resting upon the stocks, in the same position as when afloat upon the
water. Thus a variety of black vertical lines may be drawn at equal
distances upon the bottom, which is white, to form different outlines of
the ship corresponding to the timbers within. It is to be observed, that
the fashion of the inferior timbers must conform to the figure of the
midship-frame, which is placed in the fullest part of the ship; and as
the planes of all the other timbers diminish in a certain progression as
they approach the stem and stern, they are properly delineated on the
plane of the midship-frame, which also represents the depth of the keel
and length of the midship-beam.
As the two sides of a ship ought to be exactly alike, it is judged
sufficient to represent the sections of the fore-part of the ship on the
left side, and those in the after-part on the right side, so as to
perceive all the sections, as well afore as abaft, upon one plane. See
plate I. PROJECTION.
However necessary it may be to understand precisely the vertical curves
of the bottom, it is no less requisite to have a just idea of those
which are horizontal.
The horizontal, or floor plane, is that upon which the whole frame is
erected, and will be more clearly understood by previously describing
the water-lines and ribbands, of which it is composed.
When a ship floats upon the stream, it is evident that her upper-works
will be separated from the bottom by the surface of the water, which
will accordingly describe an imaginary horizontal line upon the bottom
from the stem to the stern-post.
The most elevated of those lines is termed the load-water-line, which is
supposed to be drawn by the surface of the water on the upper part of
the bottom, when she is sufficiently laden for a sea-voyage. For if we
suppose this surface a rule, and thereby describe a corresponding black
line along the vessel’s bottom, that line will be distinguished upon the
bottom, which is white, and represent what is called the
load-water-line.
If the ship is lightened of any part of her lading, and preserves the
same difference in her draught of water at the two ends, or, what is the
same thing, if she is lightened so as to preserve the same equilibrium
of the keel with regard to the surface of the water, it is evident that
she will rise higher out of the water, so that the black line already
described will be elevated above it, and another black line may be
delineated upon the bottom, close to the surface of the water, which
will exhibit a second water-line parallel to the first, but nearer the
keel in proportion to the number of feet which the ship has risen.
Thus by lightening a ship gradually, and at the same time preserving the
direction of her keel, or the angle which the keel makes with the
surface of the water, a variety of water-lines may be drawn parallel to
each other, and to the load-water-line. See a farther illustration of
these lines in the article WATER-LINE. See also their figure on a ship’s
bottom, plate I. fig. 5.
The ribbands are likewise of great utility in ship-building; they are
narrow and flexible planks placed on the bottom at different heights, so
as to form a sort of mould for stationing the inferior timbers between
the principal ones. They differ from the water-lines, inasmuch as the
latter have only one curve, which is horizontal, whereas the ribbands,
besides their horizontal one, have a vertical curve. To convey a just
idea of these curves, which cannot be represented on one draught at
their full length, without an oblique section of the ship’s length, it
will be necessary to have recourse to two planes; that of the elevation,
which exhibits their vertical curve; and to the floor-plane, upon which
the horizontal curve is expressed. See RIBBANDS.
These different lines are extremely useful in exhibiting the various
curves of a ship’s bottom, that as they are gradually diminished, their
uniformity or irregularity may be discovered by the skilful artist.
We have already observed, that the qualities required in a ship ought to
determine the figure of the bottom: a ship of war therefore should be
able to sail swiftly, and carry her lower tier of guns sufficiently out
of the water. A merchant-ship ought to contain a large cargo of
merchant-goods, and be navigated with few hands; and both should be able
to carry sail firmly; steer well; drive little to leeward; and sustain
the shocks of the sea without being violently strained.
The first thing to be established in the draught of a ship is her
length; and as a ship of war, according to her rate, is furnished with a
certain number of cannon, which are placed in battery on her decks, it
is necessary that a sufficient distance should be left between their
ports to work the guns with facility, and particularly to leave space
enough between the foremost gun and the stem, and between the aftmost
gun and the stern-post on each side, on account of the arching, or
inward curve of the ship towards her extremities.
