RE 
 
 ON A Square 
 
 under 
 
 ON A Square 
 
 ON A Square 
 
 Watek. 
 
 FOOT. 
 
 INCH. 
 
 Water, 
 
 rooT. 
 
 INCH. 
 
 Feet. 
 
 Pounds. 
 
 Pounds, 
 
 Feet. 
 
 Pounds. 
 
 Pounds. 
 
 1 
 
 64 
 
 .44 
 
 13 
 
 83-2 
 
 5.78 
 
 2 
 
 128 
 
 .89 
 
 14 
 
 896 = .4 ton 
 
 6.22 
 
 3 
 
 192 
 
 1.33 
 
 15 
 
 960 
 
 6.67 
 
 4 
 
 256 
 
 1.7tj 
 
 16 
 
 1024 
 
 7.11 
 
 5 
 
 320 
 
 2.22 
 
 17 
 
 1088 
 
 7.56 
 
 6 
 
 3j!i4 
 
 2.67 
 
 18 
 
 1152 
 
 8. 
 
 7 
 
 448 = .2 ton 
 
 3.11 
 
 19 
 
 1216 
 
 8.44 
 
 8 
 
 512 
 
 3.56 
 
 20 
 
 1280 
 
 8.89 
 
 9 
 
 576 
 
 4. 
 
 21 
 
 1324 = .6 ton 
 
 9.33 
 
 10 
 
 640 
 
 4.44 
 
 28 
 
 1792 =.8 ton 
 
 12.44 
 
 11 
 
 704 
 
 4.89 
 
 35 
 
 2240 — 1 ton 
 
 15.56 
 
 12 
 
 768 
 
 5.33 
 
 
 
 
22 HOW TO iLVKE A SHIP STAND rPPxIGHT. 
 
 CHAPTER VII. 
 
 STABILITY.— POWER OF WATER TO JfAKE A 
 SHIP STAXD UPRIGHT. 
 
 Ftabiiity oi That the most unstable of clemeuts. -water, should bo required 
 floating bodies. ^^ ^^^f^^. ^^^\^^i^^y q,. j,,;,.^, upriojjtness to heavv bodies raised 
 
 tn a great heiirht above its surtaee, w-ould appear to be an un- 
 reasonable expectation, Tsere it not accomplished every day. 
 
 If it is merely imagined that the bottom of a ship is made 
 the heaviest part, and the top the iiuhle.-<t, it would seem natural- 
 ly to follow, as a first impression, that the bottom beiiiff the 
 heaviest, would stay at the bottom, and the top being the 
 lightest, would stay at the top. This disposition of weight is 
 not what always, or often, in fact, takes place. A ^[ississippi 
 or Xorth ri^Tr steamboat is 30 feet high out of the water, and 
 ^mt 3 to 6 ft. or so deep in it. The heavy weights of its ma- 
 chinery are generally high out of the water; its boilers are en- 
 tirely above the water, reaching in some cases above the hur- 
 ricane deck. Its cargo is carried high above the water, and its 
 bottom, if not quite empty, is merely occupied by sleeping 
 apartments. Such vessels, if supported on pivots at the height- 
 of the water, would certainly tumble over, bottom up. 
 
 Such vessels are certainly top-heavy, and pivoted on Iai:tl 
 would upset. By some power, nevertheless, in the water, they 
 are kept upright and made to form huge floatmg castles, their 
 chief weights high in the air. 
 
 It is therefore a duty to examine, and afterwards to under- 
 stand and to measure, by what power water gives stability and 
 uprightness to a large top-heavy, out of water structure. 
 The upward It might hc imagined, at first sight, that the upward pressure 
 Emmm? carries of the water on the bottom should help to give uprightness to 
 weifTht, but does the Structure it upholds from lielow. But this idea will not 
 iiy. ^'™ ^'''" stand examination: to push the bottom of a vessel upwards, 
 may be simply trying to upset it, by trying to push it bottom 
 up. What is wanted is, to keep the top up and the bottom down. 
 How, out of these contradictory elements, to elicit stabilitv, 
 is neither an obvious nor an easj- investigation, for it is certain 
 that the upward pressure of the water on the bottom of a ship, 
 instead of being a cause of stability, is a powerful agent of in- 
 stability; and that the gi'eater it is in quantity, and the more 
 effectual iu power, the more it tends to upset the floating body. 
 This is a view which must be thoroughly mastered bv the Xaval 
 Architect. 
 
 Xeverthelcss, a perfect understanding of the wav in which 
 the power of water contributes to stability in a toii-heavv, out 
 of water structure, will give one a profound appreciation of, and 
 admiration for, this remarkable quality of water. The way in 
 which this unstable element gives stalnlity to a top-heavy struc- 
 ture as it reels over-is, by continuaUy traiit^fei-ruigil.^t action to 
 tlie side to which the vessel is about to fall and by continually 
 (jiving a stronger push vpirard.^^, on the falling side, so as to 
 counterbalance the falling veighl. if keeps the vessel upright. 
 
HOW TO MAKE A SHIP STAND UPRIGHT. 23 
 
 A top-heavy ship is technically called "crank" — "a drunken 
 ship" — and it really seems so ; but by art, the force of water is 
 made to pass from side to side, faster and further than the ship 
 reels, and so it is managed, that though the vessel may heel 
 over, she cannot capsize. The water then puts its strong pres- gjy"gj^JJ,'J,'it°f " 
 sure under the falling shoulder of the ship, and gives it a power- 
 ful lift. The way in which this shoulder is formed, the lever- 
 age with which the water acts, and the po-wcrful lift which it 
 gives at the right time and in, the right way, is something which 
 it requires much thought to conceive, skill to direct, and craft to 
 apply with success. This portion of the ship may be called the 
 "shoulder," to distinguish it from the bottom or "bilge" of the 
 ship. 
 
 It is the tendency of the bottom or bilge of the ship, to be 
 pushed upwards by the water, and the pressui'e of the water 
 is so great upwards, as to tend not only to keep it up, but to 
 push it too much up and upset the vessel. One way of coun- 
 teracting this, would be to put heavy weights of lead or iron 
 on the bottom of the ship, so as to keep it always, in all cir- 
 cumstances, bottom down. But to put on the bottom of a 
 ship useless wcigTit, which one does not want to carry, is not 
 merely a confession of great want of skill on the part of the 
 Architect, but is a serious sacrifice of the usefulness of the 
 ship. 
 
 It was the practice of a former day to make up for want of 
 stability by great quantities of ballast; but the Naval Architect 
 of the present day knows -how to give suflicient shoulder to the 
 ship, so as to make use of the fluidity of the water as a sub- 
 stitute for the "dead weight" of ballast; and its just application 
 is a test of his skill. 
 
 By the shoulder of the ship, is meant that part of her side shouWerofthe 
 which is just about the water-line, which is sometimes a little ^^ 
 out of, and sometimes a little under the water, as the ship reels 
 about. It is sometimes called, for that reason, the part of the 
 ship "between wind and water;" but it will be quite accurately 
 defined, if it is said that the shoulder of a ship is that part 
 which, being under the water when the ships heels over one 
 way, is then left bare, out of the water, when she heels as far 
 over the other way. 
 
 Take, for example, a ship that has been standing upright, and 
 has first leaned over on one side, until 2 feet of her skin are put 
 into the water, and then leans over just as much on the other 
 side, till 2 feet more of her skin are out of water — those 4 feet 
 of her skin on each side which lie between these extreme posi- 
 tions, may be defined "the shoulders" of the ship. It is on them 
 that she depends for power to sustain top-weight. 
 
 If from the body of the ship the two "shoulders" are taken, Under water 
 the remainder of the bottom, which never leaves the water, may body'defineT " 
 be defined as the "under water body" of the ship, and this under 
 water body is the part tending to upset her. The life of the 
 ship is, therefore, a balanced effort, the underwater • body con- 
 tinually tending to upset her, and the two shoulders, turn and turn 
 about, trying to keep her upright. The one is the "upsetting" 
 part of the ship — the other the "righting" part of the ship. — 
 
24 HOW TO MAKE A SHIP STAND UPRIGHT. 
 
 The effect of each of these contrary elements has to be measured, 
 first — by the quantity of each element; second — by the more or 
 less effectual manner in which it is applied. To make the 
 upsetting body the largest in quantity, for the pui-pose of carry- 
 ing useful loads, yet so to contrive it as to give it the least pow- 
 er for harm; to make the shoulders the smallest, yet so contrived 
 as to have the most power for good ; — that is the consummation 
 of the art of the constructor. 
 
 centre^ *'''"" ^^ every ship it will be a question depending on hef peculiar 
 structure, how much of this righting power hfts been given to 
 her; in other words, how much top weight she can carry, and 
 how high out of the water she can carry it, without upsetting. 
 The simplest way of putting it is, perhaps, to ask, at what 
 height the whole weights of the ship, herself, and all she carries, 
 might be kept without overpowering the stability, without over- 
 working the shoulders, and without upsetting the ship ? 
 
 This height is, therefore, a chief point to be calculated and 
 known; it may be called the "upsetting point." It has beent 
 called the "Meta-centre," and if this be taken to mean the point 
 beyond which you cannot go in raising the weights, it is a pro-- 
 per word enough. The limiting height of top weight is, there-' 
 fore, the proper meaning of what is called the meta-centre. But 
 the measure of this is manifestly one of the most important 
 things to be known about a ship, and on which many of its good 
 qualities depend- 
 
POWERS or SHOULDER AND UNDER-WATER BODY. 25 
 
 CHAPTER VIII, 
 
 POWERS OF SHOULDER AND UNDER-WATER 
 . BODY. 
 
 To understand the functions of the shoulder of the ship, and vesidfas aTe"- 
 those of the bottom, and the tendency of both to effect the sta^peri mental 
 bilityof the ship, it will not be necessary to Consider any but ^'"'"^ 
 the simplest form which can float. For that purpose, take a 
 square box of large size, say 36 feet wide, 2*7 feet high, and of 
 indefinite length', and sink it by a weight ] 8 feet deep in the 
 Water — each foot of length of a box of these dimensions, will 
 carry a ton weight, for every foot of its depth in fresh water ; 
 therefore, 18 feet of depth carries a weight of 18 tons. And 
 supposing the box itself to weigh 6 tons per foot, the vessel 
 vould carry beside its own weight, a weight of 12 tons. Draw 
 guch a box, and across it the line of the surface of the water, 
 which, call the "water-line.'''' Let the weight be represented 
 in square form on top of it. {See Plates, Fig. 1.) 
 ' This box truly represents a ship, the weight truly represent- 
 ing a heavy deck load proposed to be carried by the ship. It 
 niay represent the weight of. a man-of-war's . battery, or the 
 weight of an iron-eased battery, an iron-clad's turret, or any other 
 top load. 
 
 The question i-s: — th~e ability, or inability of that ship to carry 
 that weight, at that height out of the water ?■ Eor this purpose, 
 suppose it to lean over on either side, and then examine whether 
 it tends to I'eturn to the upright position and stand up, or to 
 overset and drop the weight into the sea. Draw the ship, there- 
 fore, in these two positions. (Figs. 2, 3, 4.) When this is done, 
 it' will be seen that there is a part of the ship which is never out 
 of water, but keeps always- under the water-line. This is the 
 uhder-water body of the ship, or the upsetting part of the ship. 
 
 This under-water body is bounded by, first of all, the bottom „nJp"™ate^ ""^ 
 of the ship ; secondly, by the bilges, or Corners of the bottom ; body, 
 and- thirdly, by a water-line of the ship, in each of its two oppo- 
 site positions. It is, therefore, pointed at the top, when it forms 
 ah equal sided triangle, the apex of which is ia the water-line. 
 'iwo flat surfaces, therefore, forrh the top of this under-water body, 
 and the rest of it forms the bilges and bottom, or under-water 
 sMn of the ship. The part shaded, is that part which.tends to 
 upset the ship. Let the nature of this upsetting force .produced 
 by the under-water body, be examined. (Figs. 5 and 6.) 
 
 To this end, observe that it is a symmetrical body, the right 
 and left sides being of the same size, of the same shape, and in 
 the original upright p'bsition Of the body, exactly balancing on 
 both sides. Its whole effect, then, may be assumed as concen- 
 tfated in a point . in its middle line. This point call B, or the 
 centre of effort of the under-water body! , 
 
 The buoyancy or upward pressure of this under-water body, . ^^. "■=''"" '<="*- 
 
 "^ In? to unset 
 
 will take place directly upward in the line Bb, and it will be 
 seen that this is quite on one side of the centre of the vessel. It 
 ' -^oxt to bo nqticc'a,in figs. 2 and 37 that the centre of the weight 
 i. 
 
2(; POWERS OF SHOULDER AND UNDER-WATBR BODY. 
 
 (W.) is on the opposite side of the upright line. When the ship 
 careens over to the right, the weight also inclines to the right 
 and downwards. When the ship careens over to the left, the 
 weight also inclines to the left and downwards. The direction 
 of its effect is marked by the downward line from W. 
 
 Fi-X'tid ''b^^^'o'" ^* ^^^^ '^°"*'*' ^^° observed, that ivhen the ship is lowered on the 
 
 weight. ^ "'' right side, the effect of the weight from above, is to press it 
 downwards on that side. At the same moment the effect of the 
 under-water body is equally bad in raising the opposite side out of 
 the water. The ship is beset by two opposite forces, which, 
 nevertheless, conspire in their bad effect ; one sinks the right in 
 the water, while the other lifts the left out of the water, so that 
 with opposite means both tend to overset the ship. It is thus 
 seen why the under-water body is the upsetting part of the ship. 
 The larger it is, and the greater its power to carry weight, the 
 more it will tend to overturn the weight it carries. 
 Counterpoise Some Counteracting power must, therefore, be looked to, not 
 
 necessary. jjicrely to neutralize the overturning eflTect of the top weight and 
 the upsetting force of the under-water body, but to do more than 
 neutralize them, to give a balance of righting force, which shall 
 constitute the stability of the vessel, or give her the power to 
 right herself after she has been forced over. 
 The shoulders This righting force is found in the shoulders of the ship. These 
 
 upsetting force, shoulders are formed by the two portions of the ship, on either 
 side, which lie between wind and water, and are continually 
 going in and out of th^ water on one side or on the other. "When 
 she leans over to the right, the whole of the right shoulder is put 
 under water, and when she leans to the left, the whole of the left- 
 shoulder is put under water. In fig. 4, the shades on the shoul- 
 ders distinguish them. Each shoulder consists of a wedge-formed 
 body, with its point at the middle, and the base or heel of the 
 wedge on the outside of the ship, the whole of the base or heel ^ 
 rising out of the water, and falling into it again as the ship ca- 
 reens. One-half the angle of this wedge is called " the angle of 
 heel" or "the angle of inclination," and is taken as the measure 
 Angle of iieei. of the roll or carcen of the ship. A ship, for example, is said to 
 roll or careen 15° when the angle of this wedge is an angle , of 
 30 degrees. It is convenient generally to speak of some fixed 
 angle for this purpose, and 28° may therefore be assumed. For 
 ships of war, it has been common to use 15°, as it is desirable- for 
 the sake of the guns, that the ship should not roll or careen more 
 than this ; but for merchant ships, under a press of sail, there is 
 no harm in their careening 14° in, and 14° out of water, a total 
 of 28°. These wedges or shoulders arc sometimes called -"the 
 wings," sometimes "the solids of immersion and emersion." The 
 term "shoulder," is considered the best and simplest term. 
 
 of^shoiider^""" '^° examine the effect of each shoulder, when it has been forced 
 down under water, to rise again, and raise the top weight with 
 it, one must consider the amount of its effort, the place where it 
 may be reckoned as concentrated, and the direction of its effort. 
 The quantity of its effort is measured by its buoyant power,- or 
 by the number of cubic feet of water it displaces. Its bulk in 
 water, therefore, gives a measure of its buoyant or upward force. 
 The phico in which its buoyant effort takes effect, is ubout two- 
 
POWERS OF SHOULDER AND UNDER-WATER BODY. :^T 
 
 thirds (2-3) of its length from the point of the wedge 0, (fig. 4.) 
 The effect it produces may be assumed as concentrated in R, 
 and its buoyant effect being directly upwards, tends to upright 
 the vessel on the side which has been depressed under water. 
 
 But it should be observed, that that sideof th6 ship on which ^o^Jl^,^'";!™''?,^; 
 the shoulder lies under water, is also that side on which the top weight, 
 weight tends to descend and overset ; and it is, therefoi'e, obvi- 
 ous, that the tendency of the shoulder is to help the descending 
 weight to rise up again. The tendency of the shoulder is there- 
 fore to right the ship. 
 
 But the vital question is, whether the shoulder has V^^^^' u„ie^^aier^^ 
 enough to do so ? In order to be effectual, it will hot be suffi- Uoay also, 
 cient that it should be capable of supporting the top weight 
 merel)^ It has also to counteract the upsetting tendency on 
 the opposite side, produced by the under-water body. 
 
 It must not escape notice that the under-water body is always 
 on the contrary side from the shoulder, always tending to upset 
 the ship on that side from below, so that unless the shoulder be 
 more powerful, and act more energetically than the under-water 
 body, the ship will infallibly upset. The shoulder, therefore, 
 has these two tasks at once. It must be strong enough to neu- 
 tralize the upsetting force of the under body, at the same time 
 that it sustains and counteracts the over setting force of the toi") 
 weight, and the surplus power beyond these two will right the 
 ship. 
 
 It is this sui'plus power, beyond the two effects counteracted, p„JJ^^ oT'^lhe 
 which gives stability to the ship ; its m-easure is called " the shoulder meas- 
 measure of the stability of the ship," and the art of the ship "/.' """ "•"'""" 
 builder is to make it always just as much as is wanted for this 
 purpose, and no more, for more is of itfeelf an evil, and defeats 
 other good points.* From this examination of the sources of sta- 
 bility and instability in a ship, and of the part taken in that 
 stability by the under-water body, by the shpulders, and by the 
 weight carried, one is prepared to seek exact measures of the 
 effect of each, and to obtain from thenij as a result, the measure 
 pf the stability which is achieved. 
 
 To measure the upsetting force of the under-water body, its power!^"™ "^ 
 volume is measured, after which its power is found by taking the 
 weight of an equal quantity of water or its buoyancy. Then as- 
 sume that power as applied at its centre of action, commonly called 
 ''centre of gravity." Draw a line directly upward through this 
 ■pftint, and call that "the line of action of the upsetting force." 
 Mark the place where this line cuts the water. It is on this 
 water-line that the comparison between the forces causing stabili- 
 ty can be most directly seen, and it may be called "the line of 
 comparison." 
 
 To measure the righting'force of the shoulder, in like manner shoulder. "^ *''* 
 measure its volume, then find its power-by taking the weight of 
 an equal quantity of water, or its buoyancy, reckon that as applied 
 at its centre of action (centre of gravity), draw a line directly 
 upward through this point, and call it the "line of action of the 
 righting force." Mark the place where this line cuts thp water, 
 
 * T(n) niiR'li stabltiry is almost as grs^at an evil as too little. 
 
fi>rni, 
 
 28 TOWERS OP SHOULDER AX.D UND.ER-WATIJR BOPy. 
 
 and here its action may be compared with that of the other two 
 forces. , 1 i ■ 
 
 i jp wBigiit. The third force hag been already measured.it is the top wein;ht 
 placed on the vessel, and it is IS tons for each foot of length. 
 To compare this with the others, let fall through its centre of 
 gravit}", its lirte of action, which cuts the water at some place 
 interniediate between the other two. Mark its place. The 
 watei'-line now showS the three points of comparison desired, 
 stnbuity of ' Of the three first, conipare the upsetting and righting force of 
 "'■ the bo'dy dnfl' shoulders. ' They are on opposite sides of the mid- 
 
 dle of the ship, they counteract each ot^her. In the case under 
 consideration, one^ thfe up'sfetting'" force, is much larger in quan- 
 tity than the other, the rightiiig force, — larger in the proportion 
 of 3 to 1 ; but the smaller force acts more advantageously than 
 the greatet, so much so, as to overpower it, because its centre 
 of action is four times farther from the centre of the ship on one 
 side, than the point of action of the other. The combined result, 
 ■therefore, is in favor of the righting force, and the ship has sta- 
 bility, and will right itself If the other force had preponderated, 
 it would have had instability and have overset, even without a 
 deck load. The question now remains : How much stability 
 has it? In other words, how iiiuch top weight will the ship 
 carry, and how high? ■ • ,. . , ? 
 
 The surplus To find this, multiply the volume of the under body by thp 
 nilaMlfeii.''""" distance of its line of action from the centre, subtract it from the 
 righting force multiplied by the distance of its line of action from 
 the centre ; the balance, in figures, shows the balancing quantity 
 of force the shoulder is able to carry. This may amount to a 
 weight'of 12 tons, multiplied by the distance of the line of action 
 of the top weight from the -centre of the line of comparison. If 
 this be so, the vessel has stability enough, not to be overset; if, 
 on the contrary, the sui-plus is less than this, the vessel will bo 
 •overset. This surplus sustaining power, however, is the mea^ 
 sure of stability. But, in this calculation, all' Consideration of 
 the effect of the weight of the ship itself, either in oversetting or 
 in righting, has hitherto been omitted; It may happen, and 
 does happen in practice, that tiie weight of the ship alone, with- 
 out a deck load, is enough to upset her. In such a case, the 
 weight of the deck load must be treated as the whole weight of 
 the ship, and the point of action of this weight must be 
 taken in the centre of action of the sum of all the weights 
 of all the parts of the ship and her equipment. In this view of 
 the case, one must substitute, in the calcAlation, the total weighjt 
 pf the ship as well as the weights on it, instead of the deck load, 
 and must examine the height at which the whole of these could 
 be carried without upsetting. 
 
 Sill 'rofmrtS'em 1'^'^ height is taken as a convenient way of estimating the 
 ma'sniiuii'-''- surplus righting i)owor of tjie shoulders of the ship; because, in 
 comparing different sjiips, pnp may, without reference to their 
 weights or displacements, compare their righting powers or stabili- 
 ty by the height above the water, at which they have power to 
 carry their own weights. For example, a ship which has power 
 to carry her own \\oight fi feel above the water, and another 
 which lias power to carry hev's ;> ft. out of the wnler, mav be 
 
J»0WETIS OF SHOULDISR AND UNDER-WATER BODY. 29 
 
 said to ha'TO relative stabilities of 2 to 1 ; but, if the magnitude . surplus right 
 of the ships also be coi)_sidered, aAd one is doulalo the bulk of the "ureS."'^ 
 other, and has power to carry its weight twice as high, the abso- 
 lute stability of the one may be four times that of the other, 
 'although thoiv relative stabilities, reckoned by h'cight alone, are 
 as '2 to 1. I'he upsietting power of the bottom of a ship and the 
 righting power of the shoulders are, therefore, the two rival forces' 
 wljich continually oppose one another. 
 
 "Ilhcse two forces depend entirely for their quantity, their pro- 
 portion, aiid the manner of their action, upon the forethought, 
 jknowledgo and skill qf the designer of the ship. 
 
 The proper balance of these forces, in the design, makes the 
 ship a good or bad carrier of top weight, and the height at which 
 it can carry all its weights, is a' point of the greatest value in 
 every ship, and in men-of-war especially. If a jconsiderable mis- 
 take be originally made, it is scarcely possible to correct it by 
 anytliing short of rc-building the ship. 
 
30 
 
 PROPORTIONS OF STABLE AXD UNSTABLE SHIPS. 
 
 CHAPTER IS. 
 
 Crankness 
 
 old Ships. 
 
 ox THE PBOPORTIOXS WHICH -VAKE A STABLE 
 on rXS TABLE SHIP. 
 
 diSMcnt' '^J'rf ^^^ framing the design of a ship, few things arc of greater im- 
 a shjii in ^ving portance to be clearlv seen, and unceasingly kept in mind, than 
 stabiuiT. ^jjg gg.ppj ^f ^jjg ijottom ^.Q diminish, and that of the shoulder to 
 
 ncrease, power to carry top weight. In order to give a ship 
 this good and indispensable power, it is important that the 
 Xaval Arcliitect should not, for a moment, lose sight of the con- 
 trary nature and tendency of these two forces. It is from the 
 omission of, or inadequate consideration given to these two effects, 
 that crank, unstable and unseaworthv ships have so often been 
 built. 
 Crankness. Crankncss was a general fault of ships built in the early part 
 
 of this century. It means two things : inability to stand upright, 
 and facility of being upset by top weight. The cause of crank- 
 ness is often supposed to be shallow draft of water, which would 
 be cured liy deeper immersion. This is a radical error; there 
 is no more common source of crank ships than this general im- 
 pression. The contrary is the truth, 
 of Take a square ship, like a box, filled with light material, so as 
 to' sink no deeper than one-fourth part of its breadth, it will 
 stand upright well ; fill the same with heavier materials, so as to 
 sink it to douljle that depth in the water, it will immediatelv 
 turn bottom up. This is a very common proportion of draft to 
 breadth, especially in old ships. It is sufficient to make a bad 
 ship. But' it is necessary to understand how to build crank 
 ships and ships not crank. As a general rule, then, ships with 
 a deep and large bottom and narrow shoulders, 'and ships Avith a 
 straight, upright side, and flat bottom, and sharp bilges, will bo 
 crank. 
 ^°' In most cases, ships that are crank may be cured, liy altering 
 them so as to increase the breadth of tlieir shoulder, without 
 altering their bottom.* They may also be cured by lengthening 
 them, so as to make them, with a given load, draw less water. 
 Both plans have been tried with success. 
 
 T.Si^'^'s'''" °^ '^^^ ^°^^^ ^^ ^'^® ^^^ °^ ^^^^ chapter, is given to show the 
 ' ' '■ "■ limits of the power of a square built, wall-sided ship to stand 
 upright under heavy and high loads. To each breadth there is a 
 given height, up to which she can carry top weight, and the 
 table shows with what proportion of depth in the water, to 
 breadth, she can, or cannot, cany her weights above water; thus 
 the table shows, that such a vessel, 36 feet broad and 18 feet 
 deep in the water, cannot carry her weights if their common 
 centre lie above the water, and that she would require to bo 48 
 feet broad, to carr}- them just -20 inches above the water. 
 
 In this table, the figures show that, if the whole weight 
 carried were no higher than the surface of the water, the ship 
 would, nevertheless, be incapable of standing upright, and would 
 
 Remedy 
 crankness. 
 
 ' This i^* soiocliincs done by moan.^ of -^siinnsons.'' 
 
pROPo^mo^•s of stable and unstable ships. 31 
 
 cither list over or upset. The figures show how high the cen- 
 tre of gravity of all the Avcights carried, including both the mate- 
 rial of the vessel itself and the burden with which §ho is laden, 
 might be raised above the water-line, without instability or dan- 
 ger of upset. 
 
 The value of thistablc is manifold, it shows how the extremely .^^^^" "• '''<= '''''" 
 shallow, fiat vessefs on the Mississippi and other rivers, are able 
 to stand up under their very heavy top loads, and carry enor- 
 mous floating hotels, three and four stories high above the sur- 
 face of the water. It is their small proportion of depth in the 
 water, combined with their great breadth, which does it. It is 
 this proportion which enables them to carry, not only their light 
 cabins, but also their heavy engines, boilers, fuel and deck loads 
 above the water. 
 
 It shows the proportions for floating docks, which have to take 
 ships of great weight, raise them high and dry above the water, 
 and carry them steadily there. It also shows how high the cen- 
 tre of gravity of a ship may be, which a floating dock of given 
 proportions can carry, taking into account, also, the weight of 
 the floating dock itself. It shows how the shallow floating plat- 
 forins of such contrivances as Clark's Hydraulic Docks, are able 
 to sustain ships under repair, by using the right proportion of 
 dejpth to breadth for a ship which has her centre of gravity at a 
 certain height above the ■water. 
 
 This table enables one to see, also, how the square built, wall- 
 sided, deep-bottomed ships, so often built by uninformed or care- 
 less shipwrights, turn out unstable and unseaworthy. 
 
 In using this table to judge of a ship or design, it must not be 
 forgotten, that the case shown, is that of a box-formed or wall- 
 sided vessel, nearly rectangular in shape ; but it is nearly true, 
 also, of a vessel slightly rounded ofif at the corners, and will be 
 pretty exact for many large, capacious ships. It must be care- 
 fully borne in mind, that the table shows the extreme or upsetting 
 heights to which the centre of weight must not be raised. The 
 weights of a well trimmed ship, intended to carry sail well, 
 sho,uld be kept so that the centre of gravity may be several feet 
 under the limiting height. 
 
 It should be further noticed, that the length of the vessel is 
 not given in the table. The breadth and depth being given, the 
 length has no effect on the height at which the whole load can 
 be carried. But length has everything to do with the quantity 
 of weight which that ship will carry at the height in the table. 
 Thus, a ship of 36 ft. beam, carries one ton for every foot deep ; 
 and for every foot in length, as many tons as there are feet of her 
 depth in the water; therefore, it is to be remembered, that the 
 weights carried at these heights are limited by the total displace- 
 ment .to'nnage of the floating body. With these explanations, this 
 table is a safe guide for the construction or judgment in regard 
 to rectangular, box-shaped, or wall-sided, square bilged vessels. 
 
32 
 
 PROPORTIONS OP STABLE AND UNSTABLE SHIPS. 
 
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First luethod. 
 
 THE METHOD OF MEASURING STABILITY. 33 
 
 CHAPTER X. 
 
 THE METHOD OF MEASURING STABILITY. 
 
 1. The first method, is to determine how much top weight' Two methods 
 will careen the ship to a given large angle, say 14° — out of the stabSTiy. "^ 
 perpendicular, or in war vessels T° — in order to compare the 
 
 stability of different shijjs with one another at this angle. 
 
 2. The second method, is to find the extremely small degree 
 of eareeiiing which will be produced by an extremely small top 
 weight. 
 
 By this iavestigation is discovered a curious quality belong- 
 ing to crank ships, namely, that although a very small top weight 
 may make them lean over a little, they may, nevertheless, offer 
 great resistance to a great weight tending to incline them much. 
 It is common to speak of such ships as being "tender" rather than 
 crank. 
 
 The following are the successive steps : 
 
 1st. Measure the bulk of the imder-water body, the ship be- 
 ing inclined on alternate sides to the given angle. 
 
 2d. Measure the buoyant force of that bulk, taking 36 cubic 
 feet of bulk for each ton of buoyancy. 
 
 3d. Find the place of the centre of effort at which this 
 force acts, which is the point commonly called the centre of 
 gravity of the under-water body. Xext, through the point thus 
 found, draw an upright liae — cutting the water-line at some dis- 
 tance from its middle. Then measure this distance from the 
 middle line of the ship. 
 
 4th. The line just measured, is called "the effectual dis- 
 tance of the upsetting force," and is multiplied by the number 
 of tons already found as the measure of that force, the product 
 Is called "the momentum of the upsetting body." This momen- 
 tum is taken as the measure of the upsetting force. 
 
 5th. Measure the bulk of the righting body, or shoulder un- 
 der water when the ship is inclined at the given angle. 
 
 6th. Measure the buoyant force of the bulk of the shoulder, 
 taking 36 cubic feet for each ton of buoyancy. 
 
 "Ith. Find the place of the centre of effort in the shoulder, 
 at which this force acts, which is the point commonly called the 
 centre of gravity, and is nearly two-thirds the breadth of the 
 shoulder from the centre of the ship, or one-third from the out- 
 side. 
 
 , Next, through the point thus found, draw an upright Une, cut- 
 ting the water-line at a point, of which measure the distance 
 from the middle line of the ghip. 
 
 8th. The line just measured, call the "effectual distance of 
 the uprighting force," and multiply it by the number of tons al- 
 ready found as the measure of that force, this product call "the 
 momentum of the uprighting force," and take it as a measure of 
 the uprighting force. 
 
34 THE METHOD OF MEASURING STABILITY. 
 
 inSiS*'^°stf ^*^- '^^•^^ subtract the smaller of these two momenta from" 
 biiity"""^ ^' the greater. If the upsetting force be the greater, the ship will 
 overset in that position, unless some heavy weight be placed oh' 
 the bottom, or some equivalent force be applied to prevent its 
 oversetting, and such a force will, in order to be effectual, 
 require to have a momentum at least equal to the difference. 
 
 10th. But if, on the contrary, the uprighting force be the 
 greater, the ship in that position tends to upright itself, and can 
 carry increased top weight, until, this increased momentum be-' 
 comes equal to the surplus righting momentum. 
 
 It is this surplus momentum either, way, thUt is taken to 
 :neasure the stability or instability of the ship. 
 
 11th. If the surplus righting momentum is taken and divided 
 by the entire weight of the ship, the distance will be found td 
 which this whole weight might be removed to one aide, without 
 upsetting. This distance is reckoned as another measure of 
 stability. If, now, this last measure be taken and be divided 
 by the line of the angle of inclination, the height will be ob- 
 tained to which the whole weight of the ship might be raised 
 without upsetting it; and this is a third measure of the stabili- 
 ty of the ship, and is called the measure in height of stability 
 of form. 
 
 It may be found, geometrically, by taking the former measure 
 and erecting a perpendicular to the water-line, which will culf 
 the upright middle of the ship at this height. 
 
 Thus measures of stability are obtained in three forms : 
 
 1st. Power to carry a given weight at a given distance out of 
 the middle line. 
 
 2d. Power to resist a given heeling force. 
 
 3d. Power to carry the whole weight at a certain height above' 
 the water. 
 Second metiioj. The scoond method of calculating the stability of a vessel, is 
 to calculate all the quantities given above, for some extremely 
 minute angle of deviation from the vertical position. Thik may 
 be said to measure the resistance of the vessel to deviation from 
 the vertical, whereas the former raethod measures her tenden- 
 cy to return to the vertical, after having been compelled to make 
 a great deVisttiOn from it. 
 
 Elements or Stability. 
 
 Elements of Breadth. — The stability of a vessel increases or diminishes 
 
 ' ' ''■ enormously with its variation — whether the displacement re-' 
 
 main constant, or, the draft remaining constant, the displacement' 
 
 vary with the breadth. In the latter case the height of the 
 
 meta-centre variefe as the square of the breadth. 
 
 Displacement. — If the breadth r^ain constant, the stability' 
 increases as the displacement decreases. And, since in that case 
 the centre of displacement rises, the height above the water-line,- 
 to which the vessel's load may be carried, receives a further 
 increment. 
 
 Draft. — Assuming both the breadth and displacement to re-' 
 main constant, the increase or diminution of draft lowers or raises 
 
•THE METHOD OP MEASURING STABILITY, 35 
 
 ■the centre of displacement, and with it the metOrcentre. It does ^ Eiomoiits or 
 •not otherwise effect the instantaneous stability. biabiiuy. 
 
 Stowage of Lading or Ballast. — The meta-centre indicates 
 the height to which the centre of weight of the vessel may be 
 .brought without upsetting ; and the amount of stability for veiy 
 smaU inclinations is measured by the distance between the meta- 
 centre and the centre of weight. The stowage, therefore, effects 
 the instantaneous stability, in so far as it raises or lowers the 
 centre of weight, and not farther or otherwise. As the meta- 
 centre fixes an absolute maximum, wh^ch being reached, the 
 vessel has no stability whatever, the weights must, in practice, 
 be kept considerably below it, as the vessel must have reasonable 
 Stability. 
 
 Curve Bounding Plane of Flotation or Form of Water- 
 line.- — This element of va.riation may be considered apart from 
 all others, and even independently of the proportion between 
 length and breadth. Coeteris paribus, fine lines may reduce the 
 stability, measured by the height of the meta-centre above the 
 centre of displacement, to one-half what it is in the rectangular 
 box. 
 
 Length and Lateral Sfahility. — This element may be always 
 disregarded except in the mere calculation of actual weights, pro- 
 vid(ed tjie same breadths and depths at proportionate lengths are 
 maintained. 
 
 Weight. ^-^his element is merely a factor, and is of no other 
 account in the investigation of stability. 
 
 A vessel with nothing moveable in her, has her sta^bility com- 
 pletely determined by the moments, on the water-line, of the 
 three following forces, only two of which are independent: 
 
 1st. Her weight. 
 
 2d. The upward pressure due to her displacement. 
 
 3d. The force required to keep these in equilibrium. 
 
 Distinction between Heeling and being Listed. — A vessel 
 is|said to heel when she is pushed over by an extraneous force ; 
 on the removq,l of which she would alter herj^inclination. 
 
 She is said to be listed when she has found equilibrium in any 
 position, other than upright; whether owing to an unsymmetric 
 distribution of her weights, or to any peculiarity of form. A 
 list, therefore, implies equilibrium (though unsymmetric;) heeh 
 ing excludes equilibrium. 
 
 As applied to a vessel heeling, the meta-centre has no mean- 
 ing, except to indicate how an alteration of the weights might 
 be made to give equilibrium. As applied to a listed vessel, it 
 has the same import as to a ve5.?el floating upright. In both 
 these cases, it affords practical means (^ comparing many^diffep- 
 ent forms ; especially where the variation to be considered is in 
 the water-line. 
 
36 POWERS AND PROPERTIES OF SHOULDERS. 
 
 CHAPTER XI. 
 
 POWERS AND PROPERTIES OF SHOULDERS. 
 
 s.tabHuif'^^™ The sum and substance of what is known of the nature of 
 stability is this: the shoulders alone, give to the ship righting 
 or uprighting power. No other part of the ship can be so formed 
 as to increase the righting power given by the shoulders. The 
 righting power given by the shoulders is equally effective in 
 squaring the ship to the water, whether it be still water or rough 
 wave water. 
 
 .dc^water'body"" The bottom of the ship, or the under-water body, can in no 
 way help the ship to keep upright, there is no kind of bottom on 
 which the ship can be said to rest in the water; the most that 
 any under-body can do, either by shape or size, is to take less 
 away from the stability given to the ship by the shoulders, than 
 some other shape or size of under-body takes away. Size of 
 bottom, therefore, or quantity of under-water body, lessens the 
 stability of a ship, and has to be counteracted by the power of 
 the shoulders. In short, bottom tends to upset the ship ; so 
 much so, indeed, that if it be large and powerful, it may take 
 more than the whole power of the shoulders to keep it down, 
 and prevent the ship from capsizing. A large under-body, there- 
 fore, weakens the effect of the shoulder, by the whole of its upr 
 setting power. 
 
 biJuyr*"^' ^^ It is oii^y> therefore, the surplus power of the shoulder remainr 
 ing over and beyond what is employed to keep down the under- 
 body, which is available for use in carrying a press of sail, or in 
 supporting top weight out of the water. If there be any such 
 surplus, it is a duty to find out how much there is, to see if it 
 be enough to carry a press of sail, and enough also to carry top 
 weight — then the ship may be able to do without ballast. 
 , ?i ast. ]gy. ijaiiast, in the general sense of the term, is meant weights 
 
 carried under the water — ^in contra^distinction to weights carried 
 above the water, or top weights. There are two ways of bal- 
 lasting a ship; one is, by real lading, or stowing heavy weights 
 under the water; the other is by putting weights, which are not 
 parts of the lading, nor essential parts of the ship, low down in 
 the ship for the mere purpose of helping the shoulders to carry 
 top weight — (this latter is the old principle of ballasting.) 
 
 Weight placed under the water, in either way, may be said 
 to have the following effects: first, by being under the water as 
 far as the top weights are above it, it neutralizes the bad effect 
 of these top weights, and balances them. In this way under^ 
 water weight assists the shoulders in carrying top weight. 
 
 There is another way of looking at the effect of under-water 
 weight in giving stability; it aids the shoulders in keeping down 
 the under-body. In this way, as well as in counter-balancing 
 top weight, under water weight helps the shoulders, 
 
 inptobiiKy?"" Tlius it is that there are three agents in stability; two 
 arising from the shape alone, and one from disposition of weights. 
 The shape and size of shoulder give stability of form — the shape 
 3,nd size of under-water body give instability of form ^what of 
 
POW?)RS AND PROPEETIES OP SHOULDERS. 37 
 
 the power of the shoulder remains beyond counteracting this 
 under-body, is the true surplus stability, or measure of righting 
 power, for that form. This surplus is all that can be used for 
 navigating a ship and carrying her top weights. If more sta- 
 bility be wanted, it caij be obtained by weight alone. All the 
 weights of a ship, which have their common centre of gravity in 
 the middle of th6 ghip, just between the two shoulders, neither 
 help the stability nor hinder it. Only ■jJireight placed below the 
 middle of the slioulders gives help and increases stability; and 
 if the centre of ail the weights of the ship, cargo and ballast, 
 taken together, fall above the water-line, the surplus power of 
 the shoulders ijjay enable her to carry sail — if not, there is no 
 r.esource left but to lower the weights in her, or to place ballast 
 in her bottom ; in other ■yords, to supply the defect of stability 
 .of form by adding stability of weight. 
 
 As, therefore, stability of forjpi is that power which the Naval fo^^'^^st^ "fju 
 Architect alone can confer on his ship, — while stability of weight the Navai Archi- 
 may afterwards be regulated by those vho lade, and control, and "'°'" 
 navigate the vessel, — the form and action of the shoulders are 
 the province in which the skill, contriyance, and forethought of 
 the designer of the ship can be niost povyerfully and usefully 
 employed. 
 
38 HOW TO GIVE A SHIP STABILITY, &c. 
 
 CHAPTER XII. 
 
 HOW TO GIVE A SHIF STABILITY WITHOUT 
 QBE AT BBEADTE OF SHOULD EB. 
 
 Shmi1de''r^nm a"- Breadth of shoulder, properly placed, g-ires power to stand 
 wnys ntminabie. upright, and to cany heavy weights above the water, — but eases 
 often occur in which stability is sought, and breadth of shouldeE 
 denied. This may arise from local causes, such as the narrow- 
 ness of a dock entrance, or from a wish to obtain certain other 
 qualities which may be inconsistent with great breadth. 
 
 piemrmed."^"'" ^'^ *^"* '^^*'^' t^® Xaval Architect has only the dimension of 
 length given, and the question arises: How can length help 
 him? How can it come in the place of breadth? To find out 
 how this help may be given by length to defect of breadth, one 
 must remember that if the two ends are made very fine, in pro- 
 Finc ends cor- portion to the middle bodv, thcv mav be .considered as having 
 
 to stebmn-."""' little effect in giving increased stability to the middle. But one 
 may go farther than this, and state distinctly, that in all vessels 
 with fine ends, very large portions of the two ends have merely 
 stabilit)' enough to upright themselves, and have no power what- 
 ever to help the middle body to carry top weight. These two 
 portions, therefore, may be taken as neutral parts of the vessel — 
 neither helping the middle body, nor requiring help from it ; and 
 therefore, it simplifies the subject very much to leave them altOt 
 gether out of the question. 
 
 co^JT ""f-^'j"''^ Suppose S to represent the form of the bow of a ship, and 
 taiil-see Plates. W to represent the stem of a ship, at the mean depth of 
 
 water. The form S barely stands upright with its own weight. 
 
 In like manner the form W barely stands upright with its own 
 
 weight, and a verj- slight elevation and depression of weights 
 
 would make them absolutely neutral. 
 
 It is plain, therefore, that these forms, if taken as types of a 
 certain kind of bow and stern, do not effect the stability of the 
 middle body either way. These two ends may be assumed as 
 types of the "clipper" bow and stern. Suppose T to represent 
 a "bell" bow — it will be found that instead of being any use, 
 this "bell" bow is unable to carry itself, and would require help 
 to a very great extent. TJ, on the other hand, taken as a type 
 of the Avave bow, has a powerful surplus stability at its deepest 
 immersion, while only at its lightest immersion does it need help. 
 V, which is the extreme of the "flare-out" bow, is unstable at all 
 immersions, and worse than helpless. It is plain, therefore, that 
 the Naval Architect need not trouble himself to seek much help 
 from any of thpse bows — it is to the stern that he should look 
 for any help he may want in supplying the needful stability. 
 
 ma''be''^"d*e't^ '^^ '^^ found, by long practical experience, that there exists a 
 give increased widc scope for obtaining power, stability and wcathcrliness to a 
 stability. gjjjp of limited beam, by a wise design of the after body. 
 
 A crank, narrow ship, may be rendered stable and weatherly 
 by a yery moderate alteration to the bulk and form of the after 
 body. The secret of success consists in uniting with a very fine 
 line under the water, a very full line at the surface of the water. 
 
HOAV TO GIVE A SHIP STABILITY, etc. 39 
 
 The form Y has great stability at its two deeper immersiohs,-^— 
 and is not deficient in stability oven at its lightest. So great is 
 its stability, that yny few midship sections even compete with 
 it in stability; and to most of them, it would, at its deepest 
 draughts, impart an enormous increase of that quality. 
 
 There is another point in the art of Naval Construction where Diminution or 
 the constructor can use the form of the stern with great effect — "f aiiet^body!'"'^ 
 for the power of a middle bbdy t6 carry top weight lessens as 
 the draught of water increases. This is the same as saj-ing, that 
 in proportion as heavy top^ weight presses the vessel more down 
 in the water, so does this very depth in the water diminish the 
 power of the midship body to carry its top weiglit. The reason 
 for this is already known to be, that bottom buoyancy increases 
 both the quantity of the upsetting force and the advantage with 
 ■which it acts. Xow let it be observed how the after body can 
 be used, so as exactly to counterbalance this defect of the mid- 
 dle body, and make good the stability of the ship in exact pro- 
 portion to the increasing top weight which presses it down in 
 the water. 
 
 The skillful Architect will carefully cut away bottom buoy- g ^^^■'1'"''"''^^°'^ 
 ancj' from the stern of the ship,— this will enable him to make ed. '^^°^ " 
 the run clean and fine, as he wants it to be. Nearer the middle, 
 the stern may be of the form Y, and further aft, of the form X ; 
 and finally of the form W. Each of these forms has a growing 
 surplus of stability over that necessary to support itself, in some- 
 thing like the following proportion to the increasing draught of 
 the water: Y' — 3 Avhen lightest, and '7 when deepest; X — 3 at 
 middle draught, and- 6 when deepest; — and W only 4 when 
 deepest, but negative at the two other draughts. The more, 
 therefore, of a form approaching to Y^, the .constructor C8,nput 
 into the stern, the more powerful will be the resources he will 
 have developed in the stern to aid the good qualities of the mid- 
 dle body, and to supply stabilit}' to do the work required, exactly 
 at the time and in the manner where it is most wanted. 
 
 Constructors of the old school will declaim against a full after F"" after-body 
 body — they will insist on a fine run — but in truth, there is no runVe'iow. 
 reason why either should be sacrificed, in so far as concerns its 
 practical use. On the bottom of the stern then, give the finest 
 possible run — it is there where it is wanted, there alone where 
 it is useful, so there give it to tlie utmost. Near the surface of 
 the water, on the contrary, fineness of run is not only of no value 
 to speed, but has many disadvantages of every kind. A wise 
 constructor will seek there the stability he wants; there — the 
 buoyancy may be taken in large quantity near the surface of the 
 water ; there — it may be obtained without impediment or increase 
 of resistance ; there — may be taken as much as is wanted to make 
 the vessel a good and stable ship.' A mine of good qualities is 
 here to be found, hitherto comparatively unworked, and it has 
 been unworked mainly on account of a vagiie, indefinite, but 
 wide-spread prejudice, having no better basis than the old say- 
 ing: "Cod's head and mackerel tail," (or make her as much like 
 a fish as you can.) "Cod's head," meant simply the putting the «Jori's'ifeal[ and ' 
 fullness and bluffness required for stability, to carry sail, in the Mackerel laii," 
 bow; and "mackerel tail," meant taking it away from the stern. 
 
40 HOW TO GIVE A SHIP STABILITY, &c. 
 
 In those days, it was not known that putting fullness and bluff- 
 ness in the bow, to create stability to carry sail, was putting it 
 in a place to render that sail useless, for there it prevented that 
 sail from carrying the vessel rapidly and easily through the 
 water. Whereas, the application • of Russell's wave principle, 
 enables the modem Xaval Architect to take away all that bluff 
 buoyancy from the bow, where it does so much harm, by simply 
 transferring as much or more buoyancy and stability into that 
 part of the stern where, instead of doing aifiy harm, it does good 
 in every way — in every way, because it leaves the bow fine, of 
 the form of least resistance, of the form of least disturbance, of 
 the form of greatest speed ; and it transfers to the stem heavy 
 weights which would harm the bow, and it brings bulk where' 
 it gives room, buoyancy and stability. 
 Esppciaiiy in Moreovcr, this room is given in that part of the ship where 
 fupT ^"^'"' room is generally of the greatest value, both in a mercantile point 
 of view and in ships propelled by the screvf, in a mechanical 
 point of view, for it is exactly a form of stem, extremely fine and 
 clean below, which is best suited for the screw's effective action, 
 while the buoyancy and room above are all required, in order to 
 carry and counteract the great weights and mechanical forces' 
 due to the action of a propelling power in the after end of a ghip. 
 Wave stem the j^ mine of unworked good qualities lies, therefore, in the after 
 end of a ship constructed on the wave principle, if the Xaval Ar- 
 chitect will work it with diligence, and not be diverted from using' 
 its ample resources by the prejudice he may encounter. In the 
 eye of one trained in the old school, the fullness of the new form 
 of stern may be ugliness, but it is ugliness only to the uninform- 
 ed mind, which cannot see in tha?t fullness and capacity the vir-- 
 tues hidden in its ample bulk. 
 
HOW TO MAKE A SHIP DRY AND EASY. 41 
 
 CHAPTER XZII. 
 
 HOW TO MAKE A SHIP DRY AND EASY. 
 
 There is, probably, no point in Naval construction subject to ^^^^"^ ™d dry- 
 such variety of opinion as how to obtain ease and dryness in a 
 ship, head to wind. There are several causes of this, and con- 
 sequently counterpart causes which make a ship wet, uneasy 
 and laborsome. 
 
 It , is necessary to examine this subject, to arrive at just con- the'qSesUom °' 
 elusions, because these same causes also make it either easy or 
 difficult for a ship to ride at her anchors in heavy weather, 
 or in a storm in the open sea, when lying-to. The qualities 
 proposed for consideration are among those which it is most 
 important to decide accurately, because they are those which 
 enable a ship to survive in safety the perils of the sea. 
 
 The first elements of riding easy, are form and size of bow si"ff iiows. 
 above the water. Some thirty years ago, it was believed that a 
 searworthy, comfortable, safe vessel, must have a high, wide, 
 roomy, round, bluff bow, and that such a bow would enable a 
 ship to throw aside every head wave, and rise high and dry 
 above the sea. The idea was, therefore, that great over-water 
 bulk and buoyancy was the grand consideration for securing the 
 ease, safety and comfort of the ship. 
 
 It must be admitted, that the example of the Dutch, and of .^""='» vessels 
 many others, countenanced these opinions of the old school, and 
 certainly any one who has seen how the Dutch fishing boats, 
 and the pilot boats on the coast of Holland, ride out a storm on 
 that dangerous and shallow coast, and ride safely over the break- 
 ers, would be apt to form a prejudice ia favor of a buoyant, bluff 
 bow. 
 
 There are many points to be admired in the structure of these fl,^^"e™^°'' r" 
 craft, which peculiarly fit them for their special purpose ; their pose, turno'&r- 
 bows are more bluff even than a circle, they recede inwards "'^'^' 
 under the bow-sprit, so that they are the extreme and perfection of 
 bluffhess. But there could be no greater error than to take them 
 as the type of sear-going ships, although it is a common blunder 
 to fancy that the form which answers well for one purpose on a 
 small craft, answers equally for all purposes on the scale of a 
 large ship. This ;aatural belief has, however, been the parent 
 of the greatest errors in Naval Architecture — it is an idol of tra- 
 dition. 
 
 The best constructors of the present day, hold a belief contrary Arable! '"'"'"'°" 
 to all this. It is believed to be the experience of all intelligent 
 men, who have sailed in good vessels of the modern form, that 
 the long, fine, hollow wave line bow, carried well above the 
 water, rides easy and gently head to wind, when a full bluff bow 
 could not live.* 
 
 * A marked illustration of this fact occurred during a cyclone in tlie road of Funchal, 
 Madeira, in March 1S58. An English sailing barque, (built of iron,) with the long fine 
 bow, as above, rode out the gale and heavy sea with the utmost ease and di-yness, without 
 striking any yards or spars, while the full, bluff bows went on shore and were wrecked, 
 with the exception of the U. S. Frigate "Cumberland," which was only saved by the 
 superior nature of her ground tackle and equipment, and a fortunate change in the' wind 
 at a critical moment. 
 
