137 
SHIP-BUILDING. 
of the half-breadth line, as the ending of it abaft will be 
described hereafter. 
Observe, the various Curves represented on the several 
plans used in ship-building, except where they are segments 
of circles, such as the fore part of the main half-breadth, &c., 
are drawn by small pliable battens confined thereto by 
weights, or by thin moulds made of pear-tree veneers, whose 
edges are made to geometrical curves of all kinds. 
Now the main half-breadth line being drawn, we have a 
half section of the ship lengthwise at the broadest place, 
that is at the height, and in the direction of the lower height 
of breadth line in the sheer-plan. 
Proceed now to draw the plan of projection, or body- 
plan, thus: draw an horizontal line equal to the proposed 
breadth of the ship—this is the base line. Draw thereto at 
each end a perpendicular at right angles—these are the side 
lines. Between these square up another perpendicular, 
which is the middle line to both bodies respectively; then 
the line prolonged from the upper edge of the keel is the 
base line of the body-plan. Draw in the horizontal lines, 
as may be seen in the body-plau, at the lower heights of 
breadth, by transferring their heights from the sheer-plan at 
the several frame-timbers: those before the dead-flat, set up 
in the body-plan to the right of the middle line, which are 
to represent the fore-body, and those heights abaft dead-flat, 
to the left hand for the after body. Then from the half¬ 
breadth plan take the main half breadth of each frame, and 
set it off from the middle line in the body-plan, upon its 
corresponding height of breadth-line; and from thence set 
off towards the middle line the length of their respective 
lower-breadth sweeps : thus, to describe the midship-timber, 
or dead-flat, extend the compasses to 18 feet 6 inches, the 
radii of lower-breadth sweeps at dead-flat, and draw part of 
a circle downwards, intersecting its main breadth at its hori¬ 
zontal height. 
Then the centre heights of the floor-sweeps in the body- 
plan must be taken from the curve-line representing their 
heights in the sheer-plan, which at dead-flat will be found 
to intersect the upper edge of the keel; but in the body- 
plan, its height at dead-flat is 11 feet 6 inches, and there an 
horizontal line is drawn to the distance of the centre, or its 
half-breadth from the middle line, and all the heights of 
centres are respectively set upwards above this line, on per¬ 
pendiculars squared upwards at the half-breadth of the centre 
of each floor-sweep of its corresponding frame or timber, as 
taken from the half-breadth plan; and the reason for not 
keeping the said curve-line or heights in the sheer-plan as in 
the body-plan, is because it would interfere with the curve¬ 
lines above. Now, by inspecting the Plate, it will be readily 
seen, that by raising the heights of those centres in the sheer- 
plan, consequently in the body-plan, and by narrowing their 
half-breadths in the half-breadth plan, their centres would be 
brought nearer the. middle line in the body-plan, the floor¬ 
rising would become quicker, and the ship have less bearing, 
and vice versa, more full and burthensome: thus must the 
rising and narrowing of the centres be adjusted till the body 
of the vessel has the capacity required for whatever service 
she may be designed. 
But as in this mode of construction the centres only, and 
not the length of the floor-sweeps, are given, a diagonal rib¬ 
band must be drawn in the half-breadth plan, as in Plate I. 
by setting off from the middle line at 0, 16 feet •, at B, 15 
leet 9 inches; at D, 15 feet 5 inches ; at F, 15 feet 1 inch ; 
at H, 14 feet 7 inches; at K, 14 feet; at M, 13 feet| an inch; 
at O, 11 feet 11 inches; atQ, 10 feet 4 inches ; at .S, 8 feet 6 
inches; at U, 6 feet 1 inch ; and at X, 2 feet 5 inches. Then in 
the after-body set off at 2, fig. 1, PlateII.,15 feetllf inches; 
at4, 15 feet 10£ inches; at 6, 15 feet 9 inches; at 8, 15 feet 6 
inches ; at 10, 15 feet 4 inches; at 12, 15 feet 1 inch ; at 14, 
14 feet 11 inches; at 16, 14feet5 inches ; at 18, 14 feet; at 
20, 13 feet 3§ inches; at 22, 12 feet 5 inches; at 24,11 feet 
7 inches; at 26, 10 feet 5 inches; at 28, 9feet 1 inch ; at 30, 
6 feet 7 inches; at 32, 5 feet 10 inches; at34, 4 feet; and 
at 36, 2 feet. 
