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The transverse sections in the body-plan and their corresponding stations in the half-breadth and sheer-plans are generally distinguished by letters, A, B, C, &c., those in the after-body by figures, 1, 2, 3, &c., although in very many cases figures are used for both fore and after-bodies, commencing to number from forward, omitting the greatest transverse section, which is invariably denoted by the symbol, and should there be more than one of that form they are denoted as 1, 2, 3, &c.
It must be understood that the sections in the body-plan on the right of the centre-line represent the starboard fore-body, whilst those on the left of the centre-line represent the port after-body of the ship.
It will be perceived from the preceding remarks that
The half-breadth plan
is a pro
on a vertical longitudinal plane; on a vertical athwartship plane; on a horizontal plane.
The three plans above described constitute the draught of a ship. We shall see presently their mutual dependence on each other, so that any two being given, the third may be obtained.
PROFILE AND OTHER PLANS.
6. Besides the sheer-plan, it is customary to furnish the builder with a profile of the inboard works, on which is shown the stations of the masts, catheads, channels, chain-plates, head, head-rails, cheeks and brackets, engine keelsons, shaft bearings, water-tight bulkheads; &c. A plan of the midship section should be furnished, showing the moulding or athwartship size of the timbers, the thickness of the exterior and interior planking, the connections of the beams to the sides, the dimensions of the waterways, thick-strakes, description and fastening of the knees, the position and fastening of the keelsons, &c. A plan should be furnished for the several decks, showing the positions of the beams, carlings, ledges, hatches, skylights, cabin, wardroom, steerages, warrant-officers' quarters, sick-bay, dispensary, yeoman's and other store rooms; also one for the hold, showing the position of the engines, boilers, magazines, shell-rooms, shot-lockers, chainlockers, stores, etc. These, together with the "building direc
line in the half-breadth plan are equally parallel with and equidistant from the centre line of the body-plan as the vertical longitudinal section or buttock and bow lines.
tions," which is a document containing the dimensions and general directions for combining and fastening together the principal pieces that enter into the construction of the vessel, constitute all the preparatory information required by the builder.
7. Mould-lofts in private ship-building establishments are seldom long enough to admit of laying down any large vessel in one length; in small lofts they are laid down in three or four lengths. In the government yards, the length of the mould-loft generally admits of laying the vessel down in one length.
8. The mould-loft floor being cleared, begin the process of laying down, by striking a straight line from one end to the other, or as long as the length of the vessel requires, called the base-line (Plates I. and II., Fig. 2), leaving space below, next the side of the loft, to strike in the depth of the keel.
The base-line will represent the lower edge of the garboard strake on the side of the keel, in the sheer and body-plans, above which all heights are to be set up;* and it will represent, also, the centre-line of the half-breadth plan, unless the half-breadth plan is laid down separately from the sheer-plan, in which case, the half-breadth is placed below the sheer-plan, and a line is struck in for the centre-line, parallel to the base-line, and, at a parallel distance below it, equal to one-half the greatest transverse section of the vessel.
To each of these lines, a broad batten with a straight edge is fixed for the convenience of butting the measuring batten against when setting off the distances.
TO PLACE THE FOREMOST AND AFTERMOST PERPENDICULARS, AND GET THE STATIONS OF THE TIMBERS ON THE FLOOR.
9. Set off on the base line the position of the foremost and aftermost perpendiculars, also the station of every fourth frame;
*See Plates III, and IV.
NOTE.-In the Plates, Nos. I. and II., accompanying this work, the reader will observe that the half-breadth (VII.) plan is laid down below the sheer-plan. My object in doing this is to make the lines used appear as distinct from each other as possible, and still be able to show as clearly as possible their intimate relation to each other.
these stations answer both for the sheer and half-breadth plans. The foremost perpendicular must be drawn in at such a distance from the end of the floor as to allow room for laying down the head, provided the length of the floor will admit; if not, leave room for the stern only. The length between the perpendiculars is generally measured on the load-water-line, from the fore-side of the rabbet of the stem to the after-side of the stern-post in sailing vessels, and after-side of main or forward stern-post in screw vessels having a forward and after-post. From the aftermost perpendicular, set forward the distance of dead-flat, and, as a proof of its correctness, try how the distance to some station abaft it corresponds; and if the whole distance--that is, if from the foremost perpendicular to dead-flat, added to the distance of the aftermost perpendicular from some station, together with the distance from this station to dead-flat, make the whole space between the perpendiculars as given in the "tables of ordinates" —these stations are correct. The stations of the perpendiculars are marked respectively FP and AP. The greatest transverse section, or, as it is termed, dead-flat, is invariably denoted by the symbol; as has been stated before, the stations of the frames or joints of the timbers are generally denoted by letters in the fore-body- that is, all frames forward of dead-flat, and by figures in the after-body of all frames abaft dead-flat, or by figures in both bodies, commencing to number them from forward, omitting dead-flat.