 6 
 
42 HOW TO MAKE A SHIP DRY AND EASY. 
 
 Example of ex- Eussoll (the aceomplished author and promulgator of the wave' 
 P rirnen . j.^^ theoiy) mentions a striking instance in which he illustrated 
 this some twenty years ago. He says: — "I built four cutters of 
 four large ships, all of the same dimensions, with foiir different 
 shapes of bow, a wave bow, a straight bow, a parabolic bow, and 
 a round bluff bow. I allowcdthe four captains to choose each 
 his own boat in the order of seniority. The oldest captain tooli 
 the bluffest bow, of course, as the best sea boat, and the wave 
 bow \vas left for the last. In order to test their dryness and 
 safety, head to sea, I had all four taken out together and forced' 
 through the water at the same speed by a steam tug. The speed 
 was steadily increased, until at last the water was coming over 
 the bows of the bluff cutter in such quantities that the trial had 
 to cease in consequence of the head-sea pouring into her and 
 filling her; the boat at the same time yawing about wildly, be- 
 j^ond the control of her rudder, and threatening to go down. All 
 this time the crew of the fine wave bow, at the same speed, were 
 dry, easy and comfortable ; and so there was an end, in this case 
 at least, of the prejudice that the full bow was the safe and dry 
 boat." 
 ^Behivioroffuii Qn a large scale, however, the circumstances may be very 
 different. Xevertheless, observation of the effects of propelling 
 vessels with full bows, head -on to the sea, leads to the same 
 conclusion; and it is thought that whoever has studied the be- 
 havior of a full bowed ship propelled by steam against a head' 
 sea, or riding at anchor, or laid-to head to wind in a storm, must 
 have observed the following effects of the full bow : 
 
 First. It is true, that the fullness of the bow does cause the' 
 ship to rise over the waves, and does cause the bow to ascend 
 well in the air on the coming sea. Unluckilj-, it rises too high' 
 and too far on the top of the coming sea, and it follows, that, 
 when it reaches the top of the sea, a great quantity of this bluff 
 bow is left high and unsupported in the air, and out of the water, 
 so that, for a moment, one might see right under the fore foot 
 and keel of the ship. The bow rises, but it rises too much — for 
 in the next second, t^e unsupported body falls with a rapidly 
 accelerating velocity, and descends headlong into the falling' 
 wave. Rushing down this slope, the bow by its momentum in- 
 falling, plunges deep into the hoUow of the wave. It is there met 
 by the rising face of the next wave, which again lifts it high in 
 the air, and it again plunges heavily into the hollow of the next 
 sea. It is this plunge into the succeeding sea which produces 
 that violent shock that no shij} can withstand for a long time. 
 The English steamer "Great Britain," was an example of a 
 vessel very fine below, with a great projection given to her 
 above, under the idea of obtaining seargoing qualities; in her first 
 trial, howe\'er, she received serious damage from a sea striking 
 her in the manner above described. The same thing happens 
 to a ship with a full bow out of the water when she rides out a 
 gale ; the bow receives from the ascending wave a rapidly as- 
 cending motion, till she comes to the top of the wave, and then, 
 going over the crest, the whole weight of her unsupported,over- 
 hanging bow pitches down into the succeeding hollow; half 
 buried, she is brought up with a violent shock in the folio wine; 
 
HOW TO MAKE A SHIP DRY A^D EASY. 43 
 
 isea ; and so she goes on, spending and pitching violently, over 
 .every crested ways. 
 
 It will be seen that such a vessel cannot make much headway 
 through the water, pitching and.scending on every wave; the 
 force propelling, the vessel no longer goes to speed. It goes 
 towards driving her up on the ascending wave, and down on the 
 descending wave, and each heavy stroke of the water on the im- 
 mersed bow is just so much force expended in stopping the ship, 
 straining the timbers and wasting the propelling power. Effec- 
 tive speed loses, therefore, as much by such a form as ease and 
 security. 
 
 But, it may be asked, "how should a vessel move, if not up rue™lmi' ^'"""'' 
 and down over the sea?" To which it may be replied, "up and 
 down certainly; but not violently — as gently as possible." The 
 movement up should be gentle, the vessel ascending just so 
 much, that the rising wave may not enter the ship, and descend- 
 ing on the other side just far enough to recover easily and with- 
 out a shock at the bottom of the wave. In short, the motion of 
 the vessel up and down should be a little less than that of the 
 wave, and alittle slower, instead of what is described above — much 
 more than that of the wave, more rapid and more violent. This 
 desirable equilibrium is accomplished by a certain well proper- ,vatcrbei™Vi>-*^ 
 tioning of the bulk of the over-water part of the bow to the under- prntinned to bow 
 water part of the bow. When the under-water part of the bow """" """"• 
 is very fine, the over-water part of the bow must be made fine like- 
 wise. When the under-water part of the bow is full, the out-of- 
 the-water part will have to be proportionably full, and this pro- 
 portion may be best given by so arranging it, that the bow of 
 the ship on the ascending part of the wave, and on the descend- 
 ing part of the wave, shall have nearly equal bulks, alternately 
 exposed below the water line and immersed above it. 
 
 It is to be observed, however, thfl^t at the bottom of the wave But n little 
 the way of the ship exercises more force upon the approaching 
 wave, to bury itself, than at the corresponding point of the top 
 of the wave, to rise out of the water. It is right, therefore, that 
 the out-of-the-water part of the bow should be fuller than the 
 under-water part^'ust enough to prevent her taking in a sea 
 over the bows. 
 
 It. is thought that a bow like the steamer "Great E astern, ",^_,^™P'^^f^<h'; 
 accomplishes this purpose perfectly in all weathers ; her bow, 
 Jiowever, would even in modem practice, be regarded by many 
 as too fine above the water. 
 
 It is evident, therefore, that this approximate equality of full- s,,ouJ^^be nearr 
 ness of bow above and below water, has a tendency to make the vertical, 
 sides of the bow between wind and water nearly straight, and 
 also nearly vertical. > 
 
 To this kind of bow, there exist two in marked contrast, termed 
 the "flare out bow," and the "tumble home bow." The "flare 
 out bow," is often called the "clipper bow;" and there is another 
 kind of it, formerly called the "bell bow;" and midway between 
 all these, is another sort of bow, neither tumbling home, nor 
 tumbling out, this may be styled "the upright bow." 
 
U HOW TO MAKE A SHIP DRY AND EASY. 
 
 Boll bow. The "bell bow" was a favorite form with the builders of the 
 
 packets trading between New York and Liverpool, thirty years 
 since, before the mail steam service of the Cunard and Collins 
 lines ruined that trade. It was a fancy of the builders of those 
 fine ships — to give the bows a form somewhat resembling a 
 church bell inverted, the swell outwards, or "flare out," as it is 
 called, beginning about the "light line," and flaring out all around, 
 to the top of the bulwark, so that the forecastle occupied, as it 
 were, the mouth of the bell. 
 
 There was, no doubt, something graceful and majestic about 
 the aspect of these great bows, swelling out above the breaking 
 waves, bearing up the bow of the ship by their buoyancy and 
 then coming down upon the sea with such overwhelming force 
 as to dash the waves in wild spray all around. It was a grand 
 sight, but a costly one. The bow, no doubt, buffeted the waves 
 triumphantly, but meanwhile the vessel was engaged in other 
 work than its duty. Its business was to have gone, not up and 
 down, but forward, and this the bell bow hindered, and expended 
 useful force in unnecessary but magnificent struggles. A bow 
 was wanted, that should elude the waves and pass them, escap- 
 ing its enemy not fighting it. 
 
 cupper bow. iphe clipper bow was next introduced, to accomplish the design 
 of the bell bow, without involving its defects. Believing still in 
 the advantage of a large flaring-out bow, the inventors of the 
 clipper bow endeavored to obtain the supposed advantages of 
 great buoyancy, without the impediment produced by so much 
 immersion in the water as the bell bow involved. "For this 
 purpose," said they, "let us bell the bow laterally only, but 
 draw it out longitudinally into a fine point ; thus we shall pre- 
 serve its bulk, but improve its shape." 
 
 Hence the fashion came in of prolonging the bulwarks of the 
 ship at the level of the uppof deck a great way forward, even 10, 
 30 or 30 feet in front of the actual ship, and there they were 
 drawn out into a fine point above, and joined to the real ship about 
 the water-line, everywhere with a kind of hollow flaring outside. 
 This system certainly mitigated some of the evils of the 
 bluff bell bow, and a large volume of buoyancy in the upper part 
 of the bow, enormously in excess of the part of the bow in the 
 water, was obtained. Two classes of vessels have been much 
 distinguished for the extent of this clipper bow. 
 
 Messrs. McKay, of Boston, and Messrs. Hall, of Aberdeen, 
 Scotland, introduced it largely into practice, and their vessels 
 have had remarkable success in many respects. This success, 
 however, may fairly be attributed not to this flare out bow, but 
 to very different qualities of a practical and real kind. 
 
 not'recmmnendu P^^' imitators are apt to copy defects in the model they ad- 
 ed. mire, rather than imitate its merits, and the imitators of the 
 
 clipper bow have copied its worst points. 
 
 It must always be regarded as a bad quality to have on the 
 sides of a ship large over-hanging projections, whether they "bell 
 out" or "flare out." It is enough to say, shortly, that they in- 
 jure speed, and that they give uneasy motion to a ship, and that' 
 overhanging surfaces generally strike the water violently and 
 uneasily. There can hardly result any good in a large, flaring 
 
HOW TO MAKE A SHIP DRY AND EASY. 45 
 
 out bow, whatever its -shape may be; and it must be paid for in 
 weight of material, in want of strength, in resistance to speed 
 and in uneasy motion. 
 
 The most plausible recommendation of a "flare out" bow, is, kceps'offseaai^ 
 that it throws the water off, and makes a ship dry. This is true, spray, but mot/ 
 in a certain degree, and in certain circumstances, but they are ^^ fs ten" S 
 not general, and rarely belong to the cases now under considera- gerous. 
 tion. If a vessel of fine and upright form in every respect, have 
 a slight "flare out" given to it at the top, it will turn over the 
 tops of the waves, and prevent some spray from coming onboard; 
 hut if it really strike solid water instead of spray, it will do so 
 with such force as to send that water into the air in large quan- 
 tities, and if the vessel really take in green water over the "flare 
 out" bow, the danger to the ship produced by the mass of water 
 in that place is so serious, that no imaginary beauty can even 
 justify such a defect. 
 
 It is believed that a much better form of. bow is the nearly „ ™M"Ph^'^e°" 
 upright, or say the "tumble home" bow, provided the construe- bow make a drier 
 tion of the other part of the ship will admit of it. vessel. 
 
 A dry vessel is made, not by a "bluff, overhanging" bow to 
 bruise, beat and buffet the waves, but by a long, thin snake-like 
 bow, to elude the waves, to pass through them so as never to 
 break the water at all ; in short, a bow so formed as to ofier the 
 minimum resistance ,to the passage of the vessel, through the 
 water, not in one direction merely, but in every direction all 
 round the bow, above and below. 
 
 According to this fashion, the full projection of the bow should 
 be on the water-line ; that, alone, should first penetrate the waves, 
 and the way being thus prepared, the others should gently fol- 
 low it. The top sides of the vessel, therefore, should "tumble 
 home," and the whole be rounded off so beautifully and smoothly 
 that nothing should either catch the water, stop the sea, or break 
 it. Observation and experience show that such vessels are the 
 dryest and the fastest in bad weather, as well as the easiest sea 
 vessels, and above all, the safest. If green seas ever come over 
 the bows of such vessels, they have a much smaller quantity to 
 take in, they hold much less, and what little does come in, is 
 much further back, and consequently, much less injurious. 
 
 The "tumble home" bow has never yet become "a fashion," 
 but vessels have been built with it, which have proved themselves 
 so much the better for it, that it is thought that ultimately it 
 will be generally adopted. For speed, easy riding at anchor, 
 ease in a gale of wind, or safety from shipping' a sea, no other 
 form is equal to it. 
 
 There are two exceptions, however, to this reasoning : A very ,,o^",5 bo"J?'''lB 
 small boat must have a large body above the water, if it be an not suited for 
 open boat, to prevent its being swamped, or filled with water ; bea?y """w^hte 
 and where buoyancy cannot be given by other means, it may be forward, 
 given by flaring out. 
 
 Another case is, that where the bow of a vessel is filled, as, 
 however, it ought not to be, with extremely heavy weights, cor- 
 responding buoyancy must be placed on top of the bow, to make 
 
46 HOW TO MAKE A SHIP DRY AND EASY. 
 
 it rise to the waves. This is true, but it eures one evil by means 
 of another. 
 
 watcr"'^"^ ""'^^' ^° vessel designed for great speed, ought to have much capacity 
 under water in the extreme bow, and in no case should tjjat parj 
 of the vessel be occupied with heavy weight.s. 
 
ON LONGITUDINAL STABILITY. 
 
 CHAPTER XIV. 
 
 ON LONGITUDINAL STABILITY. 
 
 If, in conformity with' the majiims growing out of the consid- Fiare of liow 
 ferations in the preceding chapter, the flaring bow (which causes ""hiTdefe^l ^°^' 
 a ship to pitch high, scend deep- and make bad weather, by strik- 
 ing heavily on the sea) is removed, a long step will have been 
 taken towards making her easy and dry, and many common 
 causes of unseaworthiness are thus got rid of. But having 
 got rid of some obnoxious features, there still remains some 
 arbitrary matters, a choice of which goes far to enhance the good 
 qualities of the ship, or to improve them. 
 
 The- over-water bulk above the water-line is got rid of; but 
 in the choice of the proportion and form of the water-line itself, 
 much has to be settled on which may improve or deteriorate the 
 ship. It by no means follows that a ship without overhanging' 
 or flare out bows- is either an easy, dry, safe or steady ship, 
 whether riding at anchor or going through a heavy head sea. 
 
 The form of the water-line itself, is a powerful agent in ease ^<>™ "f "'= 
 
 - ,, . t r o watejr-ime IS ma- 
 
 and sea-worthmess. teriai. 
 
 The power of the sea to lift a ship's bow, and the force with 
 which, when lifted and left by the wave, that bow falls down 
 into the hollow of the succeeding wave, depend on the form of 
 the water-line and on the place in which the water-line allows 
 the weights of the ship to be carried. With r'egard to the best 
 formation of watet-line for the pitching and scehding' of the ship, 
 it may be inquired", first, how shall the water-line be formed so 
 as to make the ship- ride and drive easiest through the sea ? 
 understanding by "easy," that she shall rise and fall gently, 
 slowly and not far. Fortunately, there is a measure which tells 
 this exactly. The power of the slope of a rising sea to raise a 
 ship is measured by the s^me elements and methods as those 
 by which we measure the power of the water to support the 
 ship sideways, against the depressing power of her canvass on 
 the lee side, or enable her to carry a heavy load upon one side.- 
 
 The power of a head sea to lift the bow of a ship is, therefore, 
 measured in the same way as lateral stability; only the elements- 
 are reckoned lengthwise, instead of being taken across the ship. 
 To proceed then to the consideration of measuring the tendency"gf'^^^^|^^^,™'^ 
 of the sea to raise a bow, which has been depressed under its^stabiiuy. 
 natural water-line,— let it be imagined that the bow is pressed 
 under-water by a displaced weight moved from 0, the middle 
 Of the ship, and placed in the bows at W. This weight presses 
 a wedge-like part of the bow into the water^ and raises the stern 
 Out of the water. The wedge of immersion of the bow acts by 
 its buoyancy at its centre' of effort with a righting force propor- 
 tioned to the bulk of the wedge,'and to the distance of the centre 
 of effort from- the point 0. It aets in length just as the wedge 
 of lateral immersion does in width. Its . raising power is to be 
 found, therefore, by multiplying its volume into the distance of 
 its centre of effort from 0. The power of the sea to lift the bow 
 of a ship depends, first, on the bulk of the bow immersed, and 
 
48 ON LONGITUDINAL STABILITY. 
 
 sccnding. then upon the length of the bow, on the fullness of the water- 
 line and on the place of that fullness. If a wtitor-line be full 
 forward, it will have great lifting power; if fine forward, small lift- 
 ing power. 
 
 Pitching. Having measured the power of a sea to lift a given bow, it is 
 
 necessary to measure the force with which a lifted bow, ■when 
 left unsupported, falls down upon that soa. That depends upon 
 the weight left unsupported, and on the point at which it acts. 
 If the weights lie far forward on the bow, it will fall with great 
 force into the water, descending with a speed proportioned to its 
 distance from the centre, and plunging to a depth proportioned 
 to the square of its falling velocity. 
 
 bintoi°of"w'"f m ^I'o™^ these two considerations, it is plain that a ship in 
 no weig . gpgjj^jjjg^ ^.j]j ijg j-aised out of its horizontal seat on the water- 
 line in a very high proportion inverse to its fineness of bO'W, and 
 that in pitching, the ship will plunge less in proportion as the 
 weights left unsupported, are removed from the extremities to- 
 wards the middle body of the ship. The importance in trim- 
 ming a ship, of so distributing her weights as to diminish their 
 effect in causing her to pitch heavily, is therefore evident. A 
 Effect of tiieijow fine at the extremity, but taking fullness farther aft, makes 
 ' a ship much easier than one which is leaner aft and fuller for- 
 ward. 
 
 The form and proportion of the stern has not here been noticed, 
 since the stern of a ship has not to be driven against a sea. In 
 all ordinary practice, the stern of a ship is so sheltered from the 
 sea, that overhanging form and unsupported weight, which would 
 be a source of insecurity in the bow, may be tolerated with 
 safety and convenience. What is said of the bow, may there- 
 fore apply only to the stern in a very modified form. 
 
Weatlierliness. 
 
 ON THE QUALITY OF WEATHERLINESS, 49 
 
 CHAPTER XV. 
 
 ON THE QUALITY OF WEATHERLINESS, AND 
 'how to give IT. 
 
 The nature, cause and cure of crankness or instability have 
 been considered, and' it is now known how to confer upon a ship 
 the virtues counterpart to these vices — how to make her stable 
 under every ordinary condition of load, and further, how to give 
 her power of shoulder to stand up stoutly and carry a heavy press 
 of canvas in a stiff breeze — a quality which is therefore called 
 stiffness. 
 
 This quality of stiffness under sail, or uprightness, requires 
 weatherliness — a virtue the opposite of leewardliness, A lee- ' 
 wardly ship is liable to be driven with the wind, though her head 
 may be laid in an opposite direction. By leewardliness, ships Danger of jee- 
 drive broadside on towards a lee shore, instead of lengthwise ^^rduness. ' 
 through the sea, and so lacking weatherliness, are lost. 
 
 Next, therefore, after stiffness, comes Weatherliness to go in 
 the direction intended — to make headway across the wind, 
 and against the wind, instead of driving broadside to lee^ 
 ward. 
 
 This quality is to be obtained by considering an entirely differ- Weaiheriiness, 
 ent aspect of the vessel from that hitherto examined. The ship ed. 
 has been viewed through her breadth merely, she must now be 
 looked at through her length and depth. 
 
 The full length side view of a ship, as she sits upright in the 
 water, presents a much larger extent of surface than the cross 
 view of her breadth. 
 
 A ship of 36 feet beam, and 18 feet deep in the water, may 
 have 648 square feet of immersed cross section; and, in order to 
 force the vessel through the water, those 648 square feet of mid- 
 ship section must be pushed in the direction of the length of 
 the vessel. This the propelling power of the ship must do; and 
 it may require "a pressure of 30 lbs. to push each foot through 
 the water at the rate of ten (10) miles an hour. If, therefore, 
 the sails of the ship had enough pressure of wind upon them to 
 give this force of 80 lbs. for each square foot of section, forcing 
 the vessel lengthwise, the vessel would go ten miles an hour 
 before the wind. 
 
 This, however, is not the thing wanted; for the sails may ^ ^hip may 
 be so trimmed, and the vessel's head so laid, that by means of w'ind.'^°° 
 the obliquity of the sails to the course, and of the course to 
 the wind, the force of the wind shall partly force the vessel 
 the way of the wind, and partly the way her head lies. It is 
 the business of the Commander to lay her head in the proper 
 direction, and of the officer of the deck to see that her sails are 
 trimmed to the proper angle: but it is the Naval Architect's 
 work to see that the form of the vessel prevents her driving to 
 leeward. 
 
 It must be understood, therefore, that when the ship does not 
 run straight before the wind, but lies obliquely to it, the force of 
 
 7 
 
50 ON THE QUALITY OP WEATHERLINESS. 
 
 the wind acts in two directions. Partly it forces the ship it^ 
 own way, or to leeward, and partly it forces her in the direction 
 in which her head is laid, or to windward. 
 
 The ship therefore goes in two directions— partly to leeward 
 and partly in the direction she is heading. 'The practical ques- 
 tion is, how to make the first as little as possible, and the second 
 as much as possible — or to make the ship weatherly. This the 
 Naval Architect has to do. 
 
 The means by which weatherliness is given, consists in inter- 
 posing the greatest possible obstacle between the leewardly 
 part of the wind and its effect. The ship must be so construct- 
 ed that it will be hard for her to drive to leeward, and easy for 
 her to go to windward. How then, can she be made hard, to 
 drive to leeward ? 
 
 Weatherliness The antidote to leewardliuess is large longitudinal section — 
 fo%™udtaai'sef- 648 feet of cross section are to be driven in the course of the 
 'ion- ship. There must be much more than this, and as much more , 
 
 as possible, in the other direction, at right angles. 
 
 If the constructor can put six times 648 feet between the ship 
 aiid her going to leeward, the ship is made six times as hard to 
 drive to leeward as to drive to windward. By this means, it is 
 contrived that the ship's progress to leeward shall be very small 
 in comparison to her progress to windward, even when the sails' 
 are so trimmed that there is as much force pushing her the one 
 way as the other. 
 
 Example. In considering weatherliness, therefore, he has only to see 
 
 by what means as great a surface as possible can be interposed 
 in the water, so as to prevent the ship being forced to leeward. 
 If the ship can be made' six times as long as she is broad, and 
 preserve her depth below the water all the way to an average of 
 18 feet — or say IT feet at the bow and 19 feet at the stem, 
 which is the same thing — then the ship has a longitudinal sec-- 
 tion six times 36 feet, or 216 feet long, by 18 feet deep, present- 
 ing on the whole a resisting area of 3888 feet. 
 
 Thus it is, that a considerable excess of length beyond breadth 
 is necessary to give weatherliness, and therefore it will be plain, 
 that unless adequate length be given, all the stiffness to carry 
 sail, for which so much breadth of shoulder has been given, 
 will be thrown away — because, if the ship can carry sail merely, 
 and that sail only force lier to leeward, it is useless. Stiffness, 
 therefore, or breadth of shoulder, must have length to back it, or 
 it is worthless. 
 
 The area of longitudinal section to give weatherliness, must 
 bear a due proportion to stifiiiess, and to area of cross section. 
 Stiffness measures power to drive the ship — cross section mea- 
 sures the force necessary to drive it ahead, and longitudinal sec- 
 tion measures resistance to being driven to leeward. 
 
 Another element which comes in to assist weatherliness, is 
 the ease with which the fine shape of a vessel will permit her 
 to be driven endwise through the water. It is a fact, that some 
 forms of ships are so well contrived for this purpose, as, by 
 sharpness alone, to reduce the power necessary to propel thcni,. 
 
ON THE QUALITY OP WEATHERLINESS. 51 
 
 to one-twelfth of what it would be, if they opposed to the water 
 simply a flat bow. 
 
 It must now be seen what these qualities would be in a ship gists'" t^e'"'5'on''f 
 so designed. The area to resist leeward motion has already tudmai section, 
 been made greater than that resisting forward motion, in the 
 proportion of 6 to 1; and if the form be so fine as to reduce the 
 resistance to forward motion still further in the proportion of 6 ' 
 to 1, the combined effect will be in the proportion of 36 to 1. 
 This would be a very successful achievement, for it would re- 
 duce the loss of motion, by leewardliness, to a very small quan- 
 tity. 
 
 It is generally reckoned, that the extent of sail which a ship Example of the 
 
 ■ J. T- ^ t. ' • ±- ii_ r i. effect of sail in 
 
 can carry m a iresh breeze, may be six times the area of her headway, 
 longitudinal section in the water. This, in the size of ship, 
 taken, as an example above, would give an area of sail equal 
 to 23,328 feet (or 3888 X 6.) Now this area of sail has got to 
 propel the vessel with an effective force of 30 lbs. to each square 
 foot of cross section; and as there are 86 square feet of canvas 
 for every foot of driven section, the result is, that 30 lbs. divided 
 over 36 feet, or 5-6 of a lb. is the required force of the wind on a 
 square foot. Therefore it is plain, that a little less than one 
 pound pressure on each square foot of sail, effective in the di- 
 rection of the vessel's course, would be necessary to propel her 
 ten miles an hour, and this a very moderate force of wind would 
 accomplish. 
 
 But, an equal force with this would, with a given trim of sail, lefway'"*^*^'"" 
 be pressing the ship to leeward. The effect of this other force 
 would, however, be expended on six times the area, and that 
 area has six times as much resistance to leeward as ahead. 
 Under these circumstances, the motion through the water being 
 as the square root of the force, the leeward motion would be to 
 the onward motion as the square root of 86 to 1, which is of 
 course, 6 to 1. 
 
 The result is that the ship is driven six miles forward while ,((,„''*""*'" "°" 
 she is driven one mile to leeward; and such a vessel would be 
 an ordinary full, but not fast nor weatherly ship. 
 
 There are three ways in which the Naval Architect can im- ArcSite'cif ^a ™' 
 prove th^ weatherliness of this ship. ' He may diminish the area make a ship 
 of the cross section — he .may fine the shape of the ship so as to "'^^' f '^" 
 offer less resistance — he may increase the area of longitudinal 
 section, and give increased resistance to leeway, by increase of 
 length, or increase of depth — or he may do any or all of these 
 things at once. 
 
 The process stated above, assumes that the Naval Architect ^j^n^s^'as ^^^J, 
 is at liberty to give sufficient longitudinal area by the disposi- wood 'and faiso 
 tion of the body of the ship — that is, that he can have such a """*'• 
 draft of water, and such a length of body as he may select, 
 When his ship is not of suitable dimensions, he has to resort to 
 various expedients. If he has not depth of water enough 
 naturally in the body of his ship, he has to add timber, or dead- 
 wood, as it is called, for no other purpose than to increase the 
 weatherly section of the ship. When he adds this on the bot- 
 tom it becomes keel, or false keel — and is often carried to a 
 
52 ON THE QUALITY OF WEATHERLINESS.. 
 
 great extent. If he cannot get enough in this way, he adds 
 further deadwood, in the shape of stern and cut water ; and 
 to assist and balance these, he adds as much deadwood as 
 he can in the run before the rudder. It is thus that vessels 
 with a small body may obtain a great weatherly section — and 
 racing vessels, yachts and clippers are frequently built in this 
 ■ manner, to so extreme an extent as to be nearly all deadwood 
 and keel, and little or no body. A vessel of this sort becomes a 
 mere racing phenomenon. But, nevertheless, by extending dead- 
 wood in every direction, before, abaft, and below, extraordinary 
 weatherliness may be obtained at the sacrifice of capacity. 
 Lee-hoards. When these arrangements fail, or cannot be applied, there 
 remain many expedients for securing weatherliness. The lee- 
 boards of the Dutch craft attain this. On the shallow sandy 
 coast of Holland, no deep keel is possible, and therefore, the 
 Dutch vessel at sea would drift to leeward for want of depth of 
 body; to provide against which, she carries on her lee side a large 
 flat |6oard of enormous area, which is let down into the water in 
 ' such' a manner that the whole of the board must be driven on 
 the flat side, leewardly through the water before the vessel can 
 make leeway. One of these lee-boards is carried on each side of 
 the vessel, so that either side when it comes to leeward, has its 
 own lee-board for alternate use. This is the Dutchman's substi- 
 tute for windwardly section, of which his small draft deprives 
 him. 
 
 siiding-kcei or Another substitute has been used, but it is not thought with 
 BDiitre-board. j^jjy ygj.y great degree of success as yet. It is termed a "sliding- 
 keel," or "centre-board," and is formed by providing a hollow, 
 upright aperture in the middle of the vessel, in which a large 
 flat board is contained, so that it can be lowered through a slit 
 • in the bottom, into the water, and have to be driven broadside 
 
 to leeward. * 
 
 These, however, are expedients merely in the last resort, when 
 the j^aval Architect is denied the means of giving, his vessel a 
 due proportion. If due length can be given, it is much wiser to 
 obtain weatherliness by proper length and fine form, than to seek 
 artificial expedients, either in lee-boards, or centre-boards, or in 
 exaggerated deadwood; but of none of these expedients should 
 the Naval Architect be ignorant; and it is better to obtain weath- 
 erliness by all, or any of them, than to have a leewardly vessel. 
 Another exam- In these days, a sailing ship of ordinary form, is generally 
 P'°' about six times as long as broad. To drive her at' the rate of 
 
 ten knots an hour through the water, requires about 48 lbs. of 
 force for each foot of her midship or greatest cross section. Sup- 
 pose the vessel has 100 square feet of immersed cross section, 
 requiring a force of 4800 lbs. to give her headway, and that 
 the sails are placed at such an angle, that they press equally 
 forward, and over, or so that there shall be equal forces 
 causing headway and leeway, there will then be a force of 
 4800 lbs. causing leeway; and this force is spread over 600 
 square feet, forming the immersed longitudinal section of the 
 ship. On each square foot of this section, there will be, there- 
 fore, only one six-hundreth part of 4800 lbs., or 8 lbs. per square 
 
 • Centre-boards avp only used in small vessels. 
 
ON THE QUALITY OF WEATHERLIXBSS. 53 
 
 foot of sectioB. This 8 lbs. will cause a leeway of less than 2 
 knots. This example shows the great advantage obtained in 
 sailing vessels by large hold of the water. It is plain that, by 
 giving this vessel greater length and depth, her resistance to lee- 
 way might be doubled, so that the force causing leeway would 
 be divided over double the area, and be reduced to 4 lbs. per foot. 
 Instead of 8, and this 4 lbs. per foot would only give a leeway 
 of 1.25 knots per hour. 
 
 The following table shows what happens when the sails are TaWe expiain- 
 set at an angle of 45° to the course of the ship, and the wind is 
 right abeam. In these eases there is equal pressure along the 
 ship's course, and to leeward. The lesser leeway arises from 
 two causes : the greater area of longitudinal section than of mid- 
 ship section, and the fineness of the shapes. It will be seen, that 
 in the full form of vessel, the leeway, under the pressure that 
 produces 12 miles an hour, is 2 miles an hour. Under a pres- 
 sure of 1 lb. on the sails, the headway is 10 miles an hour, and 
 the leeway 1.2-3 miles. This would be the case in a fresh breeze 
 carrying all sail. When the vessel is proportioned for greater 
 speed, with a greater proportion of length to the same area of 
 resistance, and a finer form, the leeway is reduced and the speed 
 increased. 
 
 These calculations are made upon the supposition that a ves- jesu™"*''™ °^ 
 sel's resistance to leeway is the same as that of a thin plate 
 equal to her longitudinal section. -But vessels with round bilges 
 let the water pass underneath them from one side to the other 
 more easily than a vertical plate, and so do all ships when they 
 careen much. A Uttle more leeway must be allowed for in these 
 cases. 
 
54 
 
 ON THE QUALITIES OF WEATHERLINESS. 
 
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 Finer form of Ship 
 Longitudinal 
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Bakmcti of sail. 
 
 HOW TO :SIAKE A iSHlP HA^DY. 
 
 CHAPTER XVI. 
 
 HOW TO JilAKE A SHIP HAXDY AXD EASY TO 
 
 S TEEB. 
 
 The first part of handiness consists of balance of sail; the 
 second, of balance of ship ; the third, of proportion of rudder. 
 
 TJnless sail be balanced, the ship will go just where she pleases, 
 or just where the wind pleases, instead of towards her destina- 
 tion. If there be a sail on the forward part of the vessel only, 
 the wind wiU force the forward part of the vessel to leeward, and 
 she will drive head foremost. If there be a sail ou the after part 
 of the vessel only, her stern will go to leeward and she will drive 
 stern foremost and head to the wind. In order that neither of 
 these things shall happen, the sail on the forepart of the vessel 
 must be so placed and proportioned to the quantity and place of 
 the sail on the afterpart that they exactly balance one another 
 in effect, so that neither one nor the other can prevail. This is 
 virtually to take away from the wind all power of determining . 
 the direction of the ship, and a smart officer, by properly regu- 
 lating this balance of sail, can keep the ship's head in any direc- 
 tion he pleases. 
 
 This is balance of sail, but it depends on another element. Balance of shis 
 namely: the balance of ship. The effect of sail at the bow may 
 be exactly balanced by that at the stem ; yet. nevertheless, there 
 will be no enduring balance if the bow be more easily forced to 
 leeward than the stern, for then the head of the ship would go 
 around to leeward. A balance of sail forward and aft. and a 
 balance of ship lengthwise in the water — the one called •trim of 
 sail," the other 'trim of ship'- — ^the forethought of the Xaval 
 Architect must provide. To maintain this equilibrium, depends 
 upon the abihty and thoughtfulness of the Commander of the 
 ship. 
 
 It is thus only, that a handy ship is obtained and kept so. ed^'^e'aeh othS" 
 The sails mugt balance, the body must balance, and both must be * "''"^ ° "• 
 kept together in perfect trim ; while the seamanship of the Com- 
 mander, the hand of the helmsman and the blade of the rudder 
 do the rest. 
 
 Something more, however, can still be done by th<? ^aval^^l"™^'"!"^ 
 Architect to give the sailor complete command over his ship, for quicbiess^ 
 The balance he has established is enough to deprive the wind of 
 the control of the vessel and give it to the Captam; but, the ship 
 may still reqtiire from him the exertion of very great controlling 
 force when he wishes, in the course of his manoeuvres, to change 
 the ship's head rapidly from one cotuse to another. Balance ^f 
 sail and of body will help him to do this, but it vrill not help 
 him to do it quickly. 
 
 To make a vessel verj- handv, and turn verv quicklv, her xanjeiy. uiat 
 longitudinal section should be deep, rather than long, andsS'^'^fl^ 
 when its extreme length is decided, its efteetive length "should '^["l^^ 'Jj*'^^^* 
 be diminished as much as possible by removing longitudinal "° 
 
56 HOW TO MAKE A SHIP HANDY. 
 
 area from the ends, and placing it near the middle. Above all, 
 much cut-water and fore-foot make a vessel unhandy and slow 
 to come around. 
 
 It is better, therefore, to have deadwood aft than forward, but 
 
 removed from both ends as much as possible. Rounding off the 
 
 fore-foot and shortening the heel, are the most effectual \vays to 
 
 make a ship handy without injuring her other qualities; the 
 
 effect of heel and fore-foot being to cause gripe, or resistance to 
 
 turning, Avhich is the contrary of handiness. 
 
 Effect of rudder. "With balanced ship, and balanced sail, good trim and little 
 
 gripe, not much can be wanting to handiness. The rudder must 
 
 do the rest. The rudder is nothing but a power to control, it 
 
 merely acts as a drag on one side, it always diminishes speed in 
 
 turning the ship, and the cleverest helmsman is he .who uses it 
 
 least, the best ship is that which wants it least, and the best 
 
 sailor is he who does most without it. A steersman always 
 
 shiuid beVow-y^'^^'^'ig ^ ^'^'P sil^out, steers badly. A ship requiring much 
 
 ?■■'»'— i"^' sp!"- helm is badly trimmed. Sails requiring much rudder, are badly 
 
 in„yuse . ^^^ ^^ balanced. Nevertheless, it is above all things necessary, 
 
 that the rudder should have ample power — great power, seldom 
 
 * used. A ship that will run along for hours with scarcely a 
 
 touch of the helm, is a ship well trimmed and sailed ; but when 
 
 needed, the rudder must be able to do anything, and to be able 
 
 to turn a ship, short and sharp around, may save her in an 
 
 emergency. 
 
 should "^bear^ 'a ^^^ ^^^ ^^ 8'"'® power to the ruddcr, is to proportion it to 
 
 certain proper- the length of the ship. A long ship requires a broad rudder. 
 
 togin."'^ "^'P'' It is thought, that for every 100 feet in the length of a ship, she 
 
 should have 2 feet of breadth with 1 ft. added. Thus a ship 
 
 100 feet long needs 3 feet breadth of rudder; 200 ft. long, 5 ft. 
 
 breadth; 400 feet long, 9 feet, and so on. 
 
 Shape of the As to the shape of the rudder, there is not much in it. Some 
 
 material!" ^"'^ Say the top of the rudder is the most valuable part, for the water 
 there has the most effect, and that the rudder should be widest 
 there; others say it should be widest at the bottom, for that there 
 width is most effective. Both are crotchets; but still there may 
 be something peculiar in the case of some ships, to render both 
 exceptionally true. 
 
 The fault of having the widest part of the rudder near the load 
 water-line is, that there a rough sea may strike the rudder most 
 heavily, there is less harm in making the rudder widest near the 
 keel, for being well buried under water, the wave surface of the 
 sea has less action upon it, and in bad weather the helmsman is 
 not liable, as in the first case, to have the lielm taken out of his 
 But perhaps is hand. But on the other hand, the heel of a wooden screw ship 
 Blnti™"at'''''bou! ^'^Y ^^! ^nd probably is, her weakest part, and to put more strain 
 head and heel, thati necessary on a weak place, is unwise to say the least. The 
 best way is to have the widest part of the rudder near its cen- 
 tre, rounding it off towards the top and heel, the one to keep 
 it from the force of the waves, the other to protect it from the 
 ground in a narrow and shallow channel. 
 
 It will always be a delicate question about the quantity of 
 rudder to be given to a vessel destined for any special purpose. 
 
Sow TO MAKE A SHIP HANDY. 5f 
 
 If the ship is always to bie committed to wise hands, who will cauMon as to 
 never use more than is necessary, it is safe to give plenty offi"d,frpmvi"ex- 
 fudder, leavina; it to their discretion to use it as they may desire, ^^p' '° adiscreet 
 Strictly speakmg, a smart Commander should have just as much 
 rudder as he can command' and handle, because with powerful 
 rudders, manoeuvres can he performed which are impossible 
 with small ones. To be able to turn very fast, will often give a 
 Ship the a-dv'to^a'ge of another; and in a contest for victory, or of 
 sport for a challenge cup, ability to execute difficult manoeuvres 
 rapidly, is often in itself a source of success.- A ship well in 
 hand, is often better than one Which is faster, but runs wild. 
 Therefore, put into wise hands a powerful rudder. 
 
 Unluckily, the Naval Constructor has sometimes the misfor- 
 tune to have his finest work entrusted to the hands of a fool. In 
 Such ease it Would be vastly better, if possible, that the rudder 
 should be proportioned to the capacities of the man, rather than 
 to those of the ship, and the riidder should not be so powerful as 
 to enable the ship to perform the intended manoeuvre too rapidly, 
 lest it should outrun the wits of the fool in command. The ship 
 should be able to come around only just so quickly that the 
 governing intelligence may keep pace with her movement, and 
 see what she is going to do; only, therefore, to a quick witted 
 man intrust a quick working ship. 
 
 For a slow ship and a slow Commander, a narrow rudder is 
 best. The motions of the ship' will thus be slow, they will give 
 time for thought, and will be less likely to run the ship into 
 mischief. For such ships, tvVo-thirds the dimensions given 
 itbove will be sufficient. 
 
58 BALANCE OF fiODY AND BALANCE OP SAIL, 
 
 CHAPTER XVII. 
 
 OF BALANCE OF BODY AND BALANCE OF SAIL. 
 
 iiandiness dc- It has been seen that handiness, or the ready obedience of a 
 pends^o,, balance ^j^.^ ^^ ^^^ ^.j^ ^^ ^^^ Commander, arises out of the due combi- 
 nation of balance of sail, balance of body, and power of rudder;, 
 and it has also been seen bow, without these, a vessel steera 
 wildly and can hardly be controlled in her movements. 
 
 leewardiinLs!"'' When, either through want of balance- of sail, or balance of 
 body in the water, the ship shows a tendency to fall off or fly to, 
 she is said to have two opposite defects, the first called leeward- 
 liness, the other called ardency. These defects must be corrected 
 either by trim of sail or trim of ship. If not corrected, they 
 must be counteracted by the action of the rudder; but, as the 
 rudder is a sort of stop-water applied on one side, and in no case 
 a help, speed is lost in the degree in which the rudder is used. 
 The tendency to fly into the wind, and the tendency to fall off' 
 from the wind, or ardency and its opposite, require remedies of 
 opposite kind. Ardency implies that the ship must always carry 
 weather helm; want of ardency, that she must always carry lee 
 or slack helm. Of the two evils, ardency is considered the less, 
 • and it is usual, therefore, to trim a ship so that she shall always- 
 
 carry a very little weather helm. 
 
 fot?of sau sifouid '^^^ point in the length of a ship, on both sides of which ther 
 correspond with sails balance, is called "the centre of effort of the sails," the 
 resistance.'""^'"' poiut in ttc Water on both sides of which, fore and aft, the body 
 balances — or to put it otherwise, the point in the air on both 
 sides of which, fore and aft, the pressure of the wind on the sails- 
 balances, and the point in the water on bath sides- of which, fore- 
 and aft, the resistance of the water to the leeward-liness of the- 
 ship balances, these are respectively called "the centre of effort 
 of the sails," and "the centre of lateral resistance of the ship." 
 
 In a state of perfect trim of sail and trim of ship, that is,- 
 when a ship is so perfectly balanced as to be neither ardent nor" 
 leewardly, requiring neither lee nor weather helm, the centre of 
 effort and the centre of resistance would meet exactly in the- 
 same point of the length of the ship, and so the effort of sail and- 
 resistance of water, fore and aft, exactly counterpoise one- 
 another. 
 
 Unfortunately, there are but few ships- so constructed as that 
 this coincidence shall take place and be maintained at all 
 speeds, and in all states of wind and sea; and weather. 
 
 In a perfectly mathematically formed "wave line" vessel, the 
 coincidence of the two has been found to- be exact and perfect;- 
 but by a very slight deviation from the wave form, the perfec- 
 tion of this balance is at once deranged. In order to correct this 
 want of adjustment, the centre of effort of the sails has to be 
 moved forward; and in certain cases very considerably so. — 
 (The English line of battle ship, "Duke of "Wellington," for ex-' 
 ample, in which the whole of the masts and sails had to be 
 placed forward from the true centre of resistance the space of 14 
 feet.) 
 
BALANCE OP BODY AND BALANCE OF SAIL. 59 
 
 In every vessel built on the old system, this derangement of 
 balance had to be taken into account, and allowed for, as 
 an element in the original construction of the ship. Un- 
 luckily, it was allow.ed for by guess, merely; and, therefore, 
 nothing was so common as to hear that a new vessel had to 
 undergo an entire change of arrangements from the impossibili- 
 ty of managing her, owing to the centres of effort and lateral re- 
 sistance not coinciding. In such a case the usual remedy (if Remediea ap- 
 the error was slight) was to rake the masts either a little for- P''""*- 
 ward or a little aft, in order to correct the balance of sail, or else 
 to put on a little deadwood forward or abaft, or to add a taper- 
 ing false keel, all for the purpose of restoring the lost balance ; 
 and when these expedients failed, the masts, or some of them, 
 had to be shifted — an arrangement not only expensive but de- 
 ranging to a great extent the interior economy of a ship of war. 
 
 One of the great advantages of Russell's wave line system, is 
 that the centres of effort of sail and of resistance of body coin- 
 cide. It is impossible to adjust these two centres to a more per- 
 fect balance for practical use, so as to have a ship easy to steer, 
 requiring, little helm, quite under command, and handy, than by 
 merely taking care that they coincide in the same point of length. 
 
 But this perfection of balance and handiness, is not to bo 
 obtained without an equal perfection of wave form. Every devia, 
 tion from exact truth in the form of a ship, will exhibit derange- 
 ment of balance. In exact proportion as any part of the bow is 
 filled up beyond the pure wave line, the balance of sail and of 
 resistance will be disturbed, and it will be necessary either to 
 correct the shape of the body, or to remove the centre of effort 
 of sail forward, or to shift the centre of lateral resistance aft. 
 The reason of this seems clear. The wave form is the form of 
 least resistance; the truth of which is practically shewn when 
 the vessel (in deep water) shows no bow-wave, or breaks no ^ departure 
 water at the bow. Any untruth in the wave form, at once shows froju the 'wavn 
 itself in broken water, or the well known wave at the bow, which cemre'"oreffoK 
 is bad. The appearance of this obstacle to progress shows "'' ^au forward, 
 exactly where there is an expenditure of undue force, and it is 
 this undue force and unnecessary resistance which deranges the 
 centre of lateral resistance of the ship, and shifts it forward. Its 
 tendency to do so increases with the velocity of the ship. It is 
 to meet this shift of pressure and to counteract it, that the centre 
 of effort of the sails must follow it forward. But no one can 
 tell precisely, beforehand, how much any deviation from truth 
 in the form of a ship will remove the centre of resistance, and, 
 therefore, it is impossible to say what change in the centre of 
 effort may be required to correct it. Unluckily, also, the devia- rie°''"wlui° the 
 tion arising from incorrect form, varies with the speed, so that speed, 
 the difference which will restore the balance, is not the same for 
 all speeds. No certainty, therefore, is to be obtained on this 
 point, except by the preservation of the absolute truth of the 
 wave form. 
 
 There is another curious cause of deviation between the cen- di^bo'dyfi'ves'arl 
 tres of effort and resistance. If a ship has a long straight mid- dency. 
 die body, she will have a tendency to ardency, arising from 
 length alone. Even If the two ends be .perfect ware-ends, a long 
 
60 BALANCE OF BODY AND BALANCE OF SAIL, 
 
 straight middle body will haye this tendency to disturb their 
 balance. Of this singular phenomenon of deviation, arising fron> 
 length of middle body, an .exact measure can scarcely be given; 
 but an explanation will be attenjpted. A long, parallel bodied 
 ship certainly loses her power to carry afterrSail; and the explar 
 nation is belieyed to tae, that a long ship, by the merp progress 
 of its sides through the water, drags with it, and puts into 
 motion by adhesion merely, so great a quantity of the water in 
 its neighborhood, that at the last, when near the stern, the 
 water has ceased to offer any lateral resistance, because it has 
 a,lready received the same motion as the ship itself. At the 
 stem, therefore, there is little left to resist the ship ; and so froni 
 lack of stern resistance, the after part loses power to carry after 
 sail, and the ship becomes ardent. Even wave-ends, therefore, 
 will not compensate for this fault of long middle body. If the 
 inquiry be raade as to wh3,t limit this extends, it may be replied, 
 that in a vessel with 60 feet beam, and' 90 feet middle body, it 
 has not been sensible, but with similar ends, and IDO feet midT 
 die body, it has become a very sensible quantity. This devia^ 
 tion from th,e true form, while it is attended with m,ercantile adr 
 vantages of capacity not t.p bp regarded lightly, must be taken 
 with its disadyaijtage.s, 
 pxpi^nation. Iq order, thoroughly, to apprehend the nature of this fact, 
 suppose a thin, flat board, moviijg edgewise through the water, 
 and also pressed sideways by a force like thjs wind at right 
 angles to it. Next consider what happens to a particle of water 
 placed to leeward of this thin board. When the board first 
 toijches it, it has no Leejvard moti.pn, but it immediq-tely acquires 
 it; small at first, but gradually growing, as the following parts 
 of the board successively press it, and, as each succeeding part 
 of the board finds the water already put in leeward motion, it 
 follo^ys that th.e latter parts of the board are in contact with 
 particl^s already moying so fast to leeward, that, unless they 
 accelerate their l,eeward speed, they will experience no lateral 
 pressure from the water. Hence, two effects must follow; the 
 after parts of the board will have Ipss pressure on them than the 
 fore parts, and also the after parts will be moying to leeward 
 faster than the for.e parts. This is the explanation of the 
 ardency produced by a long, parallel, middle body. 
 
 f ardc'^'c "^""^^^ Another source of derangement between the centres of effort 
 ,0 ar cncy. and resistance, will be found in any deviation from the waters 
 line which may be produced in the change of shape in tlje ves-; 
 sel, as she heels over from the pressure of side wmd. If a fulj 
 part of the ship comes into the water on heeling oyer, that part 
 will cause its own special resistance, and, so far as it deviates 
 from the tru,e form, will cause an excess of pressure at that point, 
 and a derangement of th.e centres of balance : it will in fact 
 make the vessel behave as if she had a curved keel, concave to 
 the wind. Another reagon why heeling produces ardency, is that 
 it forces the centre of effort of sail to Ipeward, so as to make 
 the masts exert a horizontal leverage, to bring the ship's head in-; 
 to the wind. Apart from heeling, there is also a small element 
 of ardency in the case of fore and aft sails, from their centre of 
 pffort being invariably to leeward. Theoretically, the bellying 
 
BALAJS'CE OF BODY AND BALANCE OP SAIL. 61 
 
 ,of square sails shotilcl tend in the same direction, but it is believed 
 that this cause is not appreciable in practice, 
 
 There is another cause of deviation, which must take effect in •*;['?™°^n^of, 
 ■all vessels, of whatever form, but its action is slight, and is not, water, 
 .except in the case of very great length of middle body, of suffi- 
 .cient conseqjjenGe to rank as an element in the adjustment of the 
 xjentres — -it is the resistance of the adhesive film of water on the 
 skin of every ship. This adhesive film is scarcely a visible 
 thickness at the bow; it increases uniformly with the distance 
 from the bow towards the stern, where it is greatest ; the in- 
 visible film seems to gro\y as it goes, by attaching to itself 
 •another and another outside film on each foot of progress, and, 
 all added together, the entire film has a thickness of a foot or 
 more on each side at the stern. This may diminish the lateral 
 resistance, but it seems just enough to giv.e the vessel that de- 
 gree of ardency which is preferable to the smallest degree of 
 the opposite quality ; and when no other source of derangement 
 than this remains, the Naval Architect may congratulate him- 
 self on having completed that part of his business satisfactorily. 
 One other soiirce of disturbance will always remain, which he 
 .can neither forsee nor prevent — the winds and the waves will 
 always act irregularly on the ship. But when he has done the 
 preceding parts of his work 'well, he will leave the mind of the 
 helmsman, and the action of the rudder perfectly disengaged 
 from all unnecessary work, and free to be disposed of in that 
 cautious, ready and prompt counteraction of the winds and the 
 waves, which is the business of the thoughtful and the watch- 
 ful seaman. 
 
 It is the duty of the ship-builder to make an exact calculation ship-tuiidpr 
 on the body of his ship, so that, when loaded in the water to "entre of1at.e?!j 
 its proper line, the lateral resistance to leeway shall be found lesismnce nf 
 at its proper point in the length of the ship. This central balanc- ^ "*" 
 ing point he calls "the centre of lateral resistance," and jit should 
 be a little abaft the centre of tlje ship. 
 
 His next duty is to make an pxact calcijlation of the sails of And then tiiB 
 his ship, so that the pressure of the wind upon all the sails may o™Bail. °^ """" 
 have its central balancing point rightly placed in reference to 
 the centre of resistance of the ship. This is called, "the centre 
 of effort of sail," and should be so adjusted, as neither to be too 
 near the bow nor too far from it. In some wave line vessels, it 
 is necessary to place the centre of lateral resistance of ship, and 
 the centre of effort of sail, precisely the one over the other, but 
 in the forms of ordinary sailing vessels, it is found necessary to 
 have the centre of resistance a little abaft the middle of the ship, 
 and the centre of effort of sail a little forward of the middle. Trim. 
 To bring the centre of resistance aft, a ship is generally trimmed 
 two feet by the stern ; and to carry the centre of effort forward, 
 additional sail, beyond the quantity proper for a vessel on an even 
 keel, is carried on tl^e boypsprit. By these means, a distance of 
 about one-t\yentieth part of the length of the ship may be placed 
 between these two centres, and in most ships this is sufficient for 
 the piirpose. On page 63, is given a table shewing the distance 
 to which trimming the ship by the stern will shift the centre of 
 resistance backwards, and also the additional area of sail on the 
 
G2 BALANCE OF BODY AXD BALANCE OF SAIL. 
 
 bowsprit, which will suffice to place an interval of onc-twonticth 
 
 of the ship's length between the centres. 
 The trim de- But, however exactly the Naval Architect may have designed 
 The" t;..m°.Mcrc"r his sliip, the tvimming"of the sails and of the ship must remain 
 J!',"" °" ^^ ™"- essentially a part of the seaman's duty, because the trim of the 
 
 btlUCtOr. 1 . . i' .n n P T •*' 4? 
 
 , ship IS chiefly a question of stowage of cargo or disposition ot 
 weights, and as this is always varying in a steam-ship, and can 
 always \x ill or well done in a sailing \'essel, the original con- 
 structor of a ship, however wise, can never dispense with the 
 watchfulness and judgment of the Commander of the vessel.* 
 Centre of re- There is another cause for constant watchfulness as to trim, 
 
 Pistance may i.ni. p ^ I'j. 
 
 vary at different m the fact that uiost ships shift their centre ot lateral resistance 
 
 speeds. forward as their speed increases, and therefore require after sail 
 
 to be diminished as the wind rises. The first duty, therefore, of 
 
 an officer in command of a new ship, or one starting on a fresh 
 
 trim, is to determine the proper balance of ship and sail. 
 
 He should shift weights forward and aft, until he finds the 
 trim which will enable him to carry the proper sails, and having 
 done this, should carefully study how the quantity of sail must 
 be adjusted in the various degrees of strength of wind, so as to 
 measure this balance. It is in this way, that a skillful Captain 
 will often make a ship fast by trim alone, whereas an ignorant 
 one will fail to find out the good points in a. ship, because he 
 does not systematically look for them, by studying her perform- 
 ance under every variety of trim at his command. In this 
 way the Captain, even more than the constructor, makes the 
 character of his ship! 
 Summary. The sum of what is known in regard to balance of body, and 
 
 balance of sail and trim, is as follows : 
 
 The middle of the length of a ship is the balance point or 
 centre of lateral resistance of a ship, if she be nearly at rest, 
 drifting to leeM'^ard, and if she' be on an even keel, with upright 
 stem and stern post. 
 