When the length of a ship is determined, it is usual to fix her breadth
by the dimensions of the midship-beam. On this occasion the shipwrights,
for the most part, are conducted by rules founded on their own
observation; for having remarked, that some vessels which by repeated
experience have been found to answer all the purposes of navigation,
have a certain breadth in proportion to their length, they have inferred
that it would be improper to depart from this proportion: but as other
ships have been constructed with different breadths, which were equally
perfect, a variety of different general rules have been adopted by these
artists, who are accordingly divided in their opinions about the breadth
which ought to be assigned to a ship relatively with her length, whilst
each one produces reasons and experience in support of his own standard.
Those who would diminish the breadth alledge, that a narrow vessel meets
with less resistance in passing through the water; 2dly. That by
increasing the length she will drive less to leeward; 3dly. That
according to this principle, the water-lines will be more conveniently
formed to divide the fluid; 4thly. That a long and narrow ship will
require less sail to advance swiftly; that her masts will be lower, and
her rigging lighter; and, by consequence, the seamen less fatigued with
managing the sails, &c.
Those, on the contrary, who would enlarge the breadth, pretend, 1st.
That this form is better fitted to preserve a good battery of guns.
2dly. That there will be more room to work the guns conveniently. 3dly.
That by carrying more sail the ship will be enabled to run faster; or,
that this quality will at least overbalance the advantage which the
others have of more easily dividing the fluid. 4thly. That, being
broader at the load-water-line, or place where the surface of the water
describes a line round the bottom, they will admit of being very narrow
on the floor, particularly towards the extremities: and 5thly. That a
broad vessel will more readily rise upon the waves than a narrow one.
From such opposite principles has resulted that variety of standards
adopted by different shipwrights; and a servile imitation of these
mechanical methods has, to the great reproach of the art, produced all
these pretended rules of proportion: for the various models they have
hitherto adopted indisputably prove their doubt and uncertainty with
regard to their proper standard. Hence these pretended mysteries which
are only to be revealed to such as are initiated into the craft! Hence
this division of the art into classes, or, according to the technical
term, into _families_, each of which affects, with becoming solemnity,
to be possessed of the true secret, in preference to all the others! And
hence violence of opposition, and mutual contempt amongst the artists!
Indeed nothing appears more effectually to have retarded the progress of
naval architecture, than the involving it in mysteries which the
professors would gravely insinuate are only intelligible to themselves.
This ridiculous affectation is nevertheless tenaciously retained,
notwithstanding the example to the contrary of some of the most able
shipwrights in Europe, who are real masters of the theory of their art,
and do honour to their profession, and who are justly exempted from the
censure to which the others are often exposed.
It is not to be expected that an art so complicated and various,
comprehending such a diversity of structures, can be treated at large in
a work of this sort. To enter into a particular detail of the theory and
practice; to explain the different parts with sufficient accuracy and
perspicuity, would of itself require a large volume, and, by
consequence, greatly exceed the limits of our design. Being thus
necessitated to contract our description into a narrow compass, it will
be sufficient to give a general idea of the subject; to describe the
principal pieces of which a ship is composed, and to explain the
principal draughts used in the construction thereof.
As the several lines exhibited in the planes of elevation, projection,
&c. will be rendered more intelligible by a previous account of those
pieces, it may not be improper to begin with reciting their names, and
giving a summary description of their uses and stations. They are for
the most part represented according to the order of their disposition in
that part of plate I. which is termed PIECES _of the_ HULL.
A. The pieces which compose the keel, to be securely bolted together,
and clinched.
B. The stern-post, which is tenanted into the keel, and connected to it
by a knee, G. It supports the rudder, and unites the sides of the ship
abaft.
C. The stem, which is composed of two pieces scarfed together: it is an
arching piece of timber, into which the ship’s sides are united
forwards.
D. The beams, which are used to support the decks, and confine the sides
to their proper distance.
E. The false post, which serves to augment the breadth of the
stern-post, being also tenanted into the keel.
