« ZurückWeiter »
Plan and Elevation of a 74 Gun Ship&c.
ELEVATION or shEER-DRAIGHT.
HORIZONTAL PLANE, The Rising'zBraidth.
370 22 77 76 22 24 26 28 30 312
of the bottom is determined by the qualities length, and exhibits the outline of the timbers which are necessary for the vessel, and conform- respectively to each other, as they are erected able to the service for which she is proposed. upon the keel. Accordingly, this draught ought The upper works comprehend all that part to present a variety of sections of the ship in which is usually above the water when the ship different places of her length, and always peris laden.
pendicular to the upper edge of the rabbet of The limits of our design will not admit of a the keel, so that the eye of the observer, when minute description and enumeration of all the placed in what may be properly termed the axis pieces of timber which enter into the construc- of the ship, may perceive the several sections at tion of a ship, nor of a particular description of one glance; that is to say, when looking full on their assemblage and union; or the manner in the stem, from before the ship, discover the fore which they reciprocally contribute to the solidity timbers ; and, when looking from behind, directly of those floating citadels. It nevertheless ap- on the stern, he shall perceive the form of the pears necessary to give a general idea of the after timbers. use, figure, and station of the principal pieces, To form a just idea of this plane, therefore, to those who are entirely unacquainted with the we ought to suppose a ship resting upon the subject. As our definitions will be greatly illus- stocks, in the same position as when afloat upon trated also by the proper figures, we have annex- the water. Thus a variety of black vertical ed to this article a plate, which comprehends lines may be drawn at equal distances upon the some of the most material draughts, as well as a bottom, which is white, to form different outlines representation of the principal pieces employed of the ship corresponding to the timbers within. in naval architecture.
It is to be observed that the fashion of the infeIt is usual among shipwrights to delineate rior timbers must conform to the figure of the three several draughts.
midship-section, which is placed in the fullest 1. The whole length of the ship is repre- part of the ship; and, as the planes of all the sented according to a side view, perpendicular other timbers diminish in a certain progression to the keel, and is termed the plane of elevation, as they approach the stem and stern, they are or sheer-draught. Plate I." Suid-BUILDING, properly delineated on the plane of the midshipfig. 1.
section, which also represents the depth of the 2. The ship is exhibited according to an keel and length of the midship-beam. end view, and stripped of her planks, so as to As the two sides of a ship ought to be exactly present the outlines of the principal timbers; alike, it is judged sufficient to represent the and this is properly termed the plane of projec- sections of the fore part of the ship on the right tion, or the vertical plane of the timbers, because side, and those in the after part on the left, so it shows the projection of their frames relatively as to perceive all the sections, as well afore as to each other.
abaft, upon one plane. See PROJECTION, plate 3. It is not sufficient to have the vertical I. SHIP-BUILDING, fig. 2, 3. curves of the bottom in different places; for a However necessary it may be to understand distinct idea of the horizontal curves is also precisely the vertical curves of the bottom, it is equally necessary and useful: this is obtained no less requisite to have a just idea of those by means of water-lines traced upon what is which are horizontal. called the horizontal plane.
The horizontal, or floor plane, is that upon The elevation or sheer draught determines the which the whole frame is erected, and will be length and depth of the keel; the length and more clearly understood by previously describprojection, or rake of the stem and stern-post; ing the water-lines and ribands of which it is the position of the midship-frame upon the keel, composed. together with that of the principal frames afore When a ship floats upon the stream, it is eviand abaft; the wales, the dimensions and situa- dent that her upper works will appear to be tions of the gun-ports, the projection of the rails separated from the bottom by the surface of the of the head and quarter gallery, with the stations water, which will accordingly describe an imaof the masts and channels.
ginary horizontal line upon the bottom from the This draught, however, conveys no idea of the stem to the stern-post. vertical curve of the ribs or timbers; for, as The most elevated of those lines is termed their projection will be only represented in a the upper horizontal or water-line; and, in order plane elevated upon the length of the keel, they to prove the fairness of the body, the several
appear in this direction no otherwise than horizontal lines are set up at equal distances as straight lines. To perceive these curves accu- above the base line, and distinguished by the rately, they must be regarded in another point water lines H, I, J, K, L, in the projection. This of view, which will represent their projection we would always recommend to be done, alupon a vertical plane, supposed to cut the keel though the water lines of many ships are not at right angles in the place where the ship is parallel with the line of the keel; for, unless broadest. For, as all ships are broader near the they are parallel with the keel, they cannot middle of their length than towards the extre answer the intended purpose of laying off the mities, it is evident that the timbers are more ship. extended in proportion. The most capacious of By lightening a ship gradually, and at the these represents what is called the midship-sec- same time preserving the direction of her keel, tion; and upon the area of this section is deli- or the angle which it makes with the surface o. neated the projection of all the others.