 Trim and rake Trim of ship hj the Stem, shifts the centre of lateral resistance 
 comiared. ^-.^j.^.^ ^j^g middle towards the stern. An inch of trim to a foot 
 of draft shifts the centre of lateral resistance abaft the middle 
 by one hundred and fortj^-fourth part of the length of the ship. 
 Or the excess, aft, represented by a fraction of the draft amid- 
 ships, (say one-sixth,) multiplied by one-twelfth of the ship's 
 length, gives the shift abaft caused )iy trim. Baking the stern 
 post and rounding the stem also shifts the centre of lateral re- 
 sistance forward or aft. 
 
 Raking the stern post, shifts this centre forward one-quarter 
 of the rake. Rounding the stem, so as to make it a quarter of 
 a circle, shifts the centre aft by about one-tenth of the draft at 
 the stem. 
 
 In the most ordinary shape of ships, these last counteract 
 each other, and if the draft fore and aft be nearly equal, the cen- 
 tre of lateral resistance at rest is in the middle of the length. 
 
 * And the Cnmmander should tJloroughly understand the design of the constructoR 
 
BALANCE OF BODY AND BALANCE OF SAIL. 
 
 63 
 
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64 BALANCE OF BODY' AND BALANCE OF SAIL. 
 
 Statical resist- The mere statical resistaace of a thin plate, floating vertically^/ 
 piVil "iJot" in '° to lateral motion, is collected at its centre of pressure, not at its" 
 ^oim, actual centre of gravity. But there is less practical error in cal- 
 
 calating by means of the latter, for several reasons; among 
 which, one is, that when lateral motion has once begun, the 
 frater is heaped up in front of the plate, while a hollo# is form-- 
 ed behind it. This creates a resistance at the surface, which 
 more than compensates for the increased pressure of greater 
 depths. In rapid motion, the centre of lateral resistance is 
 found, in practice, to be considerably above the centre of gravity 
 of the longitudinal section, instead of below it, as is the centre of 
 hydrostatic pressure. 
 Effect or mo- But the centre of lateral resistance of a ship with a full bow 
 and Water-line forward, is shifted forward from the moment she 
 has speed, because the resistance on the lee bow is greater than 
 on the weather bow, and because the resistance to a bow in mo-' 
 tion is much greater than to the stern. The leeWard motion 
 also makes the resistance fall more directly on the bow than on 
 the stern. Next, the lee bow is altered in form when the ship 
 heels over by the wind, and becomes fuller than the weather' 
 bow. Hence such vessels, as they increase in speed, experience 
 increasing pressure on the bow and not on the stern, thus driv- 
 ing the bow up into the wind, and allowing the stem to drift to 
 leeward. 
 
 This disturbance of balance of the lateral resistance of the 
 
 body of the ship has to be met in two ways. The ship has to be 
 
 trimmed b}- the stern, which helps to bring back the centi'e of 
 
 lateral resistance to the middle. Or it may be met in another 
 
 way — more sail may be carried forward to counteract this effect. 
 
 Met by trim- The shift of Centre of effort of all the sails forward, is the 
 
 ">e sail. mode of correcting this disturbance of the centre of resistance, 
 
 which is most employed by Naval Architects; but as it is not 
 
 possible to make this adjustment absolute beforehand, each form 
 
 of ship has its own peculiarity in this respect. One ship will 
 
 balance her sail with its centre exactly on the i^iddle of the 
 
 water-line, another will carry it one-tenth of her length forward 
 
 Proper balance of the middle. As a general rule, any vessel having her bow 
 
 point tor sail, -water-lines convex, may be expected to carry her balance point 
 
 of ship to balance point of sail^ — whether going free, or on the 
 
 wind — one-twentieth part of her length before the middle, reck-' 
 
 oned on the water-line, and nearly on an even keel. If the 
 
 centre of the longitudinal vertical plane be made out of the mid-" 
 
 die of the length, the centre of effort must follow it. 
 
Of the! proportion, balance, &o.y OF SAIL. 65 
 
 CHAi»TER XVIII. 
 
 OF THE PROP OR TION, BALANCE, DIVISION, AND 
 DISTRIBUTION OF SAIL. 
 
 A fine, fast fi'igate, in a teii knot breeze, can carry 36 square jaif''"*;''"^?^^^?'' 
 feet of sail for each square foot of area of midship section, and section u'suaiiy'* 
 Be the better for it; if she carried moi'e, She might be pressed ^®-^' 
 over so much, as to go slower, hence it has been common .to 
 provide a sail area of 36 square feet of canvas for one square 
 foot of midship selction; this proportion can be considerably 
 exceeded by yachts and despatch vessels — even up to 100 
 square feet, but such vessels are mere sailing phenomena rathei? 
 than ships ; nevertheless, for light winds, all vessels carry a gi-eat ' 
 
 quantity of light sail beyond their proportion of regular working 
 sail. . 
 
 Taking sail area iii the proportion of 36 square feet of sail td 
 One square foot of midship section, is merely saying how much 
 canvas the ship should have, in order to drive her. Whether 
 she will be able to stand up under it, and whether under it she 
 will prove leewardly or weatherly, are other questions — ques- 
 tions of stability stnd balance of sail. All ships tend, under a 
 side wind, to drift to leeward; the only preventive to this, is the 
 extent of the immersed longitudinal section. Which offers resist^ 
 ance throughout the whole of the letigth and depth of the ship 
 in the water. The dimensions and shape of this section determine 
 the arrangement and balance of the SEtil, and a shijD should be suffix 
 ciently weatherly to cafry an area of sail, fore and aft,, not less 
 than -six times the ar«a of this under^water longitudinal section. 
 
 As a first step to the consideration of the distribution and Equivalent sau 
 balance of sail, draw this section of the ship under its proper '"^^' 
 v/ater-line, and copy it by drawing above it a similar section in 
 the air, six times as high ; this call the equivalent sail area, 
 since it shows, without regard to the kind of ship, the quantity 
 and disposition of sail which she may carry ; and, in short, is 
 what the sails might be, or would be, if she could conveniently 
 carry them all in one. 
 
 Indeed, a vessel with one sail is perhaps more effective than ■*' °"« =*"• 
 with any other number: but the larger the vessel, the more 
 must her sails be sub-divided for convenience of handling. There 
 is also a limit to the size, at Which sails can be made strong 
 enough and stretched fiat. 
 
 If the vessel were so small that she could carty the whole 
 in one sail, she Would be What is commonly termed "a lugger," 
 and the sail "a lug sail." It is to be remarked, that the centre 
 of effort of the wind on this sail, will be precisely over the centre 
 of resistance of the longitudinal section in the water, and so 
 there will be a perfect balance of sail. 
 
 If the vessel be too long to enable the sail to-be carried in A'twoormoj« 
 one, it may be carried in two, without much alteration in shape, 
 and such a vessel Mali be the common lugger with two masts. . 
 
 9 
 
06 OF THE PROPORTION, BALANCE, &c., OF SAIL. 
 
 In like manner the sail may be divided into three, and hung 
 on three masts — then the vessel will be a three masted lugger. 
 
 Thus it is plain that this equivalent sail may be obtained in- 
 differently by one, two or three sails, on one, two or three masts, 
 as a matter of convenience merely, and that perfect freedom to 
 make any decision as to distribution is given, provided only that 
 the place and size of the sail, and therefore the balance, is main- 
 tained. 
 
 In light winds it may be desii-able to carry additional sail ; all 
 that it is necessary to observe is, that the additional sails be so 
 placed and proportioned as not to disturb the original balance. 
 
 By means of the bowsprit, the sail may be carried forward 
 until it ends in a point, taking care, however, to extend the sail 
 backward also sufficiently far to offset the addition in front, 
 otherwise the wind will tend to make the vessel sheer round, 
 and the balance will be destroyed. The whole sail will thus 
 become one large triangle. This form is extremely convenient 
 for vessels carrying fore and aft sail, but these additional sails, 
 fore and aft, may be and indeed are, mere patches. They are 
 used simply as balancing, or directing, or steering sails, to 
 steady the vessel, without any regard to their propelling power. 
 Such a triangular sail is sometimes carried by a single mast, and 
 sometimes divided, in the same manner as lug sails, and it is 
 curious to observe how differently the whims of sailors may be 
 indulged as to the mode of supporting and carrying these sails ; 
 the single sail being equally well carried by an upright mast in the 
 centre of the vessel, by a mast in the bow raking violently aft, 
 and by a mast aft raking as extremely forward, the one condi- 
 tion being fulfilled of leaving the balance of sail unchanged. 
 
 As all triangles on the same base, having the same height, 
 have the same area, when once a triangular area of sail is ob- 
 tained, it may be. changed in shape at pleasure, provided the 
 same height is maintained. It is to be observed, however, that 
 ofs^ali"'*'^'*"'* ^sthe shape of the triangle is changed, the place of effort of the 
 sail is shifted with it. For instance, two triangular sails may 
 have equal areas, but their centres of effort may be in different 
 lines perpendicular to the base, owing to their change of shape. 
 
 The balance of sail will be destroyed, if, in dividing the sail 
 area, care is not taken to see that in any new distribution made, 
 the place of the centre of effort is not shifted by that distribution ; 
 not only must the portions cut off from one part of the sail area, 
 be supplied in quantity by another, but care must be taken that 
 in their new positions the new parts do not gain or lose power of 
 balance ; power of balance being effectual distance: the designer 
 must therefore know how to calculate the exact effect of sails 
 placed at different distances. 
 
 To calculate the balance of sail, there are two simple and con- 
 venient principles. 
 
 How found in A triangular sail has its centre of effort in the line which joins 
 
 triangular sails. ^^^ ^j j^g comcrs to the middle of the opposite side, and is 
 
 nearer to the side than the corner, in the proportion of 1 to 2 ; 
 
 so that by dividing the line into three equal parts, and marking 
 
 the division which lies nearest the side, you mark the centre of 
 
OF THE PROPORTION, BALANCE, Ac, OP SAIL. 67 
 
 effort of the sail ; or it may be found by drawing lines from two 
 corners to the middle point of the opposite sides ; where these 
 lines intersect is the centre of effort. 
 
 Now it fortunately happens that the shapes of all sails, if not 
 triangles, can be divided into triangles, merely by drawing a 
 line through two opposite corners ; each part of the sail can thus 
 have its centre of effort separately found. 
 
 Havina: thus found the centres of effort of all the sails, or of ^?7. """?}" 
 
 ,.v*3 ... -. -_-r'rt-, pounded m sails 
 
 their separate parts, the next question in order is : How find of another shape 
 the joint effort or effect of any pair, or any number of triangular "' '" '""" ^^''^' 
 sails, or parts of sails? This is done by the principle of balance, 
 which is as follows : 
 
 In order that two equal sails may balance, they must be at 
 equal distances from the point round which they are intended to 
 balance, otherwise the one at the greatest will sway the other; 
 hence equal sails will only balance at equal distances. The 
 equal distances are to be reckoned from the centres of gravity 
 of the respective sails; if, therefore, there are only two equal 
 sails to the vessel, the balance is easy, for it is only necessary 
 to place their centres equidistant from the balancQ point in the 
 ship, and the sails' will balance. The joint centre of effort of 
 two equal sails, therefore, lies in the line of, and half way be- 
 tween their respective centres of effort. 
 
 But it may be a pair of unequal sails, and unequal in, any pro- 
 portion, say 2 to 3. The way to balance them is ■ to give the 
 small sail the longer end of the balance, and to give the longer 
 end the same preponderance in length over the shorter, that the 
 larger sail has over the smaller; thus the longer distance com- 
 bined with the smaller area of sail, balances the larger area 
 combined with the shorter distance. To see that they areequal, 
 it is only necessary to multiply the areas by their respective 
 distances from the centre, when these products are equal, the 
 balance sought for is obtained. 
 
 Suppose, on this principle, it is required to find the centre of 
 effort of a sail composed of two triangular parts. Find the cen-. 
 tre of effort of each part, (by the method before given,) join these 
 centres by a line, divide this whole line into as many equal parts 
 as there are fathoms of area in the whole sail, give to the lesser 
 portion a greater number of these parts and to the greater sail 
 area a leas number, dividing the line in the inverse proportion 
 of the areas ; the point of division is the joint centre of effort of 
 the sail. 
 
 If now there were a number of sails, some on one side and J"' » number 
 some on the other of an intended balance point, and the question 
 were asked,'^whether they balance: it would be necessary to 
 multiply the' areas of all the sails by their distance from the 
 balance point, and, if the sum of the products on the one side 
 were equal to the sum of the products on the other side, there 
 would be a balance. To obtain a balance, therefore, it is only 
 necessary to contrive that the sums of the products of the sail 
 areas on opposite sides by their distances from the balance points 
 (or their moments) shall be equal. 
 
 of sails. 
 
6g OF THE PROPORTION, BALANCE, &c., OF SAIL, 
 
 How baiancB It is plain, therefore, that to bring about a balance where it 
 jnay be rectised. ^^^^ ^^^ ^^j^,.^ j^ j^ pegggga^jy either to substitute a larger sail 
 
 on the wanting side for a smaller one, or to shift the place of 
 sail nearer to or farther away froip the centre, as required. A 
 ship whose sails are ill balanced, may have the defect corrected 
 in practice, by 'setting different quantities of forward or after 
 sail, or the defect may be rectified on a larger scale by shifting 
 . the place of the masts, or in a smaller degree, by causing a mast 
 to rake more or less forward or aft. "Where these remedies may 
 be inconvenient or impossible, the centre of resistance of the 
 body of the ship may loe shifted towards the centre of effort of 
 the sail by trimming the vessel a little more forward, or aft, as 
 it is plain that trimming by the stern will bring it aft, and trim- 
 ming by the head Avill bring it forward. 
 Place 01 masts. It is now necessary to establish proportions, according to 
 which the masts and sails of a ship may be divided and dis^ 
 xtributed. Take for this purpose a vessel with three masts, and 
 suppose her to be of the wave form — to be on an even keel, her 
 length to be divided into ten equal parts, and her bowsprit to 
 extend so as to bring the centre of the jib 5.41 of such tenth 
 parts beyond the stem, the extremity of the spanker being one^ 
 tenth part beyond the stern. For the distribution of sail make 
 the following division: 
 niftribution of Divide the sail area into 24 equal parts: 'ftO'Il of these are 
 .aiio..».hei>,asts.fjj^ the fore-mast; 10 for the main-mast;' 1.65 for the spanker; 
 3.35 for the other sails oil the mizen-mast; and the remainder, or 
 1.929 for the jib. 
 
 The place of t];e mizeq-mast is one-tenth from the stern, of 
 the fore-mast two-tenths from tjie bow, and of the main-mast 
 three-tenths from the mizen-mast, or one-tenth from the middle, 
 leaving four-tenths betweeij. the fore and main-masts. 
 
 Reckoning from the centre of lateral resistance of the vessel, 
 which, on an even keel, is the middle of her length, we have the 
 following arrangements : 
 
 Sail. Quantities. Effective distances. Total effect.'! or efforts. 
 
 Spanker, 1.65 X 5 = 8.25 
 
 Mizen, 3.35 X 4 = 13.40 
 
 Main, JO. X 1 = 10. 
 
 31.(55 n/Jer moments. 
 Fore, 7.071 X " 3 = 21,213 
 
 Jib, 1.929 X 5.41 = 10.436 
 
 Total, 24 31. 649 /ore moments. 
 
 The e3q)lanation of the above is simple; the five parts which 
 form the sails on the mizen, consist of 3.35 of the square or up- 
 per sails, and the other 1.65 of the spanker, which spanker has 
 its centre of effort onp division ft^rthgr aft that; the upper sails : 
 the parts which form the uppep sails are therefore multiplied by 
 4, and give an effect of 13.40, while the parts which form the 
 spanker, act at a distance of 5, and give an effect of 8.25. 
 
 The ten parts which form the main-mast sail area, are only at 
 one division from the centre, and give an effect of ten ; therefor^ 
 the total effect of the after sails is represented by figure 31,65, 
 
OF THE PROPORTION, BALANCE, &c., OP SAIL. 
 
 69 
 
 biliiucr the 
 after sails. 
 
 In the same manner the moment of the sails forward is found 
 to be, as given in the table, 31.6-19. 
 
 This gives, the balance of sail required, and it maybe ob-^j^^™ i'=''a,^n™s 
 served that the jib, though i5mall, has as much absolute effect on mast, 
 the balance of sail, as all the sail on the main-mast, nay, rather 
 larger, while the mizen, though comparatively small, actually 
 balances the fore-mast. It is convenient to remember, in work- 
 ing a ship, that the sails oi) the main-mast and the jib balance g^jijontiie fnre 
 each other — as also the sails on the mizen and the sails on the ■ ■ ■ ' 
 fore-mast — either sot alone could work the ship. It may also 
 be observed, that the jib may be made to balance exactly the 
 upper sails on the mizen-mast. 
 
 It wjU thus be seen that the total moments of the sails for- 
 ward, are represented by 31.649 — the total moment of those 
 abaft by 31.65, and the total number of componei^t parts of sail 
 .are represented by 24. 
 
 It now remains to be considered, how to proportion the vari- , 
 ous sails on these different masts.* 
 
 1st. Of the 5 parts of sail on the mizen, 1.65 go to the spanker, 
 and the remainder is divided between topsail, top-gallant sail 
 and royal in the following proportion: Mizen topsail, 1.518, 
 mizen top-gallant sail 1.073, and mi?en royal 0.^59. 
 
 2nd. Of the ten parts of sail which go to the main-mast, 3.3 
 form the course, 3.035 the topsail, 2,147 top-gall't sail, and 
 1.518 the royal. 
 
 3d. Of the 1.011 which go to the fore^mast, 2.3333 form the 
 .course, 2.141 the topsail, 1.518 the top-gall't sail, 1.013 the 
 royal. 
 
 Or condensed in tabular form as follows : 
 
 Proportions for 
 
 Masts. 
 
 Mizen. 
 
 Main, 
 
 Fore. 
 
 Sails. 
 
 f Spanker, 
 
 j Top.sail, 
 
 1 Top-gallant sail, 
 
 L Royal, 
 
 f Course, 
 
 J Topsail, 
 
 I Top-gallant sail, 
 
 l^ Royal, 
 
 I Course, 
 Topsail, 
 Top-gallant sail, 
 Royal, 
 Jib, . 
 
 1.65 X 
 1.518 X 
 1.073 X 
 0.759 X 
 
 5 
 
 3.3 X 
 3.035 X 
 2.147 X 
 1.518 X 
 
 
 2.3.33 X 
 2.147 X 
 1.518 X 
 1.073 X 
 
 3 
 3 
 3 
 3 
 
 1.929 X 5.41 
 
 8.25 
 G.072 
 4.292 
 3.036 j 
 3.3 \ 
 3.035 I 
 
 21.65 . 
 
 10 
 
 2.147 
 
 1.51.8 J 
 
 6.999 ] 
 
 6 441 ' 
 
 4.554 !■ 21.913 
 
 3.219 J 
 : 10.436 
 
 i- 31.65 
 
 31.649 
 
 J 
 
 But there 
 
 IS a third question to solve. The proportion of P^portions for 
 
 •1 1 j_iiij.-ii . n masts. 
 
 sail on eacn mast has been obtamed — the proportion of area of 
 each sail has been obtained — there remains to be found the pro- 
 portionate dimensions of each mast, which may enable them to 
 carry their respective sails. 
 
 In a three masted ship, it is necessary, both for symmetry of 
 appearance and for balance of sail, that the proportion of sail on 
 each mast should be tolerably similar; for example^-on the 
 
 •These proportions, it tnust bo observed, ars for vessels constructcil on the "wave" 
 principle. 
 
70 OF THE PROPORTION, BALANCE, &o., OF SAIL. 
 
 largest mast should be the largest topsail; on the smallest mast 
 the smallest topsail, and so on. It is also necessary that the 
 sizes of masts and spars should bear a due proportion to each 
 other throughout. 
 
 The following proportion of sails will accomplish all this. 
 Taking the three masts to have four sails, all similar, then from 
 the proportion before given, namely : 
 
 Areas of sail— Mizen 5 Fore I.Otl Main 10. 
 
 Being in the proportion of 1 1.4142 2. 
 
 In order to make up this proportion, it is only necessary tha,t 
 all the sails on the three masts should be in, as nearly as possi- 
 ble, the following proportion. 
 
 5 l.on 10 
 
 The sails on all the masts will have the proportion required, 
 1 1.4142 2 
 
 Proportions for For example, when the cross-jack vard has for its breadth of 
 ^'"■'^' sail 50 feet, then the fore yard fO. 71 "feet, main yard 100 feet, 
 
 or in that proportion. 
 
 The corresponding topsail yards should be in the same pro- 
 portion, namely: 
 
 Mizen topsail yd. 35.35 Fore 50 Main 10.11 
 
 Miz. T.-gairt yds. 25. " 35.85 50 
 
 " Royal " 11.61 " 25 35.35 
 
 It is obvious, also, that the lengths of those parts of the masts 
 and spars which carry sail, should bear to one another the simi- 
 lar ratio of 
 
 Mizen 5 Fore 1.011 Main 10 
 Or, 1 1.4142 2 
 
 Specific exam- With these general proportions in view, proceed to complete 
 the arrangement of sail on a given ship, say of 550 tons burthen, 
 whose length on the water-line is 150 feet, and draft on an even 
 Total sau area, keel 16 feet 8 inches. Taking six times the draft of water, or 
 100 feet, this gives the height of the equivalent sail area 100 
 feet ; which, by a length of 150 feet, gives a total sail area of 
 150 X 100 = 15,000 feet area. 
 
 To place tiie First — to place the masts, divide the length of water-line into 
 '"''='^- 10 equal parts.- 
 
 Distance of the mizen-mast from aft, = .1 of 150 = 15 feet 
 
 " " " fore-mast from forward, = .2 " 150 = 80 " 
 " " " main-mast from mizzen, = .3 " 150 = 45 " 
 " " " main-mast from fore-mast, =..4 " 150 — ■ 60 " 
 
 150 " 
 
 Sail area on Second — to proportion the sail area on each mast. 
 
 Mizen, five twenty-fourths of 15.000 = 5 x 625 =3125. 
 Fore, .... =1.011x625=4419.315 
 
 Main, - - - - = 10 x 625 = 6250. 
 
 Jib, ... - =1.929x625=1205.625 
 
 «ach mast. 
 
 15.000 
 
OF THE PROPORTION, BALANCE, &c., OF SAIL. 
 
 71 
 
 Mizen. 
 
 Fore 
 
 Main. 
 
 Third. — To proportion the sails on each mast. 
 
 r Spanker, 1.65 X 625 = 1031.25 
 
 1 Topsail, 1.518X625= 948.75 
 
 1 Top-gall't sail, 1.073 X 625= 670.625 
 
 [ Royal, 0.759 X 625= 474.375 J 
 
 f Course, 2.303 X 635 = 1458.125 
 
 'I'opsail, 2.147 X 625 = 1341.875 
 
 i Top-gairt sail, 1.518 X 625 = 948.75 
 [Royal, 1.073X625= 670.625 J 
 
 r Course, 3.3 X 625 = 2062.5 \ 
 
 Topsail, 3.035X625 = 1896.875 1 
 
 i Top-gall't sail, 2.147 X 625 = 1341.875 f 
 I Royal, 1.518X625= 948.75 J 
 
 Jib, = 1205 635 
 
 3125.00j 
 
 4419.375 
 
 6250.00 
 
 Area of each 
 sail. 
 
 . 15.000 
 
 Or in other words, 
 
 Spanker. 
 1.65 
 Or in the proportion of 1. 
 
 Mizen Topsail 
 L518 
 Or in the proportion of 1. 
 Mizen 
 Top-gall't sail. 
 1.073 
 Or in the proportion of 1. 
 
 Mizen Royal. 
 0.159 
 Or in the proportion of 1. 
 
 Again, 
 
 Topsail. 
 Mizen. 1.518 
 
 Or in the proportion of 2. 
 
 Main. 3.035 
 
 Or in the proportion of 2. 
 
 Fore. 2.141 
 
 Or in the proportion of 2. 
 
 Fore-course. 
 2.333 
 1.4142 
 
 Fore Topsail. 
 
 2.141 
 
 1.4142 
 Fore 
 Top-gall't sail. 
 
 1.518 
 
 1.4142 
 
 Fore Royal. 
 1013 
 1.4142 
 
 Main-course. 
 3.3 
 2. 
 
 Main Topsail, 
 
 3\035 
 
 2. 
 
 Main 
 Top-gall't sail. 
 
 2.141 
 
 2. 
 
 Main Royal. 
 1.518 
 
 2. 
 
 Example con- 
 tinued. 
 
 Top-galVt sail. Royal. 
 1.013 0.159 
 
 1.4142 1. 
 
 2.141 1.518 
 
 1.4142 1. 
 
 1.518 1.013 
 
 1.4142 1. 
 
 Now to get the length of the yards : The lower yards are Length of yards, 
 at once found by taking the square root of twice the area of the 
 courses, and for the mizen-mast, as the area of the spanker is 
 equal to the same area as that of a course, if there had been one 
 for the cross-jack yard, twice the square root of the area of the 
 spanker must be taken. 
 
 From this is found, 
 The length of the Main yard 64.23 or in the proportion of 1. 
 
 " " " Fore yard 54. " " " 0.8409 
 
 " " " Cross-jack 
 
 yard 45.41 " " " 0.1011 
 
 These proportions give at once the length of yards and hoist 
 of sail; for multiplying the length of the main yard by 0.8409, 
 we get the length of the fore yard and main topsail yard ; by 
 multiplying the length of the fore yard or main topsail yard by 
 0.8409, we get the length of the cross-jack yard, fore topsail yard 
 and main top-gall't yard, and so on, always excluding yard arms. 
 These same proportions answer for the hoist of sail ; or in other Hoist of sails. 
 
12 OF THE tROPORTlOX, BALAXCE, &c., OP SAIL. 
 
 words, half the length of the main j-ard is the hoist of the mam 
 topsail; half the length of the main topsail yard is the hoist of 
 the main top-gall't sail; half the length of the main top-gall't yard 
 is the hoist of the main royal 
 siiinmary. jj. ^,jjj ^.jj^g j^g g^p^^ ^j^j^^ ]^^ ^]-,jg arrangement there is one 
 
 yard of the length of the main yard, tivo yards of the length of 
 the main topsail yard, three yards of the length of the main top- 
 gall't yard, three j-ards of the length of the main royal yard, two 
 yards of the length of the fore royal yard, and one yard of the 
 length of the mizen royal yard. Working the aboye quantities 
 out for the yesscl whose area of sails haye been calculated, is 
 obtained for the length of 
 
 Main. Fore. Mizen. 
 
 Main yard =64.23 Fore yard =54. ' Cross-jack yd. 45.41 
 Topsail yd. =54. Topsail yd. = 45.41 Topsail yard 38.18 
 Top-gan'tj-d. = 45.41 Top-gairtyd.= 38.18 Top-gall't yd. 32.41 
 EoA-alyard =38.18 Royal yard =32.41 Royal j-ard 21.26 
 
 And when, with these figures, the areas of the different upper 
 sails are calculated, it will be found that the quantities found in 
 this manner, and the quantities found in the first manner, will 
 agree with great precision. 
 
 It will be seen, that ^yith the foregoing arrangement, a perfect 
 
 balance is obtained; that is, the centre of sail falls exactly in the 
 
 same perpendicular with the centre of lateral resistance. Now 
 
 in some ships, it is preferable to have the centre of effort some 
 
 distance forward of the centre of lateral resistance. This is 
 
 easily accomplished by means of the jib. 
 
 How the jib The centre of the jib in the foregoing calculations, was situat- 
 
 SrJr balance of^d at 5.41 from the centre or middle division. Xow by merely 
 
 sail. shifting its centre to six divisions from this middle, which in the 
 
 vessel of 150 ft. length, would be 90 ft., the centre of effort would 
 
 be brought forward 5 feet. This may seem difficult to do, as the 
 
 masts are fixed and the jib stay cannot be shifted; it therefore 
 
 remains to alter the shape of the jib, this is done in the following 
 
 manner: 
 
 Erect a perpendicular line on the sixth division from the mid- 
 dle of the water-line, then on this perpendicular the centre of 
 the jib will be situated. Lengthen this perpendicular until it 
 meets the jib stay, then lay off from this intersection equal dis- 
 tances, up and down along the stay as far as convenient, the 
 sum of these two distances will form one side of the jib. The 
 area of the jib being given, divide this area by one-half the side, 
 and with the quotient as length, draw a line parallel to the jib' 
 stay until it intersects the perpendicular lino, join this point 
 Avith the two extremities on the jib-stay and there is obtained a 
 shape of jib of the given area, and with its centre falling ex' 
 actly at the sixth division from the middle, or one-tenth oV the 
 length beyond the stem. But this degree of accuracy is much 
 greater than is required for practice, and it is necessary to guard 
 against the attempt to fix these points in the design too closely 
 before taking into consideration a multitude of practical points 
 of convenience, use and taste, which go to regulate the dimen- 
 sions of sails. In the first place, it must never be forgotten that 
 
OF tHE PROPORTION, BALANCE, &c., OF SAIL- 73 
 
 nearly all ships cany weather-helm, and that this proportion of 
 woather-helni generally increases with the wind. 
 
 It is to be observed, that the design of the sails having been . if iiitpratinns 
 
 lilt Litis nil) circ 
 
 made in proper balance, an}' change made to correct defects in maiie, buiance 
 the form of the body, should not be allowed to derange either {'^!;^^^;j_'"= ""''"- 
 the proportions or places of the sails ; but, for this purpose, the 
 whole of the sails should be removed'to their new place, and not 
 shifted with respect to each other, unless due regard be had to 
 maintaining their balance. 
 
 Another point for consideration is, that if masts are made 
 to rake, instead of standing upright, it must not be forgotten 
 that rake may shift the relative distance of the sails. 
 
 A further point is, that the convenience of the ship herself conventence 
 may interfere with the disposition of sails. A high forecastle ['i,„er'''dicra'te3 
 will shorten the foot of the foresail. A poop may seriously iu-s^iitobe used, 
 terfore with the spanker. These are points which must on no 
 account be neglected. 
 
 Perhaps the most important point that can be kept in view in ijj^^e^ofsaii"' 
 the study of the balance of sail, balance of body, placing of 
 masts, proportion of spars, and sub-division of sails, is this, that 
 in all circumstances the ship should be able to carry the greatest 
 quantity of sail with the least possible action of rudder. In a 
 perfect wave form, perfectly balanced, this has been done, and 
 in a fast sailing clipper it is vital. In such a vessel, the whole 
 of the sails mentioned would bo carried, whether the wind was 
 light or fresh, without retarding the ship by the action of the 
 helm. "When it came on to blow hard, it would only be neces- 
 sary to furl the three top-gall't sails, and the rest of the sails 
 would remain in perfect balance; blowing harder, the topsails 
 might all be reefed and a balance still maintained ; blowing a 
 gale, the spanker, jib, foresail and mainsail might be taken in, 
 and yet a perfect balance exist under close reefed topsails and 
 storm jib. Thus, in a ship built on the wave line theory, even 
 in heavy weather, the Captain would find his ship handy, fast 
 and under perfect command ; but if the vessel were not a wave 
 vessel, the following changes would take place: As soon as it 
 came on to blow fresh, the spanker, which is a most powerful 
 sail, would be found to cause an excessive degree of weather- „ , ^, .. 
 
 11 1 111 -1 1 11 '11 Balance of sair 
 
 helm, and would have to be taken m, but that would spoil the penect only i« 
 
 balance and the jib would follow the spanker, giving place to the """*'" '°™' 
 
 topmast staysail, which would at once reduce very seriously the 
 
 way of the vessel, and it would be want of balance and not stress 
 
 of weather which did it. If it came on to blow hard, it would 
 
 soon be necessary to take all sail off the mizen, except perhaps 
 
 a small storm sail for lying-to. 
 
 In ships of this class, nothing but experience will tell under 
 what sails the ship will balance, and what she will not carry ; 
 but one thing is certain, that in light winds and strong ones, the 
 balance will be entirely different, which is not the case in the 
 Wave formed ships. 
 
 10 
 
OF THE PROPORTION, BALANCE, &c., OF SAIL. 
 
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OF THE PROPORTION, BALANCE, &o., OP SAIL. 
 
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SYMMETRY, FASHION AXD HANDTNESS OF SAIL, 
 
 CHAPTER XIX. 
 
 OF SYM2IETRY, FASHION AND HANDINESS OF 
 
 SAIL. 
 
 Fashion nrsnii Hitherto tho Sails havc been studied witli rcferpiice to tbcir 
 ?XC°^'™" effect on the ship, ia so far as concerns tho work of the Naval 
 Architect. Whether they arc well proportioned in size to the 
 ship; whether they are well balanced so as to leave the ship 
 free in her niovenlents; whether they are so proportioned in 
 dimension, that they drive without ovcrpowerinp; the ship ; 
 whether they can be varied in quantity to any extent, without 
 derangement of balance, and always leave the ship under com- 
 mand of the helm; when these questions are satisfactorily answer- 
 ed, then the first g-reat requisites of the Naval Constructor are 
 accomplished. But other thinn-s are ilemanded, besides this 
 first essential — their use to the ship. The seanuin must be 
 satisfied with the figure, distribution and cut of his sails — 
 besides this, they must suit his convenience and use. They 
 must set well, stand Avell, draw well, be easily sc(, easily worked, 
 easily reefed, easilv taken in; in short, bo conveniently, easily 
 and safely handled. On this point, the will of the seaman 
 should rule the design. 
 
 The quantity and balance of sail, is the business of the Naval 
 Architect; the symmetry, fashion and cut of the sails, is the 
 vocation of the seaman, not of the landsman. The Naval Archi- 
 tect has now to consider how he shall give the seaman all he 
 wishes, in regard to fashion and symmetry, without compromis- 
 ing the other conditions on which the ship is designed. This 
 requires skill — but for this purpose, all that has been said about 
 balance of sail and of ship, forms an excellent l)asis, on which 
 may be grafted any amount of fashion and of fancy, of fitness 
 and of handiness. 
 
 Suppose a full rigged ship to havc been designed; and tho 
 place of all the principal sails, their areas, and their dimensions 
 to be laid down on a sail-draft, by the rules nlrendy given; the 
 question now raised is. How may the fashion of the sails be 
 altered, without disturbing their balance, or changing their 
 quantity ? 
 
 There is manifestly a great variety in fashion for the same 
 area. 
 
 For every square sail, therefore, there arises three main ques- 
 tions : 
 
 1st. Taper of sail, or dimiiiution of the head of each sail, 
 compared with the width at tho foot. 
 
 2d. Proportion of height to width, or spread of sail in pro. 
 portion to hoist, 
 
 3d. Sub-division of sails on a mast. 
 Taper of sails. I. Diminution of the head of the saih on a given mast. 
 
 The sails on the same mast may all have the .same taper, 
 diminishing in one strjiight line; or they may vary in taper. 
 
SYMMETRY, FASHION AND HANDINESS OF SAIL. 11 
 
 It is obvious, that whatever reason exists for a certain taper 
 in a given sail, will apply equally to that above it. That the 
 sails on all three masts should have the same taper, one and all, 
 seems evident. There seems to be a preference for having one 
 proportion for the diminution of the head of the sail running 
 through all the higher sails of the same mast, especially where 
 the sub-divisions are numerous. But, on the other hand, it is 
 a frequent practice to narrow most, the heads^of the higher sails. 
 The argument for diminishing the heads of the sails, is that 
 the higher masts and gear are lighter than the lower, and, there- 
 fore, less able to carry heavy and large sails and yards. On 
 the other hand, is the argument, that the loftier sails are not 
 spread in bad weather, but are taken in when it blows hard, so 
 that being fair weather sails, they should be large, or else they 
 arc of but little use. 
 
 The latter consideration is entitled to considerable weight. 
 The lofty sails should, it is thought, have a wider spread and a 
 smaller "proportion of height to width than has been usual 
 hitherto. There is a growing tendency in fast vessels to carry 
 large and low sails, and to obtain greater spread of sail with 
 less hoist.* 
 
 Moreover, with the adoption of iron and steel as a material 
 for masts, and wire rope for rigging, sails of great spread and 
 moderate hoist, will it is believed, be more and more used. 
 
 Three things must be remembered, in considering what dimi- 
 nution of sail may be adopted in any given ship. 
 
 1st. That, by increasing the spread of the lower sails and 
 tapering rapidly the upper, the centre of effort of the sails is 
 lowered. 
 
 2d. That, by narrowing the upper sails, they become of less 
 area and of less value. 
 
 3d. That, in altering the taper, it is only necessary to remem- 
 ber that, by so much as the alteration adds to one part of the 
 sail area on a given mast, by so much also, shall it diminish the 
 area at another part. 
 
 Thus, any amount of change or diminution may be given to 
 the sails on each mast, without changing the balance of sail 
 area on the whole ship. 
 
 II. Proportion of height to width in a given square sail, is jmist o™saii. 
 a matter of choice. 
 
 It seems that in proportion as ships sail faster, and are built 
 finer and longer, the separate sails are made broader and lower, 
 •their yards Ibnger, and their hoist less. By giving squareness 
 to a sail, not only is a larger quantity of low sail carried, but 
 the sails stand flatter and better on a wind. On the contrary, 
 there is this consideration, that yards of great length are costly 
 and heavy — heavy to carry and heavy to work ; and that, by 
 merely increasing the hoist, the same yard may be made to carry 
 much more canvas and do much more work. 
 
 This goes in favor of increased hoist; but it loses weight from 
 this further consideration, that a square sail of great height, 
 
 *Ttiis is oapcoially the case in wave line sfilps. 
 
 and 
 
78 SYMMETRY, FASHION AND HANDINESS OF SAIL. 
 
 does not stand well on a wind ; and that a fast ship will sail 
 faster on a Avind with square and low sails, than with high and 
 narrow ones. 
 
 The fact that yards of great length are heavy to carry and 
 hard to work, will therefore be a good argument in favor of 
 narrow and lofty sails for slow ships, for short' voyages, and for 
 ships with small crews. On the contrary, in long voyages, and 
 with plenty of able seamen, spread being of value, long yards 
 and moderate hoist are preferable. 
 
 The limits of proportion taken are these: When the hoist of 
 a square sail is made equal to its spread, that is to be reckoned 
 an extreme height of sail. When the hoist is one-half of the 
 greatest width, that is to be reckoned a broad and low sail. 
 They ought not be lower, since it seems wasteful, because a sail 
 of that height will stand close to the wind ; therefore, that is 
 assumed as a standard proportion of height to width. 
 
 Sub-division of III. Suh-division of sttils On a mast. 
 
 It is plain that the proportion of width to height of sail, may 
 be considered apart from taper, or diminution of head ; never- 
 theless,' a rapid rate of diminution may better suit lofty sails, 
 and a more gradual rate lower sails. But much of the symmetry 
 of a suit of sails, depends on keeping some one proportion of 
 height to width of sail, throughout the sails on the same mast, 
 and throughout the sails on the different masts of the same ship. 
 
 In fast ships, there is a strong tendency in this direction ; and 
 it is believed, that the introduction of iron masts, frees the ship 
 builder from the difficulty of finding spars of sufficient length 
 and strength in the forests, and enables him to make masts of 
 any length in one piece, without break or discontinuity, and this 
 is a great encouragement to the adoption of symmetry and 
 uniformity in the proportion and fashion of sail. It seems plain, 
 that when some one proportion of height to width has been 
 selected, as possessing the requisite qualities in the best practi- 
 cal degree, tBere can be no sufficient reason for adopting that 
 proportion in one sail on a mast, and rejecting it in the others. 
 
 Take therefore, for example sake, the sails on one mast, and 
 divide them, so that they may all have one proportion of spread 
 and hoist. That sub-division may be altered in any way found 
 most convenient for working. In men-of-war, the topsail is the 
 great working sail of the ship; it is generallj^ of great hoist, 
 and may be taken as an extreme proportion. In the double top- 
 sail sailing clipper, the same sail is cut into two sails, often of 
 a ridiculously small hoist. These are two extremes between 
 which there should be some medium. It is thought not out of 
 place to repeat here, that sub-division of sails is more a matter 
 of seamanship, than of naval construction — is more, in fact, a 
 question of working a ship, than of designing one. Generally 
 speaking, the sails liked best will be worked best. What the 
 seaman likes, will depend not merely on his experience, but on 
 the power at his disposal to work his ship, and on the value 
 that speed may have to him. Given — a stable, fine, fleet ship for 
 long voyages, it is thought better to have sails not high, but of 
 great spread. For short voyages, narrow seas, moderate speed, 
 
SYMMETRY, FASHION AND HANDINESS OF SAIL. 79 
 
 and a small ship's company, narrow sails, lofty and easily 
 worked, may be preferred: and in like manner, sails few and 
 large, or many and small, have corresponding advantages or 
 disadvantages. 
 
 Hitherto, reference has been made mainly to sails of a quad- rwe and aft 
 rangular shape or square sails, which are not only the most ^*''^' 
 universal of form and arrangement, but are universally used on 
 the largest scale. Triangular sails are not less valuable, but are 
 to be reckoned in some sort as subsidiary sails. They take their 
 form almost inevitably from other considerations, to which they 
 are subordinate. Thus, even the jib of a man-of-war, the chief 
 triangular sail, takes its shape and proportion almost exclusively 
 from the angle of the jib stay, and is decided in shape by the 
 proportion of masts and direction of rigging, which have been 
 determined by precedent considerations. 
 
 If there is less scope for choice and design in triangular sails 
 than in square saOs, there is this compensating virtue in the 
 foriner, that they are accommodating enough to take any shape 
 without loss of value. A jib covering a given length of its boom, 
 is of the same area, provided it rise to a given height, measured 
 square off the line of its boom, and does not vary with the steeve, 
 and so long as it rises to the same height, its centre of effort 
 will be at the same height taken square from the boom. 
 
 There is another point in which a triangular sail differs from 
 a square sail — it draws well, independent of its height. So long 
 as a triangular sail is not too wide fore and aft, it will set flat, 
 close to the wind, and without the large belly which great height 
 would give a square sail. The chief virtue of triangular sails is 
 this special quality of setting flat, and going close to the wind. 
 
 Spankers and the sails also have the same advantages as 
 triangular sails of standing well, and keeping flat, close to the 
 wind, but the gaff has the disadvantage of tending to sway over 
 to leeward; and the head of the sail shakes while the foot stands. 
 
 In calculating the balance and dis"tribution of triangular sails, 
 and fore and aft sails generally, it is a matter of indifference, 
 what the sort of sail is; a fore and aft sail may be substituted at 
 any point for a square sail, provided the same area is kept, and 
 the balance point or centre of effort of the sail in the same place. 
 The sails will balance the ship equally well, whether square or 
 fore and aft. 
 
 But there is this radical difference between fore and aft sails Jore and aft 
 and square sails. Fore and aft sails shift their centres of effort lemres— square 
 with their trim — they travel in circles round a fixed point, and ^*''^ ^° ""'• 
 they carry their centres round with them. Square sails never 
 shift their centres of effort, so long as they are set flat; the cen- 
 tres are fixed points on the mast around which they turn. 
 
 This shifting of the centre in fore and aft sails, is of considera- 
 ble importance, because it carries the centre of effort further 
 forward as the ship's course goes off from the wind. It returns 
 when close-hauled; but it must be kept in mind, that it is always 
 a little forward of its calculated place, and this is perhaps one of 
 the reasons why, in fore and aft rigged vessels, the centre of 
 effort of the- sails requires a smaller shift forward of the middle. 
 
80 SYAIMETIIY, FASHIOjS" AND HARDINESS OF SAIL. 
 
 Fore and aft in order to mect the shift of the centre of resistance of the body 
 of the vessel as the speed increases. It must always remain a 
 great point in favor of the square rigged vessels, that their sails 
 pivot round their centres of cflbrt, and keep their balance in every 
 trim. On the other hand, it is a quality of the fore and aft rig 
 to lie closer to the wind, and probably to yield a given sail area 
 with a smaller q,uantity of top hamper, thus suiting well the 
 chief purpose of modern sails, to serve as auxiliaries to the pow- 
 er of steam.* 
 
 But iron masts, spars and wire rigging, are daily coming more 
 and more into use, and will eventually open up a new field for 
 enterprise — at least in the merchant service. 
 
 *Tlie majdrity of the French iron clads carry large fore and- aft sails, in lieu of square? 
 •ails— probably on this accoujit. 
 
PROBLEM OF NAYAL ARCHITECTITRE. 81 
 
 CHAPTER XX. 
 
 (JOXDITIONS OF THE PROBLEM OF NAVAL 
 ARCHITECTURE. 
 
 The professional duty of the Xaval Architect is to frame and , Duty of the 
 
 ii-i* i»i- 1 t -t • • -\ ' -t Arcbitect. 
 
 complete the design of a ship — the word design implying plan, 
 use, or purpose ; and, therefore, the first duty of the Architect is 
 to ascertain accurately, note exactly, and conceive clearly, the 
 intention and pui'pose which the vessel is designed to fulfill. 
 
 If the case under consideration is that of a merchant vessel, 
 to the owner then, the Xaval Architect must apply for a clear 
 understanding of all that the ship is meant to be and to do ; and 
 therefore the following questions may be of service in eliciting 
 the information necessary befcrre commencing the design of the 
 vessel: 
 
 The owner must be asked — first, what he wants his ship to do? 
 He may answer: To trade between Xew York and New Or- ^^™pi«- 
 leans. 
 
 2. What kind of trade he proposes to carry on? Answer. — A 
 miscellaneous trade, partly merchandise, partly passengers. 
 
 3. What quantity, bulk, and nature of cargo ? Ans.^ — 500 tons 
 of dead weight ; 25,000 cubic feet of bulk, for cargo in the hold. 
 
 4. What kind and number of passengers? Ans. — 25 first class, 
 20 steerag'e passengers. 
 
 5. What sort of voyage? Ans. — Once a month, stopping no- 
 where on the way. 
 
 6. At what speed ? Ans. — An average of 8 knots. 
 
 t. Carrying much canvas or little ? Ans. — To depend mainly 
 on steam, the sails being auxiliaiy. 
 
 8. At what estimated cost per voyage ? Ans. — $1.75 per mile. 
 
 9. How much is the owner prepared to pay for his vessel ? 
 Ans.— $125,000. 
 
 10. How much is the owner prepared to pay for a more or 
 less durable ship ? how much for more or less durable engines 
 and boilers? and how much for a more 'or less complete equip- 
 ment? Ans. — Ship to be classed twelve years, A No. 1 ; engines 
 and boilers to be those least likely to fail when wanted, most 
 economical in repairs and consumption of fuel; and 15 per cent, 
 preference to be allowed on the price of good engines and boilers 
 over indifferent. 
 
 11. What draft of water? Ans. — Load draft not to exceed 15 
 feet; no other limit as to dimensions. 
 
 12. What class of Commanders and Engineers to be employed ? 
 Ans. — The best Captain and Engineer without reference to sal- 
 ary. (The owner will do well to select his Captain and Engi- 
 neer and put them in communication with the Naval Architect 
 before the ship is built.) 
 
 13. Is the ship to be confined exclusively to this trade or may 
 she have in future to be employed on other voyages? 
 
 11 
 
■82 PROBLEM OF NAVAL ARCHITECTURE. 
 
 Now from the Captain and Engineer, the Architect may re- 
 ceive information on the following questions : 
 
 14. What is the true length of the voyage according to the 
 course usually followed? 
 
 15. What has been the average performance of any known 
 vessels on the line ? 
 
 16. What would require to be the maximum speed of a vessel 
 in good sailing trim, in order to realize an average working speed 
 of eight knots an hour on the voyage ? 
 
 11. What sort of ships and engines have hitherto been em- 
 ployed to do this sort of work? 
 
 18. With how many officers and hands as crew, and how many 
 in the engine room, is this ship proposed to be worked ? 
 
 19. Besides the room required for cargo, for passengers and 
 for attendants, how much is to be reserved for machinery, for 
 coals, for ship's company, for ship's stores, for provisions and 
 equipment? 
 
 20. What is the exact nature of the equipment required for 
 this peculiar voyage ? 
 
 21. What are the weights to be carried under these respective 
 heads ? 
 
 Points of con- Thesc are the conditions of the problem, without which, as 
 siructiDii. preliminaries, the design of the ship cannot even be begun, and 
 
 all of them- must be sought, and given to the Naval Architect at 
 the outset, in order to prevent much of his work being mere 
 waste. 
 Preliminary The rcsult of all these inquiries will lead him to this most 
 conditioiis. important and primary issue, which may be said to determine 
 the chief characteristic of his ship, namely : the burden she must 
 carry and the bulk she must stow. In addition to her own pow- 
 ers to swim, she must have power to carry, and tlie total weight 
 Bulk of weight, she must Carry when full, is lOOO tons. But the vessel herself 
 will weigh a known quantity, a quantity either suggested to him 
 by some vessel he already knows, or which he must iind out by 
 calculation; but suppose it be assumed that his ship will weigh 
 500 tons in addition to the lOOd tons before stated. 
 
 The ship, therefore, with her equipment, her freight and her 
 stores, gives a dead weight to be dealt with in the design of 
 1500 tons. This is technically called "the total deep-load dis- 
 placement of the ship," and forms the first condition of the pro- 
 blem. It is the dead weight to be carried, and the question is, 
 how best to carry it? This is treated of, under the head of Dis- 
 placement (Pages 14 and 15.) 
 
 Peace and wr.r. The foregoing, drawn from the necessities of the merchant 
 service, will serve also to suggest a similar series of requisitions 
 to be made before commencing the design of a vessel of war. 
 The nature of the service on which a man-of-war is to be em- 
 ployed, the harbors she is to enter, the length of a voyage on 
 which she may be sent, the number of her crow, the weight of 
 her guns, ammunition, equipment and stores, and for a steam 
 vessel, the power required to drive her at a given speed, and the 
 coal required to take her a given distance, with a multitude of 
 
PROBLEM OF XAVAL ARCHITECTURE. 83 
 
 particulars quite as minute as those given in the ease of the 
 merchant vessel, must be obtained by the Xaval Constructor 
 before he can commence his design. 
 
 A Xaval Architect, for his own reputation, should refuse per- 
 emptorily to commence hLs desigu without full, specific and 
 detailed conditions fir~t obtained, either given to him by authori- 
 ty, or prescribed by himself if he have the power. 
 
 It is much too common a practice to ask a designer to build a 
 ship-of-war, and to teU him that it will be time enough to con- 
 sider all the details of her armament, eijuipmeut, special construc- 
 tion, and destination, after the design has been completed, and 
 while the ship is in progress This is a fallacy, it wUl not be 
 time enough, it wiU be too late. 
 
 Most of the wretched failures in this country, have been pro- 
 duced 1 ly budding the ships first, and settling what they were to 
 do afterwards. The Xaval Architect who respects his profession 
 should refiisi' to desiirn his >hip imtil all the reijuisite data has 
 been given him. Without this there can be no science of Xaval 
 Architecture, and no plan of a ship worthy of being called a 
 design. 
 
 But, when these have been obtained, the Constructor shoidd 
 arrange them, reconcile them, aud finally determine them, by 
 setting them out in a formal manner, in what may be called the 
 
 Scheme of CciXDITIUNS of CONSTHrrTION, scheme of con. 
 
 diuons. 
 
 which forms, afterwards, a programme of work to be done in 
 forming the design of a ship. 
 
 Scheme fur the Construction of a Merchant Steamer. 
 
 A miscellaneous cargo, 
 Passengers — 25 first class, 
 
 " — 20 second class, 
 
 Engines and boilers (with water). 
 Fuel and Engineer's stores. 
 Equipment and sea stores. 
 Ship's huU and internal fittings, 
 Provisions and water. 
 
 Officers, engineers, servants and crew, 7,500 
 Spare capacity and weight. 
 
 Gross capacity and weight, 90,000 1,500 
 
 Toyage of 1500 sea miles, (knots) 
 A mean speed of 8 knots. 
 Load draft, 15 feet. 
 
 Speed in smooth water, 10 knots. 
 
 Fuel per mile, 1 1-2 cwt. (168 lbs.) 
 
 r Officers, 5 ) 
 
 Ship's company: -s Engineer and assistants, 3 ,- 30 hands. 
 ( Crew and coal heavers, 22) 
 
 Time of single voyage, 8 days. 
 
 Bulks. 
 
 Weights. 
 
 Cubic feet. 
 
 Tons. 
 
 25,000 
 
 500 
 
 6,250 
 
 
 3,000 
 
 
 1, 7,5rt0 
 
 150 
 
 10,000 
 
 200 
 
 7.500 
 
 150 
 
 17,500 
 
 350 
 
 2,500 
 
 50 
 
 rew, 7,500 
 
 10 
 
 3,250 
 
 90 
 
84 PROBLEM OF NAVAL ArvClIITECTURE. 
 
 Scheme for a Man-of-war Screw Sicamcr. 
 
 Bulks. WrigJds. 
 
 Cubic feet. Tviie. 
 
 Engines, boilers (with water.) 
 Engineer's stores. 
 Fuel. 
 Guns. 
 Powder, and tanks including space for 
 
 light rooms. 
 Shot and shell. 
 Ordnance stores. 
 
 Water for 4 weeks, for men. 
 
 Bread for 6 months, for men, 
 
 Other provisions for 6 months. 
 
 Masts, yards, rigging and sails. 
 
 Spare sails and Sailmaker's stores, 
 
 Navigator's stores. 
 
 Boatswain's stores. 
 
 Carpenter's stores. 
 
 Boats. 
 
 Chain cables, 
 
 Anchors. 
 
 Officers' stores. 
 
 Paymaster and Marines' stores, 
 
 Galley and condensers. 
 
