Guns. Ft. In. Tons. Ft. Us Ill) 22 9 1200 . . . 17 0 98 . . . 21 0 1000 . . . 14 9 74 . . . 19 6 800 , . . 14 9 Thus, having gained a few of the first leading principles, we will proceed to show their utility in constructing what is galled the sheer-draught : and the neces sity of dividing the sheer-draught into three distinct plans will be evident by in spection.
First. The sheer-plan, called, in ge neral architecture, the plan of elevation. This is a section of the ship made by a vertical or perpendicular plane, passing through the middle line of the keel, stem, and stern-post, throughout the whole length of the ship.
Secondly. The half-breadth plan, call ed by architects the ground-plan. This plan consists of an horizontal view of the half-breadths of the water-lines, ribbands, main and top-breadths, half-breadth of the rising, ditto by longitudinal curves, by which the several breadths are limit ed, and, as they would appear to the eye, placed directly over, and looking down on the aforesaid sections, whether cut ting the solid (supposing a ship a solid body) either by horizontal, diagonal, or sheer planes.
Thirdly. The bodulan, or plan of pro jection, are the transverse sections of the ship, at the joint of every frame-timber, showing the half breadth of each frame timber, as it stands perpendicularly to the two former plans : hence, the frames con tained between e, or the midship, that being the broadest frame, and the stem, are represented on the right-hand aide, and the frames at aft 9 on the left hand of the middle line in the body-plan are re spectively called the fore and after body.
It may be necessary to add, that in all these plans only one half of the ship is re presented, as each side must be supposed to be exactly alike, and that they must be very accurately drawn to the dimensions given, which have all been examined by proper calculations, submitted to the most precise scrutiny, and the results have ac tually stood the best test, that is, experi ment; the said ship having been really built, and found to answer every expecta tion. Now, in the clearest manner pos sible, we will endeavour to point out the utility of these plans, in the construction of the various curves that form the body of a ship in their different points of view, whether transverse or longitudinally, as on the several plans they will present themselves in very different directions ; for, although the horizontal water-lines are represented by curves in the half breadth plan, they are straight lines in sheer and body plan, and so likewise the appearance of the timbers ; for, although they present themselves as vertical curves in the body plan, they appear as straight lines in the sheer and half-breadth plan ; these premises being well understood.
we may proceed to the construction of these several plans and first, in the Sheer plan, draw the stem keel, stern post, &c. thus : draw a straight line that shall represent the upper edge of the rab bit of the keel, more than the main half breadth of the vessel above the lower edge of the paper; then to your right hand square up the foremost perpendicu lar, allowing room to represent the head. Now, as the limits of our design will not admit of our continuing the dimensions of all the before mentioned ships ; and as only one can be selected to form the sheer draught, the 74 gun ship is made choice of, as being, of all vessels, the most hand some, and arrived to the greatest perfec tion in the construction ; therefore set aft 180 feet from the foremost perpendicular, and square up another, calling it the after perpendicular, which gives the length of the gun-deck,or first principal dimension. Then square up another perpendicular, 69.0 feet abaft the foremost one, which is the midship perpendicular marked thus e, and called dead flat. Much has been said concerning the situation of this trans verse section, it being the broadest part of the ship, and containing the greatest area of surface ; its judicious disposal will certainly facilitate the velocity of the ves sel. All have agreed, and experience has confirmed it,th at its position should always be before the middle of the vessel's length, or its centre of gravity. '1' lie French say, about the length of the vessel from aft, and nearly there may be its best position, as vessels, in genets'', have been found much better constructed since the mid ship has been fixed nearer the stern.