TO RUN IN THE HORIZONTAL AND SHEER LINES.
10. From the Tables, take the parallel distance of the water-lines from the base line, set them up on the perpendiculars, and strike in the lines. Next take the heights of the several sheer-lines, set them up on their respective stations from the base-line, and mark the height. Nail a batten on the floor, corresponding to the spots already obtained, see that the curve is perfectly fair, and mark it in—the round edge of the batten is the best to look at in fairing the sheer or other lines on the floor, and they should lay on their flat, the edge to the spots. The battens to one or all of the sheers may be placed on the floor at the same time. If, however, the sheers taper, one at a time is sufficient; when they are parallel, they may all be regulated to advantage at the same time.
TO GET THE SHAPE OF THE FORWARD EDGE OF THE RABBET OF
11. To get the shape of the forward edge of the rabbet of the stem in the fore-body; take from the Tables the distance on each sheer and water-line that the edge of the rabbet is forward or aft, as the case may be, of the forward perpendicular; place a batten to the points thus obtained, fair the curve, and mark it in on the floor. This is the boundary line of the forward part of the sheer-plan. The distance that the fore-side of the stem and gripe are forward of this line can be struck in now, or when ready to make the moulds for the stem-pieces.
TO GET THE SHAPE OF THE AFTER-EDGE OF THE RABBET OF THE STERN-POST AND CENTRE-COUNTER-TIMBER.
12. To get the shape of the after-edge of the rabbet of the stern-post and centre counter-timber; take from the Tables the distances on each sheer and water-line that the after-edge of the rabbet of the stern-post and centre counter-timber are forward or aft, as the case may be, of the after perpendicular; place a batten to the points thus obtained, fair the curve and mark it in on the floor. This is the boundary line of the after-part of the sheer-plan. The distance that the stern-post is aft of the rabbet can be struck in now or when ready to make the mould for it.
TO RUN IN THE HALF-BREADTH PLAN.
(Plate VII., Figs. 1 and 2.)
13. Having struck in a line for the centre-line of the halfbreadth plan as before described, and marked the stations of the frames in the sheer-plan down to it, proceed as follows:
Set up from the centre-line and parallel to it at either extremity of the vessel, one-half the siding size of the stem and sternposts, as given in the building instructions, and draw in a line for several feet from the extremities: this will be called the sideline. The general practice is to strike the side-line in at a distance from the centre-line equal to one-half the siding size of the keel, and has been drawn in in this way on the accompanying plan. From the Tables set off from the centre-line the halfbreadths of the water-lines and sheer-lines at their proper staions, and proceed to find their ending forward and aft.
ENDING OF WATER-LINES AND SHEER-LINES FORWARD.
(Plate IV., Fig. 1.)
14. To end the water-lines and sheer-lines forward; square down the intersection of the several lines with the fore-edge of the rabbet of the stem in the sheer-plan, on to the side-line in the half-breadth plan; with this point as a centre and the thickness of the plank at that point as a radius, describe an arc towards the centre-line, and let the lines end tangent to, or touch this arc.
ENDING OF WATER-LINES AND SHEER-LINES AFT.
(Plate III., Fig. 1.)
15. To end the water-lines and sheer-lines when they cross above the rabbet of the post; square down the intersection of these lines with the after-edge of the centre counter-timber in the sheer-plan on to the side-line in the half-breadth and end the lines at those points. The water-lines that intersect the afteredge of the rabbet of the stern-post in the sheer-plan will be ended by squaring down their several points of intersection on to the side-line, and, with these points as centres and the thickness of plank as the radius, describe an arc towards the centre-line, and let the lines end tangent to, or touch this arc. Proceed now to place battens to the spots on the stations of the frames, obtained as before described. It is desirable to regulate all the water-lines at the same time, or to have all the battens on the floor at the same time, as one line determines, to some extent, the correctness of the other. If proper care is taken in taking off the Tables from the model or plan, the variations will be inconsiderable; the battens will have to be reduced at the ends and made wedge-shaped, in order that they may be secured at their proper ending, or they can lay one above the other until regulated.
Proceed now to construct and lay down the body-plan in order that it may be regulated at the same time and made to correspond with the half-breadth.
TO CONSTRUCT THE SQUARE BODY-PLAN.
(Plates I. and II., Fig. 2.)
16. If the length of the floor will admit of it, extend the baseline of the sheer-plan out forward for the base-line of the body