 Officers, crew and effects, ( ^ — ) 
 
 Shaft alley. 
 Wing passages. 
 Ventilating passages. 
 Masts and hatchways. 
 3pare bulk and weight, 
 Weight of ship's hull. 
 
HOW TO DESIGN THE LINES OF A SHIP. 85 
 
 CHAPTER XXI. 
 
 HO W TO DESIGN THE LINES OF A SHIP. 
 
 The easiest problem, which can ever be submitted to a con- Pi-obiem hmoa. 
 structor, will be taken as an example. 
 
 Suppose a case, which very frequently occurs in practice, that 
 a certain length of ship is to be built — a certain breadth is given 
 — a certain load draft of water, and a certain light draft of wa- 
 ter,, and that these are about the ordinary proportions of a ship; 
 that no particular weight is to be carried, or work to be done, 
 beyond sailing well, or steaming at a moderate speed, and that 
 the purpose to be served is a fair, c'ommon mercantile trade, 
 such as ordinary vessels will moderately well perform ; of course 
 the owner will expect, what he may with reason expect from a 
 man of science and skill, that the vessel will be somewhat faster, 
 easier, safer and more economical, therefore somewhat more 
 valuable, than a vessel built, without design or calculation, by 
 an unskilled man. This is a very ordinary task for a Naval 
 Architect. 
 
 There are two ways in which he may set about building his 
 vessel: he may either take the model of the vessel which is 
 already the best that has been applied to the trade in question, 
 and improve upon her ; or he may at once throw all precedent 
 overboard, and give his employer an entirely new design. The 
 undertaking then will speedily shape itself as follows : Extreme 
 length and extreme breadth being given, he may determine a 
 midship section, such as will give him the requisite carrying 
 power, with good sea going qualities. Next, he will determine 
 a waterJine which will give the highest speed and least resist- 
 ance, of whiqh that length admits; or he may decide to fit her 
 for a given speed only, and adopt a water-line of greater capacity 
 fit for that slower speed. Thirdly, he will adopt a convenient 
 form of deck for the use and navigation of the ship, and on these 
 principal points he will fill in, what may be called "a skeleton 
 design," and frame an approximate calculation of the qualities 
 of the ship, which may also be called "the skeleton calculation." 
 
 (I.) To construct the midship section. watci-iine not 
 
 In. the choice of the midship section, the Naval Architect is left ' ' ""^" 
 free, to exercise with the greatest liberty his own judgment. 
 In the water-line, he has little or no choice : Nature has fixed 
 that for him. If he meddle with it, he displays ignorance or 
 presumption, and the due punishment is a spoilt water-line ; but 
 the midship section he may vary as much as he wishes to. He 
 may give the ship every sort of quality, by choosing it ill or 
 well; and with a given water-line, he may produce all sorts of 
 ships. 
 
 To illustrate this latitude of choice, suppose the architect to : choice or mid- 
 take three styles of midship section; and further, that it is neces- '"''"'' ^^'''''""" 
 sary for each of them to have the greatest speed the length will 
 allow. 
 
86 HOW TO DESIGN THE LINES OF A SHIP. 
 
 The first of these sections is to carry extremely little cargo, to 
 have little room, but to go as fast as she cau be made to go with 
 all the sail and steam power she can carry. These are the 
 practical conditions of the yacht — the swift cruizer — the opinm 
 trader — or the privateer. What such a vessel requires can be 
 readily contrived — for the conditions given, make the midship 
 section, and leave not much to choice. 
 
 Such a vessel must be all shoulder -and keel, and nothing else; 
 she is like a race horse, lanky and leggy : by being all shoulder, 
 with very little under-water body to carry, she will possess the 
 maximum of power with the raiiiinmm of weight — her fault will 
 be, that she must have an enormous keel — to prevent her iff'om 
 '^ going to leeward ; and this great mass of dead-wood or solid 
 keel, exposes -a large surface to the adhesion and friction of 
 the water. Nevertheless, it is the form of greatest power with 
 the least weight. The bottom of this midship section may be 
 formed in two ways — it may either be made elliptical, to have a 
 minimum of skin for adhesion, and be recompiled to this deep 
 keel, by two hollow curves; or it may be reconciled to the keel 
 by a long wedge bottom. The elliptical bottom is thought best 
 for iron ships ; but the other or peg-top Fhape has been much 
 For medium used in woodc'u 0]\es. Next, suppose that the capacity thus 
 
 fluaiitios. gQ.(;^ jg ^QQ small for carrying renninerativc cargo, and that a 
 
 cargo hold of a capacity mor(! usual i)i jnercajitile vessels is re- 
 quired ; in that case keep the same shoulders, and give 'a larger 
 under-water body. 
 
 For weight. Now take a third design. The ship is to carry as much as is 
 
 not inconsistent with good sea-goijig qualities; a]\d she is to 
 have room also for boilers and macliincvy of con^i(lerable pow- 
 er. This requires her sides to be nearly upright, her Tiottom 
 dead flat amidships, with only so much off her bilges, as will 
 not be inconsistejit with what she is to receive inside This the 
 form and arrangen:ient of her boilers and machincfry will gener- 
 ally determi]^e, and the boilers and mathiuery in such a vessel 
 should be treated as hallasi and kept Joia. 
 
 th^Tre^for f ^° regard to these three midship sections, it is to be noticed, 
 ■ that they are prescribed in some measure ])y the uses of the ship; 
 but the forms mentioned, come entii-ely from the judgment of 
 the constructor, and whether they have been wisely or injudici- 
 ously selected, must be judged of after the calculations have been 
 made of the various qualities, to which they give rise. 
 
 But there are one or two points, which occur to a constructor, 
 at the first glance at these forms of undcr-Avater body. It is 
 plain, the first is easiest, and the last hardest to drive. It would 
 require much more sail (or power) to drive the two last than the 
 first. 
 
 And it is equally plain, that the first is much better able to 
 carry sail than the last. The aresi of midship section of under- 
 water body is the thing to be driven; the area of the sail is the 
 driving power: but the power of the shoulders to carry the sail 
 upright, limits the quantity of sail the ship can carry. The bulk 
 of the under-water body brings with it two evils — resistance to 
 being driven through the water, and under-water buoyancy tend- 
 ing to upset the ship. 
 
HOW TO DESIGN THE LINES OP A SHIP. 87 
 
 It is plain, from these considerations, that the first shape is 
 suited for a fast ship under sail aloue — the last is suited for a 
 fast ship under steam alone, and the second form may do for a 
 moderate quantity of both, or what is known as "the mixed sys- 
 tem." 
 
 Of these three vessels, the following will probably be an ap- 
 proximation to their qualities. 
 
 The first will be powerful, wcatherly, lively and fast. The 
 last will be tei\der, easy, sluggish and; roomy. By a proper 
 medium may be obtained, in the second vessel, any compromise 
 of l^ese qualities which may be fancied. 
 
 Nothing has yet been said about the parts of midship section 
 above water; but it will be noticed, that these grow naturally 
 out of the form adopteil ujuler-water; and it will be ob- 
 served, that the above water body should lie proportioned to the 
 under-water body. The objeqj of this, is, to give adeiiuate lift- 
 ing power in a seaway, in itroportiou to the heavier under-wa- 
 ter body. 
 
 In the three designs, the midship section (a technical term) is 
 far from being actually amidslups, beijig placed at the point of 
 greatest breadth, or nearer the stern than the bow, in the pro- 
 portion of 4 to G. 
 
 (2.) Tn construct the chief ' mater-line. 
 
 For the side view of a ship, or vertical section, draw a hori- construction 
 zontal line, representing her wliole length at the main water- '^"='''" 
 line, and erect at the end of it two perpendiculars. This line is 
 called "the length of the sJiiii, the length between perpendicu- 
 lars, or the construction length." These perpendiculars are to 
 be ruling elements of construction, and are called "the perpen- 
 diculars." 
 
 Divide the length between them into ten equal parts ; take 
 four of these abaft for the length of the "run," and six of these 
 forward for the length of the "en/ raftce." l>escribe a semi-circle 
 on each half for the chief breadth. Divide the length of en- trance, how Ae^ 
 trance and this semi-circle into any (and the same) number of ^'="'"'*- 
 equal parts; the distance of the water-line from the centre line, 
 opposite each division in length of the entrance, will be the dis- 
 tance of each corresponding division of the semi-circle, from the 
 same centre line, and a line through all the points thus found, 
 will be the true wave water-line of the bow. The water-line of wave stern, 
 the run 'jvill be diiferent from this in one respect only — it will be 
 necessary to draw parallel linos to the centre line, through each 
 of these divisions of the semi-circle, which it may be convenient 
 to call "the semi-circle of construction." On each of these lines, 
 points may be found, just as if it were a bow line. These lines 
 must be prolonged aft, beyond the points thus found, to a dis- 
 tance equal to that part of the line intercepted between the 
 semi-circle of construction and the main breadth. The last found 
 »points in the parallel lines, give the line of main breadth. 
 
 The chief water-line of the bow and of the stern, or the lines Modiacation' 
 of entrance, and of run for the greatest speed which the given °tem^Md''"tern-' 
 length will admit, are thus formed. The lines thus given are p"^'- 
 absolute, and will adm^t of no deviation, without some loss: 
 
83 
 
 HOW TO DESIGN THE LINE8 OF A SHIP. 
 
 For 
 trim. 
 
 Slleer plan. 
 
 Stem. 
 
 Xcvcrthcless, some modification in the arpplication of these lineg, 
 may be admitted as expedient, and one of them is obvious. 
 
 It will be seen, that the point of the bow is SCTeStremely sharp,- 
 that it -would be in continual danger of cutting everything that 
 it touched, and being so fine, would run risk of being crushed by 
 rough usage. The stem also, for the rough work of a ship, must 
 be of considerable thickness, and the practical question is: How 
 can the line at the bow be altered to get this thickness? Shall 
 the fine part be cut off, and thus shorten the vessel? If so, she 
 will be too short for the length determined on. 
 
 The answer to the question is: Draw the bow to a few feet 
 longer than it is intended the ship shall be — then cut off this 
 water-line to the length it is intended to keep. The result ob-' 
 tained, is a thickness of a foAv inches, remaining between the 
 tAvo sides of the Avater-linc, which is just thick enough for the 
 materials of the stem. Bj' this means, is obtained the extreme 
 length required, and also the ^rength of stem necessary for 
 durability, and it will also be observecl, that the bow thus gained, 
 is of slightly greater capacity than the first attenuated line. 
 This is, therefore, called "the corrected water-line of the bow." 
 Xo such adjustment is necessary at the stern. It is enough 
 there to insert the stern-post, simply by increasing the breadth 
 between the lines, to admit the thickness of the stern-post — & 
 deviation insufficient to cause a sensible difference in the per- 
 formance of the .ship. 
 ir There is another modification of these water-lines of the fore 
 and after bodies, which ma}^ require further consideration. Both 
 entrance and run have been put in the same plane, with the in- 
 tention of leaving them so in the construction of the ship ; but it 
 may be necessary afterwards for some good reason to change it. 
 
 The Constructor must be prepared to do so. The main water- 
 line may require to go lower or higher in the vessel than is now 
 proposed, and the after part of it may have to go higher or lower 
 than the fore part, in order to gain some advantage ; but this 
 change maj- be effected, if necessary, without in any way alter- 
 ing the character of the line already drawn, it is only necessarj^ 
 to alter the height at which it should be placed, and not even 
 that, unless required. 
 
 (3). The Sheer Plan. 
 
 This gives the entire outline of the ship as we look at her 
 sideways. The top line, or upper boundary, is the line of her 
 deck or bulwark, or in short, the top of the ship, which'must be 
 laid down in order to construct the chief buttock-line in section 
 (4); the bottom is the line of her keel, the front is the line of her 
 stem or cut-water, and the after part is the line of her stern- 
 post 
 
 Begin with the stem:— Make that line follow the form of the 
 chief buttock-line and gradually grow out of it. This ought to 
 be so, because buttock-lines bound equal thickness of the ship^ 
 and a stem is merely a thin slice of the ship, and therefore, fol-* 
 lows one of the buttock-lines. As a matter of beauty and of 
 reason, therefore, it must be made a buttock-line in order that the 
 outline may harmonise with the general form. 
 
HOW TO DESIGN THE LINES OF A SHIP. 89 
 
 The form of the stem, therefore, will depend on the decision 
 taken with regard to the deck-line, and the buttock-line. If the 
 deck-line be kept well aft, so that the main buttock-line tumbles 
 home, the stem above the water will be curved backwards, and 
 so be in unison with the tumble home bow, and it will be the 
 contrary if the clipper bow be adopted. Above the water, however, 
 the mere form of the stem itself is a matter, to some extent, of 
 taste or fancy. If the general character of the bow give good 
 buttock-lines, it will not matter much whether the stem to which 
 they are joined curve out or in, except that it will always be 
 better for the stem to harmonize with the character of the bow 
 of which it forms the conspicuous outline. Some constructors 
 hesitate to give it a decided character, and express their imbe- 
 cility by leaving it perpendicular. 
 
 Below the water, on the contrary, the form of the bow is of Rpundins off 
 the greatest practical value. It has been the custom to carry 
 the stem down to an angle with the keel, to continue the keel 
 forward to meet the stem, and so form what is called "the fore- 
 foot" of the ship, giving it a great gripe, or hold of the water. 
 This gripe and fore-foot have every bad quality, being weak in 
 structure, and making the vessel hard to steer. It is thought 
 better to cut it all off, following the shape of the other buttock- 
 lines ; and further Vb carry this rounding a great way back, say 
 to one-sixth of the whole length of the ship. 
 
 By this, not only does the Constructor diminish the fore gripe 
 and ease the steerage, but the stem and fore-foot is kept out of 
 harm's way; and this has been known to save repairs and con- 
 tribute to the safety of the ship. When turning in narrow chan- 
 nels, when steering in intricate or shallow waters, or performing 
 evolutions under difficult circumstances, the fact that there is no 
 thin, protruding part near the bottom to touch the ground, to be 
 broken off, or to impede or alter the movement or direction of 
 the vessel, is often of great consequence. 
 
 By a gentle curve at the stem, therefore, the fore-keel and 
 fore-foot are kept out of harms way, and the same may generally 
 be done at the stem, where dead-wood can be spared. By curv- 
 ing the after part of the keel upwards, like the stem, both keel 
 and rudder are often saved and the ability to turn the ship cer- 
 tainly facilitated ; of course it is done to a much less extent at 
 the stem, as several feet of gripe at the bow will correspond , 
 with a few inches of trim by the stem. 
 
 But, though the keel and fore-foot are thus curved, the whole Middle put of 
 central part of the keel should be kept perfectly straight, for no B^aigit. ° °'" 
 other purpose -than to be able to support the middle of the ship 
 on blocks in the dock. This is obviously necessary, since other- 
 wise the keel would rest merely on points, instead of being 
 uniformly supported; and in the dock it is rather an advantage * 
 that the two ends of the ship should not be borne by the bloc&, 
 imless they require special repairs, when they can be then prop- 
 ped up, as may be needful. 
 
 It is not necessary that the keel should be parallel to the Trim, 
 water-line, except where there is a nan'ow limit to the extreme 
 
 12 
 
ao 
 
 HOW TO DESIGN THE LINES OF A SHIP. 
 
 draft of water, in which case, the keel should be parallel to the 
 load water-line; in most other "cases it should incline downwards 
 at the stern, so as t.o draw more water abaft than forward. 
 
 In the case of screw steamers of great power, it is a necessity 
 to have this draft, in order to get' the screw sufficiently large aod 
 sufficiently under water for effective power; and further, it is 
 convenient in sailing vessels, to be able to carry a large sail area 
 on the after part of the ship, for which greater depth of keel aft 
 than forward, affords the necessary facility. It is convenient, 
 frequently, for the same purposes, that a vessel when light, 
 should draw very much more water aft than forward, and that 
 her lading should bring her down gradually to\,an even keel. 
 This greater draft aft than forward, is usually called "the differ- 
 ence of the ship," and it is reckoned a main element in her trim, 
 
 Eake of tke Another element of the sheer plan is the rake of th'e stem-post, 
 
 stiTn-post. £^jj^ great license is allowed here. The Constructor may have? 
 
 the stern-post straight up and down, so as to make the rudder 
 
 ^ pivot fairly, or he may incline the head of the rudder back behind 
 
 the perpendicular at an angle, or he may incline the heel of the 
 rudder forward of the perpendicular; indeed, he may make the 
 line of the rudder cross the perpendicular at any angle he may 
 choose. In the first case, he will maintain the balance of his 
 original draught. In the second case, he will extend the dead-- 
 wood and increase the lateral resistance to leewardliness. In 
 the third case, he will decrease the lateral resistance, but increase 
 handiness.. In every intermediate degree between- these two, he 
 will gain one of these qualities at the sacrifice of the other. 
 
 Kudder. The effect of this inclination on the rudder itself must not be 
 
 forgotten. The inclination of a rudder increases its power to 
 turn the ship, but it also increases the resistance which the ap' 
 plication of rudder offers in every degree to the progress of the 
 ship through the water. %he action of the rudder; as has been 
 already stated, is of the nature of a hindrance to one side of the' 
 ship, so as to allow the other side to go forward at greater speed 
 thus turning the ship; but the inclination of the rudder-post has 
 a double effect, by which, when the rudder is held over, not only 
 is one side of the ship hindered, but a certain quantity of the 
 water which strikes the rudder is diverted upwards, as well as 
 to on'e side. Nevertheless, a certain amount of rake should be 
 given where very great power of rudder is needed. 
 
 Counter. Next comes the question of rake of counter, and rake of stem. 
 
 It is thought best to allow the buttock-lines to decide the rake 
 of the counter, so that when the stern is deep in the water, the 
 counter may be a continuation of the true form of the ship and 
 of her lines. A good counter of this sort, will help the ship ' 
 instead of hindering it, when the stern happens to be buried in 
 • the waves. As to rake of stern, it seems to be a matter of fancy, 
 especially in this country. It is better that the stern should 
 rake outwards, rather than it should tumble home. 
 
 Sheer. T^e upper boundary line, which appears tO' finish the ship, is 
 
 called "the sheer-line," and this, also, is a mere matter of taste, 
 though some points of it have more or less reason. In looking 
 at a ship which has little sheer, she is apt to have the appearance, 
 contrary to the truth, of being rounded down, that is to sav, as- 
 
HOW TO DESIGX THE LIXES OF A SHIP. 1)1 
 
 if drooped at the ends. Xow this is universally agreed to be so 
 ' ugly, that a considerable sheer at the bow and somewhat less 
 at the stern, are necessary to counteract it. Experience gives 
 for a vessel of 200 feet length, a sheer or rise of about 2 feet at 
 the bo\y and about 8 inches at the stern. But this is frequently 
 exceeded. 
 
 So much for the quantity of sheer. The quality of it depends ^ow drawn'"'" 
 on the exact curve which may be adopted. A parabola is deemed 
 best for the sheer curve, and to trace it, proceed as follows: — 
 Dividing the vessel into ten equal parts, six forward and four 
 abaft, rise forward successively 1, 4, 9, 16, 25 and 36 inches, 
 and abaft 1-2, 2, 4 1-2, and 8 inches. This gives a total spring 
 of 3 feet forward, ana of 8 inches aft, and makes the bow 28 
 inches higher out of the water than the stern. This proportion 
 will serve for vessels over 200 feet in length ; but for smaller 
 ones it would be an excess. Nevertheless, it is to be observed, 
 that even in very small vessels, especially when low on the 
 water, a considerable sheer forward is useful to keep them dry. 
 The sheer line is important in its structure thus far, that it is 
 usual to make the planking of the upper part of the ship, the 
 line of the ports, and the line of the decks, follow the line of 
 sheer, though it is sometimes convenient to deviate from this 
 usual rule, and to make the decks follow any line that may be 
 convenient for the internal aiTangements. 
 
 For example: when a large and room}'' forecastle is needed. The sheer line 
 without deforming the ship by raising the forecastle above the need notniTe^c- 
 bulwarks, it can be obtained by running the line of the deck {H^' c"ii^t""^- 
 straight forward, on .the level, and so following the level of the 
 water-line instead of the sheer of the rail ; in this way, the height 
 of the top of the bulwark above the deck, which amidships might 
 be 5 feet, might be 8 feet at the stem, and there is no practical 
 . inconvenience from this, which is not more than compensated 
 . for by strength and usefulness. 
 
 (4.) To Construct the Chief Vertwal Longitudinal Section 
 or Buttock-line. 
 
 In the construction of this line, there is much room for judg- chief buttock 
 ment; for though it does not possess such properties of its own ''°^' 
 as the water-line and midship section, it has the power of either 
 increasing the good qualities or aggravating the evils which the 
 ship will derive from those two primary lines. It is only second- 
 ary in importance to these, because by its means all the possible 
 good springing from the others may be favorably developed, 
 marred or neutralized. It happens, also, that this has not here- 
 tofore received the attention it deserves ; in many designs it is 
 not even to be found. It is believed that its good qualities tend 
 materially to the ease, dryness, comfort and safety of sea-going 
 ships. Inland vessels may afford to neglect it, but a practiced 
 eye can detect in the faults of this line almost instantaneously 
 the bad sea^going qualities of a defective design. 
 
 The chief buttock-line should be placed in a vertical plane What it is. 
 parallel to the plane of the keel and the perpendiculars or cen- 
 tral plane of the ship, and at one-fourth of her breadth from the 
 plane on both sides. 
 
92 
 
 HOW TO DESIGN THE LINES OF A SHIP. 
 
 Depends 
 the cycloid. 
 
 How drawn. 
 
 1 In ordinary ships this line will be found to bo of a most vari- 
 able, vague and nondescript character. The wave theory adopts 
 for it the vertical line of a sea wave, and it is thought that its 
 conformity to that shape has everything to do with the ease of 
 the vessel at sea. The vertical section of the common sea wave 
 is the common cycloid. This must be elongated for a long, low 
 vessel, and compressed for a short one. Three points through 
 which it must pass, have already been determined by the mid- 
 ship section, and by the water-line, because, as this line is dis- 
 tant from the centre one-fourth part of the breadth, it must cross 
 those three lines where they cross this vertical plane. These 
 three points are the only ones which do not admit of a free choice, 
 and it remains a part of the skill of thd Constructor to adopt 
 such a cycloid as may consist with his general design and with 
 the use of the ship. " Each of the three midship sections given, 
 places the bottom of 'the buttock-line at a different depth under 
 water, and each of the three requiwis a different cycloidal line to 
 fit it. The nature of this cycloidal line has been long Imown to 
 mathematicians as the only line in which a pendulum can so 
 swing that its vibrations, whatever their extent, shall be equal- 
 timed. There is a remarkable analogy between the swing of a 
 pendulum and the roll of a ship ; there is an equally strong re- 
 semblance between the forces which exist in a wave and the 
 forces which act on a pendulum; the mathematics of a wave and 
 of a cycloidal penduAim are nearly identical. 
 
 When, therefore, it was discovered that the forces which 
 replace the water in the run of a ship are of tlie same nature aa 
 the forces actuating a wind wave at sea in the vertical position, 
 by this discovery came the key to the vertical lines of the after- 
 body of the ship ; so the vertical lines of the fore-body were con- 
 trived, in the belief that wind waves coming into collisioii with 
 a body already perfectly fitted to the form which they themselves 
 take in undulating, unresisted free motion, would not be broken, 
 but would have free way, and that they would glide as smoothly 
 over the face of a solid cycloid as the layers of the same wave 
 glide over one another. 
 
 When, by experiment, the question was referred to the waves, 
 it was proved to be so, and a vertical cycloid thus became the 
 buttock-line of the bow of an easy and dry ship above the water, 
 just as it had already become the easy run of the wave of re- 
 placement in the stern of the ship. 
 
 The chief buttock-line is, therefore, described in the following 
 manner: The after part is formed from a semi-circle, the bottom 
 of which, is at the intersection of the midship section with the 
 vertical plane, and of which the uppermost point is as high out 
 of the water as the Constructor may choose to carry the bulwark. 
 From this describe a cycloid, and cut oft' as much of the cycloid 
 as may be desirable to adapt the portion of the stern beyond the 
 perpendicular, a point which is a matter of room and comfort 
 merely. There is choice as to whether the bow shall much over- 
 hang the water, or rise up pretty square, or tumble home. For 
 a vessel low in the water, the first might be adopted ; but never 
 for a vessel high out of the water. 
 
HOW TO DESIGN THE LINES OP A SHIP. 93 
 
 The tumble homo bow is thought to be the dryest and easiest 
 in a sea ; but there is the vertical cycloid between the two. Each 
 proportion and kind of vessel has its corresponding cycloid. 
 
 (5.) On the Main deck line. 
 
 By the main deck line is meant here the outline of that deck Main deck une. 
 which is meant to be kept in all circumstances well out of the 
 water. It is this which constitutes the chief gun deck of a 
 vessel of war — on which it is necessary, in all ordinary weather, 
 that the ports should be open, without the sea entering. There 
 have been men-of-war in which this .deck was generally under- 
 water, and after long experience, they gained the name of "cof- 
 fins." 
 
 The choice of a deck line, has a great deal to do with the use- the"main"Tec'k 
 fulaess of a ship for its purpose, more even than her behavior at ime. 
 gea. This main or construction deck is, in small vessels, the 
 uppermost or spar deck ; but in larger vessels there is a spar 
 deck above it; in the old three deckers, there were three decks 
 above it, and in the "Great Eastern," there are four decks above 
 it, and four below. As a general rule, also, when a vessel is 
 deeply laden, this deck is an eighth or a tenth of the beam of 
 the ship above the water. 
 
 A little consideration of the purposes of a main deck, will . Proper form of 
 serve to indicate how various its shape may be. In a vessel'' 
 meant to be fast, its point should be like the bow of the ship, 
 fine and sharp, because, if a full bluff deck is put on the top of 
 a fine fast bow, the ship is given the bad quality of pitching in 
 a sea way — ^the fullness of the deck line will also take from the 
 speed — counteracting the very quality intended to be gained by 
 the sharp bow under-water. 
 
 The argument in favor of sharpness, seems inconsistent with 
 a roomy deck forward, which is usually obtained by a broad 
 bell bow, flaring out wide over the water. Such a bow the old 
 school still believe in, and modern constructors would never have 
 succeeded in introducing the fine sharp deck, in opposition to 
 traditional prejudice, had it not been that the full deck line was 
 found fatal to speed. 
 
 There can be no doubt, that in fine weather, a large roomy 
 bow on deck is convenient for doing the work of the ship com- 
 fortably and handily. It is far more convenient in the man-of- 
 war, than in the merchant ship, since in chasing, it is desirable 
 to work two long chase guns through the bow ports, clear of 
 everything, and to work them well in that position. It has been 
 pretended, that it was impossible to do this on a sharp fine deck 
 line, but this has proved a crotchet of the past. 
 
 The simple fact is, that the roominess, dryness, and comfort Roomy bow 
 of a full deck line, instead of a fine one, is mere impression or bluff lines?''""* 
 belief — nothing more. If it is imagined, that a fine bow is got 
 by cutting off so much room from a full bow, and so diminishing 
 the extent of available deck room for working ship — then the 
 fine bow may be considered narrow and confined ; but the prac- 
 tical fact is the contrary of this. The fine deck line of a mod- 
 ern fast ship, is noi got by cutting anything off the length, or 
 off the width, or off the roominess of a deck; the sharp bow is 
 
94 now TO DESIGX THE LINES OF A SHIP. 
 
 obtained by adding on a fine entrance to a bluff one, and by 
 lengthening the deck; the full parts of the ship and of the deck 
 remain where they were. All that is necessary, therefore, is to 
 sec that the working parts of the ship shall, in the fine bow, be 
 kept well aft, iu the broad open space of the deck, and not cram- 
 med forward into the narrow space superadded — which should 
 be kept perfectly clear. It is a further peculiaritj' of the fine 
 bow and deck line, that the foremast stands much farther aft 
 than in the old full bow, and that there is therefore more room 
 forward of the mast; care must, therefore, be taken to keep 
 windlass or capstan, catheads and anchors, and all working parts 
 of the bow, well aft — not for room merely, but also to keep heavy 
 weights out of the extreme bow of the ship, as they are always 
 detrimental. 
 
 There is another way of looking at this matter. It is a good 
 plan to cover in the whole of the fine part of a deck forward, 
 with a light forecastle, bulkheaded off, especially in iron ships. 
 It is a great convenience, and affords good quarters for the crew; 
 it keeps the head light and dry ; while abaft the forecastle, a 
 broad roomy deck is still to be found. There is, however, anoth- 
 er way of giving a roomy deck on a sharp bowed vessel, and it 
 has been tried with success in men-of-war. An extremely fine 
 bow has been made to carry two long 8 inch guns, parallel to the 
 keel, through two wide ports, with ample room all around, to 
 train and work them freely. This was accomplished by shorten- 
 ing the deck, or stopping it very much short of the bow, carry- 
 ing the bulwark round the bow, considerably behind the stem ; 
 the real deck beyond the bulwark forming part of the head, 
 which, instead of being grated and overhanging the sea, had a 
 solid oak deck over the greater part of it, leaving the head as 
 convenient as before. In this way the bulwark of the deck left 
 the real line of the ship 30 feet short of the stem, with a line, 
 round, roomy deck, to delight an officer of the old school, by 
 giving him all he wanted on the inside, without impairing the 
 form which the sea had to have on the outside. 
 Rnoniy deck There is yet another way of placing a full, round, capacious 
 ""mmbiriiomc "^eck line on a fine, hollow^ fast water-line, and yet perfectly 
 bow. reconciling them one to another — so as to form a handsome, 
 
 symmetrical sea going vessel. This is to carry out the tumble 
 home bow — which makes a vessel dry, easy and safe. To carry 
 out this system, it is only necessary to take a tolerably full, 
 easy deck line, composed of two circular, or two parabolic ares, 
 laying them over the water-line, and so far behind it, as to be 
 easily reconciled with it, by means of the cyeloidal buttock-line; 
 a process which will be guided in a great measure, by the point 
 at which the cyeloidal buttock-line, already drawn," meets the 
 level of the deck. 
 
 Arrangement Large, capacious, roomy sterns are part of the wave form, 
 surnf ™ "' ^'^^ though apparently unsightly, give great room with less 
 cost and sacrifice, than any other part of the vessel. A small, 
 handsome, light stern, may be pretty as an eye model, but it is 
 a costly whim. There are no good qualities in a ship which are 
 not improved, and no economy which is not enhanced by a large 
 roomy stern and deck line. In a merchantman, it gives large 
 
HOW TO DESIGN THE LINES OF A SHIP. 
 
 95 
 
 passenger cabins, airy, as well as roomy, and in that part of a 
 ship which pays the owner best. In the ship of war, it gives a 
 fine roomy poop, and plenty of space for working stern guns — 
 which, however, should seldom be required in a Yankee ship of 
 war. But the roominess and fullness of the stern, in the neigh- 
 borhood of the deck line, is the greatest element of safety in that 
 most perilous of positions ; scudding in a heavy gale and sea — and 
 in most cases, may be used with advantage, to embrace the sta- 
 bility and sea going qualities of the vessel. 
 
 The best way to turn the stern to advantage, for room and 
 wholesomeness, is to carry the breadth on deck well aft, to taper 
 the ship in towards the stern but little, and even if necessary, 
 to carry the projection of the stern a good Way abaft, and be- 
 yond the perpendicular, following, however, and not extending 
 beyond the vertical buttock-line already given. Here may be 
 taken a great deal of room from the sea. But then a question square and 
 arises — shall the stern be round or square? The answer is, that J,°"°mre?™* 
 its bulk is the main point; its shape is of less consequence. If, 
 as a matter of taste, the corners are cut off, it becomes a round 
 stern ; nothing, too, is more common than to see constructors 
 cut off the stern inside, and then stick quarter galleries on the 
 outside, to make up for the corners cut off. When little is cut off 
 it is usually called "an elliptical stern," although it never is an 
 ellipse; and when much is cut off, it is called "round," though it 
 never is circular. So far as the qualities of the ship are con- 
 cerned, the precise outline of the deck astern is of little impor-- 
 tance. 
 
 The constructor is now prepared to adopt a definite form fof summafyv 
 his deck line, which is plainly a compound affair of policy and 
 taste. For a trial line, it is thought best to use forward two 
 arcs of a circle, intersecting at the bow, and having their centres 
 on a line drawn athwartship, half way between the peqiendicu- 
 lars; thence inclining by two parabolic arcs, gradually narrowing 
 to the breadth of the intended stern; and for that breadth, the 
 constructor should adopt, at the point where it passes the per- 
 pendicular, some specific proportion — 6, "I or 8 tenths of the 
 midship breadth ; finishing with whatever straight line or curve 
 may have been determined on, as regards room at thei stem. 
 Indeed, in a vessel of no great length, and without much overhang- 
 ing counter, no harm is likely to arise from carrying the full 
 breadth of the deck amidships right aft to the stem, with merely 
 sufficient curvature to give an agreeable line. 
 
 The completion of the design now reqjiires that these four 
 ruling lines be reconciled with one another. In this operation, 
 what the constructor must keep mainly in view, is to extend as 
 far as possible, through all the remaining lines of the ship, the 
 good qualities which have been established in the ruling lines. 
 
 (6.) To Construct the Remaining Water-lines. 
 
 It is most desirable that the water-lines of the entrance should secondary . 
 be as exactly as possible of the same form, on reduced breadtb, fore"ody!'^ "^ 
 as the main water-line. There will be some difiBculty in doing 
 this, especially near the keel; and the tendency of these lines 
 will be to elongate themselves forward. This is to be avoided. 
 The remaining water-lines of the after body arc to Ije construct- or after iwdy. 
 
ye HOW TO DESIGN THE LINES OF A SHIP. 
 
 ed on nearly an opposite principal. They are to deviate rapidly 
 from the chief water-line of the after-body ah-eady drawn; and 
 this they will do naturally, because the main buttock-line which 
 rules the after-body, compels the water-lines to increase rapidly 
 in fineness as they go down in the water, and to extend rapidly 
 in fullness as they rise to the surface; thus giving what is be- 
 lieved to be the best kind of stern, namely, very fine below, and 
 very full above. 
 
 In this respect it is a contrast to the bow, which is kept as 
 full as- may be, consistently with the chief water-line all the way 
 down.* It is desirable to have at least three complete water- 
 lines, in order to form a first approximation to the complete cal- 
 culation of the ship. 
 
 (1.) On the Completion of the Vertical Gross Sections or 
 Body Plan. 
 
 crosTsectfSIia. The cross sections are all to be regarded as midship sections 
 modified, but each of them giving to the part of the ship where 
 it lies, qualities which either enhance the good qualities of the 
 midship section or impair them. 
 
 A vessel with a fine, powerful midship section, may easily be 
 impaired by weak extremities, and a weak midship section may 
 be reinforced by good cross sections, especially in the after-body. 
 
 What the designer has to bear in mind, then, is to study how 
 far he can enhance, support, and carry out the qualities of the 
 main midship section in the rest of the body. In this he will be 
 materially aided by the choice which he makes of that cross sec- 
 tion which passes through the after perpendicular. To this 
 frame, being absolutely out of the water, he may give any shape 
 he pleases ; and having fixed this, he will find, that with the 
 main buttock-line it rules the entire form of the after«body, and 
 also controls materially the surface of the water-line of the stern. 
 It is this stern cross section which should be made very full, in 
 order to turn the after-body to the best possible account. But 
 this fullness must not be abrupt; otherwise, when rising and 
 falling in the sea, the counter may at times strike the water with 
 violence. 
 
 The circumstance, that this portion of the vessel remains so 
 entirely subject to the will of the designer, makes it, for the in- 
 experienced, the most difficult to decide and determine; and a 
 greater variety of forms will be found in the region of the stern 
 above water than in any other part of a ship. 
 
 General fnrm '^^^ Vertical scctions of the aftcr-body followed out in the 
 nf cross sectfmis manner indicated, will be found, as they approach the stern, to 
 of after-body, jj^^g become very fine below and very full above, and so they 
 they, should be; but in the bow, there will generally be found a 
 similar tendency of the lines to become extremely fine below, 
 and to grow full above, and there it is necessary to counteract 
 this tendency instead of encouraging it, as abaft. The bow 
 cross sections must, therefore, be made to maintain their full 
 breadth well down toward the keel, and they must not spread 
 out too rapidly at the surface of the water and above it. 
 
 * This— to make it watcr-borite. 
 
HOW TO DESIGN THE LINES OP A SHIP. 97 
 
 The reason why the faUness should be preserved below is, 
 that it is the business of the fine part of the bow, or cutwater, 
 to displace or reipove the water out of the way of that part of 
 the ship which is to follow ; and if the bow part be cut away too 
 fine, this work will not be done, and the part behind will still 
 have the work of displacement, with a blufijer entrance, and a 
 shorter time to do it in, which is the same as to say, that it 
 would then require unnecessary force, by causing unnecessary 
 resistance. The main water-line having, therefore, already ren- 
 dered the bow sufficiently fine for the service of dividing the 
 water, care must be taken not to carry this fineness farther than 
 necessar\-, or than it is carried in the chief water-line. 
 
 Much care will be needed to prevent the cross sections of the. caution, 
 bow from flaring out very much, to meet the line of the upper 
 deck. To avoid this, keep that line fine and throw it as far back- 
 wards from the fore perpendicular as conveniently practicable. 
 The cycloidal buttock-line, properly used, will help to throw the 
 deck back, and to prevent it from spreading over the fine bow ; 
 nevertheless, it will always be difficult to reconcile the wave 
 water-line, the full deck, and the cycloidal buttock-line; but 
 when it is well done, it makes the most beautiful as well as the 
 best of all sea bows. For fresh water bows, it does not matter 
 how much the deck flares out, or how much it overhangs the 
 water; it is in the sea that the true skill of the accomplished 
 Architect is to be developed. 
 
 It is not the best voyage in fine weather, but the best behavior 
 in bad weather, which gives reputation to the truly seaworthy 
 ship. 
 
 Length of Entrance asb Run. 
 There is no principle given by the wave method of construe- Fiied propor- 
 tion more important than the following: That there is a fixed "^° d' '""^ '° 
 proportion between the speed for which a ship is to be designr 
 ed, and the length of entrance and run which must be given 
 to her, in order to fit her for that speed. 
 
 The importance of obtaining such definite proportions has long 
 been felt by practical men. It was known that it was very 
 difficult, by any amount of power, to push vessels of certain 
 length and shape through the water at high velocity. Power 
 and money were wasted in vain attempts to make ships of un- 
 suitable dimensions attain high speed. Yessels were filled with 
 boilers and machinery, designed to compel the performance of 
 high velocity. Instances are known, where a double amount of 
 steam l)oiler had been provided to compel high speed in an un- 
 suitable vessel, and afterwards, these boilers had to be removed, 
 the higher speed being found impossible in that kind of ship, 
 and the highest speed of which the ship was capable, was after- 
 wards brought out with half the power. The wave principle 
 has produced the proportions in the table on page 99 of this chap- 
 ter, the cause which fixes these proportions being obvious. The 
 length of the fore body of a ship designed on the wave principle. Proportion of 
 must be the same as the length of the wave of the first order, '^stutosp-cd. 
 which moves with that speed. The length of the after body, 
 must be the same as the length of the front face of the wave of 
 the second order, movinjr \vith that velocity. 
 o 
 
98 HOW TO DESIGN THE LINES OF A SHIP. 
 
 Breadth may The wave System destroys the old idea of any proportion of 
 lenlth?*"*"" '° breadth to length being required for speed. An absolute length 
 is required for the entrance and run ; but these(|3_eing formed in 
 accordance with the wave principle for any given speed, the 
 breadth may have any proportion to that, which the uses of the 
 ship and the intentions of the Constructor require. A vessel 
 meant to go ten knots can be efficiently propelled at that speed, 
 if her length and form be right, whether she be 3 feet beam or 
 30 feet. 
 
 Cautions in Designing Wave "Vessels. 
 In designing wave vessels, it is necessary, therefore, to dis- 
 tinguish carefully three great elements of construction, viz : The 
 fore body, the after body and the middle body. The lengths 
 of the fore body and after body are indicated by the required 
 speed, and if the beam is fixed, it is only by means of a due 
 length of middle body that the required capacity, stability and 
 such other qualities are .to be given as will make the ship as a 
 whole, suit its use. Middle body is, therefore, an element de- 
 manding the careful study of the designer on the wave system, 
 and it will well reward his pains. 
 Caution against It only remains to notice the errors sometimes committed by 
 wavTsysiem.' " the novice when designing vessels on the wave system. Find- 
 ing that a hollow water-line is admissable, he rushes to the 
 extreme and makes it too hollow, and gets increased resistance ; 
 or that a fine, long entrance is good, he makes it too long, and 
 gets increased surface ; or that a full after body is admissable, 
 he makes it too full, and spoils the steering qualities of the 
 vessel. I 
 
 On the other hand, instead of going too far, he may stop short 
 too soon. When the water-line near the bow is made fine, and 
 the deck allowed to remain full, the end of the ship is overloaded, 
 and so the value of carrying weights in the centre is sacrificed 
 to a custom. It is most unwise not to reduce the weight and 
 bulk carried out of the water. No error is more common than 
 to give wave line vessels greater fineness than is required for 
 the special case, to the sacrifice of the carrying qualities of the 
 ship. The best way of avoiding these errors is, for the designer 
 not to adopt the system too hurriedly, nor introduce it too large- 
 ly into his first construction. Let him take the lines of a ship 
 he has already built and only alter them in a small degree on 
 the wave principle. He will find out thus, how far he has made 
 an improvement, and how far he has altered the ship's practical 
 points. Next time, he may make a further change in the same 
 direction, thus avoiding the error of rushing to an extreme, than 
 which, there is nothing more fatal to the success of a new method. 
 A ship all ends, with no middle, all top, with no bottom, all 
 dead wood with no capacity, is precisely one of those caricatures 
 of the wave principle, of which the world has seen a great many 
 misnamed "Clippers," in which the true purposes and uses of a 
 ship have been lost sight of, in the attempt to gain great speed 
 at the expense of every quality which makes speed desirable. 
 Praoiicai use To guard against such errors, let it never be forgotten, that 
 fn°view. * *'" the end of all ship building is to work out the purposes of the 
 owner. A ship of war has to fight, and a merchantman to carry 
 
HOW TO DESIGN THE LINES OF A SHIP. 
 
 99 
 
 cargo. To build a man-of-war which cannot fight her battery, 
 is a much greater fault than to make her slow. To build a mer- 
 chant vessel so as to have great speed at great cost, without the 
 capacity necessary to repay the owner his outRiy, is folly. — 
 Freight is the owner's object, and to earn the greatest freight, 
 is the problem submitted to the Constructor. To this object the 
 wave principle, well understo^, gives a safe and certain guide. 
 When the speed wanted for the trade is known, the wave prin- 
 ciple gives the length of entrance and run to obtain that 
 speed. When the cargo to be carried is known, the Constructor 
 can say what buoyancy he needs, and what length of middle- 
 body will carry the bulk and weight. When the draft of water 
 is given, he is ready to decide what form of midship section wilj 
 give the stiffness and weatherliness needed. When he knows 
 the weights to be carried and the bulk to be stowed, he must 
 take care that he carries them where they are supported by the 
 water, and not where, being unsupported, they weaken the ship 
 and increase its strains. If he thus keeps the uses of his ship 
 steadily in view, he will find the principles of the wave system a 
 safe guide to enable him to give his design those qualities with- 
 out a sacrifice of those other qualities which can alone enable a 
 ship owner or a Government to avail themselves of his science 
 and skill. 
 
 A Table of Proportions of Bow and Stern for Wave line 
 Ships, designed for a given Speed. 
 
 Length of Entrance and Bun. 
 
 Statuta 
 
 Length of 
 
 Length of 
 
 Statute 
 
 Length of 
 
 Length of 
 
 miles 
 
 entrance. 
 
 run. 
 
 miles 
 
 entrance. 
 
 run. 
 
 pr. hour. 
 
 Feet. 
 
 Feet. 
 
 pr. hour. 
 
 Feet. 
 
 Feet. 
 
 1 
 
 .42 
 
 .3 
 
 11 
 
 50.82 
 
 36.3 
 
 2 
 
 1.68 
 
 1.2 
 
 .12 
 
 60.48 
 
 43.2 
 
 3 
 
 3.T8 
 
 2.7 
 
 13 
 
 70.98 
 
 50.7 
 
 4 
 
 6.72 
 
 4.8 
 
 14 
 
 82.32 
 
 58.8 
 
 5 
 
 10.50 
 
 T.5 
 
 15 
 
 94.50 
 
 67.5 
 
 6 
 
 15.12 
 
 10.8 
 
 16 
 
 107.52 
 
 76.8 
 
 1 
 
 20.58 
 
 14.7 
 
 17 
 
 121.38 
 
 86.7 
 
 8 
 
 26.88 
 
 19.2 
 
 18 
 
 136.08 
 
 97.2 
 
 9 
 
 34.02 
 
 20.5 
 
 19 
 
 151.62 
 
 108.3 
 
 10 
 
 42.00 
 
 30.0 
 
 20 
 
 168.00 
 
 120.0 
 
 The lengths increase as the square of the velocities. 
 
100 
 
 HOW TO DESIGN THE LINES OF A SHIP. 
 
 Table of direct head resistance at different speeds on each 
 
 square foot of a ship^s way. 
 Power required to propel a flat fronted vessel through the 
 
 water. 
 
 Speed. 
 
 Speed. 
 
 Prdjjelling force 
 
 Propelling horse- 
 
 
 
 in pounds to 
 
 power. 
 
 
 
 Knots an 
 
 Eeet a second. 
 
 the square ft. 
 
 
 hour. 
 
 
 
 
 1 
 
 1.68889 
 
 2.85235 
 
 0.00876 
 
 2 
 
 3.37118 
 
 11.40938 
 
 0.07007 
 
 3 
 
 5.06667 
 
 25.67111 
 
 0.23649 
 
 4 
 
 6.75556 
 
 45.63754 
 
 0.56056 
 
 5 
 
 8.44444 
 
 71.30865 
 
 1.09484 
 
 G 
 
 10.13333 
 
 102.68445 
 
 1.89188 
 
 T 
 
 11.82222 
 
 139.76495 
 
 3.00424 
 
 8 
 
 13.51111 ■ 
 
 182.55014 
 
 • 4.48446 
 
 9 
 
 15.20000 
 
 231.04003 
 
 6.38511 
 
 10 
 
 16.88889 
 
 285.23460 
 
 8.75872 
 
 11 
 
 18.57778 
 
 345.13387 
 
 11.65786 
 
 12 
 
 20.26667 
 
 410.73780 
 
 15.13506 
 
 13 
 
 21.95556 
 
 482.04647 
 
 19.24290 
 
 14 
 
 23.64444 
 
 559.05980 
 
 24.03392 
 
 15 
 
 25.33338 
 
 641.71785 
 
 29.56068 
 
 16 
 
 27.02222 
 
 730.2005-6 
 
 36.34868 
 
 17 
 
 28.71111 
 
 824.32799 
 
 43.03160 
 
 18 
 
 30.40000 
 
 924.16012 
 
 51.08086 
 
 19 
 
 32.08889 
 
 1029.69691 
 
 60.07607 
 
 20 
 
 33.77778 
 
 1140.93840 
 
 70.06976 
 
 Resistance varies as the square of the velocity. 
 
 Table showing the comparative areas of water-way, resistance, 
 and carrying power to he obtained by different dimensions 
 under same shape. 
 
 Elements of first cost. 
 
 Working cost. 
 
 Remunerative work. 
 
 Breadth. 
 
 Draft. 
 
 Length. 
 
 Resistance or 
 water-way. 
 
 Floating weight or 
 tonnage. 
 
 12 
 
 6 
 
 72 
 
 60 
 
 100 
 
 18 
 
 9 
 
 108 
 
 135 
 
 337 
 
 24 
 
 12 
 
 144 
 
 240 
 
 800 
 
 30 
 
 15 
 
 180- 
 
 375 
 
 1,500 
 
 36 
 
 18 
 
 216 
 
 540 
 
 5,400 > 
 
 42 
 
 21 
 
 252 
 
 735 
 
 8,575 
 
 48 
 
 24 
 
 288 
 
 960 
 
 12,800 
 
 54 
 
 27 
 
 324 
 
 1215 
 
 18,125 
 
 60 
 
 27 
 
 360 
 
 1350 
 
 22,500 
 
 66 
 
 27 
 
 396 
 
 1405 
 
 27,125 
 
 72 
 
 27 , 
 
 432 
 
 1620 
 
 32,400 
 
FIRST APrEOXIMATE CALCULATION OF DESIGN. 101 
 
 CHAPTER XXII. 
 
 OX THE FIBST APPHOXnrjTE CALCULATIOX 
 OF A DESIGX. 
 I. Area of 2Iid)>hip Section Immc)-f:cd. 
 The area of the midship soetion furnishes the chief measure ajc" ^m^' 
 of resistance of the ship. The midship section is her fullest pai-t, L"vium. "" '^ "'' 
 and* the resistance being mensui-od by it, it is plain that the pro- 
 pelling power must be duly proportioned to it, and that each foot 
 of cross section will require a given number of pounds of force 
 to drive it through the water at a given speed. Thus, if one 
 foot of midship section should require .30 lbs. of force to drive it 
 through the water at the rate of 10 miles the hour, this 30 lbs. 
 must be supplied either by horse jiower, engine power, or sail 
 power. It is plain that for ea^h unit of section must be found 
 a corresponding unit of propelling power. Say the area of the 
 midship section is to contain 100 square feet, the first element 
 then to be written down is 
 
 Area = 100 feet. 
 
 II. Surface of Skin Immersed. 
 
 The skin of a ship might be thought to be so perfectly smooth ^Vct sUn. 
 sind water so limpid as to slip from it, but such smoothness is 
 imaginary, and water adheres. For a short race, boats are 
 lubricated with grease, or polished with black lead, and ingeni- 
 ous mechanics have invented a plan for iron ships, of blowing a 
 film of air between the skin and the water, to cut off the adhesion 
 of the water. The reason why copper has been introduced is, 
 that from a peculiar quality of that metal, sensible to the touch, 
 friction is lessened and smoothness gained. This may be prac- 
 tically exemplified by rubbing one's finger over a smooth bright 
 sheet of copper that has been steeped in salt water, it will be 
 found to have the same slippery feeling as the side of a freshly 
 caught sahnon. 
 
 With or without lubrication, it is a feet, that water sticks to 
 the skin of a ship, that the skin drags the water with it, that 
 smoothness and labrication mitigate but do not annihilate it. 
 For wood and copper, this drag is reckoned at a loss of nearly 
 1 lb. of force at 10 knots per hour, and on the surface of a com- 
 mon iron ship, it may be as much as 2 lbs., and this loss increases 
 with the velocity, and in high velocities is an important element 
 not to be omitted. The surface of Skin is, therefore, an element 
 in the calculation of a ship, and adding to the work to be done, 
 should receive separate consideration. 
 
 III. Area of Light and Load Water-line. 
 
 The area of the water-line is a material element in the power Areaofwatcr- 
 of a ship to carry saU, to carry top-weight, to acquire stifeess, "ne. 
 to ride easy and to roll gently. It is very common to measure 
 it by the proportion it bears to the midship section, and it is 
 practically found to be from six to twelve times that area or 
 more. 
 
secuou, 
 
 102 FIRST APPROXIMATE CALCULATION OF DESIGN. 
 
 Fineness of There is another proportion in which its value may be gencr- 
 
 water-ime. .^jj^. p^prcsscd, namcl.y: Its proportion to a rectangle, in which 
 
 form it shows how much of its area has been sacrificed to shape. 
 
 IV. Area of the Longitudinal Section in the Water. 
 Longitudinal This area is to woatherlincss, what the area of the midship 
 
 section is to resistance, only the object to be obtamea is the 
 exact opposite. The midship section should be in area small, 
 to obviate resistance; the area of the longitudinal section should 
 be large, in order to create resistance. Area of longitudinal sec- 
 tion when small, indicates leowardliness; when large, weathorli- 
 ncss. It is quite plain that area of load water-line and area of 
 longitudinal section have an important and close connection. If 
 a large area of load water-line be combined with a small area of 
 longitudinal immersed section, the vessel will have power to 
 carry much sail, but this power will be wasted by leewardliness. 
 On the contrary, a small area of load water-line may reduce her 
 stability so as to prevent her from carrying as much sail as her 
 large weatherly area would enable her to bear without unduly 
 drifting to leeward. These three areas mentioned, are evidently 
 bound up together in the constitution of a ship. 
 
 A given area of midship section will plainly want a largo 
 power to drive it, that large power will want a large area of 
 load water-line to carry it, and. that large power to carry sail, 
 will want a large longitudinal area to utilize it. 
 
 To obtain out of the three the greatest aggregate of useful 
 results in these points, without the sacrifice of higher value in 
 other good points, is to display the skill of an adept in Naval 
 Architecture. 
 
 V. Volume of Under-water Body or Displacement. 
 Displacement. The four former elements are areas merely, and they measure 
 
 the resistance to be overcome in doing the work, and the power 
 to be used in overcoming this resistance ; but the element of 
 displacement represents the purpose for which they all combine, 
 namely: the movement of a large mass of matter from place to 
 place by means of the floating power of water. The Construc- 
 tor must find out what is the real mass to be moved, or what is 
 the total volume of water which is to be displaced, in order that 
 this body or ship may float in the place of this water. ' To do 
 this, he must obtain a precise measure of the volume of the body 
 to be immersed, and the wcigjit of that bulk of water will exact- 
 ly measure the whole weight of the ship and contents. He 
 must, therefore, calculate the number of cubic feet which the 
 
 Light dUpiace- body of the ship contains ; first, up to the light water-line when 
 she floats without load, or as it is called "with a clean swept 
 
 Load displace- hold," and, Secondly, when she is full ladened with cargo, stores, 
 ment. persons and provisions for the voyage. 
 