the water, a variety of water lines may be drawn Thus the plane of projection limits the dif- parallel to each other. ferent breadths of a ship in various points of her The ribands are likewise of great utility in
ship-building; they are narrow and flexible ing the flood ; 4thly, That being broader at the planks placed on the bottom at different heights, load-water line, or place where the surface of the so as to form a sort of mould for stationing the water describes a line round the bottom, they inferior timbers between the principal ones. will admit of being very narrow on the floor They differ from the water-lines, inasmuch as the particularly towards the extremities; and, 5thly latter have only one curve, which is horizontal, That a broad vessel will more readily rise upon whereas the ribands, besides their horizontal the waves than a narrow one. one, have vertical curves from the main-breadth From such opposite principles has resulted upwards.
that variety of standards adopted by different We have already observed that the qualities shipwrights; and a servile imitation of these merequired in a ship ought to determine the figure chanical methods has, to the great reproach of of the bottom: a ship of war, therefore, should the art, produced all these pretended rules of be able to sail swiftly, and carry her lower tier proportion ; for the various models they have of guns sufficiently out of the water. A mer- hitherto adopted indisputably prove their doubt chant ship ought to contain a large cargo of and uncertainty with regard to their proper mercantile goods, and be navigated with few standard. Hence these pretended mysteries hands; and both should be able to carry sail which are only to be revealed to such as are inifirmly, steer well, drive little to leeward, and tiated into the craft! And hence violence of sustain the shocks of the sea without being vio- opposition and mutual contempt amongst the lently strained.
artists! Indeed, nothing appears more effecThe first thing to be established in the draught tually to have retarded the progress of naval of a ship is her length; and, as a ship of war, architecture than the involving it in mysteries according to her rate, is furnished with a certain which the professors would gravely insinuate are number of cannon, which are placed in battery on only intelligible to themselves. This ridiculous her decks, it is necessary that a sufficient dis- affectation is, nevertheless, too generally retained, tance should be left between the ports to work notwithstanding the example to the contrary of the guns with facility, and particularly to leave some of the most able shipwrights in Europe, space enough between the foremost gun and the who are real masters of the theory of their art, stem, and between the aftmost gun and the and do honor to their profession, and who are stern-post on each side, on account of the arch- justly exempted from the censure to which the ing, or inward curve of the ship towards her ex- others are often exposed. tremities.
It is not to be expected that an art so compliWhen the length of a ship is determined, it is cated and various, comprehending such a diverusual to fix her breadth by the dimensions of the sity of structures, can be treated at large in a midship-beam. On this occasion the shipwrights, work of this sort. To enter into a particular for the most part, are conducted by rules founded detail of the theory and practice, to explain the on their own observation; for, having remarked different parts with sufficient accuracy and perspithat some vessels, which by repeated experience cuity, would of itself require a large volume, and, have been found to answer all the purposes of consequently, much exceed the limits of our denavigation, have a certain breadth in proportion sign. Being thus necessitated to contract our to their length, they have inferred that it would description into a narrow compass, it will be be improper to depart from this proportion : sufficient to give a general idea of the subject, to but, as other ships have been constructed with describe the principal pieces of which a ship is different breadths, which were equally perfect, a composed, and to explain the principal draughts variety of different general rules have been used in the construction thereof. adopted by these artists, who are accordingly As the several lines exhibited in the planes of divided in their opinions about the breadth elevation, projection, &c., will be rendered more which ought to be assigned to a ship relatively intelligible by a previous account of the principal with her length, whilst each one produces rea- of those pieces, it may be proper to begin with sons and experience in support of his own stand- reciting their names, and giving a summary ard. Those who would dininish the breadth description of their uses and stations. They are, allege, 1st. That a narrow vessel meets with less for the most part, represented according to the resistance in passing through the water; 2dly, order of their disposition, in fig. 4, and termed That by increasing the length she will drive pieces of the hull. less to leeward ; 3dly, That, according to this A, the pieces which compose the keel, and principle, the water-lines will be more conveni- which are securely bolted together, and clenched. ently formed to divide the fluid; 4thly, That a B, the stern-post, which is tenoned into the long and narrow ship will require less sail to ad- keel, and which unites the sides of the ship abaft. vance swiftly; that her masts will be lower, and C, the stem, which is composed of three pieces, her rigging lighter; and, by consequence, the scarfed together, into which the ship's sides are seamen less fatigued with managing the sails, &c. united forwards.
Those, on the contrary, who would enlarge the D, the inner post, into which the transoms are breadth, pretend, Ist, That this form is better let. fitted to receive a good battery of guns ; 2dly, E, the false post, which serves to augment the That there will be more room to work the guns breadth of the stern-post. conveniently; 3dly, That, by carrying more sail, F, the pieces of dead-wood, which form the the ship will be enabled to run faster; or, that after-part of the ship. this quality will at least overbalance the advan G, the knee of the stern-post, which unites it tage which the others have of more easily divid- to the keel.