F. The knees, which connect the beams to the sides.
G. The knee of the stern-post, which unites it to the keel.
H. The apron, in two pieces: it is fayed on the inside of the stem, to
support the scarf thereof; for which reason, the scarf of the former
must be at some distance from that of the latter.
I. The stemson, in two pieces, to reinforce the scarf of the apron.
K. The wing transom: it is fayed across the stern-post, and bolted to
the head of it, having its two ends let into the fashion-pieces.
L. The deck transom, parallel to the wing-transom, and secured in the
same manner.
M. N. The lower transoms.
O. The fashion-piece on one side; the heel of it is connected with the
stern-post, and the head is secured to the wing-transom.
P. The top-timbers, or upper parts of the fashion-pieces.
Q. The sleepers, which fasten the transoms to the ship’s side.
R. The breast-hooks, in the hold; they are fayed across the stem, to
strengthen the fore part of the ship.
S. The breast-hooks of the deck: they are placed immediately above the
former, and used for the same purposes.
T. The rudder, which is joined to the stern-post by hinges, and serves
to direct the ship’s course.
U. The floor-timbers; they are laid across the keel, to which they are
firmly bolted.
V. The lower futtocks, and
W. The top-timbers, which are all united to the floor-timbers, forming a
frame that reaches from the keel to the top of the side.
X. The pieces which compose the kelson: they are scarfed together like
the keel pieces, and placed over the middle of the floor-timbers, upon
each of which they are scored about an inch and a half, as exhibited by
the notches.
Y. The several pieces of the knee of the head; the lower part of which
is fayed to the stem; the heel being scarfed to the fore-foot.
Z. The cheeks of the head or knees, which connect the head to the bows
on each side.
&. The standard of the head, which fastens it to the stem.
a. The catheads, one of which lies on each bow, projecting outwards like
the arm of a crane. They are used to draw the anchors up to the top of
the side without injuring the bow.
b. The bits, to which the cable is fastened when the ship rides at
anchor.
c. The false post, in two pieces, fayed to the fore part of the
stern-post.
d. The side-counter-timbers, which terminate the ship abaft within the
quarter gallery.
e e. Two pieces of dead wood, one afore, and another abaft, fayed on the
keel.
In vessels of war, the general dimensions are established by authority
of officers appointed by the government to superintend the building of
ships. In the merchants service, the extreme breadth, length of the
keel, depth in the hold, height between-decks and in the waste, are
agreed on by contract; and from these dimensions the shipwright is to
form a draught suitable to the trade for which the ship is designed.
In projecting the draught of a vessel of war, the first article to be
considered is her length. As all ships are much longer above than below,
it is also necessary to distinguish the precise part of her height from
which her length is taken: this is usually the lower gun-deck, or the
load water-line. It has been already observed, that water-lines are
described longitudinally on a ship’s bottom by the surface of the water
in which she floats, and that the line which determines her depth under
the water is usually termed the load-water-line. In this draught it will
be particularly necessary to leave sufficient distance between the
ports.
The next object is to establish the breadth by the midship-beam.
Although there is great difference of opinion about proportioning the
breadth to the length, yet it is most usual to conform to the dimensions
of ships of the same rate. After the dimensions of the breadth and
length are determined, the depth of the hold must be fixed, which is
generally half the breadth: but the form of the body should be
considered on this occasion; for a flat floor will require less depth in
the hold than a sharp one. The distance between the decks must also be
settled.
We may then proceed to fix the length of the keel, by which we shall be
enabled to judge of the rake of the stem and stern-post. The rake is
known to be the projection of the ship at the height of the stem and
stern-post, beyond the ends of the keel afore and abaft; or the angle by
which the length is increased as the fabric rises. To these we may also
add the height of the stem and wing transom.