 The calculation of displacement is a problem of geometry — 
 the Constructor measures the bulk of the part of the ship under 
 the light water-line, and allows one ton of weight for each 35 
 feet, (in fresh water, 36 ft.) — this gives the number of tons 
 which the ship with all her parts and appendages must weigh, 
 in order to float at the water-line required. 
 
FIRST APPHOXIMATB CALCULATION OF DESIGN. 103 
 
 Between the light water-line and the load water-line, lies Difference 
 another part of the ship, all of which will be immersed when she tue^^Vp" win 
 is laden to the load water-line. The bulk of this part must be carry, 
 measured exactly, and this bulk at the allowance of 35 feet per 
 ton, (fresh water, 36,) will show what the additional weights are 
 which the ship will carry at the intended load water-lino. The 
 displacement of this part of the ship, measures the load she will 
 carry. 
 
 The calculation of the displacement is, therefore, mere mensu- 
 ration, or a sort of superior kind of guaging. 
 
 Besides the absolute quantity of the ship expressed in tons or co-e£Bciunt of 
 cubic feet, it is convenient to express the bulk in terms of her fl"<'"'=''^- 
 extreme dimensions. If the ship were a mere box, her bulk and 
 displacement would at once be found by multiplying together 
 her length, breadth and depth, the product of these in feet divi- 
 ded by 35 (or 36) would be the displacement in tons of that part 
 of the box (or ship) immersed, and would therefore represent the 
 weight of the whole. 
 
 But the ship may be sp-pposed to be a box with its corners, 
 pared off, and it will, therefore, sufficiently express the deviation 
 of a ship from the box form if the Constructor places it so as to 
 show how much of the box is lacking. He therefore expresses 
 the volume of his ship by the fractions 1-2, 2-3, 3-4, or 8-10, , or 
 decimally 0.5, 0.66, 0.15 or 0.8, to show how much the bulk re- 
 tained in the ship is less than it might have been if the corners 
 had been kept on. It truly represents the sacrifice of quantity 
 to quality in a ship of which the extreme dimensions have been 
 determined, and the fraction is called "the co-efficient of fine- 
 ness." 
 
 VI. Volume of Shoulder or Power of the Ship. 
 
 The shoulder has been defined to be that partiof a ship which sbouider. 
 is alternately immersed or emersed as she is equally inclined 
 from one sideAo the other. This inclination is here assumed as 
 14° on one side, and 14° on the other — which gives about one- 
 eighth the beam of the ship as the heel of the "wedge," (one- 
 eighth is a good proportion.) In men-of-war the shoulder is 
 frequently called "the part between wind and water," and men- 
 of-war in smooth water, are not supposed to careen more than T 
 degrees, though it is very probable that in rolling, they will heel 
 over 1 degrees more; in fact, in fast vessels 14° is by no means 
 uncommon, when carrying a heavy press of sail by the wind. 
 This inclination brings a depth of side under the water, equal 
 to about one-eighth part of the ship's beam. 
 
 Now these wedges of immersion and emersion, or "the shoul- Wedges of im- 
 ders," must be accurately measured, and in a vessel of curvilinear Snerelon.™'' 
 outline, the back of the wedge will have a double curvature, re- 
 quiring a little judicious geometry to guage it. 
 
 The constructor having exactly measured the volume of each 
 of these shoulders or wedges in cubic feet, converts his measure- 
 ment into tons, by dividing either by 35 or 36, as the case may 
 be, the result is one element by which to measure the power of the 
 shoulder. ' . 
 
104 FIRST APPROXIMATE CALCULATION OF DESIGN. 
 
 VII. Volume of Out-of-water Body. 
 
 Out of water This IS the volume of room in the ship above the water-line, 
 oonJidcrubie. " or the surplus buoyancy, and is a material element in the safety 
 and sea-worthiness of a ship. An ordinary ship with very little 
 of her body above the water is dangerous, because, if by acci- 
 dent, she ships water and retains it, she will sink. When the 
 sea runs high, the upper body is requii-ed to lift the ship over 
 the waves, otherwise they roll over her; sometimes (as in our 
 Monitors,) it is desirable to make vessels so low, that the sea 
 may run freely over them; but in this case, careful provision is 
 made that the decks are made perfectly water-tight. These 
 vessels are however exceptional. 
 Effect ot tno Merchant vessels have been lost by lading them so deeply, 
 dcj;p an iinmcr- ^j^^^^ .^^ -^^^ Weather they became easily submerged. Moreover, 
 a vessel deeply immersed, has very little lateral stability ; a 
 hoinogeneous body entirely immersed has none whatever. Such 
 vessels are therefore exposed to great risk of capsizing, as well as 
 foundering. It is therefore desirable, at the load water-line, to 
 note what relation the bulk of the out-of-water body bears to the 
 under-water body, as there is a certain ratio which it is desira- 
 ble neither to exceed nor to fall short of. Its volume, therefore, 
 should be indicated by a fraction, showing that it is I, i, \, or 
 any other suitable part of the under-water body. 
 
 VIII. Volume of Internal Body or Room in a Ship. 
 Internal roomi- This is a Very different element from the displacement, which 
 
 measures the whole space which a ship occupies in the water, 
 and the dead weight both of herself and what she carries. The 
 volume now under consideration, represents the void left in the 
 inside of the hull, or the empty space. The thickness of the- 
 proposed hull has, of course, everything to do with this. Iron 
 ships have, therefore, more room in them than wooden ones, be- 
 cause the hull is thinner. The hull of a 1000 ton ship in iron 
 may be reckoned throughout as ^bout 6 inches thick all over,* 
 but a wooden one of the same size may be taken* t three times 
 Iron ships have *^^® *'^^*''^'^®^^- -A- double bottomed iron ship takes much more 
 
 the most. room off the inside than a single bottomed one, but any well 
 
 contrived iron ship is much more roomy than a wooden one. 
 Commercial Roominess in merchant ships is a source of great profit, and 
 
 ?OTminess."''^°" for this reason it should be approximately ascertained at the out^ 
 set. In all war vessels, properly built, there is generally room 
 for more weights than the ship is able to carry, and in all de- 
 signs of a ship, there should be an early approximation to the 
 proportion between the displacement, (which represents the dead 
 weight she can carry,) and the volume of internaVbody, (which 
 represents the space she has for stowing those weights.) 
 
 It often happens that when this proportion is not accurately 
 settled beforehand, a ship has a great deal of room to contain 
 cargo, without displacement enough of under-water body to 
 enable her to carry the dead weight of that cargo; and it may 
 also happen that she has plenty of displacement to carry more 
 freight, without having room to stow it. Mercantile tonnage, by 
 
 *This must not be confounded with the thicliness of the "skin" alone, wliicli in iron 
 merchant vessels is seldom more than Jf of an iiieli, 1 he above includes frame, Ac. 
 
Ves:jel's length. 
 
 FIRST APPROXIMATE CALCULATION OF DESIGN. 105 
 
 tvhich ships are classed, charged and chartered, is now-ardays 
 fixed by measuring the room inside of the ship, as on this depends 
 the "registered" tonnage placed on the register of the ship. 
 
 ToNXAGE Law of the U. S., Approved May 6th, 1864. 
 
 The register of every vessel shall express her length and 
 breadth, together with her depth and the height under the third 
 or spar deck, which shall be ascertained in the following manner: 
 
 The tonnage deck in vessels having three or more decks to the Tonnage deck, 
 hull, shall be the second deck from below; in all other cases the 
 upper deck of the hull is to be the tonnage deck. 
 
 The length from the fore part of the outer planking on the 
 side of the stem, to the after part of the main stern-post of screw 
 steamers, and to the after part of the rudder post of all other 
 vessels, measured on the top of the tonnage deck, shall be ac- 
 counted the vessel's length. 
 
 The breadth of the broadest part on the outside of the vessel beani?'^**''"' °' 
 shall be the vessel's breadth of beam. A measure from the un- 
 der side of tonnage deck plank, amidships, to the ceiling of the 
 hold, (average thickness,) shall be accounted the depth of the i,M^'^ °^ "'" 
 hold, * 
 
 If the vessel has a third deck, then the height from the top of 
 the tonnage deck plank to the under side of the upper deck plank, thFspa" deck!'' 
 shall be accounted as the height under the spar deck. 
 
 All measurements to be taken in feet and fractions of feet ; and how ^tak™^am{ 
 all fractions of feet to be expressed in decimals. eipresseii. 
 
 The register tonnage of a vessel shall be her entire internal na^S'^w tewiuu" 
 cubical capacitv in tons of 100 cubic feet each, to be ascertained and tow ascer- 
 as follows: " •=^'"'' 
 
 Measure the length of the vessel in a straight line along the 
 npper side of the tonnage deck, from the inside of the inner plank 
 (average thickness) at the side of the stem, to the inside of the 
 plank on the stern timbers, (average thickness,) deducting from 
 this length what is due to the rake of the bow in the thickness 
 of the deck, and what is due to the rake of the stern timber in 
 the thickness of the deck, and what is due to the rake of the 
 stern timber in one-third of the round of the beam ; divide the 
 length so taken into the number of equal parts required by the 
 following table, according to the class in such table to which the 
 vessel belongs : 
 
 Table op Classes. 
 
 1st. Vessels of which the tonnage length, according to the ciass ist. 
 above measurement, is fifty feet or under, into six equal 
 parts. 
 
 2d. Vessels over fifty, and not exceeding one hundred feet in class 2d. 
 length, into eight equal parts. 
 
 3d. Vessels over one hundred, and not exceeding one hun- ciass 3d. 
 dred and fifty feet in length, into ten equal parts. 
 
 4th. Vessels over one hundred and fifty, and not exceeding two ^^^^ ^'^• 
 hundred feet in length, into twelve equal parts. 
 
 5th. Vessels over two hundred, and not exceeding two bun- '"^^ ^'^■' 
 dred and fifty feet in length, into fovrteen equal parts. 
 14 
 
106 FIRST APPROXIMATE CALCULATION OP DESIGN. 
 
 Class 6th. 6th. Vessels of which the tonnage length, according to the 
 
 above measurement, is over two hundred and fifty feet long,, 
 into sixteen equal parts. 
 
 area '^f""^^';T Thcu the hold being sufficiently cleared to admit of the required 
 how ascertain- depths and breadths being properly taken, find the transverse 
 '"'• area of such vessel at each point of division of the length, as 
 
 follows ! 
 Transverae Measure the depth at each point of division from a point at a 
 
 distance of one-third of the round' of the beam below such deck, 
 or, in case of a break, below a line stretched in continuation' 
 thereof, to the upper side of the floor timber, at the inside of the 
 Hmber strake, after deducting the average thickness of the ceiling, 
 which is between the bilge-planks and limber strake ; then, if 
 the depth at the midship division of the length do not exceed 
 sixteen feet, divide each depth into four equal parts; then 
 measure the inside horizontal breadth at each of the three points 
 of division, and also at the upper and lower points of the depth, 
 extending each measurement to the average thickness of that 
 part of the ceiling which is between the points of measurement^ 
 number these breadths from above, (numbering the upper breadth 
 one, and so on down to the lowest breadth ;) multiply the second 
 and fourth by four, and the third by two — add these products 
 together, and to the sum add the first breadth, and the last or 
 fifth; multiply the quantity thus obtained bj- one-third of the 
 common interval between the breadths, and the product shall be- 
 deemed the transverse area; but if the midship depth exceed 
 sixteen feet, divide each depth into six equal parts, instead of 
 four, and measure as before directed, the horizontal breadths at 
 the five points of division, and also at the upper and lower points 
 of the depth ; number them from above as before — multiply the! 
 second, fourth and sixth by four, and the third and fifth by two; 
 add these products together, and to the sum add the first breadth 
 and the last or seventh; multiply the quantities. thus obtained 
 by one-third of the common interval between the breadths, and 
 the, product shall be deemed the transverse area. 
 Resisier ton- Having thus ascertained the transverse area at each point of 
 ?aTea'!°'' ^''"' division of the length of the vessel, as required above, proceed to- 
 ascertain the register tonnage of the vessel in the following- 
 manner: 
 
 Number the areas successively, one, two, three, &c., number 
 one being at the extreme limit of the length at the bow, and the 
 last number at the extreme limit of the length at the stern ; then 
 whether the length be divided according to the table into six or 
 sixteen parts, as in classes one and six, or any intermediate 
 number, as in classes two, three, four and five, multiply the 
 second and every even numbered area, by four, and the third 
 and every odd numbered area (except the first and last) by two;,- 
 add these products together, and to the sum add the first and 
 last, if they yield anything; multiply the quantities thus obtained 
 by one-third of the common interval between the areas, and the 
 product will be the cubical contents of the space under the ton- 
 nage deck; divide this product by one hundred, and the quotient 
 being the tonnage under the tonnage deck, shall be deemed to 
 
FIRST APPROXIMATE CALCULATION OF DESIGN. 107 
 
 be the register tonnage of the vessel, subject to the additions 
 hereinafter mentioned. 
 
 If there be a break, a poop, or anv other permanent closed in ^hen there is 
 
 1 1 1 J.1 ' 11 -1 1 1 J! " •'real! "r Poop 
 
 space on the upper decks, on the spar deck, available for cargo on the upper or 
 or stores, or for the berthing or accommodation of passengers or^P" •'"''■ 
 crew, the tonnage of such space shall be ascertained as follows : 
 
 Measure the internal mean length of such space in feet, and 
 divide it Into an oven number of equal parts, of which the dis^ 
 tance asunder shall be most nearly equal to those into which the 
 length of the tonnage deck has been divided ; measure at the 
 middle of its height, the inside breadths, namely: one at each 
 end and at each of the points of division, numbering them suc^ 
 cessively , one, two, three, \-c.; then to the sum of the end breadths 
 .add four times the sum of the even numbered breadtiis and twice 
 the sum of the odd numbered breadths, except the first and last. 
 and multiply the whole sum by oue-third of the common interval 
 between the breadths; the product will give the mean horizontal 
 area of such space, then measure the mean height between the 
 planks of the decks, and multiply by it the mean horizontal area; 
 divide the product by one hundred, and the quotient shall be 
 deemed to be the tonnage of such space, and shall be added to 
 the tonnage under the tonnage decks, ascertained as aforesaid. 
 
 If the vessel has a third deck or spar deck, the tonnage of the ^^''j^'j i>»a ia 
 space between it and the tonnage deck shall be ascertained as 
 follows : 
 
 ]Measure in feet the inside length of the space at the middle 
 of its height from the plank at the side of the stem, to the plank 
 on the timbers at the stern, and divide the length into the same 
 number of equal parts into which the length of the tonnage deck 
 is divided; measure (also at the middle of its height) the inside 
 breadth of the space at each of the points of division, also the 
 breadth of the stem and the breadth at the stern; number them 
 successively, one. two. three, <.Ve.. commencing at the stem; 
 multiply the second and all the other even numbered breadths 
 by four, and the third, and'all the other odd numbered breadths 
 (except the first and last) by two; to the sum of these products 
 add the first and last breadths ; multiply the whole sum by one- 
 third of the common interval between the breadths, and the 
 result will give in superficial feet the mean horizontal area of 
 such space ; measure the mean height between the plank of the 
 two dtcks and multiply by it the mean horizontal area, and 
 the product will be the cubical contents of the space; divide this 
 product by one hundred, and the quotient shall be deemed to be 
 the tonnage of such space, and shall be added to the other ton- 
 nage of the vessel ascertained as aforesaid. And, if the vessel 
 has more than three decks, the tonnage of each space between 
 decks, above the tonnage deck, shall be severally ascertained in 
 the manner above described, and shall be added to the tonnage 
 of the vessel ascertained as aforesaid. 
 
 In ascertaining the tonnage of open vessels, the upper edge of Toanaae of 
 the upper strake is to form the boundary line of measurement, '''"° ^*^^'^" 
 and the depth shall be taken fiom an athwartsbip line, extend- 
 ing from the upper edge of said strake at each division of the 
 lenarth. 
 
108 FIRST APPROXIMATE CALCULATION OF DESIGN. 
 
 resa^h'^n '" b^' ^^^ register of the vessel shall express the number of decks, the 
 
 of ^decks,""ion- tonnage under the tonnage. deck, and that of the between decks, 
 
 nage, &c. above the tonnage deck ; also, that of the poop or other enclosed 
 
 spaces above the deck, each separately. In every registered 
 
 United States ship or vessel, the number denoting the total 
 
 Tonnage to be registered tonnage shall be deeply carved or otherwise perma- 
 
 marked on ihe ncutly marked on her main beam, and shall be so continued; and 
 
 main beam. jf j^ ^^ ^^^ ^j^^^g cease to be SO continued, such vessel shall no 
 
 longer be recognized as a registered U. S. vessel. 
 
 The foregoing may l)e simplified into a formula as follows; 
 
 Area =[A + 4P + 2Q]x r-3. 
 
 Where A = sum of the first and last ordinates, 
 
 4 P = sum of the even ordinates multiplied by four, 
 2 Q = sum of the remaining (or odd) ordinates multi. 
 plied by 2, 
 and r- = the common interval between the ordinates. 
 A ship is said to be 1000 tons burthen, therefore, when she 
 has 100,000 cubic feet of space. This is now the technical ton- 
 nage of the Custom House ; but ship owners sometimes reckon 
 40 or 50 cubic feet to the ton, according to the nature of the trade 
 that the shipper is chartering for. 
 
 IX. Critical Points in a Ship, 
 
 Cfitisai points, The Constructor has hitherto considered certain important 
 areas and volumes of a ship, on the mutual proportions and rela- 
 tions of which, her qualities and powers must depend; beyond 
 these, however, there remain certain critical points or places 
 which are material to the whole behavior of the ship. Unless 
 he first knows these critical points, he knows nothing about 
 where he should place one thing or where another. Situation, 
 is a material part of Naval Construction ; masts may be placed 
 right or wrong, machinery, boilers, coals, heavy cargo, light car- 
 go, provisions, water, guns, anchors and cables, everything, in 
 short, that a ship is to contain and carry, as well as every parti, 
 cle of weight in the hull itself, may* be placed either right or 
 wrong; and even a very small weight may be so placed as to 
 enhance some virtue or exaggerate some defect, 
 
 X. On the place of the Centres of Gravity of the Midship 
 
 Section, and of the Vertical Sections parallel to it. 
 Centre of gray- The position of the centre of gravity of the immersed body of 
 s'/cuon. '""'"'"' a ship is a material element in her behavior and qualities at sea. 
 The place of the centre of gravity of the midship section con 
 tributes more powerfully to determine the vertical height of that 
 centre of gravity than any other section of the ship, and the higher 
 that centre of gravity rises towards the surface of the water, the 
 greater is the stability. Its depth below the surface, when the 
 ship is light,' and when she is laden, is therefore a material ele- 
 ment in her character — and in every trial design, its place ought 
 to be well marked, 
 
 Other cross Bcc- The qualities of the ship will also be affected somewhat by the 
 
 tjons. position of the centre of gravity of the vertical sections before 
 
 and abaft the midship section, and to show how these rise and 
 
 fall, and modify the whole, it is recommended that a line be 
 
FIRST APPROXIMATE CALCULATION OF DESIGN. 109 
 
 drawn on the sheer plan, connecting all the centres of gravity 
 of the vertical cross section* fore and aft. This line will be in- 
 structive, in showing the general character of the foreand after f^H^^^j^'J^^y/''- 
 body, in improving the character of. the midship section, as re- 
 gards stability or in weakening it. Where the line rises, the 
 stability is improved, where it falls, it is weakened. 
 
 XL On the place of the centres ofgravitij of the Water-lines. 
 
 The place of the centres of gravity of the water-lines form ele- . oentre ofgrav- 
 ■ments in the determination of the place of the centre of gravity l^ini^gt". '"'^ 
 of the ship lengthwise, and they should be carefully marked on 
 the sheer plan and connected by a line. This line of centres of 
 gravity of water-lines will either shift forward as the ship goes 
 down in the water, or shift aft, or remain stationary in a vertical 
 line ; if it shift aft, it will show that, as the ship gets deeper and 
 deeper in the water, the heavy weights ought to be stowed aft, 
 if the contrary, then they ought to be brought forward; if neither, 
 they ought to be equally distributed toward both ends. Thus, 
 the line connecting these centres of gravity becomes a perma- 
 nent rule for- the practical stowage of the ship, exceedingly use- 
 ful to the Naval Officer, and ships "may thus be distinguished 
 from each other, accordingly as these centres of gravity run for- 
 ward or aft. 
 
 The distance of the centre of gravity, also, of each half of the — tn breadth, 
 load and light water-lines, on each side of the centre of the ship, 
 from that centre, is an element in the stability of the ship. 
 
 XII. On the Place of the Centre of Gravity of the Longi- 
 tudinal Vertical Section. 
 
 As this is the section which gives weatherliness to the ship, i^^^f^l"^ S^''-' 
 and keeps her from drifting to leeward, the knovv ledge of the tudinai suction, 
 position of its centre of gravity, is most important to the proper 
 placing and arrangement of all the masts, spars, rigging and 
 sails. This centre is the balance point of the lateral pressure of 
 the ship on the water, and the balance point of the pressure of 
 the sails under the wind, must be so placed as exactly to corres- 
 pond with it; otherwise, if the sails and masts are too far aft 
 in relation to this point, the ship will be ardent, which carried 
 to the extreme is a very bad quality, or if they are too far for- 
 ward, she will carry lee helm, which is a worse quality. In Balance of sail, 
 order to secure a perfect balance, the centre of gravity of this 
 section, and the centre of gravity of the sails, (centre of effort,) 
 must be accurately obtained. 'In some vessels, these centres 
 must be directly over each other; but in full bowed vessels, the 
 bluffness of bow deranges the balance; and this must be correct- 
 ed by carrying the centre of gravity (centre of effort) of the 
 sails considerably forward of the centre of gravity (centre of 
 resistance) of the longitudinal section. 
 
 In one case, (a line of battle ship,) this was as much as 15 
 feet. In a fine, wave built ship, these centres go most accurate- 
 ly together. 
 
 Of course, the placing of the masts is by this means regulated 
 and determined. 
 
110 FIRST APPROXIMATE CALCULATION OF DESIGX. 
 
 XIII. On the Place of the Centre of Oravity of the VoU 
 
 ume of Displacement, or Centre of Buoyancy. 
 Centre of buoy- Tbis point iiiust be found, because it is the centre (or balance 
 
 ''"''^' point) of the whole upward pressure of the water on the ship; 
 
 whatever may be the variety and shape of the parts of a ship, 
 the joint power of them all, united to support a given weight, 
 balances at this point. It Mas already been shown that all the 
 , In length. weights must be so distributed as that they shall all balance 
 each other exactly, so that their united centre of gravity shall 
 come precisely over the centre orgravity of the displacement, 
 
 depth. ^^^ °' otherwise the ship will be pressed down out of its intended 
 place some way or other. 
 
 The determination of the horizontal place of the centre of dis-- 
 placement of the wtole ship, is not the only thing necessary for 
 the balance of the ship, but the vertical distance of that centre 
 of displacement, below the water-line, is an element of calculan 
 tion in her stability. 
 
 For these two purposes, it is necessary to take, as one of the 
 elements of a ship, first, the place of the centre of displacement, 
 either before or abaft the middle of lehgtli of the ship ; second, 
 the distance of the centre of displacement below the water-line. 
 The distance before or abaft is generally reckoned in feet, and 
 the distance below the water-lines in fractions of the main 
 breadth. The smaller this fraction is, the greater will be the 
 stability; for the distance of this point below the water, is a 
 measure of the tendency of the under-body to upset the ship. 
 
 XIV. On the Place of the Centre of Gravity of the Vol-. 
 
 limes of the Immersed Fore and After Bodies. 
 
 Centre, of grav- When a ship breasts the sea, her fore body has to be lifted by 
 
 afte"*^(Hsp1ae"e"-''the waves, SO as gradually to raise the ship out of the hollow 
 
 msn^js^affect on to the top of the wave. In lifting, the ship is said to 'scend, 
 
 (from ascend,) and when she goes over the crest, and pitches 
 
 down the slope on the opposite side, the fore body is raised out 
 
 of the water, to plunge afterwards into the ascending slope of a 
 
 second wave, until the buoyancy of the fore body and the lifting 
 
 power of the second wave again raise the bow, towards the crest 
 
 of the wave, and thus lead the body over a second wave. This 
 
 pitching and 'scending is mainly done by the fore body; and, in 
 
 order to measure and appreciate its good or ba,d qualities in this 
 
 respect, the position of its centre of displacement should be known. 
 
 The after body also contributes its share to the movement of 
 
 the, ship, and its action is similar to that of the fore body in 
 
 many respects, with an important difference, however, due to 
 
 the ordinary forward motion of the vessel. The wave strikes the 
 
 bow with a force, which the stern in a great measure escapes. 
 
 But it is necessary to know the place of its centre of gravity of 
 
 displacement also. 
 
 It is only necessary to remark here, that the further the cen- 
 tre of gravity of the fore body lies forward of that of the vessel, 
 the greater will be the force with which the wave compels the 
 fore body to rise, or allows it to fall ; and the same, in a less 
 degree, holds good of the after body. It is usual therefore to 
 state, in fractions of the length of the fore body, the distance of 
 
 pitching 
 
¥IRST APPROXIMATE CALCULATIO>[ OF DESIGN. Ill 
 
 its centre of displacement from that of the vessel, reckoning from 
 that centre to the forward perpendicular, and in like manner for 
 the after body abaft to the after perpendicular. 
 
 Thus, if the fore body were pyramidal, its centre of gravity tre^of gmvf""? 
 would be one fourth, or 0.25; if ellipsoidal, it would be three- some special 
 eights, or 0.375; or if wedge form, one-third, or 0.33) and if a ''"■""• 
 square box, one-half, or 0.5. 
 
 XV. On the Place of the Centre of Gravity of the Upper 
 
 Body of a Ship, above the Water, and of its Fore 
 
 and After Parts. 
 These are to be found and recorded in like manner with those . centre of gmv- 
 of the under body, and for like reasons. If these are found to "ody. "'''"''' 
 correspond with those of the ilnder-water body, the ship Will 
 have this advantage, that the fore body in lifting its own top- 
 weight, will apply its raising force exactly under the centre of 
 weight to be lifted ; and when the under-water body supports 
 the out-of-water body, it will apply its force directly under the 
 weight to be raised, and by this means the straining of the ship 
 will be the least possible. 
 
 XVI. On the Place of the Centre of Gravity of the Internal 
 
 Boom of the Ship, and of its Fore and After Bodies. 
 
 If it be conceived that the whole of the ship is uniformly filled centre of grav- 
 with a homogeneous cargo, (say tea or sugar, coals or cotton, the whoil^hif" 
 wool or corn,) or any other uniform weight, it is plain that no 
 discrimination or discretion can be used in stowing the weights. 
 The cargo being all of one sort, there is no- latitude .for dispos- 
 ing heavy or light weights, where it would be most proper for 
 them to be carried; the condition is simply that the ship must 
 be filled and take her chance. In such a ship everything de- 
 pends upon the original design ; if when she is full, she is found 
 to be badly trimmed, perhaps down by the head, or say down 
 by the stern — it is too late to help it. 
 
 It is, therefore, indispensable that the Constructor should 
 know where the centres of weight of the internal hold, 
 stowage and bulk of such a ship lie.* He must ascertain, 
 first, the centre of gravity of her entire internal capacity, and. 
 then of the fore and after holds ; and if these fall over the cor- 
 responding centres of gravity of displacement of the ship when 
 at her loa,d water-line, then the cargo will exactly balance, and 
 the trim of the ship will be perfectly maintained; if not, a differ- 
 ence will be manifested, which will give him the measure of 
 how much she will be out of trim when laden. If this differ^ 
 ence be. inevitable, no remedy remains, except the empirical one 
 of putting in some ballast; and the places of these centres of • 
 gravity will be needed for the calculation of how much ballast 
 the ship Will require, and where it should be placed. This is a 
 sufficient reason why the centres of gravity of roofti for cargo 
 should be calculated with the same accuracy as those of the 
 centres 'of displacement, and in a similar manner. 
 
 XVII. 071 the Place of the Centres of Gravity of the 
 
 Shoulders of the Ship. 
 When a ship heels 'over under the pressure of wind and sail, centre ofgrar. 
 it is the power of the shoulder only, that enables her to stand "'""' ''"'"'*"^ 
 
 *Th3 Stevedore sliould knnw this also. 
 
112 FIRST APPROXIMATE CALCULATION OP DESIGFN, 
 
 up under it, and therefore it is necessary beforehand to know,, 
 not merely the bulli of the shoulder or its quantity, but the man- 
 ner of its application, more or less advantageous, to sustain 
 the pressure it is required to withstand. A given quantity of 
 sail may be applied high up on a mast, or lower down, and a 
 given quantity of shoulder will require to be applied either far- 
 ther aAvay from the ceutre of the ship, or nearer, to suffice for 
 this effort. The centre of effort of sail and the centre of effort of 
 shoulder have, therefore, both to be found, and both to be 
 measured, from the central axis round which, speaking roughly, 
 the ship has turned in heeling. This measure is generally given 
 in feet, but the centre of the shoulder may also be reckoned in 
 fractions of the half breadth of the ship. Thus, in a wall-sided,, 
 square ship, it would be at two-thirds of the half breadth ; and in 
 a wedge shaped ship, between one-half and two-thirds. 
 
 XVIII, On the Weight of the Htill of a Ship, and the 
 place of its Centre of Gravity. 
 Weight of how, Por the purposes of theoretical calculation merely, it is a 
 roughly!" good, though rough approximation, to take the whole skin of a 
 
 ship, including her deck, as of a given uniform thickness and 
 weight ; and if the Constructor knows ffom his own experience,, 
 the total probable weight of such a hull, he will find it sufficient- 
 ly near the truth, to make a first calculation in this manner. Of 
 course it is not true, absolutely, in any case, as scareely ever 
 are two ships built alike in distribution of materials ; but it is 
 sufficiently near the truth to enable the dexterous ship-builder 
 to make it absolutely true in the ultimate practical result, by 
 a. thoughtful distribution of all the weights of the ship, as to 
 which he has free choice. 
 More accurate All this will Serve Only for a first approximation; then, vwfcen 
 must 'then ^ all the details of the actual structure and equipment of the ship 
 be made. are finally settled, and everything placed, a final calculation 
 
 must be made with great accuracy, showing the absolute, vol- 
 umes and weights of the hull, and of its different sub-divisions, 
 and the positiotis in height, length and breadth of the centres of 
 gravity, both of figure and (where practicable) of actual weight, 
 as well as the areas and centres of the principal planes. When 
 this is done, the Constructor will see whether his centres of 
 gravity of displacement coincide with the position of the centre 
 of gravity of the hull, and with those of the Weights which the 
 ship is to carry, so that the ship, as a whole, as- well as each 
 part of her, may do its work perfectly, and that her trim, on go- 
 ing to sea, may be found to be exactly as originally intended. 
 
 When the designer has found the place of all of these points,, 
 has measured the areas of all these surfaces, and has guaged all 
 the volumes and capacities mentioned, he has then the elements 
 which will enable him to judge of the qualities of his ship. 
 
 He may arrive at this judgment in two ways, either by com- 
 paring the elements thus obtained with all the similar elements 
 of a known ship, whose good qualities he means to imitate, or 
 he may .proceed to make an absolute mathematical determina- 
 tion of the qualities of his ship, without reference to any other" 
 vessel.* 
 
 •See Chap. VIII Kusscll's Naval Architecture. 
 
SHIPS FOR WAR. 113 
 
 CHAPTER XXIII. 
 
 SHIPS FOB WAB. 
 
 A man-of-war, in general structure, may differ from a merchan1> Purpose of a 
 man either very little or very much. A first class clipper differs "*'"' 
 very little either in size, pi'oportion, shape or qualities from a 
 fast sailing frigate of equal tonnage ; it is mainly in the interior 
 arrangement, fitting and equipment that they differ. Both equal- 
 ly require that the design of the hull shall be stable, weatherly, 
 fast, easy and handy, and that their structure shall be stout and 
 staunch, and that their driving power shall be such as to give 
 them the speed required. The Constructor, then, need only con- 
 sider the points in which their purposes require that they should 
 differ. 
 
 As the purpose of the merchantman is to carry freight and To achieve vie - 
 earn profit, so the object of a man-of-war is to fight and achieve 
 victory. Strong to destroy, comes in the place of strong to carry; 
 but just as carrying power does the merchant no good, if it does 
 not earn profit, so fighting power does the nation no good if it 
 does not win victory. To win, is the work of both. The ques- 
 tion, therefore, which underlies the whole design, construction 
 and equipment of a man-t)f-war is, how to win a victory? What 
 are the points, then, in a man-of-war which will enable her to win 
 a victory ? 
 
 The first point is, that she has the speed to find her enemy. . conditions of 
 
 ' ' victory. 
 
 To find the enemy the ship must be faster, otherwise she may 
 
 never find and, consequently, never fight her adversary.* When 
 
 the enemy is found, the Commander must have the power to 
 
 choose his time to fight, for choice of time and place in an , action Choice of time 
 
 is half the victory. Above all, then, speed is the first condition speed'' Sges- 
 
 of victory. semlal. 
 
 If what has just been said is true of an action between ship and 
 ship, it is much more true of a fleet; therefore, all the ships com- 
 posing that fleet should, without exception, have tlfesame uniform 
 highest rate of speed ; otherwise, it will not be the Admiral who 
 chooses time and place for the battle, but it will be the slow 
 ships that decide. The presence in the fleet of a few slow ves- 
 sels, may be enough to lose him the battle. 
 
 The next point essential to victory is, choice of distance. — , ^^"''^ "^ ^'^ 
 Whether he shall engage at long or short range, often decides 
 the fate of an action. The fast ship can, if she chooses, keep at 
 long range out of the way of the shot of her enemy, and destroy 
 that enemy by her guns of longer range, if she posesses them. 
 If, on the contrary, it is the enemy which has the longer range, 
 the fast ship caIn destroy the inequality of range by coming 
 rapidly to close quarters with her adversary ; so that, in either 
 case, the slow ship is nearly in the power of the faster. The 
 fast ship and the fast fleet then, command the victory. 
 
 The next point after speed, is steadiness, A ship of war must g„iftJn™i'|^fo"4v, 
 be regarded as the platform of a floating battery ; if this platform 
 be steady, her guns may aim true, and deliver destructive flre ; 
 if not, they fire wildly and do little execution. To waste amuili- 
 
 * It will he remembered by the readers of Naval history, that much of Nelson's time was 
 lost in fruitlessly endeavoring to find the French fleet.- 
 
 15 
 
114 8H1PS FOR WAR. 
 
 tion is to fail. A stable platform in a ship of war, is one of tte 
 highest achievements of naval science. An unstable platform; 
 is caused, sometimes, by an undue balance of weights in the' 
 ship, which gives her spontaneous rolling motion ; sometimes by 
 a form which gives her a tendency to adapt herself to every 
 change on the surface of the sea. But a ship may be constructed 
 so as to give the sea the least power over her, either to make her 
 roll or pitch. 
 
 The fine ends of the wave system accomplish the one, the round 
 tumble home side accomplishes the other ; so that as to a ship's 
 own tendency to roll, a low meta-centre and a low centre of 
 gravity do all that is possible to prevent that. 
 
 The wonderful combination of ease with stal)ility and steadi- 
 ness of platform, which distinguished the old French vessels of 
 M. Sane, are to be attributed to the success with which he gave' 
 effect to the tumble home side, the low meta-centre and the cen- 
 tre of gravity. 
 
 The frigate "Constitution'' was also a notable instance of thisj. 
 very few ships built since, have exceeded her in these qualities. 
 
 Stability of platform, and consequent steadiness, are another 
 condition of victory. If, in a given sea, one vessel delivers her 
 fire with sure and steady aim, and the other fires wildly, victory 
 cannot long remain matter of doubt. 
 
 ^t^f uTbiutv" -^® ^^^® °^ ^■'^^P ^^^ everything, in a merchantman, to do with 
 ' qjiantity of cargo, so the size of a ship has considerable to do 
 with successful action between men-of-war of the broadside pat- 
 tern. The odds are in favor of the larger ship. This is untrue 
 in one sense and true in another. It is taken for granted that 
 the larger the ship the heavier the battery ; and it is by the 
 weight of the broadside she can deliver in a given time, that the 
 power of a ship of war is measured. Between two ships then 
 of different size, it must be supposed that the weight of the' 
 iDroadside is proportioned to the size of the ship, or that the 
 greater tonnage carries with it the heavier armament, and the- 
 larger ship's company to work it. This being so, the victory 
 will be on the side of the larger ship. 
 
 Power of bat- Power of battery is, therefore, the next element of victory, 
 '"^' and the best ship is that which can carry and Work the most' 
 
 powerful battery. But now the question arises, what shall be' 
 called the most powerful battery? Shall it be the greater num-- 
 ber of guns, the greater size of the guns, or the greater weight 
 of broadside ? It is now generally admitted that victory lies 
 with the larger guns and the heaviest broadside, and that a 
 number of guns of small calibre are Worthless. 
 
 Height of bat- The basis of construction, then,, of a man-of-war, may be said 
 °'^' to be the weight of armament she is to carry, and the speed at 
 
 which she is to carry it, just as in the merchantman, it is the 
 weight of cargo she has to receive, and the speed at which she 
 has to deliver it; the object of both being to carry a given weight 
 to a given place. But the difficulty with a man-of-war is, that she' 
 has to carry her weights in the wrong place ; the merchantman 
 carries her weight in her hold ; the man-of-war has to carry hers 
 on her decks. The deck of the man-of-war is her battery plat- 
 
SHIPS FOR WAR. M5 
 
 form, that her guns may be carried well out of the water, which 
 IS au obvious conditioa (except in certain peculiarly built ves- 
 fiels)* of fighting them successfully. Men-of-war with a low gun 
 deck, must shut in their ports in a heavy sea, and that deck is 
 useless. The loss of the lower gun deck in an old fashioned 
 line-of battle ship was only a partial disarmament, but in the 
 jnodern ship it is total defeat. 
 
 The armament to be carried, and the height at which it is to 
 be carried, must first be settled then; — 4 and 5 feet out of water 
 was the old style ; 6 to 7 is the height of the ports of the ships 
 of the French Navy; 8 to 9 of the ships of the British Xavy; 
 11 feet was the height of the TJ. S. Steam Frigate Merrimac's 
 midship port. 
 
 That, therefore, may be called the ruling condition of the 
 modern fleets of the broadside type. 
 
 The weight of the heaviest broadside ship of to-day, may be weiEht of mod- 
 taken at 50 guns, of, say 12 tons each, or 600 tons of weight car- "" ^'■'■^'^■ 
 Tied in a single tier at 9 ft., or in a double tier at 13 feet. This 
 is the problem th&,t English and French Architects have had to 
 solve. How to carry such a tremendous weight steadily at the 
 given height? How they have solved it — ^tbe splendid ships in 
 their respective Xavies are witnesses. 
 
 Next comes a new condition of Naval Construction arising out power of cn- 
 the modern invention of iron armor. You can destroy the enemj- durance. 
 if your ship has the speed to catch him, and battery enough to 
 smash and ■ sink him ; but an important question remains, your 
 powers of endurance and his. "He who stays wins." Therefore 
 power to endure the enemy's fire, is next in value to the power 
 with which you deliver your own broadside. The assistance of ' 
 
 iron is therefore sought. With iron armor, the ship may endure 
 the enemy's battering, and in this case, power of endurance is 
 ultimate and sure victory. 
 
 The endurance of iron armor is found to consist in two quali- . Endurance of 
 ties, and onh'two: weight and toughness; without weight in ag"inst 'round 
 the armor it is impossible to stop the moving weight in the shot, ^^"^■ 
 and without toughness, it is impossible to hold on against the 
 shot for a sufficiently long time to arrest its speed. The weight 
 of the armor struck, diminishes the speed of the motion commu- 
 nicated to it, and the toughness of the armor serves to spread . 
 the motion around the point struck, and to extend this motion 
 forward along with the ball, so as to I'etain hold of it with most 
 force through tfie longest time. This is the whole virtue of 
 armor. Light armor is of no use, because, in proportion to its 
 lightness, it receives more motioti; rigid or hard armor is of no 
 use, because it cannot spread the impact of the shot and keep 
 hold of it long enoughtto arrest it. Hence all sorts of shapes 
 of armor — all attempts to use thin armor — all attempts to use 
 hard steel or tough plastic iron to arrest the shot, have failed; 
 the part of the armor struck by a round shot has to be at least 
 as heavy as the shot itself to keep it out, and at least so tough 
 as to spread the blow over an area two or three times its own 
 diameter, and be able at the same time to yield and bear without 
 fracture, an indent nearly the thickness of the plate itself: these 
 qualities attained, the armor is shot proof. The question of ar- 
 
 *Tlie "Monilora" for instance. 
 
IIG SHIPS FOR WAR. 
 
 mor is, therefore, shortly this: It should be two-thirds, at least, 
 
 the diameter of the round shot fired at it, and should be of that 
 
 tough and plastic material that Si),efaeld and Pittsburgh have 
 
 produced so successfully. 
 
 Armor plating But wheu Cylindrical bolts can be fired with the same velocity 
 
 hllcTcd rifle sho^as round shot, still heavier armor and new conditions will be 
 
 jiite tiie "wiiii- required to resist it; but there will still remain this question: 
 
 "'"'' '■ Whether the punched holes of the rifled shot will do greater harni 
 
 than the battering and punching power of the heavy round shot 
 
 like the 15 and 20 inch? The problem of endurance maybe 
 
 considered as solved, when ships can be coated with armor 
 
 which hardened spherical shot, of the above calibre fired with an 
 
 initial velocity of 1500 feet per second, cannot pierce. 
 
 Against speed Power of endurance, therefore, is bound up in these three 
 
 weig^ht?' ^" things: weight and quality of armor, and weight and speed of 
 
 shot, with which also go weight and size of gun. For the pur^ 
 
 poses of Naval Construction it may be given as a general rule, 
 
 that the thickness of the armor should be at least two-thirds the 
 
 diameter of the spherical sjiot, and the gun 'about a hundred 
 
 times the weight of the shot. 
 
 Thje 8 inch shot vsrill have to be stopped with 5J inch armor, 
 the 9 iijch shot with 6 inch armor, the 12 inch shot with 8 inch 
 armor, the 15 inch shot with 10 inch armor, and the 20 inch 
 shot with 15 inch armor, These are the conditions <)f endurance 
 to be met at present. 
 
 But armor to a ship, like armor to a soldier, is plainly an encum, 
 brance and embarrassment, as well as a defence. It is a great 
 weight to carry; it is top weight, and therefore hard to carry; 
 it is winged weight, and therefore slow to move, but hard to 
 stop when moving. Armor, then, adds a new difficulty to cout 
 struction, of the same nature as a heavy battery of guns, with this 
 addition, that it is nauch greater in quantity. 
 
 Weight of ar- The armament of the side pf one of the English iron clads for 
 
 '""''■ a single gun only, vi»hen 5 inches thick, weighs 30 tons; and if 
 
 a two decker, 20 tons for each gun. It is plain, therefore, that a 
 
 ship which was able to carry 5 ton guns on its deck may be 
 
 quite unable to carry those guns with the addition of 20 or 30 
 
 tons of armor for each gun, and assuming that a 15 ton gun is 
 
 the future armament of a broadside ship, she will have to carry 
 
 with each of these guns 60 tons of arnjor, if a single decker, or 
 
 40 tons of armor if a double decker! 
 
 Necessities of These considerations enable one to understand and measure 
 
 aSg" o'ut" the work to be done by an iron plated armor ship. If her guns 
 
 ,Qf arinor. ije light and numerous, and her armor thin, she may be able to 
 
 carry it over her whole length, with only so much additional 
 
 breadth as suffices to carry the weight of armor and armament — 
 
 to carry it in respect to buoyancy and in respect to stability; but 
 
 when the weight of the guns and the thickness of the armor are 
 
 increased so much that the dimensions to which the Constructor 
 
 may be limited are inadequat^e to carry them, he Ijas to begin 
 
 afresh, and seek new conditiorjg ofi structure. 
 
 Partial bauery It is thus that the partial batt,ery system has grown out of 
 w^enj.. /exti-eme weight of battery and of arnior ; the size of a ship is 
 
SHIPS ¥0R WAR. HT 
 
 limited by the naiTowness and shallowness of the channels it 
 has to navigate, and by sea-going qualities. Docks and harbors 
 sometimes limit these dimensions, but it is less costly to alter 
 docks or dredge harbors than to haye a fleet over-matched and 
 defeated ; and it is agreed that the ^'hole question is one of gain- 
 ing victory. 
 
 If, therefore, the Constructor has a given length, width and 
 depth, it is clear that these dimensions limit the power of the 
 ship to the weight of guns and armor she can carry; and it is 
 no longer a question, as in the old wooden ships, of carrying her 
 battery or gun platform along her broadsides from stem to stern; 
 so many guns and so much armor as she can securely carry, she 
 may take, and to that quantity she is limited by the conditions 
 of her existence. These conditions have given rise to the modern 
 system of partial batteries, of which the '-Ironsides" of our ser- 
 vice, the "Warrior" and "Achilles" of the . English Navy, and 
 the "Magenta" and "-Solferino" of the Frignch Navy, are notable 
 instances. 
 
 The "Warrior's'' gun platform, occupies only 220 feet of her 
 length; the "Solferino's" double tier gun battery only 150 feet of 
 her length; the "Bellerophon's" only 150 feet on a single deck. 
 
 Necessity, therefore, and not choice, has been the origin of , Grows out of 
 
 t]l6 TlPC6SS]tl€S Ot 
 
 the partial battery system ; and the sailors of past navies, who iron armor, 
 regret the continuous batteries of the old wooden fleets, should 
 remember that it is simply impossible to carry a greater weight 
 higher out of the water, with stability and sea-worthiness, than 
 the laws of nature will admit. 
 
 ■There are two important considerations belonging to the par- Practical pro- 
 4ial battery system — one, is the great stability of platform- and partial battery 
 admirable sea qualities which arise from the concentration of ^s'^"""* 
 great weights on the central body of the ship, instead of carry- 
 ing them out to the ends. 
 
 To a modern fast screw steamer fine ends are indispensable ; ■• 
 to coyer these fine eijds with heavy armor and broad gun plat- 
 forms, is to p^oduc^ in every way a bad sea-going ship ; no more 
 armor must «xtend towards the ends than is indispensable for 
 the ship's endurance ; and, therefore, it is enough that it be 
 carried ijp to the first deck out of water, and as far forward as 
 the ship needs protection ; this done, the armament and armor 
 should be concentrated in the centre, where the middle body has 
 power to support them, and where action pf the sea on the ends 
 of tbe ship will not much disturb their stability. The battery 
 thus concentrated in the middle, the extremities of the vessel 
 may serye for all that accomtnodation for officers and crew, which 
 can only be well given where there is plenty of room, light and 
 air; and it is only this system which can thus combine in the 
 same ship an impregnable fortress in the centre, and a roomy, 
 well ventilated home in the two ends. The partial battery sys- 
 tem, therefore, is the best solution of the problem of heavily 
 ^rmed, iroij ,cl^(J, distant cruizing, speedy and sea-worthy ships. 
 
 The form, jthereforB, which the problem of modern naval con- ooncUtiotis of 
 struction takes, is this: Such a length of ship as will enable °^^j^'™=^'°" °^ 
 her to attain the speed necessary to catch her enemy, choose her ^^* "" 
 time and place of action, and fix her own . distance for engage- 
 
118 SHIPS FOR WAE. 
 
 ment. The dimension of her breadth will next be fixed by the 
 height at which her gun platform must be carried above water, 
 while the number of guns which that platform must contain, 
 should be limited entirely by the quantity she can steadily sustain. 
 The partial battery thus becomes a fortress, within which must 
 be included whatever is most vital and valuable — guns, ammu- 
 nition, engines and boilers. 
 • Turret system. Q^g of the forms of partial battery, is the circular form or re- 
 volving turret, which deserves separate notice, since a kind of 
 rivalry has arisen between it and the fixed partial battery ; but 
 in reality, there is no antagonism, both being parts of the same 
 system, capable of being used together or separately, under 
 peculiar circumstances, to which either is the better fitted. The 
 case to which the revolving turret is peculiarly suited, is this; 
 A ship has not always the power of running close to her enemy, 
 and sustaining his fire with closed ports, until she is fairly 
 alongside and ready to deliver a broadside. The case is frequent- 
 ly that of her having to chase an enemy, out-manceuvre her, or 
 pass a battery, through a sinuous course or tortuous channel. 
 In such a case, there occur many positions of the ships where 
 broadside guns are of no avail — not having the lateral training 
 suflScient for the purpose. 
 
 advantage"""" '^^^ revolving turret has therefore the following advantages: 
 It supplies a convenient and easily handled mounting for a very 
 large gun ; it has machinery which enables that gun to be work- 
 ed with a very small crew, trained with the greatest ease, and 
 aimed with the greatest exactness round any number of degrees 
 of a circle, so that its aim may be, at all times, independent^ of 
 the course of the vessel; and it secures these advantages with 
 a very small opening of port, and therefore with comparative 
 safety to the gun's crew, by carrying round with the gun, 
 on the same revolving platform, a complete shield of armor. It 
 is, in short, a revolving round tower, containing a couple of guns, 
 or a single gun, on parallel fixed platforms on the inside ; these 
 guns having no lateral train of themselves, but merely eleva- 
 tion and depression. The training is done by machinery, with 
 steam from the boilers, which carries this turret round, a centre- 
 balancing pivot or spindle directly over the keel of the ship. 
 
 The word of command diverts the turret to the right or left, 
 slow, quick or stop — while the Captain of the gun stands, lock- 
 string in hand, with his eye on the sight, ready to fire at the in- 
 stant his gun bears upon the enemy. A trial of this arrange- 
 ment through a great war, has convinced most officers that this 
 is the perfection and luxury of gunnery. 
 
 v^aZge^oriurl '^'^^ ^^ turret system is valuable only in special cases. It 
 ret and broad- enables a vesscl to carry a greater weight of iron, to protect her 
 side vessels. gyy^^ and hull — on the other hand, the guns are few in number, 
 and their fire extremely slow. The turret ship cannot afford to 
 throw away a shot, and must come to close quarters to fight, 
 and unless she possesses great speed this cannot be done. For 
 the defence of a coast line, and for an action in which ship is 
 pitted against ship, actual war has proved the turret system to 
 be the better of the two. For the reduction of forts and bat- 
 
SHIPS rOH WAK. 119' 
 
 teries, and for distant and lengthened cruises, the broadside 
 evstem has the advantage. 
 
 The operations against Charleston, and the reduction of Port 
 Fisher, during our late war, abundantly proved the merits of the 
 two sj-stems, as illustrated in the case of the "Monitors" and 
 "jS'ew'lronsides." The views here expressed are not therefore 
 exclusively partisan to either system, and the following is sug- 
 gested as a plan which the rivalry between the two parties has 
 prevented both from adopting. 
 
 When the number of guns is small, say four, and the ship is b„^^sylt°ms!'"^ 
 of sufficient size, conveniently to carry them, let her carry four 
 guns in two turrets, and use both systems together. Place two* 
 turrets, one in the after body and one in the fore body, afore and 
 abaft the engine room ; then enclose the whole space on deck 
 between the two, so as to form a broadside battery, the bow 
 turret might sweep 270° of the horizon, the stern turret the 
 same, and in addition to the turrets in the ship, with 60 feet of 
 engine room, have a broadside of four guns, or eight in all on 
 each broadside ; the whole length of battery not to exceed 120 
 feet of the centre of the ship. 
 
 The protection of boilers, magazine and machinery, and the 
 deck immediately under the feet of the gun's crew, is by far the 
 most important feature of protection. The protection of the' 
 gun's crew or of the battery, is not so important for the follow- 
 ing reasons: Xaval action with long range guns, will com- 
 mence as soon as the ships are within range of each other, and 
 will probably conclude before coming to close quarters. It will, 
 therefore, be the destruction of the ship, rather than the slaughter 
 of the crew, which will decide the battle. The ship's hull, as a 
 whole, will be the target aimed at; therefore, the men will be 
 quite ready to fight their guns as'of old, without personal pro-- 
 tection, provided the deck on which they stand is made safe. 
 
 For a multitude of purposes, fleet eruizers, with partial pro-- 
 tection and great speed, would be most useful. They need 
 never be reckoned as ships of the line of battle, nor take higher 
 rank than fast eruizers. They could always choose when to 
 fight and when to avoid action. They would never be expected 
 to lay alongside of shot proof batteries, as they could render 
 more important service without the chance of entailing national 
 discredit. 
 
 Much has been said of protecting the water-line of a ship, as skfety of un- 
 if the water-line was something tangible and defined. The tj^j^ i ■^»«'="'* p^^"*-^-- 
 ter-line in a sea-way, is just what the fancy of the sea and stress 
 of weather choose to make it; an abstraction, not a reality. ' The 
 whole thin part of the bow and stern are liable to be out of wa- 
 ter. Protection of a water-line is, therefore, a fictitious element 
 of safety against the gunner, who watches his time to deliver 
 his shell near the bow or stern of his enemy's ship, the moment 
 the wave leaves the stern or bow bare. The only protection 
 thin, fine ends can receive, is the sub-division horizontally, verti- 
 cally and longitudinally by bulkheads — forming water tight 
 compartments. 
 