H, the apron, which is fayed on the inside of keel, by which we shall be enabled to judge of the stem, to support the scarf thereof; for which the rake of the stem and stern-post. The rake reason the scarf of the former must be at some is known to be the projection of the ship at the distance from that of the latter.
height of the stem and stern-post, beyond the I, the stemson, which reinforces the scarf of the ends of the keel afore and abaft; or the angle by apron.
which the length is increased as the fabric rises. K, the wing transom, which is fayed across To these we may also add the height of the stem the stern-post, and bolted to the head of it, have and wing-transom. ing its two ends let into the fashion-pieces. As a ship is much broader at the middle than
Lthe deck transom, parallel to the wing-tran- at the extremities, the arms of the floor-timber som, which is secured in the same manner. will form a very obtuse angle at the extreme M, the filling transom.
breadth; but this angle decreases in proportion N, the lower transoms.
to the distance of the timbers from the midship0, the foremost fashion-piece on one side; the section, so that the foremost and aftmost ones heel of which is connected with the dead-wood, will form a very acute angle. and the head is secured to the wing-transom Shipwrights differ extremely in determining P, the middle fashion-piece.
the station of the midship-section; some placing Q, the after fashion-piece.
it at the middle of the ship's length, and others R, the side counter-timber, which steps on the farther forward. They who place it before the end of the wing-transom.
middle, allege that, if a ship is full forward, she S, the sternson.
will meet with no resistance after she has opened T, the gripe.
a column of water; and that the water so disU, the lengthening piece on the side counter- placed will easily unite abaft, and by that means timber.
force the ship forward; besides, having more V, the scarf of the after-piece of the keel. power on the rudder, in proportion to its distance
W, the pieces which compose the kelson, and from the centre of gravity ; this also comes nearer which are scarfed together, and placed over the the form of fishes, which should seem the most middle of the floor timbers, upon each of which advantageous for dividing the Auid. When the they are scored about an inch.
rising of the midship-floor-timber is decided, we Y, the several pieces of the knee of the head; may then proceed to describe the rising-line the lower part of which is fayed to the stem; the of the floor, on the stern-post abaft, and on the heel being scarfed to the gripe.
stem afore. In vessels of war the general dimensions are The height of the lower-deck is the next thing established by authority of officers appointed by to be considered. It is determined in the midthe government to superintend the building of dle by the depth of the hold; and some builders ships. In the merchant-service the extremo make it no higher than the stem; but they raise breadth, length of the keel, depth of the hold, it abaft as much above its height in the middle height between decks and in the waist, are agreed as the load-water-mark, or draught of water abaft, on by contract; and from these dimensions the exceeds that afore. With regard to the height shipwright is to form a draught suitable to the between decks, it is altogether arbitrary, and trade for which the ship is designed.
must be determined by the rate of the ship, and In projecting the draught of a vessel of war, the service she is designed for. It is also necesthe first article to be considered is her length. sary to remember the sheer of the wales, and to As every ship is much longer above than below, give them a proper hanging; because the beauty it is also necessary to distinguish the precise and stateliness of a ship greatly depend upon part of her height, from which her length is their figure and curve, which, if properly drawn, taken : this is usually the lower gun-deck, or the will make her appear airy and graceful on the load-water-line. It has been already observed water. that water-lines are described longitudinally on a We come now to consider the upper-works, ship's bottom by the surface of the water in and all that is above water, called the deadwhich she floats, and that the line which deter- work : and here the ship must be narrower, so mines her depth under the water is usually termed that all the weight lying above the load-waterthe load-water-line. In this draught it will be line may thereby be brought nearer the middle particularly necessary to leave sufficient distance of the breadth, when of course the ship will be
less strained by the working of her guns, &c. The next object is to establish the breadth by But, although some advantages are acquired by the midship-beam. Although there is great dif- diminishing the breadth above water, we must ference of opinion about proportioning the be careful not to parrow her too much; as breadth to the length, yet it is most usual to there must be sufficient room left on the up. conform to the dimensions of ships of the saine per-deck for the guns to recoil. The security of rate. After the dimensions of the breadth and ihe masts should likewise be remembered, which length are determined, the depth of the hold requires sufficient breadth to spread the shrouds. must be fixed, which is generally half the breadth: A deficiency of this sort may indeed be in some but the form of the body should be considered measure supplied by enlarging the breadth of the on this occasion ; for a flat floor will require less channels. depth in the hold than a sharp one. The dis We shall now proceed to explain the plane of tance between the decks must also be settled. elevation or sheer-draft of a modern seventy
He may then proceed to fix the length of the four gun ship as represented in Plate I. fig. 1.
between the ports.