SHIP-BUILDING. 



frame (3), 2, 4, 6, to 36 in the after-body, as fhewn in 

 P/atel. Now ®, (A), (r), (2), and (3), are called 

 flats, as they are the timbers which are placed in the flat 

 part of the rtiip amidfhips, have no bevellings, and confe- 

 quently do not partake of the rifmg. 



The lower height of breadth is an imaginary line, not 

 only to aflill in the conftruftion of the body, but a line 

 confining the greateft breadths in the fliip, all fore and aft, 

 and (hould next be determined upon. Its height at is 

 2 1 feet 3 inches above the upper edge of the keel ; and that 

 the faid height of breadth fhould be higher afore and abaft 

 is only reafonable as a referve, to be a fupport to the veiTel 

 when heeling by the preffure of the wind upon the fails ; 

 for when a fhip is clofe-hauled by the wind, and lies much 

 over, the weather-fide would lofe much of the breadth, 

 whereas, on the contrary, the lee-fide would then gain con- 

 fiderably, and meeting with a greater refillance, be enabled 

 to carry the greater fail ; therefore forward at the rabbet of 

 the ftem its height is 29 feet, and abaft at the counter- 

 timber 29 feet 6 inches ; and all the heights between fliould 

 form a fair curve, like the ticked line in the fheer-draught, 

 F/att I. 



It may here be remarked, that flat-floored fhips do not 

 require their height of breadth to be raifed fo high forward 

 and aft, for by their conftruftion they are ttiffcr under fail, 

 and carry their weight of cargo low down. 



The body below the lower height of breadth may now be 

 formed, as tlie frames or bends, when put together, and the 

 joint placed to the fore-mentioned perpendiculars, the fides 

 of every port will be formed fo as to cut none of the prin- 

 cipal timbers, and are fo difpofed as to weaken the fliip as 

 little as poffible. Now as capacity, velocity, &c. depend 

 upon the figure of the immerl^ed part of the body, and be- 

 caufe the properties which every fhip ought to pollcfs are, 

 in a manner, fubverfive of, or in oppofition to, each other, 

 as before obferved, the great art certainly is fo to form the 

 body, that none of the deflred qualities (hall be omitted, 

 giving, at the fame time, preference to that which is moll 

 required. In fhips of war, capacity, ftability, velocity, and 

 ftrength, are eflfentially neceli'ary ; the firft and fecond wc 

 fliall endeavour to prove by calculations hereafter ; the third 

 may be affirmed, as the veflcl was aftually built, and anfvvered 

 that purpofe ; and the lad is now fo well ellabhihed in the 

 Britifh navy as to need little addition. 



The half-breadth plan muft be next drawn : thus, draw 

 a ftraight line below the (heer-plan, as in P/ate I., the whole 

 length of the fliip, and parallel to the upper edge of the 

 keel, which line will reprefent the middle line of the (hip, 

 at any height pafiing fore and aft, or lengthwife ; ob- 

 ferving to keep the faid middle line fufficiently below the 

 fcale, fo as to admit of the main half-breadth line coming 

 clear of it. 



Then fquare down from the flieer-plan all the perpendi- 

 culars or joints of the frame-timbers, to the middle line of 

 the half-breadth plan, and likewife the foremott and after- 

 perpendicular. The main half-breadth line may now be drawn, 

 by fetting-off from the middle line in the plan the follow- 

 ing half-breadths at each refpeftive timber ; thus, at 0, 

 24 feet ; at F, 23 feet i li inches ; at H, 23 feet 1 1 inches ; 

 at K, 23 feet 10 inches ; at M, 23 feet 5^ inches; at O, 

 23 feet ; at Q, 22 feet 2 inches ; at S, 20 feet 4 inches ; at U, 

 17 feet 6 inches ; at X, 12 feet 6 inches ; and to end this 

 line at the fore part, let the height of the breadth-line in the 

 fheer-plan, where it interfefts the aft-fide of the rabbet at the 

 ftem, be fquared down to the middle line in the half-breadth 

 plan, and likewife the fore part of the lleni : upon the lines 

 laft fquared down, fet off the half-fiding of the ftem from 



the middle line and parallel thereto, which is ten inches ; 

 then, with compafles, take the thicknefs of the bottom plank, 

 which is four inches, and defcribe the rabbet of the Item by 

 the triangle fliewn in the half-breadth plan ; from thence a 

 fair curve line drawn through the half-breadths fet oil, forms 

 the half-breadth line to ®. In the fame manner fet off^ the 

 half-breadths abaft ({-, and draw in the remainder of the 

 half-breadth line, as the endii:g of it abaft will be dcfcribcd 

 hereafter. 