120 SHIPS POK WAR. 
 
 Water-tight Having decided upon the quantity of armor to be carried, this' 
 compartments. sui3.(jiyjgjon into Water tight com|>artments, becomes the great 
 element of safety and endurance. It gives the means of sus- 
 tslining damage to the hull for the longest time with the least 
 danger. 
 Absolutely es- To the utmost then, even at the loss of some convenience, the 
 of-war. "' interior of the ship should have transverse bulkheads, longitudinal 
 bulkheads and iron decks, all watef tight; air tight even, if possi- 
 ble. The contents of all spaces should, to a great extent, be car- 
 ried as it were in tanks. All openings for ordinary accommoda-^ 
 tion, should have water tight iron hatches, covers and doors; and 
 closing all these openings, would be the first preliminary to action.- 
 Powerful steam pumps shoald also be furnished as a necessity 
 for casualty. 
 
 lik^*" w ha" )en ^ vessel without such minute division, is not only liable to 
 if men-of-war be sunk, but, loDg before that, is liable to overturn from di-; 
 wfth "the 'wafer- ™^^i^'^®'^ Stability; but an iron armored ship with these provis-- 
 tight compart^ ions for action, ably carried out, may be regarded during a pro-^ 
 ™°" ' tracted action as equally proof against artillery, water and fire.- 
 
ENaLISH IRON^ OL^D FLEET, 
 
 [122i 
 
 L«ug'th on L. W. lino, in fuct, 
 
 Breadth extrenio, ...... in foot. 
 
 Depth at sick-, 
 
 Moan draft of water, ..----" 
 
 Tonnage (builder's,) ..... 
 
 Height of lower portsill above L. W. line, - - in feet. 
 
 Area of immersed midship soctiou, - - - in sq. feet. 
 " of L. W. lino, 
 
 Tons per inch, immersion, . - . - - 
 
 Disphicoment, - - - in Ions. 
 
 Thickness of armor plates, exclusive of backing, - in inches. 
 
 Weight of hull of vos.seI, .... - iu tons. 
 
 " " total armor, inclusive of bulkheads, - - " 
 
 " " engines, boilers and water, ... " 
 
 " " guns, ammunition, &c., ... " 
 
 " " equipment, stores and fuel, - - - " 
 
 Number of men, ...... 
 
 Nominal horse power of engines. 
 
 Depth of centre of gravity of all the weights below L. W. line, ft. 
 " " " " " of displacement " " " " 
 
 Height of mcta-eentre above centre of displacement, 
 " " " " " centre of gravity of weight. 
 
 Number of guns, protected, - - - - - 
 
 Total number of guns carried, - - - - - 
 
 Speed iu knots, over measured mile, - - - - 
 
 Depth of armor below L. W. lino, - - - - in feet. 
 
 Class I. 
 
 Ship of the 
 line. 
 
 402 
 08 
 50 
 28 
 
 8834.74-94 
 9 
 
 icn 
 
 21,.3(iO 
 
 51 
 
 12,738 
 
 5 
 
 4400 
 
 2500 
 
 2000 
 
 720 
 2300 
 
 900 
 2000 
 
 3.23 
 
 12, 
 14.2(i 
 
 5.49 
 70 
 90 
 14 
 
 Class II. 
 
 Frigate of 
 "Warrior' 
 
 Class. 
 
 380 
 
 58 
 
 30 
 
 20 
 0212.42-94 
 
 10 
 
 1000 
 
 17,889 
 
 40 
 7250 
 
 4.5 
 2500 
 2297 
 1000 
 
 400 
 1100 
 
 000 
 1250 
 —1.0 
 
 7.42 
 l(i.72 
 
 8.30 
 
 20 
 
 40 
 
 14 
 5 
 
 Class III. 
 
 Corvette 
 of "Bcllero- 
 phon" class. 
 
 300 
 
 50 
 
 38 
 
 24 
 4240 
 
 9.5 
 
 1075 
 
 13,440 
 
 32 
 7000 
 
 
 1500 
 2000 
 1000 
 
 200 
 1250 
 
 (;oo 
 
 1000 
 
 10.5 
 13.01 
 
 20 
 
 20 
 
 13 
 
 5 
 
 Corvette 
 w i t h t w o 
 turrets. 
 
 285 
 
 52 
 
 33.5 
 
 24 
 35,i7 
 
 17 
 
 1078.00 
 
 11,903.54 
 
 2S.4S 
 
 5006 
 
 4.5 
 2800 
 810 
 000 
 280 
 1023 
 300 
 800 
 
 9 
 
 4 
 
 4 
 
 13,5 
 
 5 
 
 Corvette. 
 
 300 
 
 48 
 
 33.5 
 
 20 
 
 3201,8-94 
 
 8 
 
 820.14 
 
 11,134.05 
 
 20 
 
 4741 
 
 4.5 
 
 1280 
 
 1550 
 
 800 
 
 250 
 
 (;oo 
 
 400 
 1000 
 2.03 
 8.94 
 11.15 
 4.84 
 
 20 
 
 20 
 
 13 
 4 
 
 Class IV. 
 
 Corvcttej Iron cor- 
 witli miui-'vette witli- 
 muniprotec-'out protuc 
 tion. tion. 
 
 251 
 
 40 
 
 18 
 
 12 
 1900.30-94 
 
 10* 
 390 
 7100 
 
 17 
 1950 
 
 4.5 
 724 
 300 
 355 
 125 
 412 
 400 
 500 
 
 1 
 
 5.10 
 
 13.05 
 
 9.49 
 
 10 
 
 12 to 13 
 
 4 
 
 Partial 
 battery cor 
 votte. 
 
 250 
 
 40 
 
 18 
 
 12 
 
 1900,30-94 
 
 10* 
 
 307.20 
 
 0309.90 
 
 15 
 
 1700 
 
 724 
 
 355 
 125 
 402 
 400 
 500 
 4 
 5.5 
 13 
 12.5 
 
 10 
 10 to 17 
 
 270 
 
 40 
 
 17 
 
 12.5 
 
 2070.50-94 
 
 0.5 
 
 428.18 
 
 8008.84 
 
 20 
 2218 
 
 4.5 
 800 
 050 
 3. ".5 
 125 
 304 
 400 
 500 
 
 
 5.5 
 
 12 
 
 0.5 
 
 10 
 
 10 
 
 13 
 G 
 
 Gunboats. 
 
 Class I. 
 
 Class II. 
 
 138 
 
 25.5 
 
 14.5 
 
 10.5 
 
 417.44-74 
 
 8.5* 
 208 
 2553 
 
 
 504 
 
 4.5 
 170 
 100 
 
 75 
 
 50 
 
 97 
 
 100 
 
 
 4.1 
 0.43 
 2.33 
 
 4 
 9 
 3.5 
 
 140 
 
 23 
 
 9.5 
 0,75 
 
 350 
 
 8,5* 
 
 114 
 2500 
 
 
 340 
 
 4.5 
 
 135 
 
 50 
 
 45 
 
 25 
 
 90 
 
 00 
 
 
 2.5 
 
 9 
 0.5 
 2 partial 
 
 2 
 
 9 
 2.5 
 
 Class III. 
 
 100 
 
 22 
 
 8. 
 
 4.5 
 
 217 
 7.5* 
 
 95 
 1794 
 
 4.5 
 211 
 
 4.5 
 
 82 
 
 47 
 
 21 
 12.5 
 
 36 
 
 30 
 
 2 
 9 
 
 partial. 
 
 1 
 
 6 to 7 
 
 1.5 
 
 Wave form 
 turret ves- 
 sel. 
 
 175 
 
 25 
 
 12.5 
 
 8 
 
 553 
 7. 
 
 140 
 2025 
 
 3. 
 
 450 
 
 200 
 
 64 
 
 75 
 12.5 
 
 80 
 
 100 
 
 3.5 
 9 
 
 1 turret. 
 
 1 
 
 13 
 
 CLASS I. — A ship of the lino, iron clad. 
 
 CLASS II. — A frigate of " Warrioi-" class with lighter draft 
 
 to 
 
 CLAislS 11. — A irigate oi \\ arrun' cuiss wiin iigiiier oraii. 
 
 CLASS III. Tiie third column in this class, is a vessel having all her guns, magazine and engine room protected. She carries 18 l)roadside 
 
 fire in a lino parallel to her keel; she is, further, able to carry four guns more, two forward and two aft, in shot proof batteries on the upper deck 
 CLASS lY. The first vessel in this class, has only her two magazines, engine and boilers i)rotcctcd ; she is able to carry a large quantity of 
 
 - -.1.;.. .,.:*-!, ,^.,,*- nmr iM'.-ifi^rtf ii-iii SIio nnTrtj"»t: n \ri^r\' Inrtri' nlliintltv nf* r'n.Tivn^ Hot ioii iiiv^nt (rii7i*a \\'hi">ii Tint", in n^^tliin rti'i* lii'\nG*>rl in nnii',j fl^^^'^^ m 
 
 guns on her lower deck, the two fore and after-most ones being able 
 
 per ship without any protection, 
 a line nearly parallel to the keel 
 
 ^,..„ ^, ^„p.„„ ^.,. , ^..„, .„ v„ ^.v..j pj quantity of canvas. The second vessel, or 
 
 She carries a ver)- large quantity of canvas. Her ten i)ivot guns, when not iu action, are housed in pairs, fpre and aft along centre of the deck; 
 The hull being comparatively low, she is a diflicult target to hit. 
 
 the "Alabama" class, is a fast clip- 
 four on each side are able to lire iu 
 
 * In Class IV, and all the classes of gunboats, the height of the lower port-sill above the water-line has been given as height of centre of muzzle of gun above the water-line, these vessels having no ports. 
 
SHIPS FOR WAR. 
 
 121 
 
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122 
 
 SHIPS FOR WAR. 
 
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THE DRAWINGS. 123 
 
 CHAPTER XXIV. 
 
 THE DRAWINGS. 
 It is absolutely necessary in order to scientifically construct a student of Na- 
 
 T u , 1 1 • "^ 1 j^i 1 -n 1 ,-, val Architecture 
 
 vessel, that the designer, whether owner or builder, should should under- 
 thoroughly understand ship drawing. dra'wing."' 
 
 The first process towards building a properly constructed ves- Fif^' ^tep to- 
 
 ,., K ,T.ni IT wards Ihe con- 
 
 sel, is to make accurate drawings of her on paper, upon a reduced struction of a 
 scale. From these drawings, other drawings are made or "laid v^^^^'- 
 ofif," upon the mould loft floor. Prom these last mentioned draw- 
 ings in chalk, moulds of thin deal are made, and by the help of 
 these moulds, the timbers composing the "frame" of the vessel 
 are cut out, and the frame put together. 
 
 The drawings from which a ship is constructed are three in ^^^e plans of a 
 
 , ° ^ shjp drawing. 
 
 number : 
 
 1st. The sheer plan, containing a series of longitudinal vertical 
 sections. 
 
 2d. Tfie half-breadth plan, containing a series of longitudinal 
 transverse sections.' 
 
 3d. The body plan, containing a series of transverse vertical 
 sections. 
 
 The student should begin by copying a set of drawings, which to commenceTy 
 is quite easy. Like other arts it requires a little practice, but '??'''"= ""iP'^^ °^ 
 aftei- a few attempts he will become dexterous in the Use of the ^ '^ "'™''^^" 
 irregular curves and the drawing pen. There are three methods 
 of copying: 
 
 First. By a tracing of the original on prepared transparent j,,^'"*''^'''^'^''''^" 
 paper or muslin, placed over it. 
 
 Second. By placing the original pkn over a sheet of paper, 
 and pricking the principal points through with a fine needle so 
 as to mark the lower sheet; guided by these points, the draughts- 
 man can fill in the detail; a little practice, only, being necessary 
 and an expert draughtsman requiring but a few points. Care 
 must be taken to hold the needle upright. 
 
 The third plan is, to measure the principal points with a pair g^^yJI,*' """''' °^ 
 of dividers, or a scale, and to transfer these points to the copy, 
 this is the best method for the student. After copying one or 
 two drawings in this manner, he will become acquainted with 
 the connection between the different lines in the plans. Some 
 draughtsmen stretch their paper on the drawing board by the 
 sponging process which presents an excellent surface for draw- 
 ing on; but when cut from the board, the paper invariably con- 
 tracts, and therefore the drawing will be more or less inaccurate 
 according to the extent of this contraction. 
 
 The best method is to hold the paper to the board with Mode of pre- 
 "thumb tacks." Suppose then, that the student is to copy g, p^"''^ paper, 
 ship drawing. It is only necessary to describe the order in 
 which the lines should be copied, the connection between them, 
 and the method of ending them. 
 
 As a general rule, the lines representing the victual parts of colore used in 
 the vessel are' drawn in black; the water-lines or horizontal sec- ^'"'' ^™"''"^" 
 
124 THE DRAWINGS 
 
 tions below the load water-line is green ; those lines which are 
 not part of the vessel, but are of use in making the drawing, in 
 ticked black ink; and the inboard work or profile, in red ink. 
 
 siiad'^"" *"* '^^^ ^'^^^ ^^ supposed to come from the right hand upper cor- 
 ner of the paper, and consequently the upper and right hand sides 
 of a solid are represented by fine or thin lines ; those on the lower 
 or left hand, by thicker Imes ; thus, the lower side of the keel is 
 thick, the fore side of the masts are thin, &c. The drawing 
 should be completed w pencil before ink is used, 
 
 draiT""*'"''^ The middle line of the half-breadth plan is first drawn, and 
 
 from this line as a base, all breadths are measured — perpendicu. 
 
 lar to it, the foremost perpendicular, and then, at their proper 
 Vertical sec- distances, the lines corresponding to the other vertical sections 
 "°°^- are to be drawn. 
 
 ^Load water fije load water^iue of the sheer plan, is drawn parallel to the 
 
 middle line of the half-breadth plan, and consequently the se& 
 
 tions are yertieal to it,* 
 Load water Prom the load water-line all heights and depths are measured, 
 base "h? yachts^ it is therefore the base of the sheer and body plans. The rabbet 
 but rabbet of jjj^g j^^^ lowcr sidc of the keel in the sheer plan are next drawn, 
 
 keel in larger . ^ iiij. 
 
 vessels. the intcrmodiate water-lmes are sometimes drawn parallel to 
 
 the load water-line and sometimes at equal distances between it 
 and the rabbet line of the keel ; in the former case there is less 
 trouble in transferring the heights to the body plan, in the latter 
 they are better adapted for making the calculations. 
 Sheer lines. The several sheer lines must next be set off, the heights taken 
 from the water-line on each section, and a penning batten made 
 to pass through the points, and a line drawn along the batten, 
 stem, rake of The Stem, rabbet of stem, the stern-post and its rabbet are 
 
 stern ani} coun- ^^^^ j^ order. The counter may be copied by drawing in the 
 original a continuation of' the rake of the counter through the 
 water-line to some other line below it-; this line transferred to 
 the copy will give the rake of the countet. The detail of this 
 part is then easily filled in. 
 Paif-breadths. The different half-breadths of the water-lines and of the sheer 
 lines must next be transferred from the original, and a thin ba1> 
 ten "penned" to pass through the points in each section. Some 
 practice and considerable patience, is necessary in using the 
 penning battens and weights on it; if the batten is too pliant, 
 the line may not be a fair curve, and«f too stiff it is difBcult to 
 confine it in its proper position. 
 Endinjs of the Thc endipgs of the sheer lines and water-lines in the half- 
 
 lines. breadth plan are obtained by squaring down from the sheer plan 
 
 the intersection of each line respectively with the fore edge of 
 the rabbet of the stem, or the after edge of the rabbet of the 
 stern-post, as the case may be, to the middle lino of the half- 
 breadth plan, and from these spots set off from and perpendicu- 
 lar to the middle line half the siding of the stem or stern-post at 
 the respective heights, these latter spots will be the endings, 
 required. 
 
 *This, however, is not always the case, for it isnsual to make theupper edge! of the rabbet 
 of the keel the basinof the sheer and body |ilans, but where there i,< much diKV-rcncn in thu 
 ^raft of water forward and aO, the toad \vatcr-linc i? preferable. 
 
THE l)IlAWIN(iS. 
 
 125 
 
 Water lines. 
 
 After body. 
 
 The middle line of the body plan is drawn square to the base, bo^jj'''la'n.''"° "^ 
 and the half siding of the stem and stern-post on each side of it. 
 It is usual to make the base of the sheer and body plans in one 
 line, and therefore, when the load water-lifie is the base, a con- 
 tinuation of it from the sheer plan will be both the base and the 
 load water-line of the body plan also. When the other water- 
 lines are parallel to the base they may also be continued, but 
 when not parallel, the distance of each water-line from the Ijase 
 must be transferred from the sheer to the body plan. Lines 
 drawn square to the middle line at these heights will represent 
 the vertical height of each water-line at each section in the body 
 plan, and on these lines the respective half-breadths, taken from 
 the half-breadth plan, must be set off from the middle line, the 
 several sheer lines are transferred in a similar manner. A curve 
 passing through the points thus found will give the shape of 
 that section in the body plan. The better way, is, to take off 
 the heights and breadths of each section separately, commencing 
 ■with the midship section which is often drawn on both sides ; 
 the section of the fore-body being drawn on the right, and those pore body. 
 lOf the after-body on the left hand side of the middle line. The 
 sections of the body plan will end at the half siding of the keel, 
 stem or stern-post as to breadth, and at the lower edge of the 
 rabbet of the keel as to depth in each section. 
 
 When the iiitermediate water-lines are parallel to the base, 
 the breadths have merely to be set off on them. In drawing 
 these sections of the body plan, the irregular curves must be 
 used, and each line drawn in small pieces. After a little prac- 
 tice this is very easy, although, at first, some difficulty may be 
 experienced in forming fair and correct curves. By tracing about 
 .a dozen body plans the student will become accustomed to the 
 use of the curves. When the body plan is so far completed it 
 jnay be necessary to "fair the body" by running diagonal and 
 buttock liniss. In transferring the former from the body to the '""'>'• 
 half-breadth plan, the distance of each section is taken on the 
 line of the diagonal from the middle line of the body plan and 
 applied to the corresponding section of the half-breadth plan. A 
 batten passed through these points will detect any unfairness in 
 the line, which must be corrected. A diagonal line ends in the Diagonal lines, 
 half-breadth plan at the height of its intersection with the half 
 siding of the stem or stern-post in the body plan, transferred to 
 the rabbet in the sheer plan, and squared down to the half-breadth; 
 on this, the diagonal distance of the middle line to the half siding 
 line of the body plan is set off, wiich gives the ending required. 
 
 A buttock line in the body and half-breadth plans is drawn 
 parallel to the middle line, the distances of its intersection with ' 
 each section from the base, are transferred from the body to the 
 sheer plan, and a batten passing through these spots will detect 
 any unfairness, or, as a further proof the intersection of each 
 water-line with the buttock line in the half-breadth plan may be 
 squared up to the respective water-lines in the sheer plan; if the 
 buttock line of the sheer plan does not agree with these last 
 f(?und points some alteration must be made until the body is 
 fair, which is the case when all the intersecting points exactly 
 coincide,, and the diagonal, buttock and water-lines of each plan 
 
 Ffliringr the 
 
 Buttock and 
 . bow lines. 
 
126 THE DRAWINGS. 
 
 are fair lines. The forward portion of the buttock lino is called 
 the boiv line. 
 
 drawta^'™°''™ ^^ *^^ foregoing description, the body, and half-breadth plans 
 
 are drawn to the outside of the plank ; in the ship-builder's 
 
 ship-ijuiidcrs working drawings the out side of the timbers only, is shown. In 
 
 working draw- this, case the sections of the body plan and the water-lines of the 
 
 half-breadth plan are ended by describing an arc of a circle with 
 
 the- radius of the thickness of the plank from the ending before 
 
 found as a centre ; the lines will end at the back of this arc. 
 
 Best mode of The best rule in copying a drawing is to take as few points 
 
 co^pyinga law- ^^ possible from the original, and to find the points in one plan 
 
 from those in another; by this means any error is much less 
 
 likely to produce an unfair or impracticable drawing. 
 
 Example of Having now given some general idea of the method of copy- 
 
 constmction on . i • i - 1.7 j. t j_ n j. j.i j. j.- 
 
 the tentative sys-ing a Ship drawing, the student may proceed to the construction 
 '■"'"■ of a yacht on the simplest or tentative system, in which the 
 
 amateur Constructor takes an existing vessel or vessels of known 
 good qualities, most nearly resembling that which he proposes 
 to construct, as his guide, and proceeds to adopt that which is 
 good in the vessel he establishes as his model, and to improve 
 upon that which is bad. 
 
CONSTRUCTIOX. 127 
 
 •CHAPTER XXV. 
 
 CONSTRUCTION. 
 Having decided upon the following principal points, namely: Preliminary. 
 
 1. Displacement. 
 
 2. Length. 
 
 3. Breadth. 
 
 4. Depth.' 
 
 5. Drag. 
 
 6. Rake of the stem and stern-post. 
 
 Y. Height of the deck above the load water-line, amount of 
 sheer, and height of the bulwarks. 
 
 8. Position of the midship section. 
 
 9. Form and area of the midship section. 
 
 10. Load water-line, its ratio to 'displacement, midship section 
 
 and circumscribing parallelogram. 
 
 11. C^tre of gravity of Displacement. 
 
 12. Inclined water-line. 
 
 13. Stability. 
 
 14. Size of rudder.' 
 
 15. Area and centre of effort of sails, and position of latter in 
 
 regard to centre of lateral resistance. 
 
 16. Angle of sail. 
 
 IT. Size of masts and spars, and rake of masts. 
 The next thing to be considered, is, by what system the ves- 
 sel should be constructed : 
 
 The common method of designing a vessel, is that which dis- ordinary sy«- 
 cards all mechanical rules for forming the various lines, and relies '*'"■ 
 entirely on a consideration of those forms, which experience has 
 taught are best adapted to the particular object in view. 
 
 To enable a' Constructor to design a vessel by this method 
 (by far the most common one in this country) it is essentially 
 necessary that he be provided with drawings and calculations 
 of vessels of similar size already built; from these he can adapt 
 and modify such parts as be considers are applicable to his pur- 
 pose. When the rough drawing is made, the displacement, areas 
 of midship section and load water-line, and the position of the 
 centre of gravity of displacement must be calculated; should the 
 results differ materially from those of the precedents, the Con- 
 structor must consider the probable effect of such difference upon 
 his intended vessel, and then make such alterations in the design 
 as he imagines necessary, repeating the calculations and making 
 further alterations if requisite, until the result accords with his 
 intention, and unless anything very novel or extraordinary is 
 attempted this method will succeed pretty well, though of course, 
 much will depend upon tte proficiency of the Constructor, and 
 the extent and quality of his precedents. Without these, the 
 system is obviously insufficient. 
 
128 CONSTlir'C'riOX. 
 
 of Y.TcouTuf- '^^^ system given in the greater part of this work, is familiarly 
 sell." ° known as the "wave" system of Mr. J. Scott Russell, and the? 
 
 shortest and best idea of it is as follows : 
 
 The genesis of the wave curves is as follows: The length of 
 the fore-body as compared with the length of the after-body, is- 
 as 6 to 4, therefore the w^hole length is divided into ten eqtial 
 parts, and six allotted to the fore-body. A circle whose diame-- 
 ter is equal to the half-breadth determined on, is described with 
 its circumference touching the central line where the fore and 
 after bodies join, its circumference is divided into sixteen equal 
 parts, and the central lines of the fore and after bodies are each- 
 divided into eight equal parts; then for the curve of the fore^ 
 Fure body. body from the foremost division on the central line, lay off the 
 perpendicular distance of the central line from the first or lowest 
 division on the circumfefence of the circle, and from the second 
 division on the central line, the perpendicular distance of the 
 second division on the circle, and so of each of the eight divisions ; 
 then through these points draw a litje, and it will be the wave 
 line curve forward. The curves of all the water-lines are similar. 
 After body. YoT the after-body lines, are drawn from the divisions on the- 
 circle parallel to the central line, on whieh the distances of the- 
 divisions on the central line from the fore-end of the after-body 
 are respectively laid off from the divisions. A line drawn through 
 these points will give the wave curve for the after-body. 
 "Chapman's" But there is another system of Naval Construction, discovered 
 fcoiic system!'"^* ^J the Celebrated Swedish Admiral, Chapman, and known as 
 "the parabolic system >" audits applicabilitj^, completeness, and 
 simplicity render it admirabh^ adapted for every description of 
 vessel. 
 
 chapm£%ys- ^^ ^* * Constructor can determine every particular of his ves- 
 tern. sel; he can be certain that she will have the required displace-- 
 
 ment, possess the proper amount of stability and trim as he' 
 intends, he has nothing to do, But after making '<& few prelimi- 
 nary calculations, to proceed to trace the Vertical sections of the' 
 Great latitude ^°^y P^^°- '^^''^ ^° ^he advafltagos of the system stop here, as' 
 given to the con- evcry Variety of form, both of water-line and vertical section is 
 structor. equally applicable ; in fact the Constructor has great latitude in 
 
 the shape of his vessel, so long as he does not depart from the' 
 areas and centres of gravity settled upon at the outset. The 
 outline of this method of construction is simply this:' 
 ^Origin of the Chapman endeavored to discover hotv far the areas of con- 
 jem'*'"''"^" ^'"" secutive sections of the best known vessels followed any regular' 
 law. He, therefore, divided the area of each section by a con- 
 stant quantity, the breadth of the midship section, and set off 
 distances proportional to these quotieHts on perp'endiculars to a 
 base line, the perpendiculars being placed at intervals equal to 
 the distance between the sections, and he found that the curve 
 which passed through the ends of these perpendiculars, might 
 be conveniently represented as a parabolical curve, both in the' 
 fore and after bodies, the vertex of the curve being at the middle' 
 of the base line, and the line representing the midship sectiou 
 forming the axis. 
 
CO^vSTRUCTION. 
 
 129 
 
 Assuming then the fundamental equations 
 D 
 
 n = . 
 
 IM — D 
 
 & = (n + 2) X a 
 
 (1) 
 (2) 
 (3) 
 
 Chapman's fun- 
 damental equa- 
 tion. 
 
 y =px 
 Where D is the load displacement in cubic feet, 
 
 I is the length of the load water-line in feet. 
 a is the distance of the centre of gravity of displace- 
 ment from the middle of the water-line in feet. 
 k is the distance of the midship section from the mid- 
 dle of the water-line in feet. 
 n being what is termed the exponent of the parabolic 
 
 curve. 
 p the parameter. 
 The two last quantities being used to assist the calculations ; 
 n is. determined from equation (1), andp from the formula 
 
 r I 
 
 = 2 
 
 + *: 
 
 M 
 
 (4) 
 
 which is, in fact, a particular form of (3), and where, when the 
 centre of gravity of displacement is abaft the middle of the water- 
 line, the plus sign is used for the fore-body, the minus sign for the 
 after-body, and vice ver:-a when the centre of gravity of displace- 
 ment is before the middle. 
 
 X and y being co-ordinates of the curves, or in other words y 
 is the distance of any one section from the midship section, and 
 X the difference between a line representing the area of the mid- 
 ship section, and a line representing the area of any one section. 
 
 From this last definition, it follows, 'that 
 Area of section — M — x 
 
 yn 
 
 and from (3) x (5) 
 
 P 
 
 The Constructor has now the means of ascertaining the areas 
 of the successive sections, by calculating n and p, and then sub- 
 stituting the successive values of y in the equation (5). 
 
 In practice the calculations are confined to one-half the vessel 
 only, and therefore, instead of x and M, one-half of these values 
 is taken ; and with some degree of inaccuracy in the tables, as 
 usually constructed, these halves are treated as whole areas. 
 
 For the sake of illustration, suppose the Constructor about to 
 design a schooner yacht, 
 Where ft. 
 
 Load displacement = D = 5040 
 
 Length of load water-line = I = 80 
 Area of midship section =M= 110 
 Distance of the centre of gravity of displacement from the 
 middle = a = 1-6 ft. abaft. 
 
 17 
 
 Example, 
 
1130 
 
 Example. 
 
 CONSTRUCTION''. 
 D 
 
 Now to find n which = - 
 
 ZM — D 
 
 5040 
 
 (1) 
 
 = 1.34 
 
 80 X 110 — 5040 
 
 Next, k = (n + 2) X a (2) 
 
 or = (1.34 + 2) 1.6 = 5.25 abaft. 
 
 Then for the fore-body , 
 
 I 
 
 log. 2 jp = log. 2 -^ 2 
 
 . + k 
 
 80 
 
 -+5.25 
 ). =log. ^ 2 
 
 M 
 
 55 
 
 : 478165 = log. 3, 
 
 For the after-body 
 
 log.2p=log 2-^2 
 
 [^ 1 
 
 — k 
 
 2 
 
 n 
 
 ^=log. ^ 
 
 M 
 
 80 ] 1-34 
 
 5 25 
 
 2 l- = 3245167=log2.11 
 
 55 
 As this quantity is used in multiplication only, the logarithm 
 of it only need be found ; then, by substituting the successive 
 values of y in the equation 
 
 a; = — ' 
 
 P 
 which must be calculated by logarithms, the following table is 
 constructed: 
 
 For the fore-body x = 
 
 2/1.34 
 
 
 
 
 Half area of M. S. 
 
 y 
 
 
 X 
 
 X 
 
 or distance from 
 
 the 
 
 2 
 
 =: 
 
 midship section. 
 
 
 or abscissa. , 
 
 2 
 half area of section. 
 
 feet. 
 
 
 square feet. 
 
 square feet. 
 
 7.5 
 
 
 4.95 
 
 50.05 
 
 15.0 
 
 
 12.5 
 
 42.5 
 
 22.5 
 
 
 21.5 
 
 33.5 
 
 30.0 
 
 
 31.7 
 
 23.3 
 
 37.5 
 
 
 42.8 
 
 12.2 
 
 For the after-body x ■ 
 
 2.11 
 
 2/ 
 or distance from 
 midship sections 
 
 the 
 
 X 
 
 or abscissa. 
 
 Half area of M. S. 
 
 X 
 
 2 
 half area of section. 
 
 feet. 
 7.5 
 15.0 
 22.5 
 80.0- 
 
 square feet. 
 
 7.05 
 
 17.9 
 
 30.7 
 
 45.2 
 
 square feet. 
 
 47.95 
 
 37.1 
 
 24.3 
 
 9.8 
 
COXSTRUCTIOX. 1?>1 
 
 A little careful study of the foregoing calculation will enable 
 any one, with a slight knowledge of logarithms to comprehend 
 the working of the system. No more calculations than the fore- 
 going are I'equired, as the position of the centre of gravity, the 
 displacement and the area of the midship section, are all, by 
 Chapman's method, pre-determined quantities, and form the 
 basis of the design, therefore to calculate them after the de- 
 sign is completed, would be merely a useless repetition. 
 
 Before proceeding with the construction drawing of the expPr'ienc.r'i'ifis 
 schooner yacht taken as an example, it will be well to give the shovvnuibKu-e- 
 principal proportions which experience has shown to be useful hereireated ai. 
 and applicable to such vessels. 
 
 The breadth generally = the length x -26 for fast schooners. 
 
 The depth " — the breadth x .3952 
 
 The area of midship section = breadth x depth x -6. 
 " " " load water-line = breadth x length x .TQ21. 
 
 Load displacement in cubic feet = length x breadth x depth 
 X .3623. 
 
 The midship section from the fore end of the water-line zm 
 length X -SlY. 
 
 The centre of gravity of displacement from the fore end of the 
 water-line = length x -55 for schooners. 
 
 Or generally = length x .02 abaft the middle. 
 
 In making the construction drawing, the same order is to be oamum to the 
 observed as in copying, but the draughtsman is left to his own 
 resources, as to the dimensions and forms of the different parts. 
 His first care should be to understand distinctly and exactly the 
 sort of vessel required. Let it be assumed, then , that this 
 schooner yacht is to be 144 tons, or 5040 cubic feet the displace- 
 ment required. The draft of water not to exceed eleven feet, 
 and that she is to have as much speed as is consistent ■ with a 
 certain degree of accommodation. In Fincham or Marrett, the 
 student will find tables giving the dimensions of some vessel of 
 suitable character and similar displacement, and is thus enabled 
 to fix the length of the water-line at 80 feet, then the breadth 
 = .26 1= 20.8 feet. 
 
 But, in this case, as the breadth is rather limited, and ac- 
 commodation is a desideratum, it may probably be better to 
 give a small additional breadth to ensure sufficient stability, dis- 
 placement and accommodation. Suppose, therefore', the' breadth 
 is determined at .2T I = 21.5 feet, then the depth = .3952 b = 
 8.5 feet. 
 
 If to this is added one foot for the depth of the keel below its 
 rabbet, the mean draft of water is made 9.5 feet, and with the 
 maximum draft of eleven feet aft, this gives eight feet for the 
 draft of water forward. This, however, is rather more "drag" 
 than may be advisable, and therefore, the draft forward may be 
 increased to nine feet with advantage. 
 
132 
 
 CONSTRUCTION. 
 
 • The load displacement = length x breadth x depth x -36 
 = 5,296 cubic feet = 151 tons, an excess of seven tons abc 
 that required, or 
 
 displacement, 5040 
 
 __1 = = .3447 
 
 length X breadth x depth, 14620 
 
 or the proportion the displacement (5040 cubic feet,) bears 
 
 the circumscribing parallelopipedon. 
 
 The Constructor will judge by comparison, whether this p 
 portion is adapted to the required purpose, if not, some alte 
 tion in the dimensions must be made. 
 
 The area of the midship section = breadth x depth x. -6 
 110 square feet. 
 
 The exponent of the parabolic curve, 
 
 D ^ 5040 
 n = = = 1.34 
 
 ZM— D 
 
 80 
 
 5040 
 
 X 110 
 
 Taivio of n in Whicli nearly corresponds with the value of n in the case 
 yauiit 'America.' ^j^g y^pj^^ "America," and, therefore, it may be presumed tl 
 the proposed vessel will, by assigning that value to n, be of p 
 portionate fullness in relation to the dimensions. 
 
 The distance of the centre of gravity of displacement ab 
 the middle of the. load water-line, will be length x -02 I = 
 feet = a, and the midship section will be from (2) 1.6 (1.34 + 
 =r 5.25 feet abaft the middle. 
 
 The calculations for the areas of the sections of this ves 
 have already been given, (page 130,) and therefore no repetit: 
 is here necessary. 
 
 Having arranged these preliminaries, the drawing may 
 commenced, the sheer, rake of the stern, and form of the count 
 can be taken from tables, or from other drawings, and altered 
 Midship eec- suitthe Constructor's judgment. The midship section in the sh 
 "• plan, must be drawn at its proper distance from the fore end 
 
 the load water-line, and the other sections at the determii 
 distances from the midship section; in the present case they 
 placed at intervals of seven feet six inches. In designing 
 midship section, which is done in the body plan, care must 
 taken that the half area = 55 square feet exactly; the sect 
 being sketched in by the eye — its area may in this prelimim 
 part of the work be found by the "old rule'^ thus: 
 Ordinates. 
 
 Commence- 
 ment of the 
 drawing. 
 
 Load water-line. 
 
 lO.tS (half 
 
 Second water-line. 
 
 10.1 
 
 Third water line, 
 
 7,0 
 
 Fourth water-line. 
 
 2.4 
 
 Keel, 
 
 . 3 (half.) 
 
 25.025 
 
 2.2 = distance between water-lii 
 
 55.055 
 
CONSTUUdTION. 
 
 ■1 '>o 
 J .)0 
 
 Wave lines. 
 
 It is hardly to be expected that, at the first trial, the midship 
 section will be drawn of the correct area, but after one or two 
 alterations it will generally be obtained. When this is done, 
 the load water-line from the midship section to the fore end 
 must be drawn in the half breadth plan. Having determined 
 from Fincham or Marrett's tables of construction, or from other 
 sources, the angle which it should make with the middle line 
 forward, a line can bo drawn for some distance from the ending 
 at that angle; then, with a small penning batten, the breadth 
 at the midship section is joined to this line; this will give a 
 "straight" water-line. When any hollow is required in the wa- 
 ter-line, the batten may be continued to the ending, describing 
 the hollow required, or the load water-line may b'e formed accord- 
 ing to Russell's wave system, if the Constructor prefers that 
 system. 
 
 The half breadth lines of the deck and roughtree rail may 
 next be. drawn, of such shape as the Constructor thinks best. A 
 section intermediate with the midship section and foremost 
 extremity drawn in the body plan, (the half breadth of the load 
 water-line being taken from the half breadth plan,) and altered, 
 if necessary, until its half area corresponds with the area already 
 determined for such section, will give a guide for drawing the 
 other water-lines of the fore body in the half breadth plan. 
 When the remaining sections are drawn, if their areas do not 
 agree with th.e calculated areas, alterations must be made. 
 
 The after body is proceeded with in a similar manner, and 
 when the whole of the sections are completed, the designer may, 
 perhaps, require some alterations to be made. 
 
 When such alterations from the original plan, involve any 
 considerable change of form or alteration of the several sectional 
 areas, it may be ad.visable to calculate the displacement and the 
 position of the centre of gravity of displacement, &c., in order to 
 prevent too great a deviation from the original intention; but 
 when no alteration, or at least only a slight one is made, this is 
 not necessary. Plate II shows a design for a schooner yacht in 
 conformity with the foregoing dimensions and calculations, and 
 without any material alterations from the established areas, in 
 order to show how well adapted for construction the parabolic 
 system is. 
 
 To complete the vessel, the masts and sails have to be Masts ana sails, 
 arranged. The area of the vertical longitudinal section =1 xJi' 
 = 80 X 10 = 800: area of load water-line = Z x 6 X -T = 
 1204, these sums multiplied together — 963200, which is the 
 co-eflBcient for the dimensions of the spars. (See table III, pp. 
 36, 31, Marrett's yacht building.) 
 
 The centre of effort should be placed at .006 of the length of centre of ef- 
 load water-line = .48 feet abaft the centre of gravity of vertical*^" °*'^''"' 
 longitudinal section, and at the height of the centre of effort, the 
 main-mast will be one-tenth of the length of the water-line — 8 
 feet abaft the centre of the vertical longitudinal section. The 
 fore mast will be .844 of the length of the water-line = 27.5 feet 
 before the main-mast. 
 
 With these positions, a sail drawing as in PI. Ill must be 
 made to the dimensions given in Marrett's table of schooners' 
 
134 CONSTRUCTION, 
 
 spars ; and the area of sail and position of centre of elTort, both 
 as to height and length calculated. If the results do not agree 
 with the established position for the centre of effort, some change 
 must be made, either by re-adjusting the proportion of fore and 
 after sail, or by moving the masts and preserving the same 
 measurement of spars, as it is imperatively necessary that a 
 proper and correct balance of sail should exist, otherwise, the 
 care of the Constructor in designing the hull has been complete- 
 ly thrown away. 
 
 If the vessel is constructed on the wave theory, the mode of 
 balancing the sail has already been shown. 
 
CALCULATION' H. 135 
 
 CHAPTER XXVI. 
 
 MAKING THE CALCULATIONS. 
 
 The calculations for an ordinary vessel, are exceedingly simple calculations. 
 > — a little method and arrangement, however, shorten the process 
 amazingly. 
 
 Two rules (generally known as Sterling's rules) are used by 
 the majority of Constructors, they are briefly as follows : 
 
 Divide the base of the area, bounded by a curve, into any even eui« i«t- 
 number of equal parts, which of course, gives an uneven number 
 of ordinates. The general expression of the rule is then 
 
 r 
 Area =[A + 4P + 2Q] — 
 
 3 
 Where A = sum of the first and last ordinates, 
 
 4 P = sum of the even ordinates multiplied by 4, 
 2 Q = sum of the remaining ordinates multiplied by 2, 
 and r =? is equal to the linear measurement of the com- 
 
 mon interval between the ordinates. 
 
 The above formula may also be put in the following form; 
 (A ) 2r 
 
 Area= ■^_ + 2P + Qi-x — 
 (2 ) 3 
 
 The second of Sterling's rules is as follows : 
 
 Divide the base of the area, bounded by a cun'e, into a num- Euieznd. 
 ber of equal intervals which shall be in number a multiple of 
 three, which, of course, will give one additional to the number 
 of ordinates, then the area of the figure may be determined by 
 the following formula: 
 
 St* 
 Area = .Ja + 2P+3q|x — 
 *- -* 8 
 
 where A = Sum of the first and last ordinates, 
 
 2 P — sum of the 4th, *rth, 10th, 13th, &c., multiplied 
 
 by 2, 
 
 3 Q = sum of the remaining ordinates, multiplied bv 3 
 
 or 2nd, 3rd, 5th, 6th, 8th, 9th, &c. r is the 
 common interval as before. 
 
 This formula may also be modified as follows: 
 f A ) 3r 
 
 Area = .) _ + P + 1.5 Q f- x — 
 (2 ) 4 
 
 In the first rule, the curve bounding the area is supposed to 
 be a portion of a common parabola, while, in the second rule, the 
 qurve is assumed to be a .cubic paralDola. The results from either 
 rule, differ in so trifling a degree as to be practically insignifi- 
 cant. 
 
 The plan of calculation most applicable for a small vessel like 
 the yacht in question, is as follows: 
 
sev 
 ties in. 
 
 136 OALCULATIOXS. 
 
 Pian of caicu- On the drawing of the vessel, (Plate II,) fix Xo. 1 section, in the 
 tabilTto "luiShe sheci'plan at some determinate place, such as the fore end of the 
 erai quami- Joad water-line, then divide the length of that line into any uneven 
 number of equal parts by lines perpendicular to it, which will 
 represent the vertical sections. Draw a body plan of these sec- 
 tions to the outside of the plank, and having the load water-line 
 as a base in the sheer plan. Divide the distance from the load 
 water-line, to the line of the lower edge of the rabbet of the keel 
 continued, at No. 1 section into an odd number of equi-distant 
 parts, as five inclusive, also divide the corresponding distance at 
 the aftermost section, into a like number of equi-distant parts, 
 draw lines from No. 1 section to the aftermost section joining 
 these divisions, and transfer the heights of the intersections of 
 these lines with the sections, to the body plan. A table must 
 now be ruled similar to the accompanying form, and the half 
 breadth of each section at each water-line measured from the 
 body plan, inserted in its proper place in the table. (See Table, 
 p. 136J.) 
 
 A description of each column, is as follows : 
 a. The number of the vertical section. 
 Distance be- &. The distance between the water-lines at each section respec- 
 lines— infw"" '"^' tively ; it is thus found: the distance of the load water-line to 
 niumi. the lower edge of the rabbet of the keel at No. 1 section, is eight 
 
 feet, and at No. 11 section' it is 9.875 feet, then as No. 1 and 
 No. 11 sections are seventy-five feet apart, it follows that the 
 difference of draft of water in seventy-five feet, is 1.875 feet, and 
 the difference between each section when (as is in this case) they 
 are 7.5 feet apart is 
 
 1.875 X '7.5 ,„... 
 _ ^.1875, 
 
 as there are four'water-lines the distance between them, at each 
 succeeding section will be increased by the fourth part of .1875 
 = .047 feat. At No. 1 section, the water-Jines are two feet apart; 
 at No. 2, 2 + .047 = 2.047 ft. apart, and so on. 
 
 c. The number by which the ordinates are to be multiplied in 
 finding the displacement by horizontal sections. 
 
 d. The ordinates of the lowest Ipngitudinal section, or half 
 siding of the keel at each section. 
 
 e. The ordinate of the lowest water-line. 
 /. The ordinate of the third water-line. 
 g. The ordinate of the second water-line. 
 h. The ordinate of the load water-line. 
 
 i. The sums of the ordinates as multiplied. 
 
 k. The half areas of the sections = i2L. thus, for No. 1 sec- 
 
 ,. 72.2 X 2.282 ,, „ , . ^ 
 
 tion, = 54.9 square feet. 
 
 I. The half areas of the sections multiplied by the numbers iti 
 column c respectively, the sum of the column I multiplied by 
 one-third of the common interval between the sections, gives one- 
 
 Z X 7.5 
 half the displacement in cubic feet, or s X 2 = whole 
 
CALCULATIONS FOR A SCHOONER YACHT OF BIGIHTY FEET LENGTH. [136^ 
 
 a 
 
 b 
 
 c 
 
 T-H 
 
 d 
 
 e 
 
 / 
 
 g 
 
 h 
 
 i 
 
 k 
 
 I 
 
 m 
 
 n 
 
 
 
 P 
 
 r 
 
 s 
 
 ( 
 
 u 
 
 V 
 
 w 
 
 
 
 keel 
 
 wl.4 
 
 wl.3 
 
 wl.2 
 
 Iwl.l 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Gi 
 
 ^ 
 
 1—1 
 
 
 1 
 
 2-000 
 
 -3 
 
 n 
 
 -3 
 
 -3 
 
 •3 
 
 -3 
 
 -3 
 
 to 
 
 CO 
 
 tb 
 
 00 
 CO 
 
 1— 1 
 
 2-4 
 
 2-4 
 
 
 
 -3 
 
 
 
 -3 
 
 -3 
 
 -3 
 
 -3 
 
 
 
 
 *? 
 
 CT 
 
 CO 
 
 j 
 
 -03 
 
 2 
 
 2-047 
 
 
 ■6 
 
 1-4 
 
 2-1 
 
 2-8 
 
 114 
 
 45 6 
 
 1 
 
 45-6 
 
 11-2 
 
 11-2 
 
 2-8 
 5-9 
 
 2-5 
 
 26 
 
 10-4 
 
 10-4 
 
 
 -3 
 
 IN 
 1-3 
 
 op 
 2-7 
 
 CO 
 
 4-1 
 
 00 
 
 21-95 
 
 3 
 
 2-094 
 
 5-5 
 
 22-9 
 
 45-8 
 
 2 
 
 91-6 
 
 11-0 
 
 ?2-0 
 
 4-8 
 
 5-4 
 
 10-8 
 
 21-6 
 
 
 m 
 -3 
 
 1-8 
 
 4-1 
 
 to 
 1—1 
 
 lis 
 
 166-37 
 
 4 
 
 2-141 
 
 ■«* 
 
 6-1 
 
 7-8 
 
 34-2 
 
 1368 
 
 3 
 
 410-4 
 
 31-2 
 
 93-6 
 
 8-4 
 9-8 
 
 7-0 
 8-7 
 
 7-7 
 9.2 
 
 30-8 
 18-4 
 
 92-4 
 
 
 m 
 
 
 ob 
 
 
 cc 
 
 474-55 
 
 5 
 
 2-188 
 
 <N 
 
 -3 
 
 2-0 
 
 5-1 
 
 7-8 
 
 9-4 
 
 431 
 
 86-2 
 
 4 
 
 344-8 
 
 18-8 
 
 75-2 
 
 736 
 
 
 fO 
 
 o 
 
 6 
 
 CC 
 
 
 830-50 
 
 6 
 
 2-235 
 
 ^ 
 
 -3 
 
 2-2 
 
 6-1 
 
 9-4 
 
 10-3 
 
 to 
 
 51-5 
 
 206-0 
 
 5 
 
 1030-0 
 
 41-9 
 
 
 10-7 
 
 9-9 
 
 10-3 
 
 41-2 
 
 206-0 
 
 
 CO 
 
 00 
 
 do 
 
 
 to 
 co 
 
 CO 
 
 o 
 I— 1 
 
 20 
 
 6-0 
 
 1092-73 
 
 7 
 
 2-282 
 
 (M 
 
 -3 
 
 2-3 
 
 6-4 
 
 9-8 
 
 10-? 
 
 
 54-9 
 
 109-8 
 
 6 
 
 658-8 
 
 21-4 
 
 
 11-0 
 
 10-4 
 
 10-7 
 
 21-4 
 
 128-4 
 
 
 n 
 
 6^ 
 
 00 
 
 CO 
 
 o 
 
 128-4 
 
 1225-04 
 
 8 
 
 2-329 
 
 -* 
 
 -3 
 
 n 
 
 1-7 
 
 5-3 
 
 8-7 
 
 10-3 
 
 48-7 
 
 194-8 
 
 7 
 
 1383-6 
 
 41-2 
 
 388-4 
 
 JO-8 
 
 9-7 
 
 10-3 
 
 41-2 
 
 288-4 
 
 
 .00 
 
 to 
 t-l 
 
 CO 
 
 CO 
 
 CO 
 
 o 
 
 1092-73 
 
 9 
 
 2-376 
 
 
 -3 
 
 CO 
 
 1-1 
 
 3-6 
 
 6-6 
 
 to 
 
 9-1 
 
 37-5 
 
 75-0 
 
 8 
 
 600-0 
 
 18-2 
 
 145-6 
 
 10-3 
 
 8-2 
 
 9-2 
 
 18-4 
 
 147-2 
 
 
 a: 
 
 753-57 
 
 iO 
 
 2-423 
 
 -3 
 
 -8 
 
 1-9 
 
 4-0 
 
 7-0 
 
 CO 
 
 24-5 
 
 98-0 
 
 9 
 
 882-0 
 
 28-0 
 
 252-0 
 
 8,7 
 
 5-8 
 
 7-2 
 
 28-8 
 
 259-2 
 
 
 CO 
 
 CO 
 
 oo 
 
 CO 
 
 o 
 to 
 
 
 343-00 
 
 11 
 
 2-470 
 
 i-( 
 
 ■3 
 
 -4 
 
 -7 
 
 1-2 
 
 3-2 
 
 CO 
 
 I— 1 
 
 9-3 
 
 9-3 
 
 10 
 
 930 
 
 3-2 
 
 32-0 
 
 4-4 
 
 2-5 
 
 3-5 
 
 3-5 
 
 350 
 
 
 n 
 
 to 
 
 -^J* 
 A 
 
 op 
 
 (N 
 
 CO 
 
 32-77 
 
 
 
 
 
 3-0 
 
 14-2 
 
 37-1 
 
 59-5 
 
 74-7 
 
 340-4 
 
 1009-7 
 
 5539 8 
 
 225-7 
 
 1254-4 
 
 
 
 
 225-2 
 
 1262-2 
 
 6033-24 
 
 Section No. I. — -25 feet abaft fore end of load-water Vfk; distance between the vertical seetions 7-5 feet. 
 Section No. II. — 4-75 before after end of load-water line; keel below rabbit 1 foot. 
 
CALCULAflONg; ^ 137 
 
 displacement, which divided by 35, gives the disfilacement in Distanci; be- 
 tons of that part of the vessel included within the limits of the fine™ hoV™'"' 
 calculation, to this must be added the keel, rudder, &c., thus, ''''"'"'• 
 
 lOOG.T X — -X 2 = 5048.5 cubic feet = 144.2 tons. 
 3 
 
 m. The multipliers for finding the distance of the centre of 
 gravity of displacement from No. 1 section. 
 
 On 
 n. The products of Z x w, then — x common interval between 
 
 I : 
 
 the sections, — distance the centre of gravity of displacement 
 5539.8 
 
 is from No. 1 section or — x 7.5 = 41.2 feet. 
 
 1009.1 
 
 0. The ordinates of the load water-line multiplied by the num- 
 bers in column c respectively, the sum of these products multi-j 
 plied by one-third of the common interval between the sections, 
 will give half the area of the load water-line, thus: 
 
 7.5 7.5 
 
 X — ^he half area of the load water-line, or 225'7 x — X 
 
 3 3 
 
 2 = 1128.5 squafe feet = the whole area. 
 
 p. The products m and o for finding the distance of the centre 
 of gravity of the load water-line from No 1 section. The sum 
 of these products divided by the sum of column o, and the quo- 
 tient multiplied by the common interval, gives the required dis- 
 p 
 
 tance, or x 7"5 = the distance of the centre of gravity of the 
 
 Oo ' 
 
 1254.4 
 
 load water-line from No. 1 section = x 7.5 = 41.68 feet. 
 
 225.8 
 r. The ordinates of the immersed water-line when the vessel 
 is inclined 10°. 
 
 s. The ordinates of the emetsed Water-line wheH the vessel is 
 inclined 10°. 
 
 t. The sums of r anrf s. 
 
 u. The products of t and c. The sum; of this column multi- 
 plied by one-third of the common interval, gives one-half of the 
 area of the inclined water-line, thus 
 
 7.5 . 7.5 
 
 Ou X — X 2 = the whole area, or 225.2 x — X 2 =: 1126 
 
 3 3 
 
 square feet. 
 
 *. The products of u and m M finding the distance of the cen- 
 tre of gravity of the^inclined water-line from No. 1 section, then 
 V 1262.2 
 
 -'— X 7.5 = distance required, or x 7.5 = 42.03 feet. 
 
