Thus we have endeavoured briefly to explain the nature and uses of the principal draughts used in the construction of a ship, which reciprocally correspond with each other in the dimensions of length, breadth, and depth. Thus the plane of elevation is exactly of the same length with the horizontal or floor-plane. The several breadths of the timbers in the floor-plane and that of the projection are mutually transferable; and the real height of the timbers in the projection, exactly conforms to their height in the elevation. Thus let it be required to transfer the height of the wing-transom from the elevation to the projection:
Extend the compasses from the point K, in the elevation, down to the dotted line prolonged from the upper-edge of the keel, and setting the other foot in the point p, then shall the line K p be the perpendicular height of the wing transom: transfer this from the middle of the line B A C, in the projection, to the point K in the perpendicular A F, then will A K be the height of the wing-transom in the plane of projection: and thus the height of all the transoms may be laid from the former upon the latter.
Again, let it be required to transfer the main-breadth of the midship-frame from the projection to the horizontal plane: Set one foot of the compasses in the point ⊕ on the perpendicular C E, and extend the other along the main-breadth-sweep ⊕ G, till it touches the perpendicular A F parallel to C E: lay this distance upon the horizontal plane from the point u in the line of the ship’s length, B A C, along the plane of the midship-frame to the point ⊕; so shall the line ⊕ W U be the breadth of the midship-frame on the horizontal plane.
Thus also the top-timber-breadth, or the distance of each top-timber from the middle of the ship’s breadth, may be in the same manner transferred, by extending the compasses from the line B A C, in the horizontal plane, to the top-timber breadth-line, upon any particular timber, as 1, 2, 3, &c. which will give its proper dimensions thereon.
In the same manner the breadths of all the timbers may be laid from the projection to the horizontal plane, and vice versa, from that to the projection. Thus the height of each timber may also be transferred from the elevation to the projection, &c.
The principal utility of these draughts therefore is to exhibit the various curves of the ship’s body, and of the pieces of which it is framed, in different points of view, which are either transverse or longitudinal, and will accordingly present them in very different directions. Thus the horizontal curves of the transoms and water-lines are represented on the floor-plane, all of which are nearly streight lines in the elevation and projection; and thus the vertical curves of the timbers are all exhibited on the projection, although they appear as streight lines in the elevation and floor plane.
Before this article is closed, it may be necessary to remark, that the various pieces represented in plate [I]. as well as the lines in the draughts which have not been already defined, are copiously explained in their proper places; as it would have been contrary to the plan of this work to have given a more enlarged description of them here.
That the reader, however, might be better enabled to comprehend the scope of this article, it was judged necessary to give a general sketch of naval architecture itself; to collect into one point of view the most material draughts by which a ship is constructed, and to describe, as concisely as possible, the several parts of which they are composed.
The principal parts of a ship also, which are here reduced into a narrow compass, will be represented at large in different places of this work, to illustrate those explanations whither it may be necessary to refer, in order to understand the subject more clearly. Thus the stern, the quarter, the midship-frame, the bow and head, of a ship of 74 guns, are exhibited on a scale of ¼ of an inch to a foot; by which all the subordinate parts may be distinctly viewed, and their combination and arrangement sufficiently understood.