Naval ARCHITECTURE (continued)

It is usual among shipwrights to delineate three several. draughts.

First, The whole length of the ship is represented according to a side view, perpendicular to the keel, and is termed the plane of elevation, or sheer-draught. Plate I.

Plate 1

Second, The ship is exhibited according to an end view, and stripped of her planks,. so as to present the outlines of the principal timbers; and this is properly termed the plane of projection, or the vertical plane of the timbers, plate I. because it shews the projection of their frames, relatively to each other.

Third, It is not sufficient to have the, vertical curves of the bottom in different places, for a distinct idea of the horizontal curves is also equally necessary and useful: this is obtained by means of water-lines, traced upon what is called the horizontal plane. In this draught, the curves of the transoms called the round-aft, is also marked, and sometimes the breadth and thickness of the timbers.

The plane of elevation, plate I. determines the length and depth of the keel; the difference of the draughts of water; the length and projection, or rake, of the stem and stern-post; the position of the mid-ship frame upon the keel, together with that of the principal frames afore and abaft; the load-water line; the wales, the dimensions and situations of the gun-ports, the projection of the rails of the head and stern-gallery, with the stations of the masts and channels.

This draught, however, conveys no idea of the vertical curve of the ribs or timbers; for as their projection will be only represented in a plane elevated upon the length of the keel, they will appear in this direction no otherwise than as straight lines. To perceive these curves accurately, they must be regarded in another point of view, which will represent their projection upon a vertical plan; supposed to cut the keel at right angles in the place where the ship is broadest. For as all ships are broader near the middle of their length than towards the extremities, it is evident that the timbers are more extended in proportion. The most capacious of these represents what is called the midship-frame; and upon the area of this frame is delineated the projection of all the others.

Thus the plane of projection limits the different breadths of a ship in various points of her length, and exhibits the outline of the timbers respectively to each other, as they are erected upon the keel. Accordingly, this draught ought to present a variety of sections of the ship in different places of her length, and always perpendicular to the surface of the water;

Reference Works