Vol. XXIII. No. 1560. 
Now to end this diagonal, it must be drawn in the body- 
plan thus; set up the middle line from the base 12 feet 2 
inches, and on the base, from each side of the middle line, 
11 feet 9 inches, then draw the diagonal ticked line, as 
shewn in Plate I. In draughts, diagonal lines are distinguished 
by red ink. Then in the body-plan draw the half-siding of 
the stem in the fore-body, and the half-siding of the stern- 
post in the after-body : for the latter set up 26 feet above the 
base, and at that height set off from the middle line 10 inches 
in the half-siding of the post at the head, and 9 inches in the 
forebody, the half siding of the stem at that height; and on 
the base line 7| inches from each side of the middle line, the 
half-siding of post and stem at the heel; then draw straight 
lines to each spot set off, and the half-siding of the stern-post 
and stem will be represented in the body plan. Now to 
complete or end the diagonal line on the half-breadth plan, 
its height or intersection at the post and stem must be taken 
in the body-plan, and transferred respectively to the foreside 
of the rabbet of the stem, and aft-side of the rabbet of the 
post in the sheer-plan, and from thence let them be squared 
down to the middle line of the half-breadth plan; then take 
with compasses the half thickness of the post and stem in the 
body-plan, in the direction of the said diagonal line, and set 
them off respectively from the middle line in the half-breadth 
plan on the lines last squared down; and from the inter¬ 
section as a centre, sweep an arc towards the midships, with 
compasses opened to the thickness of the rabbet taken diago¬ 
nally ; then a fair curve drawn through all the spots as 
above set off, touching the back of the arcs, will form the 
diagonal line at the floor-heads as shewn in the half-breadth 
plan. 
Now may the timbers, as far as the floor sweeps are useful, 
be completed in the body-plan below the lower height of 
breadth, beginning a dead flat; thus, take the half-breadth 
of the floor diagonal at 0 in the half-breadth plan, and set 
it down the diagonal from the middle line in the body-plan ; 
then take the half-breadth of the floor-sweeps in like manner, 
and set it off from the middle line in the body-plan on the 
horizontal line before drawn at its height, and from the inter¬ 
section extend the compasses to the half-breadth of the floor 
diagonal, and sweep an arc upwards from the dead-rising, 
which is six inches at 0 ; then with the reconciling-sweep, 
which is of a long radius compared with the others, unite the 
lower-breadth sweep and floor-sweep together; for the more, 
the midship-frames deviate from the segment of a circle, the 
less will be the rolling motion of the ship; unite the floor- 
sweep with the upper edge of the rabbet of the keel with a 
curve or straight line, and the midship-timber will be formed 
below the lower breadth. In the same manner may be 
formed the frame-timbers B, D, F, H, and K, in the fore-body 
and 2, 4, 6 , 8 , 10, to 24 in the after-body by setting oft'the 
half-breadth of each frame’s diagonal as at 0 , their corres¬ 
ponding heights of breadths, main half-breadths, and centres 
of each sweep, as before directed, and by reconciling the 
lower-breadth sweeps and floor-sweeps together, and ending 
them into the rabbet at the keel; thus the midship part of 
the body will be formed from K forward to 24 abaft. 
Hence it may be readily conceived, that bodies full or 
sharp, either for burthen or velocity, may be constructed by 
altering the radii of the different sweeps; and unless bodies 
of ships could be constructed from some geometrical figure, 
a more certain method than the above cannot be given. 
The body being thus far formed, that is from K forward 
to 24 abaft, proceed to prove it by horizontal lines, and 
finish the remaining part forward and aft. These lines are 
generally called water-lines, as the ship’s bottom at the sur¬ 
face of the water, supposing the keel kept parallel thereto, 
would be of the same figure as those lines represented in the 
half-breadth plan, with the addition of the thickness of the 
bottom plank in that direction. The upper one is called the 
load-water line, or line of floatation, when the vessel is sup¬ 
posed fit for sea; the other water-lines may be equally divided 
between the upper or load-water line, and upper edge of the 
keel or rabbet. Although a ship may draw more water abaft 
2 N than 