Obferve, the various curves rcprefented on the fevera! 

 plans ufed in ftiip-building, except where they are fegments 

 of circles, fuch as the fore part of the main half-breadth, &c. 

 are drawn by fmall pliable battens confined thereto by 

 weights, or by thin m.oulds made of pear tree veneers, whofe 

 edges are made to geometrical curves of all kinds. 



Now the main half-breadth line being drawn, we have a 

 half feftion of the (hip lengthwife at the broadeft place, 

 that is at the height, and in the direction of the lower height 

 of breadth line in the fheer-plan, P/nle I. 



The immerfed part, or body of the fliip under water, muft 

 be next formed, and the capacity of the veiiel afcertaincd, 

 before the upper works, or that above the water, need come 

 under confideration; it is therefore necellary to defcribe in 

 what manner the feveral forms of (hips' bodies are to be con- 

 ilrufted. In the royal navy, the raidfiiip parts of the body 

 of fliips are formed by fegments of circles called fweeps ; 

 fuch are the lower and upper breadth-fweeps, floor-fweep, 

 ajid reconciling-fweep, their feveral centres being given bv 

 lines, except the reconciling-fweep, whole centre is without 

 the limits of the draught. The lower-breadth and floor- 

 fweeps are joined by the reconciling-fweep, and make a fair 

 curve from the lower height of breadth to the rifing-line, 

 by which the floor-fweep is governed ; then, by drawing a 

 ftraight or curving line from the upper edge of the rabbet 

 of the keel to touch the back of the floor-(wecp, the form 

 of the midfhip part of the body b«low the lowir height of 

 breadth will be complete. 



Obferve, the floor-fweep forms the body at the floor- 

 heads, particularly along the midfliip part of the body, and 

 is limited by an horizontal line above tlie keel in the body- 

 plan, and its dillance above the keel at the niidfhip-timber 

 is called the dead-rifing. The rifiiig of the floor in the flie.^r- 

 plan is a curve line interfering the dead-rifing at the mid- 

 fhips ; and in flat-floored, or burthenfome (hips, it continues 

 nearly parallel witli the keel for fonie diftance afore and 

 abaft tlic midfliip-timber ; and all the timbers, where the 

 rifing is parallel with the keel, are called flats, as before 

 obferved. Tlte rifing-line, which governs the floor-fweeps, is 

 not the Icaft interefting of the feries, becaufe it exhibits, on 

 many points, general dednflions, and tends to eftablilh theo- 

 ries which may ferve to diredl future obfervations ; and the 

 method of conftrufting the midlhip-floors of fhips, where ve- 

 locity is preferred, by lengthening the radii of the floor- 

 fweep forv.ard and aft, is preferable to the rifing-line, as 

 ufed in conftrufting merchant- (hips for burden, where the 

 radii of the floor-fweep= all fore and aft are of the fame 

 length as at the midfhip-timber ; becaufe by the former me- 

 thod, every floor-timber from the dead-flat is graduated by a 

 larger circle. By the Litter method, not only the conftruc- 

 tion, but the laying-off the fhip is facilitated, becaufe in any" 

 fliip conftrufted by the fame length of radii, we may venture, 

 fo far as the rifing-line is continued, not only to form all the 

 lower part of the fliip on the draught, but alfo on the m-ould- 

 loft-floor, without running any ribband or horizontal lines 

 till that part is finiflied. Again, this method aflfords a 

 greater affiftance, as by it the floors may be conftrufted all 

 fore and aft ; but the floors near the midfhips only can be 



conftrufted. 



