tit 



SHIPBUILDING. 



SHIPBUILDING. 



Mo 



hip* U demanded of the naval architect which shall fulfil all the 

 neceantira of fighting ahips; but thoae of the latter class will |K> 

 more conveniently treated of under STKAM-VESSEL. 



Wh % n a hip ia to be constructed, the first consideration i the 

 required amount of tonnage. Thi being once determined, a knowledge 

 of the purpose fur which the ship U intended regulates the lmil.1. r in 

 hii fixing the amount of midship area, from which all the other ilim. u 

 -. u- :. -.,!'!. In I.niiiiiiL.- :!i' INftd t'.' i.i..i-li:p -ivli.iii. tin' I I 



qualitiea of the ship chirlly depend on the selection of the breadth (or 

 beam u it u called) for on thia rent* the important question of 

 stability or stiffness under sail. It is customary to consider the 

 primary form of the ship as a quadrangular prism of contents equal to 

 the required tonnage : of course its midship section will be a rectan- 

 gular parallelogram. Suppose, for example, it were required to build 

 a ship of certain tonnage [TONNAUE], whose midship sectional area U 

 to be 805 square feet, and the beam 85 feet, then ff = 23 feet the 

 depth. The primary body plan and whole breadth plan would be as 

 under : 



Fig. 1. 



r i. u n would be the midship area, c D the beam, c o the depth. 

 Now although this represents the amount of displacement for tonnage, 

 it requires the skill and taste of the naval architect to adapt the out- 

 line of such capacity to the requirements of the ship, having proper 

 regard to speed, carrying qualifications, rolling, stability, &c. &c. This 

 is to be done by an interchange of areas in the following manner : 

 Suppose a moderate amount of speed is to be blended with average 

 carrying qualities, the dotted curve would be so drawn as to let the 

 area I compensate for the abstracted area B ; or if speed in particular 

 be desirable, then the area r would compensate the area A. It will 

 thus be manifest that a wide range of form is open to the shipbuilder, 

 while his chief aim is not to disturb the amount of area of the mid- 



ship section. And again taking the form of the ship at the load-water 

 line the primary parallelogram would be A B c D, a horizontal section 

 of the primary quadrangular prism as under, 



Now in order to shape the ends BO as to give sailing qualities, it, as 

 in the former case, again taxes the skill of the builder to interchange 

 areas, so as not to disturb the gross displacement : in the above 

 figure we have supposed the area marked a to be taken from the 

 parallelogram and transferred to a' ; that marked c to be tran- ; 

 to c" : b to 4' and d to <f. Hence the outline in plan and section is 

 determined, and drawings representing the necessary intermediate 

 elevations and sections, generally on a scale of a quarter of an inch 

 to a foot, are prepared, and copies of these, enlarged to the full size of 

 the objects which they represent in the intended ship, are traced with 

 chalk on the floor of an apartment called the "mould-loft." The 

 length of the loft is generally equal to half that of the greatest ship 

 which it may be proposed to build, and of the whole height of the hull 

 in addition ; so that there may be traced upon it a horizontal plan of 

 half the ship in the direction of its length, and beyond one extremity 

 of the plan a representation, in the same plane, of a transverse section 

 of the ship in a vertical plane at the place of its greatest breadth. 

 Such plan and section being laid down, there are drawn with chalk, 

 from their proper places in the plan, representations of the timber ribs 

 or frames as they would appear in as many transverse sections of the 

 ship : pieces of plank about three-quarters of an inch thick are then 

 cut so as to correspond to the forms of the timbers ; and these, which 

 are called the moulds, become the patterns by which the timbers are 

 to be cut from the tree or log of wood. But, as such a mould can only 

 give the form of the timber in the direction of its length, and as the 

 oblique positions in which the timbers stand in the ship may cause the 

 angle which the faces of each timber make with one another to be 



acute or obtuse, and to vary in the same piece, certain marks on the 

 surfaces of the boards are used to indicate the directions in which the 

 sides of the timbers are to be cut. The operation of cutting the 

 timbers agreeably to the forms of the mould-boards is called " con- 

 verting." 



A row of blocks of oak are placed on the building-slip (ground cut 

 in an inclined plane descending towards the water) in the direction of 

 the length of the intended ship, so that their upper surfaces may be 

 in a plane making an angle of about three degrees with the horizon ; 

 and on these blocks U laid the keel A B, fig. 3. This, which is the 

 lowest timber of the ship, extends from one end to the other, and upon 

 it is raised the whole fabric ; it is of elm, and for a large ship it con- 

 sists of two or more pieces scarfed together at their extremities. 

 Timbers, called the " dead-wood," are then placed at c and D longi- 

 tudinally upon the keel from each extremity of the latter towards its 

 middle ; the upper surface of this mass is cut in a curvilinear form 6, 6, 

 and with this line the bottom of the ship's body is to coincide. At A 

 and B, the extremities of the keel, the stern-post and stem-post are set 

 up : the Utter is curved near the bottom ; and if the stern is to be 

 what is called square, a particular frame, consisting of two transoms or 

 horizontal timbers, and two side-pieces, is fixed above the stern-post, 

 in order to determine the form which is to be given to this part of the 

 ship. The sides and upper surface of the keel and dead-wood are cut 

 to receive the floor timbers (the lower portions, d e, fig. 4, of those 

 timbers which are to form the ribs of the hull) : these are placed across 

 the keel perpendicularly to its length, and the other portions (called 

 futtocks), tf,fg, ftc., of which each rib is formed, are placed succes- 

 sively above them, abutting end to end, or the head of a lower one 

 against the heel of that which is immediately above it. The ends of 

 the futtock-pieces in every rib are made to fall near the middle of the 

 length of those in the rib on each side of it ; and they are united 

 together by cylindrical coaks, or plugs of wood, which enter about two 

 inches into those ends at the places of junction ; c, e, r, *c.. ti</. ", 



represent sections of the ribs made by a plane passing longitudinally 

 through the middle of the keel, and the interior surfaces of parts of 



Tig. 4 



the ribs appear at d, d, &c. The ribs were formerly placed so that 

 their planes were perpendicular to the keel, but Dr. Inman lias dis- 

 posed them so as to be in vertical positions when the ship floats 

 upright Except near the two extremities of the ship, their planes are 

 perpendicular to a horizontal line drawn in the plane of floatation 

 through the whole length ; but at the bows always, and at the stern if 

 the latter is to be curvilinear, the vertical planes with which the ribs 

 on each side coincide are oblique to the length of the ship, in order 