After these dimensions are settled, the timbers may be considered which
form the sides of the ship. A frame of timbers, which appears to be one
continued piece, is composed of one floor-timber, U, whose arms branch
outward to both sides of the ship; (See plate I. PIECES _of the_ HULL)
two or three futtocks V V, and a top-timber, W. The futtocks are
connected to the upper arms of the floor-timbers on each side of the
ship, and serve to prolong the timber in a vertical direction: and the
top-timbers are placed at the upper part of the futtocks for the same
purpose. All these being united, and secured by cross-bars, form a
circular enclosure, which is called a frame of timbers, _couple d’un
vaisseau_. And as a ship is much broader at the middle than at the
extremities, the arms of the floor-timber will form a very obtuse angle
at the extreme breadth; but this angle decreases in proportion to the
distance of the timbers from the midship-frame, so that the foremost and
aftmost ones will form a very acute angle. Floor-timbers of the latter
sort are usually called crutches.
Shipwrights differ extremely in determining the station of the
midship-frame; some placing it at the middle of the ship’s length, and
others further forward. They who place it before the middle, alledge,
that if a ship is full forward, she will meet with no resistance after
she has opened a column of water; and that the water so displaced will
easily unite abaft, and by that means force the ship forward; besides
having more power on the rudder, in proportion to its distance from the
center of gravity: this also comes nearer the form of fishes, which
should seem the most advantageous for dividing the fluid.
When the rising of the midship-floor-timber is decided, we may then
proceed to describe the rising-line of the floor, on the stern-post
abaft, and on the stem afore.
The height of the lower-deck is the next thing to be considered: it is
determined in the middle by the depth of the hold; and some builders
make it no higher than the stem; but they raise it abaft as much above
its height in the middle, as the load-water-mark, or draught of water
abaft, exceeds that afore. With regard to the height between decks, it
is altogether arbitrary, and must be determined by the rate of the ship,
and the service she is designed for.
It is also necessary to remember the sheer of the wales, and to give
them a proper _hanging_; because the beauty and stateliness of a ship
greatly depend upon their figure and curve, which, if properly drawn,
will, make her appear airy and graceful on the water.
We come now to consider the upper-works, and all that is above water,
called the dead-work: and here the ship must be narrower, so that all
the weight lying above the load-water-line will thereby be brought
nearer the middle of the breadth, and of course the ship will be less
strained by the working of her guns, &c. But although some advantages
are acquired by diminishing the breadth above water, we must be careful
not to narrow her too much; as there must be sufficient room left on the
upper-deck for the guns to recoil. The security of the masts should
likewise be remembered, which requires sufficient breadth to spread the
shrouds. A deficiency of this sort may indeed be in some measure
supplied by enlarging the breadth of the channels.
With regard to the qualities required in the construction of a ship, to
fit her for the various purposes of navigation, the reader is referred
to the article BOTTOM.
We shall now proceed to explain the sheer draught, or plane of
_elevation_, of a sixty gun ship; wherein we have been attentive to make
the same letters refer to the same objects, as in the explanation of the
PIECES, as above; at least when the same objects are in both figures; a
conduct we shall invariably pursue throughout this work, although it
seems to have been forgot by our predecessors. Thus in all the plates of
ship-building, the keel, whether separate or joined, is represented by
A, the stern-post by B, the stem by C, the beams by D; unless where
those objects do not _all_ appear, and then something else is placed
instead thereof. Thus in plate III. of the deck, where the keel cannot
be seen, the main hatchway is represented by A, as not being inserted in
any figure wherein the keel appears.
A A. The keel, whose upper edge is prolonged by the dotted line p q,
upon the extremities of which are erected perpendiculars which determine
the height of the wing transom, K, and length of the gun-deck, K C.
A B. The stern-post.
A C. The stem.
D D. The quarter-gallery, with its windows.
E F. The quarter-pieces, which limit the stern on each side.
F. The taffarel, or upper piece of the stern.
F G. Profile of the stern, with its galleries.
H. The gun ports.
I. The channels, with their dead-eyes and chain-plates.
K. The wing-transom.
K G. The counter.
L B. The deck-transom.
M N O. The first, second, and third transoms, of which O K is the third
or lowest.
_m_ O L P. The direction of the fashion-piece, having its breadth canted
aft towards the stern.
Q R. The main skeeds, for hoisting in the boats clear of the ship’s
side. L Q Z. The main wale, with its sheer afore and abaft.
D R X. The channel wales, parallel to the main wale.