 Ow 225.2 
 
 w. The cubes of the ordinates of the load water-line reqMi'ed 
 for finding thej^height of the metarcentre above the c6ntre of 
 gravity of displacement. The sum of this column multiplied by 
 
 18 
 
138 . CALCULATIONS. 
 
 two-thirds of the common interval, and the product divided hy 
 the number of cubic feet in the displacement, gives the height of 
 
 6033 24 7.5 
 
 the meta-ccntre, thus x — X 2 = 5.915 = height of the 
 
 5048. 5 3 
 metarcentre above the centre of gravity of the displacemenL 
 Volume of dis- To find that part of the displacement which is before the centre 
 taTe^bodf. "^ of gravity, this latter point being 41.2 feet abaft No. 1 section, 
 it will be 3.8 feet before No; 1. The displacement between Nos. 
 1 and 1 taken from columni I, is 2884.5 cubic feet, from this must 
 be subtracted the cubical content of that part between No. f and 
 the centre of gravity = area of No. 1 x 3-8 = 109.8 x 3.8 = 
 417 cubic feet; thus making the displacement before the centre 
 vo)umeofriis-of gravity 2467.5 cubic feet; and the displacement abaft that 
 after-bod"' "^ Centre will be the whole displacement minus 2467.5 = 258l cubic 
 feet. 
 Centre of gray- The distance of the centre of gravity of the fore-body from the 
 "•om"cenTre'""rf centre of gravity of displacement, will be for the part between 
 buoyancy. Nos. 1 and 7, from column n 
 
 2.4 X = 
 
 45.6 X 1= 45.6 
 
 45.8x2= 91.6 
 
 136.8x3= 410.4 
 
 86.2x4= 344.8 
 
 206.0 X 5 = 1030.0 
 
 54.9 X 6 = 329.4 
 
 576.9 225L8 
 
 2251.8 
 
 3.9 Which multiplied by the coHimon interval 
 
 576.9 
 
 7.5 = 29.25 feet = distance the centre of gravity of that part 
 between Nos. 1 and 7 is from No. 1 section. The centre of 
 gravity of the part between No. 7 and the centre of gravity of 
 
 3.8 
 displacement will be 45 = 43.1 feet from No. 1, and com* 
 
 2 
 bining these distances we have 
 
 Cubic contents. Movements. 
 2884.5 X 29.25 = 84371 
 417.0 X 43.1 = 17972 
 
 63399 
 
 2467.5 66399 
 
 = 26.9 feet the distance of the centre of gravity of the 
 
 2467.5 
 
 fore-body from No. 1; then 41.2 — - 26.9 = 13.9 feet, which 
 will be the distance of the centre Of gravity of the fore-body from 
 the centre of gravity of displacement. 
 
 Centre of grav- Por the aftcr-body, a similar method is pursued, except that 
 "Sn?*^ centre'"!it' ^^ ^^^^ ^ase the Smaller moment is positive. The result gives- 
 buoyancy, the distance as 13.5 feet. 
 
CALCULATIONS. VPyO 
 
 To find the distance the centre of gravity of displacement is _to find iiie po- 
 below the load water-line, multiply the sums of the products of „" buoyancy"'"' 
 the ordinates of the water-lines multiplied by the numbers 1, 4, 
 2, 4, •! respectively by 0, 1, 2, 3, 4 respectively, commencing from 
 the load water-line downwards ; the sum of these products divi- 
 ded by the sum of the first products, and the quotient multiplied 
 by the distance between the water-lines at the centre of gravity 
 of displacement will give the required distance, thus ; 
 
 Load water-line 
 
 74. t X 1 = 14.7 X 
 
 
 Water-line (2) 
 
 59.5 X 4 == 238.0 x 1 = 
 
 = 238.0 
 
 " (3) 
 
 37.1 X 2= 74.2 X 2 = 
 
 r 148.4 
 
 " (4) 
 
 14.2 X 4 = 56.8 X 3 r; 
 
 = 170.4 
 
 Keel 
 
 3.0 X 1 = 3.0'x 4 = 
 
 = 12.0 
 
 446.7 568.8 
 
 The distance between the water-lines at the centre of gravity 
 is thus found; as the length between the extreme sections is to 
 the difference of depth in that length, so is the length from No. 
 1 section, to the centre of gravity to the difference in depth due 
 to that part of the length ; or, 
 
 feet. feet. feet. feet. 
 80. : 2 : : 41.2 : 1.03 
 this added to the depth at No. 1 section, gives the whole depth 
 at the centre of gravity = 8 + 1.03 = 9.03 feet, which divided 
 by 4, (the number of water-lines,) = the distance the water-lines 
 are apart at the centre of- gravity = 2.26 feet. 
 
 568.8 
 
 Then x 3. 26 = 2, 877 feet the required distance, 
 
 446.7 
 
 This method of finding the height of the centre of gravity of 
 each water-line, is not always strictly correct, because the centre 
 of gravity of displacement longitudinally, may not be at the 
 centre of gravity of displacement, but the error is so trifling as 
 to be practically insignificant. In the foregoing calculations the 
 keel is omitted, its dimensions are, length 80 feet, depth 1 foot, 
 and breadth 7 inches, the cubic content is therefore 48 feet. 
 
 There is also a trapezium between No, 2 section and the 
 stern-post, the depth 10 feet, length 5 feet, and mean breadth 1 
 foot = 50 cubic feet; the total displacement is therefore 
 5048.5 + 48 + 50 = 5146.5 cubic feet = 147 tons. 
 
 A full understanding of the reason for each step in the pro- ''Reasons for the 
 cess of the calculations, greatly facilitates the proceeding. temf""'° ^''^" 
 
 The first and principal object is to find the area of each verti- 
 cal section. If the section were a rectilinear triangle, nothing 
 more would be required than to take the sum of half of the two 
 extreme ordinates and multiply it by its depth, but the sections 
 of a ship have one side of the triangle curvilinear, and therefore 
 this easy method of finding the area, would give an erroneous 
 result, as it does not include the space contained between the 
 right line and the curve. 
 
 There are three methods of obtaining a more correct area, the 
 rule for the first method has not been given, as although it is the 
 simplest known, it is too inaccurate for most cases. 
 
140 
 
 CALCULATIONS. 
 
 '■Short" rale. This I'ule is: — Divide the section into a number of equi-distaui 
 ordinates, add half the sum of the first and last ordinates to the 
 sum of the remaining ordinates. and multiply their sum br the 
 distance between them, applying this rule to section T of the 
 table, we have: 
 
 Ordinate 1 — .3 Ordinate 2 — 2.3 
 
 5 — lO.t " 3 — 6.4 
 
 2] 11.0 
 
 5.5 
 18.5 
 
 4 — 9.8 
 
 18.5 
 
 24.0 
 
 2.282 distance between the ordinates. 
 
 54.768 required half area. 
 Which is slightly different from the tabulated area, 
 'l^of^'ertinss But it is better to use Sterling's rules given at the commeiice' 
 ™ioin a.^"ch!ij^ ment of this chapter. The first of these is sometimes called 
 man's' rule. "Chapman's" rule — the second, the "three-eights" rule. 
 
 By the first we would have 
 Ordinate 1 — 0.3 Ordinate 2 — 2.3 Ordinate 3 — 6.4 
 - 5 _ lO.T " 4 — 9.8 2 
 
 A. 
 
 11.0 
 48.4 
 
 P. 
 
 12.1 
 
 4 
 
 2 Q. 12.8 
 
 12.8 
 
 4 P. 48.4 
 
 r 2.282 the distance between the ordinates, 
 
 3) 164.76 
 
 54.92 the required half area. 
 
 r 
 as determined from rule area =[A + 4P + 2Q] — 
 
 3 
 the curve bounding the area being supposed to be a portion of 
 a common parabola, 
 
 and as the The second rule may be applied in a similar manner, but the 
 rijfe7" ."""Ihree area Hjust bs divided into that number of equal divisions, which 
 pius'one rule." -will be a multiple of 3. So as to make the number of ordinates 
 a multiple of 3 with one added. 
 
 Which » rule As a general rule in calculating areas or displacement, when 
 the water-lines or sections are very round, or when the vertical 
 sections are more than five feet apart, either Chapman's rule or 
 the '-three-eights" rule should be employed, but when the lines are 
 tolerably straight, and the ordinates are less than five feet apart, 
 the "short rule" will give a result sufficiently accurate, and from 
 its greater simplicity is to be preferred, or the two rules may be 
 combined with advantage, as when the vertical sections are 
 
 may be used. 
 
CALCULATIONS. Ml 
 
 much curved, but the water-lines rather straight, thus, to calcu- 
 late the displacement, taking the half areas found by Chapnijin's nispirc" m"mi"° 
 rule from column k, page 186J. 
 
 By vertical sec - 
 ' tioiis. 
 
 SectioE 
 
 L 1. 
 
 2.4 (half,) 
 
 
 2. 
 
 11.4 
 
 
 3. 
 
 22.9 
 
 
 4. 
 
 34.2 
 
 
 5. 
 
 43.1 
 
 
 fi. 
 
 51.5 
 
 
 7. 
 
 54,9 
 
 
 8. 
 
 48.7 
 
 
 9. 
 
 37.5 
 
 
 10. 
 
 24.5 
 
 
 11. 
 
 9.3 (half) 
 
 334.55 
 
 7.5 distance between the sections. 
 
 2509.125 half displacement. 
 
 o 
 
 5018.25 whole displacement. 
 When the water-lines are parallel and equi-distant, the dis- By horizontal 
 placement may be found by taking- the areas of the water-lines =<^'="°"^- 
 and applying either of the rules to them ; in the case of the yacht 
 whose displacement we are calculating, the water-lines not being 
 equi-distant and parallel, it is almost impracticable to obtain an 
 €xact result in this way ; though a tolerably good approxima- 
 tion may be obtained as in the following example, the distance 
 between tke water-lines being supposed to be that at the middle 
 of the length, or at Xo. 6 section, then taking the areas of the 
 water-lines by the "short" rule, and completing the calculation by 
 Chapman's rule we have 
 
 Keel 3.0 X 1 = 3.0 
 
 Water line (4) 14.2 X 4 = 56.8 
 
 " (3) 37.1 X 2= 74.2 
 
 " (2) 59.5 X 4 =. 238.0 
 
 Load water-line 74.7 X 1 = 74.7 
 
 
 446.7 
 7.5 
 
 common interval. 
 
 3) 3350.25 
 
 1116.75 
 
 c ^^' f distance between the war 
 
 ^.^OO 
 
 1 ter-lines. 
 
 2495.9 half displacement. 
 9 
 
 4991.8 whole displacement, 
 which differs very little from the more laborious process, and if 
 not quite so correct, is useful as a check on the accuracy of the 
 work. 
 
ity. 
 
 142 CALCULATIONS. 
 
 Finding iiie po- In Calculating the distance of the centre of gravity of displace- 
 b'u'oyancy!""^'"''^iiieiit from Xo. 1 section, it IS required to find the moment of 
 each section, which is its distance multiplied by its contents, the 
 sum of these moments divided by the sum of the contents will 
 give the distance required, but as this process involves large 
 sums of figures, it is curtailed by multiplying the area of each 
 section by the number of its place, from No. 1, if then the sum 
 of the areas so multiplied is divided by the sum of all the areas, 
 and the quotient is multiplied by the distance between the sec- 
 tions, the same end is gained with a less amount of figuring. 
 
 centresofgrav- The position of the other centres of gravity are calculated on 
 the same principle. 
 
 Height of meta- The height of the meta-centre above the centre of a-ravity of 
 centre of buoy- displacement, being a measure of the comparative stability of 
 
 ancy. 
 
 2 y d X, 
 
 the ship, is estimated from the expression - § in which 
 
 3 D 
 
 y = the ordinatcs of the half breadth load water section, 
 d X 7= the increment of the length of load water section. 
 D = Displacement in cubic feet. 
 
 The ordinates are taken from the table, column iv, and cubed, 
 and the calculation made in accordance with the rules previously 
 given, pages 137, 138. 
 Calculations It will thus be Seen that the calculations for a small vessel are 
 of^erfomianc?.'' extremely simple and easy of performance, indeed any one tolera- 
 bly well versed in simple arithmetic may complete the whole of 
 the calculations for a vessel of, say 200 tons in less than an 
 hour, when equi-distant vertical sections and the water-lines at 
 their proper height are drawn in the half breadth and body 
 plans. 
 To find area of It now Only remains to find the area and position of the cen- 
 rf effort* ""'"' tre of effort of the sails. 
 
 The area of triangular sails like the jib, is found as follows : 
 Area of trian- Make a skctch (by scale) of the sail on paper, the luff being 
 guiar sails. ^j^^ hypoth^nuse, the foot the base, the after leech the perpen- 
 dicular, then from the clew let fall a perpendicular to the luff, 
 multiply the length of luff by length of this perpendicular and 
 divide by 2, the result is the required area. 
 Centre of grav- The Centre of gravity (or of effort) of any triangular sail like 
 ityo atiianguar^j^^ ^^^^ .^ found bv bi-secting the length on the luff, then two- 
 thirds the distance from this point to the clew, set off on a 
 straight line, is the position of the centre of gravitj- required. 
 Area of a tra- When the shape of the sail is a trapezium, like the mainsail of 
 reziutn. ^ schooner, the area is ascertained by dividing the whole plane 
 
 into two triangles by a diagonal, finding the area of each triangle, 
 and adding them together. 
 
 To find the To find the centre of gravity of the same sail, divide it by 
 «f"Bame! ^"^"'^^ lines into four triangles, find the centre of gravity of each, then 
 draw lines from these centres — where they intersect, is the centre 
 of gravity of the whole sail. 
 
CALCULATIONS. 
 
 143 
 
 The area of the sails of the schooner (Plate III,) calculated in Areaofsaiisof 
 the foregoing manner will be as follows : aTan°exampiiir" 
 
 Areas in sq. feet. 
 Jib, - 992 
 
 Foresail, 1290 
 
 Mainsail, 2028 
 
 4310 
 
 The position of the centre of effort as to height above the wa- Height of cen- 
 ter-line, is found by multiplying the area of each sail, bj"" the /bove load water 
 perpendicular distance of its centre of gravity from the water- "'"'• 
 line, then dividing the sum of these products or moments by 
 the sum of the areas, the quotient is the required distance, thus: 
 
 Height of C. of Gr. above L, 
 
 Areas in sq. feet. W. line in feet. Momenta. 
 
 Jib, 992 X 25.6 = 25395- 
 
 Fore sail, 1290 X 32.0 = 41280- 
 
 Main sail, 2028 ■ X 31.6 — 64084- 
 
 4310 
 
 ) 130719 
 
 30.33 
 
 or height of the centre of effort above the load water-line. 
 
 The distance of the centre of effort from any per[jendicular to f"^*''™ "f J^™' 
 the water-line, considered as an initial point, is found by divid- ly determined, 
 ing the difference of the moment of sail before and abaft that 
 perpendicular by the area of sail ; according as the excess of the 
 momenta is before or abaft the perpendicular, so will the posi- 
 tion of the centre of effort be ; thus : 
 
 Areas, square 
 feet. 
 
 Distance of the centre of 
 gravity from a perpen- 
 dicular at the centre of 
 the longitudinal section 
 in feet. 
 
 Momenta. 
 
 Jib, 
 
 Fore sail, 
 Main sail. 
 
 992 X 
 1290 X 
 2028 X 
 
 35.1 before 
 6.0 before 
 215 abaft 
 
 — 34819 
 
 — 7140 
 + 551T0 
 
 4310 
 
 or [34819 + n40 — 55110] — 4310 = < 3.06, which is the 
 
 distance the centre of effort of all the sails is abaft the centre of 
 gravity of the immersed longitudinal section. 
 
144 DE«1GX Oi' A MAX-OF-WAK. 
 
 CHAPTER XX V.I I. 
 
 HOW TO SET ABOUT THE DESIGN OF A MAN--- 
 OF-WAH. 
 
 EMftpie of (Iff- When a merchant ship is spoken of, it is' usual to say avesset 
 sign of a man-of- of SO many tous, indicating the vessel's capacity and the weight 
 '"''"' she can carry; but when a man-of-war is spoken of, it is usual ttf 
 
 designate her by the number of guns she carries, meaning, of 
 
 course, her weight of metal. 
 
 A Naval Architect may be able to design a merchant vessel 
 to perfection, and yet be totally unable to design a man-of-war; 
 especially with the modern ships is this a task most difficult, 
 they carry a quantity of heavy iron plates in such a position 
 that, when no special care is bestowed upon the design, the 
 vessel must prove a perfect failure. In a merchant vessel the 
 weights are carried below, while in a man-of-war they are nearly 
 a]l carried above the water-line. 
 
 Suppose a man-of-war is to be designed to carry 50 guns, and 
 . of these 36 upon the main deck and 14 on the spar deck, the 
 latter being distributed on the forecastle and quarter deck, while 
 the main deck guns are distributed 18 in each broadside. It is 
 the length of the ship that is mainly aifected by the 36 broad- 
 side guns. Experience has proved that the lower port sill must 
 be at least 9 feet out of the water, but in some vessels, that 
 height has been increased to 10 and even to 11 feet. Suppose' 
 the height determined to be 10 ft. 6 inches, the ports to be 3 feet 
 high and a space of 2 feet kept above the upper port sill, then 
 the Constructor has already a height out of water of 10.5 ft. -(- 
 3 -f 2 = 15 ft. 6 inches. 
 
 This will be the height out of water of the top of the beattl of the' 
 upper deck at the side of the ship. He has, therefore, already made 
 a side wall for the Ti'essel's battery of, say, 16 feet out of water^ 
 Now what should the length of this side wall be ? In former 
 days the space between the guns was seldom more than 8 feet. 
 The distance now-a-days, on account of lateral train, is extended 
 to 15 and even 18 feet,* but assume 15 feet as a distance from 
 centre to centre. The Constructor has therefore, for the length 
 to be occupied by his battery, 18 x 15 = 270 feet. 
 
 Suppose further, that the speed of the vessel is to be 13 knots; 
 to this speed belongs a length of ship of 160 feet, or a length of 
 entrance of 94 feet, and a length of run of 67 feet.f Make the 
 length of the ship then, say 300 feet, and assume the beam to be' 
 52 feet, or a proportion of 6 to 1. The Constructor has then the 
 following preliminary dimensions: 
 
 Length 300 feet. 
 
 Ditnenpi6ftB^ 
 
 Breadth 52 " 
 
 Height of lower port sill above L. W. line, 10 ft. six inches. 
 Next comes the element of draft. A man-of-war must always 
 be supposed in a loaded condition, or down to her load water' 
 
 Draft of water. 
 
 * For Xr inch gim on iron carriage, 18 feet. ' 
 
 1 Supposing that she is designed according to the ''Wave" system. Sec Table, p< 99. 
 
DESIGN OF A MAN-OF-WAR. 
 
 145 
 
 line, that water-line being the line on which she has got to do 
 the work. The light water-line may, therefore, be left out of the 
 question. Now if this man-of-war were to be of box form or of 
 rectangular shape with square bilges, the table on page 32 would 
 give the critical proportions of draft to breadth, for by that table 
 it is seen that to a beam of 54 feet belongs a critical draft of 22 
 feet, and that such a form would not be able to carry top-weight. 
 The adopted beam is, however, 52 feet, and therefore the Con- 
 structor may safely assume a draft of 22 feet, especially as he 
 intends probably to give rise of floor to the midship section. 
 Suppose, further, that the co-efficient of fineness of the midship 
 section is 0.8: the area of the midship section will then be 22 x 
 52 X -8 — 915 2 square feet. Now is the time for the designer 
 to see in bow far he can adopt fine lines and still have displace- 
 ment enough to carry the weight required. 
 
 For a speed of 13 knots, it was seen that a length of entrance 
 and run was needed of 161 feet, which, subtracted from 300 ft., 
 leaves a length of middle body of 139 feet. Hence the Con- 
 structor has for the displacement. 
 
 Middle body, 121,212.8 cubic feet. 
 
 The ends, , 87,840.0 
 
 Total, 215,052.8 
 
 But the Constructor needs 6,300 x 35 = 229,500 cubic feet. 
 He has, therefore, 220,500 — 215,052.8 = 5447.2 cubic feet, or 
 155.6 tons too little. 
 
 To make this up, the midship section may be made fuller with- 
 out damage; say 950 square feet nearly. The displacement is 
 thus increased to 224,000 cubic feet; more than enough; and 
 then, taking the fraction of 0.6 for the fineness of the ends, the 
 Constructor has the following: 
 
 Length on load water-line, 300 feet. 
 
 " of entrance, 94 
 
 " ran, 67 
 
 " straight middle body, 139 
 
 Beam, 
 
 Draft of water, 
 
 Depth at the side, 
 
 Area of immersed midship section, = 22 x 52 
 square feet. 
 
 Displacement of middle body 131,983 cubic feet, or 3771 tons. 
 Displacement of fore and after-bodies together 91,770 cubic 
 feet, or 2623- tons, or 
 
 131,983 cubic feet — 3771 tons. 
 91,770 " " = 2622 " 
 
 52 
 22 
 42 
 X .83 = 949.52 
 
 Total, 
 Required, 
 
 223,753 " 
 220,500 •■ 
 
 6393 
 6300 
 
 Surplus, 
 19 
 
 3,253 ■■ 
 
 93 
 
 Displacement 
 
 Q.uantitiea. 
 
146 DESIGN OP A MAN-OF-WAR. 
 
 This surplus might easily be rectified by m aiding the lines 
 finer, or, in other words, by taking a little away from the middle 
 body and making longer ends. But the Constructor may be 
 satisfied that with the given dimensions and proportions, the 
 ship will carry her weights. 
 
 Stability. Now comes the question of stability, for which (following 
 
 Russell's mode of treating the subject) he obtains the following: 
 
 Volume of shoulder of the ends = O.lStS x & X L x c + 
 0.3927 X 6"- X c, wherein 6 = 26 L = 161, and c = 13; hence 
 height of meta-centre above L. W. line = 1.992 feet. 
 
 Taking approximately the centre of displacement as 10 feet 
 below the load water-line, the interval of 11.992 or nearly 12 
 feet is obtained. This may seem small, but it must be considered 
 that the power of the shoulder is taken at its minimum, and, in 
 reality, may be increased from 25 to 50 per cent, while the bot- 
 tom buoyancy is maintained. 
 Weights. The next point is to see the effect the weights will have. 
 
 The guns are to weigh say 500 tons, and the centre of gravity 
 of this weight is to be, say 13.5 feet above the L. W. line.. The 
 centre of gravity of the hull a-lone may be supposed to be in the 
 load' water-line, which should be the case in men-of-war, their 
 hulls generally being as much out of water as in it. Further, 
 suppose the centre of weight of the engines, boilers, coals, &c., 
 to be situated at half the draft, or 11 feet below the water-line. 
 To find, therefore, the common centre of gravity, or the centre 
 of all the weights, the 
 
 Moment of guns = 500 x 13.5 = 6750 foot tons, 
 
 " of masts, spars, &c., = 155 x 80 = 12,400 foot tons. 
 
 Considering these moments as negative, their sum is 19,150 tons"; 
 then. 
 
 Moment of hull, = 3000 x 
 
 " of engines, boilers, &c., = 1 000 x H = 11,000 foot tons, 
 of coals, = 1000 X 11 = 11,000 foot tons, 
 
 of sundries, ~ 738 x 10 = 7380 foot tons. 
 
 Considering these last as positive, their sum is 29,380; deduc1> 
 ing from this the negative moments, there remains 29,380 — 
 19,150 = 10,230 foot tons, and this divided by the sum of all the 
 weights, gives the place of the common centre of gravity as 
 10,230 
 
 = 1.6 feet below the load Water line. 
 
 6393 
 
 The distance of the centre of all the weights from the meta- 
 centre, will, therefore, be equal to 1.992 + 1.6 = 3.592 feet. The 
 moment of stability with weight, at an angle of 14° 2', is there- 
 fore 8.592 X 6393 x 0.2425; or 5568.4 foot tons. 
 
 Sail area. The next point is to determine the sail area. In merchant 
 
 ships six times the longitudinal area is taken ; in sailing yachts 
 6 to 12 times that area, but in men-of-war, from 6 to 4 times the 
 
DESIGN OF A MAN-OF-WAR. 147 
 
 area is usual, the old frigates having, generally, but 4 times the 
 area of longitudinal immersed section. 
 
 Assume the sail area to be five times the longitudinal area, or 
 5 X 300 X 22 = 33,000 square feet of canvas, or taking the 
 proportion of 36 square feet of canvas to every square foot of 
 pidship section, the sail area would be 84,182 square feet. The 
 smaller quantity, however, is better, and this will give a length 
 of main-yard of 90 feet — hence 88 feet is the height of the centre 
 of effort above the water-line. 
 
 Supposing the pressure on the sails to be equal to 1 lb. to the f tawiity umJer 
 square foot, it results that there is 34,182 lbs. acting with a 
 leverage of 88 square feet; but since the vessel has careened 14° 
 2', the cosine of this angle must be introduced as a factor. This 
 gives 1291.26 foot tons as the upsetting moment due to the 
 sails. Now the moment of stability with weight being 5568.4 
 foot tons, it is seen that there is surplus stability sufficient to 
 bear'a pressure of 4J lbs. instead of 1 lb. on each foot of standard 
 sail area, which is a margin more than sufficient. 
 
 The sail area, therefore, might be, if necessary, much increased, 
 the ship having ample stability. 
 
 The next question is, whether the engine^ will drive the ship Engine power 
 13 knots per hour? For this purpose, the Constructor must see "'''^^^^'"^" 
 what head resistance is to be overcome. 
 
 By table on page 100, it will be seen that to a speed of 13 
 knots, belongs a head resistance of 482 lbs. to every square foot 
 of midship section. The length of bow gives for a diminished 
 fraction (52-94) = .306. The Constructor, therefore, has for 
 head resistance 949.52 x 3.06 x 482 = 140,046 lbs. 
 
 Horse power necessary to overcome the above equal to 19..2 
 X .306 x 949.52 = 5578.62 indicated horse power. 
 
 For the wet surface, the following is a near approximation : 
 Periphery of midship section, 80 feet- 
 
 Skin of middle body, 80 x 139.0 = 11,120 square feet. 
 
 Skin of fore and after bodies, 80 x 161 x .5 = 6,440 " 
 
 Total =: 1Y,560 " 
 
 or, at 1 lb. equal to 17,560 lbs. 
 
 Horse power necessary to overcome the last named element 
 of resistance, is 
 
 17,560 
 
 X 19.25 = 701.28 indicated horse power. The total 
 
 482 
 
 power required is, therefore, 5578,62 -f T01.-28 = 6279.90. 
 
 Suppose the engines to have worked up to five times their 
 nominal power, this nominal power would then be equal to 
 1255,98 horse power. To this must be added one-fifth for slip, 
 and the power consumed by the engines themselves, and the 
 Constructor finally gets for the power required to do the work 
 1507.17 nominal, or 7535.85 indicated horse power. 
 
148 DESIGN OF A MAX-OF-WAR. 
 
 Uiineusions. 
 
 Hence there is for the man-of-war 
 
 in 
 
 question 
 
 the following 
 
 rincipal dimensions: 
 
 
 
 
 
 Length on L. W. line, 
 
 
 
 
 300 feet. 
 
 " of entrance, 
 
 
 
 
 94 " 
 
 " run, 
 
 
 
 
 67 ■• 
 
 " " middle body, 
 
 
 
 
 139 " 
 
 Breadth, extreme. 
 
 
 
 
 52. " 
 
 Depth at side, 
 
 
 
 
 42 •■ 
 
 Draft of water. 
 
 
 
 
 22 " 
 
 Tonnage, builder's, 
 
 
 
 
 3866 tons. 
 
 Displacement, 
 
 
 
 
 6393 ■' 
 
 Speed, in knots, 
 
 
 
 
 13 
 
 Area of immersed midship' section 
 
 
 
 949 sq. ft. 
 
 Distance between the ports, 
 
 
 
 
 15 feet. 
 
 Height of lower port-sill above 
 
 L. 
 
 W 
 
 line, 
 
 10 ft. 6 in. 
 
 Number of guns. 
 
 
 
 
 50 
 
 Indicated horse-power required, '7535-85 
 
 From M'hich the drawings are made, a"nd the ship corfstructed. 
 
APrENDlI. 
 
 An Explanation of the Terras, and of some Elementary Principles, Requisite to l)c Under- 
 stood in tlie Tlieory and Practice of Sliip-lmilding, 
 
 AFLOAT. — Borne up by,' or floating in, the water. 
 
 AFTER-BODY.— That part of a ship's body abaft the midships or dead-flat. This 
 term is more particularly used in expressing the figure or skape of that part of the ship. 
 
 AFTER TIMBERS.— All those timbers abaft the midsmips or dead flat. 
 
 AIR FUNNEL — A cavitv framed between the sides of some timbers, to admit fresh 
 air into the ship, and convey the foul air out of it. 
 
 AMIDSHIPS. — In midships, or in the middle of the ship, either with regard to her 
 length or breadth. Hence- that timber or frame which has the greatest breadth and 
 capacity in the ship is denominated the midship bend. 
 
 ANCHOR-LINING. -rThe short pieces of plank, or of board, fastened to the sides of 
 the ship, or to stant'ons under the fore channel, to prevent the bill of the anchor from 
 wounding the ship's side, when fishing the anchor. 
 
 TO ANCHOR STOCK.— To work planks in a manner resembling the stocks of 
 anchors, by fashioning them in a tapering fnrm from the middle, and working or fixing 
 them over each other, so that the broad or middle part of onfe plank shall be immediately 
 above or below the butts or ends of two others. This method, as it occasions a great 
 consumption of wood, is only used where particular strength is required, as in the 
 Spikkettings under ports, &c. 
 
 AN-END. — The position of any mast, &c., when erected perpendicularly on the deck. 
 The top-masts are said to be an-end when they are hoisted up to their usual stations. — • 
 This is also a common phrase for expressing the driving of any thing in the direction of 
 its length, as to force one plank, &c., to meet the butt of another. 
 
 ANGLE OF INCIDENCE.— The angle made with the line of direction, by an imping- 
 inebody, at the point of impact; as that formed by the direction of the wind upon the 
 sails, or of the water upon the rudder, of a ship. 
 
 APRON. — A kind of false or inner stem, fayed on the aftside of the stem, frdm the 
 head down to the dead-wood, in order to strengthen it. It is immediately above the fore- 
 most end of the keel, and conforms exactly to the shape of the stem, so that the con- 
 vexity of one applied to the concavity of the other, forms one solid piece, which adds 
 strength- to the stem, and more firmly connects it with the keel. 
 
 ARCH OF THE COVE. — An elliptical moulding sprung over the cove at the lower 
 part of the taff'arel. 
 
 BACK OF THE POST.— The after-face of the Stern Post. 
 
 BACKSTAY" STOOL.— A short piece of broad plur.k, bolted edge-ways to the ship's 
 side, in the range of the channels, to project, and for the security of, the dead-eyes and 
 chains for the Backstays. Sometimes the channels are left long enough to answer the 
 purpose. 
 
 BACK-SWEEP.— See Fkames. 
 
 BALANCE FRAMES. — Those /ramcs, or bends of timber, of the same capacity or 
 area, which are equally distant from the centre of gravity. See Frames. 
 
 BALL.AiST. — A quantity of iron, stone, or gravel, or such other like materials, depos- 
 ited in a ship's hold, when she has no cargo, or too little to bring her sufficiently low in 
 
 A 
 
2 EXPLANATION OF TERMS USED IN SHIP BUILDING. 
 
 1he water. It is used to counterbalance the effort of the wind upon the sails, and give; 
 the ship a proper stability, that she may be enabled to Carry sail, without danger uf over- 
 setting. 
 
 HARK. — A name given to ships having three masts without a mizen top sail. 
 
 BARREL. — The main piece of a capstan or steering wheel. See Capstan. 
 
 BATTENS. — In general, light scantlings of wood. In ship-building, long narrow laths 
 of fir, their ends corresponding and fitted into each other with mortice a'nd tenon, used 
 in setting fair the sheer-lines on a ship. They are paintefJ blaclc in order to be ihe more 
 conspicuous. Battens used oB the mold-loft floor, are narrow laths, of which some are 
 accurately graduated and raar&ed with feet, inches, and quarters, for setting off distances. 
 Battens for gratings are narrow thin laths of Oalj.- 
 
 BEAMS. — The substantiail pieces of timber which stretcb across the ship, frofti side 
 to side, to support the decks and keep the ship together by means of the Kneesi &c.,- their 
 ends being lodged on the clantps,- keeping the ship to her breadth. 
 
 BEAM ARM, OR FORK BEAM, is a curved piece of timber, nearly of the depth of 
 the beam, scarphed, tabled* and bolted, for additional security to the sides of beams 
 athwart large openings in the decks, as the main hatchway and the mast-rooms. 
 
 BREAST BEAMS are those beams at the fore-part of the quairter deck and poop, 
 and after part of the forecastle. They are sided larger than the rest ; as they have an 
 ornamental rail in the front, formed from the solid, and a rabbet one inch broader than its 
 depth, which must be sufficient to bury the deals of the deck; and one inch above for a 
 spurn-water. To prevent splitting the beam in the rabbet, the nails of the deck should 
 be crossed, or so placed, alternately, as to form a sort of zigzag line. 
 
 HALF-BEAMS are short beams introduced to support the deck where there is no 
 framing, as in those places where the beams are kept asunder by hatchways, ladder waysj 
 &c. They are let down on the clamp at the side* and near midships into fore and aft 
 carlings. On some decks they are, abaft the mizen-mast, generally, of fir* let into the 
 side tier of carlings. 
 
 THE MIDSHIP BKAM is the longest beam of the ship,- lodged in the midship-frame 
 or between the widest frame of timbers; 
 
 BEARDING. — The diminishing of the edge or surface of a piece of timber, &c., from 
 a given line, as on the dead-wood; clamps, plank-sheersj fife-rails,- &c. 
 
 BE.'iRDING-LINE. — A curved line occasioned by bearding the dead--wood to the 
 form of the body ; the former being sided sufficiently, this line is carried high enough to 
 prevent the heels of timbers from running to a sharp edge, and forms a rabbet for the 
 timbers to step on ; hence it is often called the Steppins Line. 
 
 BED. — -A solid framing of timber' to receive and to support the mortar in a Bomb 
 Vessel. 
 
 BEETLE, — A large mallet used by Caulfcers for driving in their reeming irons to open 
 the seams, in order for caulking. 
 
 BELLY. — The inside or hollow part of compass or curved timber, the outside of which 
 is called the Back. 
 
 BELL-TOP. — A term applied to the top of a quarter gallery when the upper stool is 
 hollowed away, or made like a rim,- to give more height, as in the quarter galleries of 
 small vessels, and the stool of the upper finishing comes home to the side, to complete 
 overhead. 
 
 BEND-MOULD, ih whole moulding. A mould made to form the futtocks in the 
 square body, assisted by tne rising^square, and floor-hollow. 
 
 BENDS. — The frames or ribs that form the ship's body from the keel to the top of the 
 side at any particular station. They are first put together on the ground. That at the 
 broadest part of the ship is denominated the Midship-Bend or Dead-Fdat. The fore 
 part of the Wales are commonly called Bends. 
 
 BETWEEN-DECKS. — The space contained between any two decks of a ship. 
 
 BEVEL. — A well know/i instrumentj composed of a stock and a moveable tongue, for' 
 taking of angles on wood, &c.j by shipwrights called Bevellings. 
 
 BEVELLING BOARD. — A piece of deal on which the bevellings or angles of the) 
 timbers, &c., are described.- 
 
 BEVELLINGS.— The windings or angles of the timbers, &c., a term applied to any 
 deviation from a square or right-angle. Of Bevellings there arc two sorts, denominated 
 
EXPLANATION OF TERMS USED IN SHIP BUILDING. 3 
 
 0lnndiag Bevellings anfl Under Bevellings. By the former is meant an obtuse angle or that 
 which is loithoul a square ; and, by the ialter, is understood an acute angle or that which 
 is within a squarii. 
 
 BILGE. — That part of a ship's floor, on either side of the keel, which has more of 
 an horizontal than of a perpendicular direction, and on which the ship would rest if laid 
 on the ground '. or, more particularly, those projecting parts of the bottom which are op- 
 posite to the heads of the floor^timbers anjidships, on each side of the keel. 
 
 BILGE TREES, OR BILGE PIECES, OR BILGE KEELS.— The pieces of tim- 
 ber, fastened under the bjlge of boats or other v£ssels,_to keep them upright when on 
 shore, or to prevent their falling to leeward when sailing. 
 
 BILGEWAYS.— A squara bed of timber, placed under the bilge of thb ship, to sup- 
 port her while launching. 
 
 BINDINGS.-^The iron links which surround the Diad Eyes. 
 
 BINDING STRAKES.— Two strakes of oak plank, worked all the way fore an] aft upore 
 the beams of each deck, withjn one strake of the coap)ings of the main hatchway, in order 
 •to strengthen the deck, as that strake and the midship strakes are cut off by the pumps, &c. 
 
 BINS. — A sort of large chpsts, or erections in stoFe-rooms, in which the stores are 
 deposited. They are generally 3 or 4 feet deep, and negtrly of the same breadth. 
 
 TO BIRTH^UP. — A terra generally used for working up a topside or bulk-head with 
 board or thjn plank. ■ 
 
 BLACK-STRAKE. — Abroad strake, which is parallel to, and worked upon the upper 
 leAge of, the Wales, in order to strengthen the ship. Jt derives its name from being paid 
 with pitch, and is the boundary for the painting of the topsides. Ships having no ports 
 jiear the WaleSj have generally two black-strakes. 
 
 BLOCKS FOR BUILDING THE SHIP UPON, are those solid pieces of oak timber 
 fixed under the ship's keel, upon the groundways. 
 
 BOARD.^Timber sawed to a less thickness than plank ; all broad stuff of or under one 
 jnch and a half in thickness. 
 
 BODIES. — The figure of a ship, abstractedly considered, is supposed to be divided 
 jnto different parts, or figures, to each of which is given the appellation of Body. Hence 
 we have the terms F.qb.e Bout, Afteji Body, Cant Bodies, and Square Body. Thus 
 the Fon Body is the figure^ or imaginary figure, of that part of the ship afore the mid- 
 ships or dead-flat, as seen from ahead. The Jfler Body, in like manner, is the figure of that 
 part of the ship abaft the midships, (jr dead-flat, as seen from astern. The Cant Bodies are 
 distinguished into Fore and ^fter, aijd signify the figure of that part of a ship's body or 
 timbers, .as seen from either side, v/hich form the shape forward and aft, and whose planes 
 make obtuse. angles with the midship line of the ship ; those in the Fore Cant Body being 
 inclined to the stem, as those in the After one are to the stern post. The Square Body 
 comprehends all the timbers whose areas or planes are perpendicular to the keel and 
 square with the middle line of the ship ; which is all that portion of a ship betvireen the 
 Cant Bodies. 
 
 BOLSTERS.. — Pieces of oak timber fayed to the curvature of the bow, under the 
 Hawse-Holes and down upon the upper or Jower cheek, to prevent the cable from rubbing 
 .against the cheek, 
 
 BOLSTERS FOR THE ANCHOR LINING, are solid pieces of oak, bolted to the 
 ship's side, at the fore part of the fore chains, on which the stantiong are fixed that re- 
 ceive the anchor lining. The fore end of the bolster should extend two feet or more before 
 the lining, for the convenience of a man's standing to assist in fishing the anchor. 
 
 BOLSTERS FOR SHEETS, TACKS, fee, are small pieces of fir or oak fayed under 
 the Gunwale, &c., with th,e outer surface rounded to prevent the sheets and other rigging 
 from chafing, 
 
 BOLTS.— Cylindrical or square pins of iron or copper, of various forms, for fastening 
 and securing the different parts of the ship, the guns, &c. The figure of those for fasten- 
 ing the timbers, planks, hooks, knees, crutches, and other articles of a similar. nature, is 
 cylindrical, and their sizes are adapted to the respective objects for which they are in- 
 tended to secure. They have round or saucer heads, according to the purposes for which 
 they may be intended ; and the points are fore-locked or clinched on rings to prevent their 
 drawing. Those for bolting the frames or beams together are generally square. 
 
 BOTTOM. -^AU that part of a ship or vessel that is below, the Wales. Hence we use 
 the epithet sharprboltomed for vessels intended for quick-sailing, and fall-botlomed for such 
 jis are designed to carry large cargoes. 
 
4 EXPLANATION OF TERMS USED IN SHIP BUILDING. 
 
 BOW. — The circular pari of the ship forward, terminafedi at the rabbet of the stem. 
 
 BRACES. — Straps of iron, copper, or mixed metal, secured with bolts and screws in 
 the stern post and bottom planks. In their after ends are holes to receive the pintles by 
 which the rudder is hung. 
 
 BREADTH. — A term more particularly applied to some essentia] dimensions of the 
 extent of a ship or vessel athwartships, as the BjiEAETH-lixTiiEME, and the Bkeadth- 
 MouLTED, which are two of the principal dimensions given in the building of the ship. 
 The Extreme Brendtli is the extent of the midships or dead-flat with the thickness of the 
 bottom plank included. The Breadth-Moulded, is the same extent without the thickness 
 of the plank. 
 
 liREADTH-LINE. — A curved line of the ship lengthwise, intersecting the timbers at 
 their respective broadest parts. 
 
 BREAK. — The sudden termination or rise in the decks of some merchant ships, where 
 the aft and sometimes the fore part of the deck is kept up to give more height between 
 decks, as likewise at the Drifts. 
 
 BREAST-HOOKS. — Large pieces of compass timber fixed within and athwart the 
 bows of the ship, of which they are the principal security, and through which they are 
 well bolted. There is generally one between each deck, and three or four below the lower 
 deck, fayed upon the plank. Those below are placed square to the shape of the ship at 
 their respective places. The Breast-Hooks that receive the ends of the deck-planks are 
 also called DeckHooks, and are fayed close home to the timbers in the direction of the 
 decks. 
 
 BUOKEN-BACKED OR HOGGED.— The condition of a ship when the sheer has de- 
 pEirted from the reguhr and pleasing curve with which it was originally built. This is 
 often occasioned by the improper situation of the centre of gravity, when so posited as not 
 to counterbalance the effort of the water in sustaining the ship, or, by a great strain, or, 
 from the weakness of construction. The latter is the most common circumstance, parti- 
 cularly in some Clipper ships, owing partly to their, great length, sharpness of flour, or 
 general want of strength in the junction of the component parts. 
 
 BUM-KIN, OR MORE PROPERLY BOOM-KIN. — A projecting, piece of oak or fir, on 
 each bow of a sliip, fayed down upon the False Rail, or Kail of the Head, with its heel 
 cleated against the Knight-head in large, and the bow in small, ships. It is secured out- 
 wards by an iron rod or rope lashing, which confines it downward to the knee or bow, and 
 is used for the purpuse of hauling down the fore-tack of the fore-sail. 
 
 BURTHEN. — The weight or measure that any ship will carry or contain when fit for sea. 
 
 BUTT. — Thejoints of the planks endwise, also th.e openinir between the ends of the 
 planks when worked fur caulking. Where caulking is not used, the butts are rabbetted, 
 and must fay close. 
 
 BUTTOCK. — That rounding part of the body abaft bounded by the fashion-pieces; and, 
 at the upper part, by the wing transom. 
 
 BUTTOCK-IJNES.— (On the Sheer Draught.) Curves, lengthwise, representing the 
 ship as cut in vertical sections. 
 
 CAMBER. — Hollow or arching upwards. The decks are said to be cmjiif rerf when their 
 height increase toward the middle, from stem to stern, in the direction of the ship's length. 
 
 CAMEL. — A machine for lifting ships over a bapk or shoal, originally invented by the 
 celebrated De Witt, for the purpose of conveying large vessels from Amsterdam over the 
 Pampus. They were introduced into Russia by Peter the Great, who obtained the model 
 when he worked in Holland, as a common shipwright, and are now used at St. Petersburgh 
 for lifting .ships of war built there over the bar of the harbour. A Camel is composed of 
 two separate parts, whose outsides are perpendicular, and insides concave, shaped so as to 
 embrace the hull of a ship on both sides. Each part has a small cabin, with sixteen 
 pumps and ten plugs, and contains twenty men. They are braced to the underparl of the 
 ship by means of cables, and entirely inclose its sides and bottom. Being then towed to 
 the bar, the plugs are opened, and the water admitted until the Camel sinks with the ship, 
 and runs aground. Then, the water being pumped out, the Camel rises, lifts up the vessel, 
 and the whole is towed over the bar. This machine can raise the ship eleven feet, or in 
 other words, make it draw eleven feet less water. 
 
 CANT. — A term signifying the inclination that any thing has from a square or perpen- 
 dicular. Hence the shipwrights say, 
 
 CANT-RIBBANDS, are those ribbands that do not lie in a horizontal or level direction, 
 or square from the middle line, but nearly square from the timbers, as the diagonal rib^ 
 bands. See RiBE.iNDS. 
 
EXPLANATION OF TERMS USED IN SHIP BUILDING. 5 
 
 CANT-TIMBERS, are those timbers afore and abaft, whose planes are not square with, 
 or perpendicular to, the middle-line of the ship. 
 
 CAPS.— Square pieces of oak, laid upon the upper blocks on which the ship is built, to 
 receive the keel. They should be of the most freely grained oak, that they may be easily 
 split out when the false keel is to be placed beneath. The depth of them maybe a few 
 inches more than the thickness of the false keel, that it may be set up close to the mam 
 keel by slices, &c. 
 
 A CAP SCUTTLE.— A framing composed of coamings and head ledges, raised above 
 the deck, with a flat or top which shuts closely over into a rabbet. 
 
 CARLINGS.— Long pieces of timber, above four inches square, which lie fore and aft, 
 in tiers, from beam to beam, into which their ends are scored. They receive the ends of 
 the ledges for framing the decks. The Carlings by the side of, and for the support .of, the 
 mast, which receive the framing round the mast called the partners, are much larger 
 than the rest, and are named the Mast Caelings. Besides these there are others, as the 
 Pump Carlings, which go next without the Mast Carlings, and between which the pumps 
 pass into the well ; and also the Fire-Hearth Carlings, that let up under the beam on which 
 the Galley stands, with pillars underneath, and chocks upon it,, fayed up to the ledges 
 for support. 
 
 CARVEL WORK.— A term applied to Cutters and Boats, signifying that the seams of 
 the botlom-planking are square, and to be tight by caulking as those of ships. It is op- 
 posed to the phrase Clincher-built, which see. 
 
 CAULKING. — Forcing oakum into the seams and between the butts of the plauk, &c., 
 with iron instruments, in order to prevent the water penetrnting into the ship. 
 
 CEILING OR FOOTWALING.— The inside planks of the bottom of the ship. 
 
 CENTRE OF CAVITY, OR OF DISPLACEMENT.— The centre of thatpart of the 
 ship's body which is immersed in the water ; and which is also the centre of the vertical 
 force that the water exerts to support the vessel. 
 
 CENTRE OF GRAVITY.— That point about which all the parts of a'body do, in any 
 situation, exactly balance each other. Hence, 1. If a body be suspended by this point as 
 the centre of motion, it will remain at rest in any position indifferently. 2. If a body be 
 suspended in any other point, it can rest only in two positions, viz. when the centre of gravity 
 is exactly above or below the point of suspension. 3. When the centre of gravity is sup- 
 ported, the whole body is kept from' falling. 4. Because this point has a constant tenden- 
 cy to descend to the centre of the earth, therefore' — 5. When the point is at liberty to 
 descend, the whole body must also descend, either by sliding, rolling, or tumbling over. 
 
 CENTRE OF MOTION— That point of a body which remains at rest whilst all the 
 other parts are in motion about it-; and this is the same, in bodies of one uniform density 
 throughout, as the centre of gravity. 
 
 CENTRE OF OSCILLATION.— That point in the axis or line of suspension of a vi- 
 brating body, or system of bodies, in which if the whole matter or weight be collected', 
 the vibrations will still be performed in the same time, and with the same angular velocity, 
 as before. 
 
 CENTRE OF PERCUSSION, in a moving body, is that point where the percussion or 
 stroke is the greatest, and in which the whole percutient force of the body is supposed to 
 be collected. Percussion is the impression a body makes in falling or striking upon 
 another, or the shock of bodies in motion striking against each other. It is either direct 
 or oblique ; direct when the impulse is given in a line perpendicular to the point of con- 
 tact ; and oblique when it is given in a line oblique to the point of contact. 
 
 CENTRE OF RESISTANCE TO A FLUID.— That point in a plane to which, if a 
 contrary force be, applied, it shall just sustain the resistance. 
 
 CHAIN OR. CHAINS —The links of iron which are connected to the binding that 
 surround the dead-eyes of the channels. They are secured to the ship's side by a bolt 
 through the toe-link called a chain-bolt. 
 
 CHAIN-BOLT. — A large bolt to secure the chains of the dead-eyes, for the purpose of 
 securing the masts by the shrouds. 
 
 CHAIN-PLATES. — Thick iron plates, sometimes used, which are bolted to the ship's 
 sides, instead of chains to the dead-eyes, as above. 
 
 CHAMFERUVG. — Taking off the sharp edge from timber or plank, or cutting the edge 
 or end of any thing bevel or aslope. 
 
EXPLANATION OF TERMS USED IN SHIP BUILDING. 
 
 CHANNELS. — The broad projection or assemblage of planks, fayed and bolted to tho 
 ship's sides, for the purpose of spreading the shrouds with a greater angle to the dead- 
 eyes. They should tlierefqre be placed either above or below the upper deck ports, as 
 may be most convenient. But it is to be observed that, if placed too high, they strain the 
 sides too much; and if placed too low, the shrouds cannot be mode to clear the ports with- 
 out difliculty. Their disposition will therefore depend on that particular whicli will pro^ 
 duce the, greatest advantage. They should fay to the sides only where the bolts oome 
 through, having an open space df about two inches in the rest of their, length, to admit a 
 free current of air, and a passage for wef and dirt, in order to prevent the sides from rotr 
 ting. 
 
 CHANNEL WALES.— Three or four thick strakes, worked between the upper and 
 lower deck ports in two decked ships, and between the upper and njiddle deck ports in 
 three decked ships, for the purpose of strengthening the topside. Tliey should be placed 
 m the best manner for receiving the chain and preventer bolts, the fastenings of the deckr 
 knees, &c. 
 
 CHEEKS. — Knees of oak-tinjber which support the knee of the head, and which they 
 also ornament by their shape and mouldings. They form the basis of the head, and connect 
 the whole to the bows, through which and the knee they are bolted. 
 
 *CHESTREKS.— Pieces of oak timber fayed and bolted to the topsides, one on each 
 side, abaft the fore-channels, with a sheave fitted in the upper part for the convenience 
 of hauling home the main tack. 
 
 CHINE. — That part of the waterways, which is left the thickest, and above the deck^ 
 plank. It is bearded back that the lower seam of spirketting may be more conveniently 
 ■ caulked, and is gouged hollow in front to forn} a watercourse. 
 
 TO CHINSE. — To caulk slightly with a knife or chisel, those seams or openings that 
 will not bear the force required for caulking in ^ more proper manner. 
 
 CLAMPS. — Those substantial strakes worked within side the ship, upon which the ends 
 of the beams are placed, 
 
 CLEAN. — A term generally used to express the acuteness or sharpness of a ship's body: 
 as when a ship is formed very actfte or sh^rp forward, and the same aft, she is said to be 
 clean both forward and aft. 
 
 CLINCHER-BUILT. — A term applied to the construction of soipe vessels and boats, 
 when the planks of the bottoni are so disposed, that the lower edge of every plank over- 
 lays the next under it, and the fastenings go through and clinch or turn upon the timbers. 
 It is opposed to the term Carvel-work. 
 
 CLINCHING- OR CLENCHING.— Spreading the point of the bolt upon a ring, &c., 
 by beating it with a hammer, in order to prevent its drawing. 
 
 COAMINGS. — The raised borders of oak about the edge of the hatches and scuttles, 
 which prevent water from flowing down from 08^ the deck. Their inside upperedge has a 
 rabbet to receive the gratjngs, 
 
 COMPANION. — In ships of war, the franjing sjnd sash lights upon the Quarter-Deck 
 or Poop, through which the light passes lo the Commander's apartments. In merchant 
 ships it is the birthing or hood round the ladder way, leading to the master's cabin, and in 
 small ships js chiefly for the purpose of keeping the sea from beating down. 
 
 CONVERSION. — The art of lining and moulding timber, plank, &c,, with the least 
 possible waste. 
 
 COPING.-^Tijrning the enqls of iron lodging knees so 9s they njay hook into the beams, 
 
 COUNTER. — A part of the Stern ; the I^ower Coimter being that arched part of the 
 stern immediately above the wing transom. Above the Lower Counter is the Second 
 Counter, the upper part of which is the under part of the Lights or Windows. The Couhx 
 ters are parfed by their rails, as the lowep counter springs from the tuck^^rail, and is ter- 
 minated on the upper part by the lower counterrrail. From the upper part of the latter 
 springs the upper or second counter, its upper ptjrt terminating in thd upper counter rail, 
 which is imojediately under the Lights. 
 
 COUNTER-SUNK. — The hollows in iron-plates, &c., which are excavated by an in^ 
 strument called a Counter Sunk B)tt, to receive the heads of screws or nails so that they 
 may be flush or even with the surface. 
 
 COUNTER TIMBERS.— The right-aft timbers which form the stern. The longest run 
 up and form the lights, while the shorter only run up to the under part of them, and help 
 to strengthen the coxinlcv- . The side coiinter timbers arp mostly formed of two pieces 
 
EXPLANATION OF TERMS USED IN SHIP BUILDING. ^ 
 
 snarphcd together in consequence of their peculiar shape, as they not only form the riglit- 
 aft flguW of the stern, but partake of the shape of the topside also. 
 
 COVE. — The arch moulding sunk in at the foot or lower part of the tafifarel. 
 