S U S. The sheer rail, parallel to the wales.
T _t_. The rudder.
A t F. The rake of the stern.
V W V. The waist-rail.
P _i i_. The drift-rails abaft; and _i_ a, the drift-rails forward.
T U C. The water-line.
X X. The rails of the head.
Y. The knee of the head, or cutwater.
Z Z. The cheeks of the head.
a a. The cat-head.
M ⊕ C. The rising line of the floor.
_k_ _u_ C. The cutting-down line, which limits the thickness of all the
floor-timbers, and likewise the height of the dead-wood afore and abaft.
⊕ _u_ U W. The midship-frame.
_a_, _b_, _c_, _d_, _e_, _f_, _g_, _h_. The frames or timbers in the
fore-body of the ship, i. e. before the midship frame.
1, 2, 3, 4, 5, 6, 7, 8, 9. The timbers in the after-body, or which are
erected abaft the midship-frame.
As the eye of a spectator is supposed in this projection to view the
ship’s side in a line perpendicular to the plane of elevation, it is
evident that the convexity will vanish, like that of a cylinder or
globe, when viewed at a considerable distance; and that the frames will
consequently be represented by strait lines, except the fashion-piece
abaft and the knuckle-timber forward.
It has been already observed, that the plane of projection may be
defined a vertical delineation of the curves of the timbers upon the
plane of the midship-frame, which is perpendicular to that of the
elevation. It is necessary to observe here, that the various methods by
which these curves are described, are equally mechanical and arbitrary.
In the latter sense, they are calculated to make a ship fuller or
narrower according to the service for which she is designed, and in the
former they are drawn according to those rules which the artist has been
implicitly taught, to follow, or which his fancy or judgment has
esteemed the most accurate and convenient. They are generally composed
of several arches of a circle, reconciled together by moulds framed for
that purpose. The radii of those arches therefore are of different
lengths, according to the breadth of the ship in the place where such
arches are swept; and they are expressed on the plane of projection
either by horizontal or perpendicular lines; the radii of the breadth
sweeps being always in the former, and the radii of the floor sweeps in
the latter direction. These two arches are joined by a third, which
coincides with both, without intersecting either. The curve of the
top-timber is either formed by a mould which corresponds to the arch of
the breadth-sweep, or by another sweep, whose center and radius are
without the plane of projection. The breadth of the ship at every
top-timber is limited by an horizontal line drawn on the floor-plane,
called the half-breadth of the top-timbers. The extreme breadth is also
determined by another horizontal line on the floor-plane; and the lines
of half-breadth are thus mutually transferable, from the projection and
floor-planes, to each other.
The necessary data by which the curves of the timbers are delineated
then are, the perpendicular height from the keel, the main or principal
breadth, and the top-timber breadth: for as a ship is much broader near
the middle of her length than towards the ends, so she is broader in the
middle of her height than above and below; and this latter difference of
breadth is continued throughout every point of her length. The main
breadth of each frame of timbers is therefore the ship’s breadth nearly
in the middle of her height in that part: and the top-timber breadth is
the line of her breadth near the upper ends of each timber. It has been
already observed, that as both sides of a ship are alike, the artificers
only draw one side, from which both sides of the ship are built:
therefore the timbers abaft the midship frame are exhibited on one side
of the plane of projection, and the timbers before it on the other.
Plane of PROJECTION, Plate I.
A. The keel.
B C. The line which expresses the upper-edge of the keel, from which the
height of each timber, and height of its different breadths are
measured.
B D and C E, perpendiculars raised on the line B C, to limit the ship’s
extreme breadth and height amid-ships; or, in other words, to limit the
breadth and height of the midship-frame.
A F. A perpendicular erected from the middle of the keel to bisect the
line of the ship’s breadth in two equal parts.
F * 9. The half-breadth line of the aftmost top-timber; being the
uppermost horizontal line in this figure.
Note. The seven lines parallel to, and immediately under this, on the
right side of the line A F, are all top-timber half-breadths, abaft the
midship-frame; the lowest of which coincides with the horizontal line D
E.