 CRAB. — A sort of little Capstan, formed of a kind of wooden pillar, whose lower end 
 works in a socket, whilst the middle traverses or turns round in partners which clip it in 
 b. circle. In its upper end are two holes to receive bar|, which act as levers, and by which 
 it is turned round and serves as a capstan for raising of weights, &c. By a machine of 
 this kind, so simple in its construction, may be hove up the frame timbers, &o., of vessels 
 when building. For this purpose it is placed between two floor timbers, while the part- 
 ners which clip it in the middle may be of four or five inch plank fastened on the same 
 floors. A block is fastened beneath in the slip, with a central hole for its lower end to 
 work in. Besides the Crab here described, there is another sort, which is'shorter and por- 
 table. The latter is fitted in a frame composed of cheeks, across which are the partners, 
 and at the bottom a little platform to receive the spindle. 
 
 CRADLE. — A strong frame of timber, &c., placed under the bottom of a ship in order 
 to conduct her stfeadily in her ways till she is safely launched into water sufficient to float 
 her. 
 
 CRANK. — A term applied to ships built too deep in proportion to their breadth, and 
 from which they are in danger of over-setting. 
 
 CROAKT. — A term applied to plank when it curves or compasses much in short lengths. 
 
 CROSS SPALES. — Deals or fir plank nailed in a temporary manner to the frames of 
 the ship at a certain height, and by which the frames are kept to their proper breadths, 
 until the deck-knees are fastened. The main and top-timber breadths are the heights 
 mostly taken for spalling the frames, but the height of the ports is much better, yet this 
 may be thought too high if the ship is long in building. 
 
 CRUTCHES OR CLUTCHES.— The crooked timbers fayed and bolted upon the foot- 
 Waling abaft for the security of the heels of the half-timbers. Also stantioiis of iron or 
 wood whose upper parts are forked to receive rails, spare masts, yards, &c. 
 
 CUP. — A solid piece of cast-iron, let into the siep of the Capstan, and in which the iron 
 spindle at the heel of the capstan works. See Capstun. 
 
 CUTTING-DOWN LINE.— The elliptical curve line, forming theupperside of the floor- 
 timbers at the middle line. Also the line that forms the upper part of the Knee of the 
 Head above the Cheeks. The cutting down line is represented as limiting the depth of 
 every floor timber at the middle line, and also the height of the upper part of the dead- 
 wood afore and abaft. 
 
 DAGGER. — A piece of timber that faces on to the poppets .of the bilgeways,- and 
 crosses them diagonally, to keep them together. The plank that secures the heads of the 
 poppets is called the Dagger Plank. The word Dagger seems to apply to any thing that 
 stands diagonally or aslant. 
 
 DAGGER-KNEES. — Knees to supply the place of hanging knees. Their side arms 
 are brought up aslant or nearly to the undersicfe of the beams adjoining. They are chiefly 
 used to the lower deck beams of merchant ships, in order to preserve as much stowage in 
 the hold as passible. Any strait hanging knees not perpendicular to the side of the beam 
 are in general termed Dagger-Knees. 
 
 DEAD-FL^T A name given to that timber or frame which has the greatest breadth 
 
 and capacity in the ship, and which is generally called the Midship Bend. In those ships 
 where there are several frames or timbers of equal breadth or capacity, that which is in 
 the middle should be always considered as Dead-Flat, and distinguished as such by this 
 character +. The timbers before the Dead-Flat are marked A, B, C, &c., in order ; and 
 those abaft Dead-Flat by the figures 1, 2,3, &c. The Timbers adjacent to Dead- Flat, and of 
 the same dimensions nearly, are distinguished by the characters (A) (B)&c.and (1) (2) &c. 
 
 DEAD-RISING, OR RISING LINE OF THE FLOOR.— Those parts of the floor or 
 bottom, throughout the ship's length, where the sweep or curve at the head of the floor 
 timber is terminated or inflects to join the keel. Hence, although the rising of the floor at 
 the midship-flat Is but a few inches above the keel at that place, its height forward and aft 
 increases according to the sharpness of form in the body. Thei efore the rising of the floor 
 in the sheer plan, is a curved line drawn at the height of the ends of the floor timbers ; and 
 limited at the main frame, or dead-flat by the dead rising : appearing in flat ships nearly 
 parallel to the keel for some timbers afore and abaft the midship frame ; for which reason 
 these timbers are called.^o(s.- but in sharp ships it rises gradually from the main frame, 
 and ends on the stem and post. 
 
8 EXPLANATION OF TERMS USED IN SHIP BUILDING. 
 
 DEAD-WATER. — The eddy water which the ship draws after her at her seat or line 
 of floatation in the water, particularly close aft. To this particular, great attention should 
 he paid in the construction of a vessel,- especially in those with square tucks, for such being 
 carried too low in the water, will be attended with great eddies or much dead-water. — 
 Vessels with a round huttock have but little or no dead-water, because, by the rounding 
 or arching of such vessels abaft, the water more easily recovers its state of rest. 
 
 DF^.\D-WOOD. — That part of the basis of a ship's body, forward and aft, which is 
 formed by solid pieces of timber scarfed together lengthwise on the keel. These should 
 be sufficiently broad to admit of a stepping or rabbet for the heels of the timbers, that the 
 latter may not be continued downwards to sharp edges ; and they should be suffi- 
 ciently high to seat the floors. Afore and abaft the floors the dead-wood is continued to 
 the cutting down line, for the purpose of secuiing the heels of the Cant-timbers. 
 
 DEPTH IN THE HOLD.— The height between the floor and the lower deck. This is 
 one of the principal dimensions given for the construction of a ship. It varies according 
 to the height at which the guns are required to be carried from, the water; or, according 
 to the trade for which a vessel is designed. 
 
 DIAGONAL LINE. — A line cutting the body-plan diagonally from the timbers to the 
 middle line. It is square with, or perpendicular to, the shape of the timbers, ornearly so, 
 till it meets the Middle Line. 
 
 DIAGONAL RIBBAND. — A narrow plank, made to a line formed on the Half breadth- 
 plan, by taking the intersections of the diagonal line with the timbers in the body-plan to 
 where it cuts the middle line in its direction, and applying it to their respective stations 
 on the Half-breadth-plaB, which forms a curve to which the ribband is made as far as the 
 Cant Body extends, and the square frame adjoining. 
 
 DOG. — Ah iron implement used by shipwrights, having a fang at one, or sometimes at 
 each, end, to be driven into any piece for supporting it while hewing, &c. Another sort 
 has a fang in one end and an eye in the other, in which a i-ope may be fasteaed, and used 
 to haul any thing along. 
 
 DOG SHORE. — A shore particularly used in Launching. 
 
 DOUBLING. — ^Planking of ships^ bottoms twice. It is sometimes done to new ships 
 when the original planking is thought to be too thin'; and, in repairs, it strengthens the 
 ship, without driving out the former fastenings. 
 
 DRAUGHT. — The drawing or design of the ship, upon paper, describing the diflerent 
 parts, and from which the ship is to be built. It is mostly drawn by a scale of one quarter 
 of an inch to a foot, so divided or graduated that the dimensions may be taken to one inch, 
 
 DRAUGHT OF WATER.— The Depth of water a ship displaces when she is afloat. 
 
 DniVER. — The foremost spur on the bilgeways ; the heel of which is fayed to the 
 foreside of the foremost poppet, and cleated on the bilgeways, and the sides of it stand 
 fore and aft. It is now seldom used. 
 
 DRUMHEAD. — The head of a capstan, formed of semi-circular pieces of elm, which, 
 framed together, form the circle into which the capstan-bars are fixed. 
 
 DRUXEY. — A state of decay in timber with white spungy veins, the most deceptive 
 of any defect. 
 
 EDGING OF PLANK. — Sawing or hewing it narrower. 
 
 EKEING. — Making good a deficiency in the length of any piece by scarphing or but- 
 ting, as at the eiid of deck-hooks, cheeks, or knees. The Ekeing at the lower p"art of the 
 Supporter under the Cathead, is only to continue the shape and fashion of that part, being 
 of no other service. We make this remark because, if the Supporter were stopt short 
 without an ekeing, it would be the better as it causes the side to rot, and it commonly ap- 
 pears fair to the eye in but one direction; The Ekeing i^ also the piece of carved work 
 under the lower part of the Quarter-piece at the aft part of the Quarter-gallery. 
 
 ELEVATION, — The orthographic draught, or perpendicular plan of a ship, whereon 
 the heights and lengths are expressed. It is called by shipwrights the Sheer-Draught. 
 
 ENTRANCE. — A term applied to the fore part of the ship under the load-water line-j 
 as, "She has a fine entrance," ^c. 
 
 EVEN KEEL. — A ship is said to swim on an even keel when she draws the game quan- 
 tity of water abaft as forwards. 
 
 FACING. — Letting one piece, about an inch in thickness, on to another, in order to 
 strengthen it. 
 
fiJCPLANATlON OF' TERMS (JSED tN SHIP BUILDING. g 
 
 fAIR. — A term to denote the evenness or regularity of a curve or line. 
 
 FALLING-HOME, or, »y some, TUMBLING HOME.— The inclination which the 
 Ibpside has within from a perpendicular. 
 
 FALSE-KEEL. — A second keel, composed of elm-plank, or thick stuff, fastened in a 
 slight manner under the main keel; to prevent it from being rubbed. Its advantages also 
 are, that, if the ship should strike the ground, the false keel will give way, and thus the 
 main keel will be saved; and it will be the means of causing the ship to hold the wind 
 better. 
 
 FALSE-POST. — A piece tabled on to the after part of the heel of the main part of the 
 stern post, jt is to assist the conversion and preserve the main post should tthe ship 
 tall aground. 
 
 FALSE-RAIL. — A rail fayed down upon the upper side of the main, or upper rail of 
 the head. It is to strengthen the head-rail, and forms the seat of ease at ihe after end 
 next the bow. 
 
 FASHION PIECF.S. — The timbers so called from their fashioning the after part of the 
 ship in the plane of projection, by terminating the bieadth and forming the shape of the 
 stern. They are unitetf to the ends of the transoms and to the dead-wood. 
 
 TO FAY. — To join one piece so close to another that there shall be no perceptible space 
 between them. 
 
 FILLING-TIMBERS. — The intermediate timbers between the frames that are gotten up 
 into their places singly after the frames are ribbanded and shored. 
 
 FLAIRING. — The reverse of Falling or Tumbling Home. As this can be only in the 
 fore-part of the ship, it is Said that a ship has a flairing-bow, when the topside falls out- 
 ward from a perpendicular. lis uses are, to shorten the Cathead, and yet keep the anchor 
 clear of the bow. It also prevents the sea from breaking in upon the Forecastle. 
 
 FLATS. — A name given to the timbers a-midships that have no bevellings, and are sim- 
 ilar to dead-flat, which is distinguished by this character X. See Dead-flat. 
 
 FLOOR. — The bottom of a ship, or all that part on each side [of the keel which ap- 
 proaches nearer to a horizontal than a perpendicular direction, and whereon the ship rests 
 Ivhen aground. 
 
 FLOORS, OR FLOOR TIMBERS.— The timbers that are fixed athwartthe keel, and 
 tipon which the whole frame is erected. Th6y generally extend as far forward as the 
 fore-mast,- and as far aft as the after square timber; and sometimes, one or two cant-floors 
 are added. 
 
 FLUSH.^^With a continued even surface: As a flush deck, which is a deck upon 
 one continued line, without interruption, from fore to aft. 
 
 FORE BODY.— That part of the ship's body, afore the Midships or Dead-flat. See 
 Bodies. This term is more particularly used in expressing thefgure or skajie of that part 
 of the ship. 
 
 FORE-FOOT.— The foremost piece of the keel. 
 
 FORE-LOCK. — A thin circular wedge of iron, used to retain a bolt in its place, by 
 being thrust through a mortise hole at the point of the bolt. It is sometimes turned or 
 twisted round the bolt to prevent its drawing. 
 
 FORE PEEK.— Close forward under the lower deck. 
 
 FRAMES. — The bends of timber which form the body of the ship ; each of which is 
 composed of oae floor-timber, two or three /uifocfcs, and a top-limber on each side- which 
 being united together, form the frame. Of these frames, or bends, that which encloses 
 the greatest space is called the midship or mainframe or bend. The arms of the floor 
 timber form a very obtuse angle ; and in the other frames, this angle decreases or gradu- 
 ally becomes shafper, fore and aft^ with the middle line of the ship. Those floors which 
 form the acute angles afore and abaft are called the Rising Floors. A frame of timbers is 
 commonly formed by arches of circles called Sweeps, of which there are generally five/ 
 1st. The Floor Swefp, which is limited by a line in the Body Plan perpendicular to the 
 plane of elevation, a little above the keel; and the height of this line above the keel is 
 called the Dead Rising. The upper part of this arch forms the head of the floor timber. 
 2nd. The Lower Breadth Sweep; the centre of which is in the line representing the lower' 
 height of breadth. 3rd. The Reconciling Sweep; this sweep joins the two former without 
 intersecting either; and makes a fair curve from the lower height of breadth to the rising 
 line. If a straight line be drawn from the upper edge of the keel to touch the bacK 
 
10 EXPLANATION OF TERMS USED' IN SHIP SUILDINGf. 
 
 of the floor sweep, the form of the midship frame below the lower height of breadth w'ilJ 
 be obtained. 4th. The Upper Breadth Sweep; the centre of which is in the line represent- 
 ing the upper height of breadth of the timber. This sweep described upwards forms the 
 lower part of the top-timber. 5th. The Top-Timber Sioeep, or Back Sweep, is that which 
 forms the hollow of the top-timber. This hollow is, however, very often formed by a 
 mould; so placed as to touch the upper breadth sweep, and pass through the point limiting 
 the half-breadth of the top-timber. 
 
 FRAME TIMBERS.— The various timbers that compose a frame bend ; as the flooi^ 
 limber, the first, second, third, and fourth, futtocks, and top timber, which are united, by 
 a proper shift, to each other, and bolted through each shift. They are often kepi open, 
 for the advantage of the air, and fillings fayed between them in wake of the bolts. Some 
 ships are composed of frames only, and are supposed to be of equal strength with others 
 of larger scantling. 
 
 FUTTOCKS.— The separate pieces of timber of whicfi tlie frame timbeps are composed.- 
 They are named according to their situation, that nearest the keel being called tlie first 
 fultock, the next above, the second futlock, &.c. 
 
 GARBOARD STRAKE.— That slrake of the bottom which is wrouglit next the t«el,. 
 and rabbets therein. 
 
 GRIPE. — A piece of elm timber that completes the lower part of the knee of the head, 
 and makes a finish with the fore-foot. It bolts to the stem, and is farther secured by twc 
 plates of copper in the form of a horse-shoe, and therefrom called by that name. 
 
 GROUNDWAYS. — Large pieces of timber, generally defective, which are laid upott 
 piles driven in the ground, across the dock or slip, in order to make a good foundation to' 
 lay the blocks on, upon which the ship is to rest. 
 
 GUNWALE. — That horizontal plank/which covers the heads of the timbers betwee» 
 Ihe main and fore drifts. 
 
 HALF-TIMBERS. — The short timbers in the cant bodies which are answerable to the' 
 lower futtocks in the square body. 
 
 HANGING-KNEE. — Those knees against the sides whose arms hang vertically or per-' 
 pendicular. 
 
 HARPINS. — Pieces of oak, similar to ribbands, but trimmed and bevelled to the shape' 
 of the body of the ship, and holding the fore and after cant bodies together until the ship 
 Is planked. But this term is mostly applicable to those at the bow ; hence arises the phrase 
 "lean and full harpin," as the ship at this par* is more or less acute. 
 
 HEAD. — The upper end of any thing ; but more particularly applied to all the work' 
 fitted afore the stem, as the Figure, the Knee, Rails, &c. A "Scroll Head" signifies that 
 there is no carved or ornamental figure at the head, but that the termination is formed and 
 finished off by a vatute, or scroll turning outwards. A "Fiddle Head" signifies a similar 
 kind of finish, but with the scroll turning aft or inwards. 
 
 HEAD-LEDGES. — The 'thwartship pieces which frame the hatchways and ladder- 
 ways. 
 
 HEAD-RAILS. — Those rails in the Head which extend from the back of the figure to 
 the cathead and bows, which are not only ornamental to the frame, but useful to that p4rt 
 of the ship. 
 
 HEEL. — The lower end of a tree, timber, &c. A ship is also said to Heel when she is 
 not upright but inclines under a side pressure. 
 
 HOGGING. — See Broken Backed. A ship is said to Hog when the middle part of her 
 keel and bottom are so strained as to curve or arch upwards. This term is therefore op- 
 posed to Sagging, which, applied in a similar manner, means, by a different sort of strain, 
 to curve downwards. 
 
 HOLD. — That part of the ship below the lower deck, between the bulkheads, which is 
 reserved for the stowage of ballast, water, and provisions, in ships of war, and for that of 
 the cargo in merchant-vessels. 
 
 HOODING ENDS. — Those ends of the planks which bury in the rabbets of the stem: 
 and stern post. 
 
 HORSE-IRON. — An iron fixed in a handle, and used with a beetle by caulkers, to 
 horse-up or harden in the oakum. 
 
 HORSE-SHOES. — Large straps of iron or copper shaped like a horse-shoe and let into^ 
 
EXPLANATION OF TERMS USED IN SHIP BUILDING. H 
 
 the stem and gripe on opposite sides, through which they are boiled together to secure the 
 gripe to the sjem. 
 
 HULL.— The whole frame or body of a ship, exclusive of the masts, yards, sails, and 
 rigging. 
 
 IN AND OUT.— A terra sometimes used for the scantling of the Timbers the moulding 
 way, but more particularly applied to those bolts in the knees, riders, &c., which are 
 driven through the ship's sides, or athwartships, and therefore called "In and out bolts." 
 
 INNER POST.— A piece of oajc timber, brought on and fayed to the foreside of the 
 main stern-post, for the purpose of seating the Transoms upon it. It is a great security 
 to the ends of the plants, as the main post is seldom sulficiently afore the labbet for that 
 purpose, and is also a great strengthener to that part of the ship. 
 
 KEEL. — The main and lowest timber of a ship, extending longitudinally from the stem 
 to the stern post. It is formed of several pieces, which aie scarphed together endways, 
 and form the basis of the whole structure. Of course it is usually the first thing laid 
 down upon the blocks for the constrijction of the ship, 
 
 KEELSON OR, MouE com.monlt, KELSON. — The timber, formed of long square pieces 
 of oak, fixed within the ship exartly over the keel, (and which may therefore be considered 
 as the counter part of the latter) for binding and strengthening the lower part of the ship ; 
 for which purpose it is fitted to, and laid upon, the middle of the iloor timbers, and boiled 
 through the flobrs pnd keel. 
 
 KNEES. The crooked pieces of oak timber by which Ihe ends of the beams are secured 
 to the sides of the ship. Of these, such as are fayed vertically to the sides are called 
 Hanging-Knees, and such as are fixed parallel to, or with the hang of, the deck, are callid 
 l,odging- Knees. 
 
 KNEE OF THE HEAP. — The large flat timber fayed edgeways upon the fore-part of the 
 stem. It is formed by an assemblage of pieces of oak coaked or tabled together edgewise, 
 by reason of its breadth, and it projects the length .of the Head. Its fore part should form 
 a handsome serpentine line, or inflected curve. The principal pieces aie named the JUain- 
 piece and Lacing. 
 
 LABOURSOME. — Subject to labour, or to pitch and roll violently in a heavy sea.'by 
 which the masts and even the hull may be endangered. For, by a series of heavy rolls 
 the rigging becomes loosened, and the masts at the same time may strain upon the shrouds 
 with an effort which they will be unable to resist ; to which may be added, that the con- 
 tinual agitation of the vessel Ioosen= her joints, and makes her extremely leaky. 
 
 TO LAP OVER OR, UPON.^— The mast carlings are said to lap upon the beams by rea- 
 son of their great depth, and head-ledges at the ends lap over the coamings. 
 
 LAP-SIDED. — A term expressive of the condition of a vessel when she will not swim 
 upright, owing to her sides being unequal. 
 
 LAUNCHING-PLANKS. — A set of planks mostly used to form the platform on each 
 side of the ship, whereon the bilgeways slide for the purpose of launching. 
 
 LAYING-OFF, OR LA YING-DOWN.— The act of delineating the various parts of the 
 ship, to its true size, upon the mould-loft floor, from the draught given for the purpose of 
 making the moulds. 
 
 LEDGES. — Oak or fir scantling used in framing the decks, which are let into the car- 
 lings athwartships. The ledges for gratings are similar, but arcli or round up agreeably 
 to the head ledges. 
 
 LENGTHENING. — The operation of separating a ship athwartships and adding a cer- 
 tain portion to her length. It is performed by clearing or driving out all the fastenings in 
 wake of the butts of those planks which may be retained, and the others are cut through, 
 The after end is then drawn apart to a limited distance equal to the additional length pro- 
 posed. The Keel is then made good, the floors crossed, and a sufficient number of timbers 
 raised to fill up the vacancy produced by the separation. The kelson is then replaced to 
 give good shift to the new scarphs of the Keel, and as many beams as may be necessary 
 are placed across the ship in the new Interval, and the planks on the outside are replaced 
 with a proper shift. The clamps and footwaling within the ship are then supplied, the 
 beams knee'd, and the ship completed in all respects as before. 
 
 TO LET-IN. —To fix or fit one timber or plank into another, as the ends of carlings in- 
 to the beams, and the beams into the clamps, vacancies being made in each to receive the 
 other. 
 
 LEVEL LINES, — Lines determining the shape of a ship's body horizontally, or square 
 from the middle line of the ship. 
 
12 EXPLANATION OF TERMS USED IN SHIP BUILDIN«. 
 
 LIMBER PASSAGE. — A passage or channel formed throughout the whole length of 
 the floor, on each side of the kelson, for giving water a free communication to the pumps. 
 It is formed by the Limber-Strake on each side, a thick strake wrought next the kelson, 
 from the upper side of which the depth in the hold is always taken. This strake is kept 
 at about eleven inches from the kelson, and forms the passage fore and aft which admits 
 the water with a fair run to the pump-well. The upper pijrt of the Limber Passage is 
 formed by the Limber-Boards, which are ipaxle to keep out all dirt and other obstruc- 
 tions. These boards are composed of short pieces of oak plan}c, one edge of which is fitted 
 by a rabbet into the limber strake, and the other edge bevelled with a descent against the 
 kelson. They are fitted in short pieces for the convenience of taking up any one, or more, 
 readily, in order to clear away any obstruction in the passage. When the limber boards 
 are fitted, care should be taken to have the butts in those places where the bulkheads come, 
 as there will be then no difficulfy in taking those up which come near the bulkheads. A 
 hole is bored in the middle of each butt to adpiit the end of a crow for prizing it up when 
 required. To prevent the boards from being displaced, each should be marked wilh a line 
 corresponding with one on the Limber Strake. 
 
 LIMBER HOLES gre square grooves cut through the underside of the floor timber, 
 about nine inches from the side of the Keel on each side, through which water may run 
 toward the pumps, in the whole length of the floors. 'J'his precaution is requisite in mer- 
 chant ships only, where small quantities of water, by the heeling of the ship, may come 
 through the ceiling and damage the cargo. It is for this reason that the lower futtocks of 
 merchant ships are cut ofi" short of the Keel, 
 
 LIPS OF SCARPHS. — The substance left at the ends, which would otherwise become 
 sharp, and be liable to split; and, m Pther cases could ijot bear caulking as the scarphs of 
 the keel, stem, &c. 
 
 MAIN BREADTH. — The broadest part of t^he ship sjt any particular timber or frame, 
 which IS distmguished on the sheer-draught by the upper and lower heights of breadth 
 lines. 
 
 MAIN WALES. — -The lower Wales; which are generally placed on the lower breadth, 
 and so that the main-deck kneerbolts may come into thenj. 
 
 MANGER. — An apartment e:$tending athwart the ship immediately within the hawse- 
 holes. It serves as ^ fence to interrupt the passage of water which may come in at the 
 hawse-holes, or from the cable wfien heaving in; and the water thus prevented from run- 
 ning aft is returned info the se% by the manger scuppers, which are larger than the other 
 scuppers on that account. 
 
 MAULS.— Large hammers used for driving treenails, having a steel face at one end, 
 and a point or pen dr&wn out at the other. Double-headed Mauls have a- steel face at each 
 end, of the same size, and are used for driving of bolts, &c. 
 
 META-CENTRE. — That point in a ship above whjch the centre of gravity must by no 
 means be planed ; because, if it were, the vessel worjl4 be liable to oyerset. The mela- 
 centre, which has also been called ihe shifting-cenlre , depends upon the situation of the cen- 
 tre of cavity ; for it is that pojnt where a vertical line drawn from the centre of cavity 
 cuts a line passing through the centre of gravity, and being perpendicular to the Keel. 
 
 MIDDLE I4NE. — A line dividing the ship exactly in the middle. In the horizontal or 
 half-breadth plan it is a right line bisecting the ship from the sten) to the stern-post; and, 
 in the plane of projection, or body plan, it is a perpendicular linp bisecting the ship from 
 the keel to the height of the top of the side. 
 
 MOMENTA, OE Moments.— The plural of Jlfome»i(«ni. 
 
 MOMENTUM of a heavy body, or of any extent considerecl as a heavy body, is the 
 product of the weight multiplied by the distance of its centre of gravity from a certain 
 point, assumed at pleasure, which is called the centre of the momentum, or from a line 
 which Is called the axis of the momentum. 
 
 MORTISE. — A hole or hollow made of a certain size and depth in a piece of tiojter, 
 &c. in order to receive the end of another piece with a tenon fitted exactly to fill it. 
 
 MOULDS. — Pieces of deal or board made to the shape of the lines on the Mould Loft 
 Floor, as the Timbers, Harpins, Ribbands, &c. for the purpose of cutting out the different 
 pieces of timber, &c., for the ship. Also the thin flexible pieces of pear-tree or box used 
 in constructing the draughts and plans of ship, which are made in various shapes; viz. to 
 the segmenls of circles from one foot to 22 feet radius, increasing six inches on each edge, 
 and numerous elliptical curves, with other figures. 
 
 MOULDED. — Cut to the mould- AJso tbe size or bigness of tjie timbers that way the 
 
 plDUld is laid, ^ff SfDED. 
 
EXPLANATION OF TERMS USEP IN SHIP BUILDING. 13 
 
 NAILS. — Iron pins of vnrious descriptions for fastening board, plank, or iron work; 
 siz : Deck Mdls, or Spike JVni/s, wliich are from 4 iiiclies and a half to 12 inches long, have 
 snug heads, and are used for fastening planks and the flat of the decks. Weight Jfails are 
 similar to deck nails, but not so fine, have squiire heads, and are used for fastening cleats, 
 i&c. Rihhand Miits are similar to weighl nails, with ti.is difference, that they have large 
 round heads, so as to be more easily drawn. They are used for fastening the ribbands, 
 ;&c. Clamp JVVu/s are short stout nails, wilh large heads, for fastening iron clamps. Port 
 Nails, double and single, are similar to clamp nails, and used for fistening iron work. — 
 Jludder Aoiis are also similar, but used chiefly for fastening the pintles and braces. Fill- 
 ing ^'aits are generally of cast iron, and driven very thick in Ihc bottom planks instend of 
 copper sheathjiig.* SAeBl/iirig-JVai/s are used to fasten wood sheathing on the ship's bottom, 
 to preserve the plank, and preventthe filling nails fiomtearing iltoo much* J^nils of sorts 
 are 4, 6, 8j 10, 24, 30, and 41) penny nails, all of different lengths, and used for nailing 
 board, &c. Scupper Miils are short nails, with very broad heads, used to nail the flaps of 
 the scuppers. Lend .N'aits are small round-headed nails for nailing of lead. FlatJ^ails are 
 small sharp-pointed nails, with flat thin heads, for nailing the scarphs of moulds. Sheathe 
 ing J^ails for nailing copper sheathing are of metal, casi in moulds, about one inch and a 
 quarter long ; the heads are flat on the uppej- side and eonnter-sunk belnw : the upper side 
 is polished to obviate the adhesion of weeds Boat J\fails, used by Boat-builders, are of 
 ■various lengths, generally rose headed, square at the points, and made both of copper and 
 iron 
 
 OAICUM. — Old Rope, untwisted and loosened like hemp, in order to be used in caulking, 
 
 To OVER-LAUNCH. — To run the butt of one plank to a certain distance beyond the 
 next butt above or beneath it, in order to make stronger work. 
 
 PALLETTING. — A slight platform, madp above the bottom of the Magazine, to keep 
 the powder from moisture. 
 
 PALLS. — Stout pieces of iron, so placed near a capstan or windlass as to prevent a rcr 
 coil which would overpower the men at the bars when heaving. 
 
 PARTNERS.— Those pieces of thin plank, &c., fitted into a rabbet in the Mast op 
 Capstan carlings for the purpose of wedging the mast and steadying the Capstan. Also 
 any plank that is thick, or above the rest of the deck, for the purpose of steadying what^ 
 ever passes through the deck, as the pumps, bowsprit, Sac. 
 
 To FAY. — To lay on a coat of tar, &c., with a mop or brush, in order to preserve the 
 wood and keep out water. When one or more pieces are scarphed together, as the beams, 
 &c., the inside of the scarphs are paid with tar as a preservative ; and the seams after they 
 Are caulked are payed with pitch to keep the water from the oakum, &c. 
 
 PINK. — A ship with a yery narrow round stern ; whence all vessels, however small, 
 having their sterns fashioned in this manner, are said to be pink-sterned. 
 
 PINTLES,— Straps of mixed metal, or of iron, fastened on the rudder, in the same man- 
 ner as the braces on the stern post, having a stout pin or hook at the ends, with the points 
 downwards to enter in and rest upon the braces on which the rudder traverses or turns, 
 3S upon hinges, from side to side. Sometimes one or two are shorter than the rest, and 
 work in a socket brace, whereby the rudder turn* easier. The latter are called Dumb- 
 Pintles, Some are bushed. 
 
 PITCH. — Tar, boiled to a harder and more tenacious substance, 
 
 PITCHING. — The inclination or vibration of the ship lengthwise about her centre of 
 gravity ; or the motion by which she plunges her head and after-part alternately into the 
 hollow of the sea. This is a very dangerous motion, and when considerable, not only re- 
 tards the ship's way, but endangers the masts and strains the vessel. 
 
 PLANKING. — Coyering the outside of the tinjbers with plank ; sometimes quaintly 
 called Skinning, the plank being the outer coating, when the vessel is not sheathed. 
 
 PLANK-SHEERS, OR PLANK-SHEER.-^The pieces of plank laid horizontally 
 over the timber-heads of the Quarter.-Deck and Forecastle, for the purpose of covering 
 the top of the side, hence sometimes palled Covering-Boards. 
 
 POINT-VELIQITE. — That point where, in a direct course, the centre of effort of all 
 the sails should be found. 
 
 POPPETS — Those pieces (mostly fir) which ate fixed perpendicularly between the 
 ship's bottom and the bilgeways, at the fore and aftermost parts of the ship, to support 
 her in launching. 
 
 PUMP. — The machine, fitted in the wells of ships, to draw water out of the hold. 
 
 ' Obsolete. 
 
l-i EXPLANATION OF TERMS USEO IN SHIP BUILDING. 
 
 PUAIP CISTERNS — Cisterns fixed over the heads of the pumps, to receive the water 
 «iatil it is conveyed through the sides of the ship by the Pump-dales. 
 
 PUMP-DALE3. — Pipes fitted to the cisterns, to convey tlie water from them through 
 the ship's s.ides. 
 
 QUARTER-GALLERIES.— The projections from the Quarters abaft, fitted with 
 sashes and ballustors, and intended botii for convenience and ornament to the aft part of 
 the ship. 
 
 To QUICKEN. — To give anything a greater curve. For instance, " To Quicken the 
 Sheer," is to shorten the radius by which the curve is struck. This term is therefore op^ 
 posed to straightening the sheer. 
 
 RABBET. — A joint made by a groove, or channel, in a piece of timjier cut for the pur- 
 pose of receiving and securing the edge or ends of tlie planlcs, as the pjanks of the bottom 
 into the keel, stem, or stern post, or the edge of one plank into another. 
 
 RAG-BOLT. — A sort of bolt having its point jagged or barbed to make it hold the 
 more securely. 
 
 IIAKK. — The overhanging of the stem or stern beyond a perpendicular with the keel, 
 or any part or thing that forms an obtuse angle with the horizon. 
 
 RAM^LINE. — A small rope or lin.e sometimes used for the purpose of forming the 
 shter or hang of the decks, for setting the beams, fair, &c. 
 
 RASING. — The act of marking by a mould on a piece of timber; or any marks made by 
 a tool called a rasing-lcnifc. 
 
 To RECONCILE. — Te moke one piece of work answer fair with the moulding or shape 
 of the adjoining piece ; and, more particularly, in the reversion of curves. 
 
 REEMING. — A term used by caulkers for opening the seams of the planks, that th? 
 oakum may be more readily admitted. 
 
 REEMING-IRONS. — The large irons used by caulkers in opening the seams, 
 
 RENDS, — Large open splits or shakes in timber; particularly in plank, occasioned by 
 its being exposed to the wind or sun, ^c. 
 
 RIBBANDS. — The longitudinal pieces of fir, about five inches square, nailed to the 
 timbers of the square body (those of the same description in the Cant Body being shaped 
 by a mould and called Harpins) to keep the body of the ship together, and in its proper 
 shape, until the plank is brought on. The shores are placed beneath them. They are 
 removed entirely when the planking conies on. The difference between Con/ Ribbands and 
 Square or Horizontal Ribbands is, that the latter are only ideal, and used in laying-off. 
 
 RIBBAND-LINES.— The same with diagonal lines. 
 
 RISING. — A term derived from the shape of a ship's bottom in general, which gradu- 
 ally narrows or becomes sharper towards the stem .and the stern-post. On this account it is 
 that the Eloor, towards the extremities of the ship, is raised or lifted above the keel : 
 otherwise the shape would be so very acute, as not to he piovided from' timber with suffi- 
 cient strength in the middle, or cutting-down. The floor timbers forward and abaft, with 
 regard to their general form and arrangement, are therefore gradually lifted or raised 
 -ipon a solid body of wood called the dead or rising wood, which must, of course, have 
 more or less rising as the body of the ship assumes more or less fullness or capacity. See 
 Dead Rising. 
 
 The RISING OF BOATS is a narrow strake of board fastened within side to support 
 the thwarts. 
 
 RISING FLOORS. — The floors foiward and abaft, which, on account of the rising of 
 the body, are the most difficult to be obtained, as they must be deeper in the throat or at 
 the cutting down to'preserve strength. 
 
 RISING-LINE. — An elliptical line, drawn on the plan of elevation, to determine the 
 sweep of the floor-heads throughout the ship's length, which accordingly ascertains the 
 shape of the bottom with regard to its being full or sharp. 
 
 ROLLING. — That motion by which a ship vibrates from side to side. Rolling is there- 
 fore a sort of revolution about an imaginary axis passing through the centre of gravity of 
 the ship ; so that the nearer the centre of gravity is to the keel, the more violent will be 
 the roll ; because the centre about which the vibrations are made is placed so low in the 
 bottom, that the resistance made by the keel to the volume of water which it displaces in 
 Tolling, bears very little proportion to the force of the vibration above the centre of grav- 
 
EXPLAJfAT'lON OF TERMS USED L\ SHIP BUlLDINtf. 15 
 
 hy, the radius of which extends as high as the mast-heads But, if the centre of gravity 
 is placed highef above the Iceel, the radi'.fs of the vibration will not only be diminished, 
 but suih an additional force to oppose the motion of rolling will be communicated to that 
 part of the ship's bottom as may contribute to diminish this movement considerably. It 
 may be observed that, with respect to the formation of a ship's body, that shape whicl'i 
 approaches nearest to a circle is the most liable to roll; as it is evident, that if this be 
 agitated in the water, it will have nothing to restrain it ;• because the rolling or rotation 
 about its centre displaces no more water than when it remains upright ; and, hence, it be- 
 comes necessary to increase the depjh of the keel, the rising of the flooYs, and the dead- 
 wood afore and abaft. 
 
 ROOM AND SPACE. — The distance from the moulding edge of one timber to the 
 moulding edge of the next timber, which is always equal to the breadth of two timbers, 
 and two to four inches more. The room and space of all ships that have ports should be 
 so disposed, that the scantling of the timber on each side of the lower ports,' and the size 
 of the ports fore and aft, may be equal to the distance of two rooms and spaces. 
 
 ROUGH-TREE RAILS. — In men-of-war the broad plank running fore and aft cover- 
 ing the heads of the top timbers^ thus forming the bottom of the hammock netting. In 
 merchant vessels the rails along the waist and quarters, nearly breast high, to prevent per- 
 sons from falling overboard. This term originated from 1;he practice in merchaAt ves- 
 sels of carrying their rough or spare gear in crutch irons along their waist. 
 
 RUDDER-CHOCKS. — Large pieces of fir,' to fay or fill up the excavation on the side 
 of the rudder in the rudder hole ; so that the helm being in midships the rudder may be 
 fixed, and supposing the tiller broke another might thus be replaced. 
 
 RUN.— ^The narrowing of the ship abaft, as of the floor towards the stern-post, where 
 it becomes no broader than the post itself. This term is also used to signify the running 
 or drawing of a liiae on the ship, or mould loft floor,- as "to run the wale line," or deck 
 line, &c, 
 
 SCANTLING. — The dimensions given for the timbers,- planks, &c. Likewise all quar- 
 tering under five inches square, which is termed Scantling ; all above that size is called 
 Carting. 
 
 SCARPHING. — The letting of one piece of timber or plant into another with a lap, in 
 such a manner, that both may appear as one solid and even surface, as keel-pieces, stem- 
 pieces, clamps, &c. 
 
 SCUPPERS. — Lead pipes' let through the ship's side to convey the water from the decks. 
 
 SEAMS. — The openings between the edges of the planks when wrought. 
 
 SEASONING. — A term applied to a ship kejft standing a certain time after she is com- 
 pletely framed and dubbed out for planking, which should never be less than six months 
 when circumstances will permit. Seasoned Pkmk or Timber is such as has been cut down 
 and sawn out one season at least, particularly when throughly dry, and not liable to shrink. 
 
 SEATING. — That part of the floor which fays on the dead-wood ; and of a transom 
 which fays against the post. 
 
 SENDING OR 'SCENDING.— The act of pitching violently intothe hollows or inter- 
 vals of the waves. 
 
 SETTING OR SETTING-TO.— The act of m?king the planks &c., fay close to the 
 timbers, by driving wedges between the plank, &c., and a wrain-stafF. Hence we say, "set 
 or set away," meaning to exert more strength. The power or engine used for the purpose 
 of setting is called a Sett, and is composed of two ring-bolts, and a wrain-stafF, cleats, 
 and lashings. • 
 
 SH.\KEN OR SHAKY.— A natut-al defect ih pla-nk or timber when it is full of splits 
 or clefts and will not bear fastening or caulking^ 
 
 SHEATHING. — A thin sort of doubling, or casing, of fir-board or sheet copper, and 
 sometimes of both, over the ship's bottom, to protect the planks from worms, &c. Tar 
 and hair, or brown paper dipt in tar and oil, is laid between the sheathing and the bottom. 
 
 SHEER.— The longitudinal curve or hanging of ship's side in a fore and aft direction. 
 
 SHEER-DRAUGHT. — The plan of elevation of a ship, whereon is described the out- 
 board works, as the wales, sheer-rails, ports, drifts, head, quarters, post, and stem, &c. 
 the hang of each deck inside, the height of the water lines, &c. ' 
 
 SHEER-STRAKE. — The strake or strakes wrought in the topside, of which the upper 
 edge is wrought well with the toptimber line, or top of the side, and the lower edge kept 
 *ell with the upper part of the upper deck ports in midships, so as to be continued whole 
 all fore and aft, and not cut by the ports. It forms the chief strength of the upper part of 
 
16 
 
 EXPLANATION OJ* TERMS U^ED IN SFllP BUILDINCf. 
 
 the topside, and is therefore always worked thicker than the other strakes, and scarpfied 
 ■with Hook and Butt between the drifts. 
 
 SIDING OR SIDED. — 1 he size or dimensions of timber the contrary way to the 
 moulding, gr moulded side. 
 
 SIRMARKS. — The different places marked upon the moulds where ihe respective bev- 
 ellings are to be applied, as the lower sirm4rK, floor sirmark, &c, 
 
 SLIDING PLANKS aire the planks upon which the Bilgeways slide in Launching. 
 
 SLIP. — The foundation laid for the purpose of building the ship upon; and launching' 
 her. 
 
 To SNAPE. — To hance.Or bevel the end of any thiihgso as to fay up'on an inclined plane. 
 
 SNYING. — A term applied to planks when their edges round or curve upwards. The 
 great sny occasioned in full bows, or buttocks is only to be prevented by introducing 
 Steelers. 
 
 SPECIFIC GRAVITY. — The Comparative difference in the weight or gravity of two 
 bodies of equal bulk; hence called also, relative or comparative gtavity, because we judge 
 of it by comparing one body with another. 
 
 A TABLE OF SPECIFIC GRAVITIES. 
 
 Lead 11.S25 
 
 Fine Copper 9000 
 
 Gun Metal 8784 
 
 Fine Brass 8350 
 
 Iron from.... 7827 to 7645 
 
 Cast Iron 7425 
 
 Sand 1520 
 
 Lignum Vitae 1327 
 
 Ebony 1177 
 
 Pitch 1150 
 
 Rosin 1100 
 
 Mahogany 1063 
 
 Box Wood 1030 
 
 Sea Water 1030 
 
 Tar 1015 
 
 River Water 10119 
 
 Rain Water 1000 
 
 Oak .■ , 925 
 
 Ash -.. 800 
 
 Beech 700 
 
 Elm 600 
 
 Fir 548 
 
 Cork 240 
 
 Common Air 1.232 
 
 These numbers being the weight of a cubic foot, or 1728 cubic inches, of each of the 
 bodies in avoirdupois ounces ; by proportion, the quantity in any other weight, or the 
 weight of any other quantity, may be readily known. 
 
 For Example. — Required the content of an irregular piece of oak, which weighs 761bs. 
 or 1216 ounces. 
 
 Sp. gr. oz. Wt. oz; 
 Here as 92S ; 1216 
 
 cul) in. cub. in. 
 
 : 1728 : 2271=1 ft. 543 inches cubic, the contents. 
 
 SPIRKETTING. — A thick strake, or strakes, wrought within side upon the ends of the 
 beams or waterways. In ships that have ports the spirketting reaches from the waterways 
 to the upper side of the lower sill, which is generally of two strakes, wrought anchor- 
 stock fashion ; in this case, the planks should always be such as will work as broad as pos- 
 sible, admitting the butts be about six inches broad. 
 
 SQUARE BODY, — The figure which comprehends all the timbers whose areas or 
 planes are perpendicular to the keel, which is all that portion of a ship between the cant- 
 bodies. See Bodies. 
 
 SQUARE-TIMBERS. — The timbers which stand square with, or perpendicular to, thp 
 keel. 
 
 SQUARE TUCK. — A name given to the after part of a ship's bottom when terminated 
 in the same direction up and down as the wing transom, and the planks of the bottom end 
 in a rabbet at the foreside of the fashion-piece; whereas ships with-a buttock are round 
 or circular, and the planks of the bottom end upon the wing- transom. 
 
 STABILITY. — That quality which enables a ship to keep herself steadily in the water, 
 without rolling of pitching. Stability, in the constrilction of a ship is only to be acquired, 
 by fixing the centre of gravity at a certain distance below the meta-centre ; because the 
 stability of the vessel increases with the altitude of the meta-centre above the centre of 
 gravity. But, when the meta-centre coincides with the centre of gravity, the vessel has 
 no tendency whatever to remove out of the situation intr> which it may be put. Thus, if 
 the vessel be inclined either to the starboard of larboard side, it will remain in that posi- 
 tion till a new force is impressed upon it : in this case, therefore, the vpssel would not be 
 able to carry sail, and is consequently unfit for the purposes of navigation. If the meta- 
 centre falls below the common centre of gravity, the vessel will immediately overset. 
 
 STEELER. — A name given to the foremost or aftermost plank, in a strake which drops 
 Sihort of the stem and stern post, and of which the end or butt nearest the rabbet is worked 
 
E'XPLANATION OF TERMS USED IN SHIP BUILDING. 17 
 
 ■Very narrow and well forward or aft. Their use is, to take out the snying edge occasioned 
 by a full bow, or sudden circular buttock. 
 
 STEM. — The main timber at the fore part of the. ship, formed, by the combination of 
 Seyeral pieces, into a circular shape, and erected vertically to receive the ends of the bow- 
 planks, which are united to it by means of a rabbet. Its lower end scarphs or boxes inlo 
 the keel, through which the rabbet is also carried, and the bottom unites in the same 
 •manner. ^ 
 
 STEMSON. — A piece of compass timber, wrought on the aft part of the apron within- 
 -side, the lower end of wbich scacphs into the kelson. Its upper end is continued as high 
 as the middle or upper deck ; and its use is to succour the scarphs of the apron, as that 
 does those of the stem. 
 
 STEPS OF THE MASTS.— The steps into which the "heels of the masts are fixed, are 
 large pieces 'of timber. Those for the main and fore masts are fixed across the kelson, 
 and that for the mizen toast upon the lower deck beams. The holes or mortiaes into which 
 the masts step, should have sufficient wood on each side, to accord in strength with the 
 tenon left at the heel of the mast, and the hole should be out rather less than the tenon, as 
 an allowance for shrinking. 
 
 STEPS FOR THE SHIP'S SIDE.— The pieces ofH^uartering, with mouldings, nailed 
 'to the sides amidship, about nine^inches asunder, from the Wale upwards, for the conve- 
 nience of persons getting on board. 
 
 STERN FRAME.-^The strong frame of timber, composed of the sterff-post, transoms, 
 ■and fashion-pieces, which form the basis of the whole stern. 
 
 STERN-POST.-^The principal piece of timber in the stern frame on which the rudder 
 is hung, and to which the transoms are bolted. It therefore terminates the ship below the 
 . wii^-tEanson^ apd its lower end is tenoned into the keel. 
 
 STIVING. — The elevation of a ship's cathead or bowsprit ; or the angle which either 
 makes with the horizon, generally called Steeve. 
 
 STOPPINGS-UP. — The poppets, timber, &c. used to fill up the vacancy between the 
 upper side of the bilgeways and the ship's bottom, for- supporting her when launching. 
 
 STRAIGHT OF BREADTH.— The space before and abaft dead-flat, in which the ship 
 -is of the same uniform breadth, or of the same breadth as at X Or tJead-flat-. Set Deau- 
 
 PLAT. 
 
 STRAKE. — One breadth of plsck wrouglit from one end of the ship to the otbei^ eithe-r 
 within or without board. 
 
 TABLING. — Letting ome 'piece of timber into another by alternate scores or projections 
 •from the middle, so that it cannot be drawn asunder either lengthwise or sidewise, 
 
 TAFFAREL, OR TAFF-RAIL.— The upper part of the ship's stern, usually orna- 
 mented with carved work or mouldings, the ends of which unite to the quarter-pieces. 
 
 TASTING OF PLANK OR TIMBER.— Chipping it with an adze, or boring it with 
 a small auger, for the purpose of ascertaining its quality or defects. 
 
 TO TEACH. — A t«rm applied to tlie direction that any line, &c., seems to point out.-^ 
 Thus we say "let the line or mould teach fair to such a spot, rase," &c. 
 
 TENON. — The square part at the end of one piece of timber-, diminished so as to fix in 
 a hole of another piece, called a mortise, for joining or fastening the two pieces together. 
 
 THICKSTUFF. — A name for sided timber, exceeding four inches, but not being more 
 than twelve inches, in thickness. 
 
 THROAT. — The inside of knee timber at the middle or turn of the arms. Also the 
 midship part of the floor timbers. 
 
 TOP AND BUTT. — A method of working English plank so as to make good conver- 
 sion. As the plank runs very narrow at the top clear of sap, this is done by disposing the 
 top end of every plank within six feet of the butt end of the plank above or below it, let- 
 ting every plank work, as broad as ;it will hold clear of sap^, by which method only can 
 every other seam produce a fair edge. 
 
 TOPSIDE. — A name given to all that part of a ship's side above the main-w-ales^ 
 
 TOP-TIMBERS.— The timbers which form the topside. The first general tie*- which 
 *eaoh the top are ealled-the long toprtimbers, and those below are called t4ie S'feort top-tim- 
 '■faers. See Fkames. 
 
 >C 
 
1;8 EXPLANATION OF TERMS USED IN SHIP BUILDING. 
 
 TOP TIMBER LINE.— The curve limiting the height of the sheer at the given breadth, 
 of the top-timbers. 
 
 TOUCH.— The broadest part of a planlt worlfed top and butt, which place is six feet 
 from the butt end. Or, the middle of a plank, worked anchor-stock, fashion. Also the 
 sudden angles of the stern-timbers at the counters, &c. 
 
 TRAIL-BOARDS.— A term for the carved work, between the cheeks, at the heel of 
 
 the figure. ^ 
 
 TR ^NSOMS.— The thwartship timbers which are bolted to the stern-post in order to 
 form the buttock; and of which the curves, forming the round aft, are represented on the 
 horizontal, or half-breadth plan of the ship. 
 
 TREAD OF THE KEEL.— The whole length of the keel upon a straight line. 
 
 TREENAILS.— .Cylindrical oak pins driven. through the planks and timbers of a vessel 
 to fasten or connect them together. These certainly make the best_fastening when driven-, 
 quite through, and caulked or wedged, inside.. They should be made of the very best oak,, 
 cut neaf the butt,, and perfectly dry or well seasoned. 
 
 THE TUCK.— The aft part of the ship where the ends of the planks of the bottom are 
 terminated by the tuck-rail, and all below the wing-transom when it partakes of the figure 
 of the wing-transom as far as the Fashion-pieces. See Square Tuck. 
 
 TUCK-RAIL. — The rail which is wrought well with the upper side of the wing-transom,, 
 and forms a rabbet for the purpose of caulking the butt ends of the planks of the bottom.. 
 
 WALL-SIDED. — A term applied to the topsides of the ship when the main breadth is 
 continued very low down and very high up, so that the topsides appear strait and upright 
 like a wall. 
 
 WASH-BOARD. — A shifting strake along the topsides of a small vessel, used occasion-- 
 ally to keep out Ihe sea. 
 
 WATER LINES, OR LINES OF' FLOATATION.— Those horizontal lines, sup- 
 posed to be described by the surface of the water on the bottom of a ship, and which are 
 exhibited at certain, depths upon the sheer-draught. Of these,, the most particular are 
 those denominated, the Light Water Line and the ioad Witter Line; the former, namely, 
 the Light Water Line, being that line which shews the depression of the ship's body in 
 the water, when light or unladen, as when first launched? andthe latter, which exhibits 
 the same when laden with her guns and ballast, or cargo. In the Half-Breadth Plan these 
 lines are curves limiting the Half-breadth of the ship at the height of the corresponding 
 lines in the Sheer Plan. 
 
 WATER WAYS. — The edge of the deck next the timbers, which is wrought thicker 
 than the rest of the deck, and so hollowed to the thickness of the deck as to form a gutter.- 
 or channel for the water to-run through to the scuppers. 
 
 WHOLE. MOULDED. — A term applied: to the bodies of those ships which are so con- 
 structed that one Mould made to the midship bend, with the addition.of a floor hollow, will, 
 mould. all the timbers,, below the main breadth,. in, the square body. 
 
 WINGS. — 'The places next the side upon the. orlop, usually parted off in ships of war, 
 that the carpenter andhis crew may have access round, the ship, in time of action, to plug 
 up shot-holes,. &c. 
 
 WING-TRiANSOM:. — The uppermost transom, in the stern frame, upon which the- 
 heels of the counter timbers are let in and rest. It is by some called the main transom. 
 
 WOOD-LOCK..— .A piece of elm, or oak, closely fitted, and sheathed with copper, in 
 the throating or score of the pintle, near the load water line; so that, when the rudder is, 
 hung, and the woodrloot nailed, in its place, it cannot rise, because the latter butts against, 
 the under side of the Brace, and, butt of the score. 
 
 WR.4IN BOLTS. — Ring bolts, used, when planking, with two or more forelock holes in 
 the end for tak(og-in the sett, as the plank, &c., works nearer the timbers. 
 
 WRAIN STAVE. — A sort of stout billet of tough, wood-, tapered, at the ends so as to. 
 go into the ring of the wrainbolt to make the SPtts necessary for bringing-to the planks or 
 thick-stuff to the timbers, 
 
ERRATA. 
 
 Sage 20, top of the page, 
 
 (( 54 it te (( (f (c 
 
 " 74, 3d line from side, " 
 
 " 77, last line, " 
 
 " 86, 13th line from top, " 
 
 " 99, last line, " 
 
 " 136, 39th, 40th, 41st, and 42d lines," 
 
 " 136J, last line, " 
 
 " 138„ 33rd line,, « 
 
 for "heany," 
 
 " "qualities," " 
 
 " "qualities," " 
 
 " "heigth," " 
 
 " "mnst," " 
 
 "square," " 
 
 "ordinate," " 
 
 "No. n," " 
 
 "movements," " 
 
 'read heavy. 
 " quality. 
 " quantities, 
 " height. 
 " must. 
 " squares. 
 " ordinates. 
 " No. XI. 
 moments.. 
 
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