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plan; on this erect a perpendicular as centre-line for both forward and after-bodies, the half-siding size of the keel must be struck in on either side of the centre-line; these are called sidelines, and in a propeller the swell of the post in the vicinity of the shaft must be drawn in, in the after-body plan. Draw from the base-line two lines parallel to the centre-line, one on either side of it, at a distance equal to one-half the breadth of the greatest transverse section; these are termed boundary-lines of the body-plan. Next set up the height of the water-lines from the base-line on the boundary-lines and draw or strike in the lines across both bodies.
TO OBTAIN THE SHAPE OF THE TRANSVERSE SECTIONS OR MOULDING EDGES OF THE FRAMES IN THE SQUARE BODY-PLAN.
17. Having provided a number of small pine battens about one-half of an inch square, and long enough to take off the greatest half-breadth and depth of the vessel, proceed as follows:Hold one end of the batten against the strip placed to the centreline in the half-breadth plan, at the perpendicular or station of the joint of the frame, and mark the intersection of each water-line and sheer-line; transfer these half-breadths to the body-plan and set them off from the centre-line on their corresponding waterlines, being careful to set off the half-breadths accurately and in their proper body,--that is, all those forward of dead-flat in the fore-body, and those abaft it in the after-body.
Before the half-breadths of the sheer-lines can be set out in either body, the proper height for setting them out must be obtained, viz.: Place one end of the batten against the base-strip in the sheer-plan and mark the intersection at the height of each sheer-line; transfer these heights to the body-plan and set them up on the side and boundary-lines in their respective bodies, and draw or strike in level lines at these heights; then, upon these lines set off the corresponding half-breadths as already obtained from the half-breadth plan; by this means a spot is obtained in the body-plan at the height of the breadth for every frame.
To end the heels of the square frames; set down below the base-line at its intersection with the side-line in each body the thickness of the rabbet of the bottom plank, as taken from the building instructions; take a pair of dividers and open them to correspond with this distance: one leg is placed at the intersection of the base and side-lines; the second leg is placed on the
side-line below, and an arc is swept from the base-line inward, the compasses turning on the lower leg below the base-line. It must be observed that in the case above the base-line was the upper edge of the rabbet on the side of the keel; in the plan it is the lower edge of the rabbet on the side of the keel, consequently the thickness of the rabbet must be swept in above the base-line. It is assumed that the keel is of a parallel thickness, consequently but one sweep is necessary for ending all the square frames in either body. The frame-lines all end tangent to, or touch, this arc. By cutting out a thick piece of plank with the proper sweep, and screwing it down on the floor in the body-plan at its proper place, it will be found very handy to place the lower end of the frames' battens against, as they can then lay over each other and also be ended properly.
The battens, which should be about one-half to three-fourths of an inch square, may now be placed on the floor and secured by nails driven in at short intervals on either edge of the battens; the rounding side of the battens being set to correspond with the half-breadths as before obtained, the lower end secured at the ending marked for them. The battens should now be made perfectly fair in both the half-breadth and body-plans, any alteration in one body being made at the corresponding place in the other. The water-lines cut the frames in the body-plan so obliquely, as to point out readily any unfairness; at the same time, act with the greatest caution, in order to preserve the shape of the body as nearly as possible. Before marking in the shape of the frames proceed to prove the heels of the timbers by getting in the bearding-line.
TO OBTAIN THE BEARDING OR STEPPING-LINE.
(Plates I., II., and VII., Figs. 1 and 2.)
18. The bearding or stepping-line is obtained from the body and half-breadth plans, by taking from the body-plan, on а batten, the heights above the base-line to the intersection of each joint of frames with the side-line, and setting them up on their corresponding stations from the base-line in the sheer-plan; squaring up also from the half-breadth plan, the points where the several water and sheer-lines intersect the side-line, on to their corresponding lines in the sheer-plan; a curve passed through the points thus obtained, breaking in fair with the after-edge of the
rabbet of the stem forward, and fore-edge of the rabbet of the stern-post aft, will give the bearding or stepping-line in the sheerplan, which is run in as a broken, not a full line.
The heels of the timbers being found to agree with this line by the fairness of the curve, the frames may now be marked in with pencil or chalk on the body-plan, and the water-lines and sheerlines in the half-breadth, and the battens taken up.
The rising or height of the bearding-line above the base-line will be found in the Tables, these measurements having been taken from a draught; but, in working from a set of Tables taken from a model, and laid down direct on the floor, no measurements for this line would appear.
VERTICAL LONGITUDINAL SECTIONS, OR BUTTOCK AND BOW-LINES.
(Plates I., II., and VII., Figs. 1, 2.)
19. The water-lines being horizontal sections, proceed to prove the frames in the body-plan again by vertical longitudinal sections. They are the boundaries of planes which are supposed to pass fore-and-aft through the whole length of the ship, and parallel to the middle plane of her; these lines, by projection, are indicated by straight lines in the body, and half-breadth plans laid off at equal distances from the centre-line, generally the same distance as the water-lines, so that where the half-breadth is laid down that the base of the sheer-plan answers for the centreline of the half-breadth, less lines would be required as the water-lines in the sheer-plan would answer for the projection of the sections in the half-breadth plan. In the sheer-plan they are curves bounding the sectional areas, and denoting by their form and regularity the symmetry of the vessel as well as the fairness of her. Though it may not be desirable to run in on the floor no more lines than necessary, both on account of despatch and to prevent confusion, yet, as a fair body is the main object, we must spare no pains nor number of lines to effect it.
These section-lines are distinguished as being dotted or broken lines in all three plans, and are marked according to their distance from the centre-line, viz., 2 ft., 4 ft., 6 ft., &c., Vertical Section-Lines.
METHOD OF TAKING OFF THE VERTICAL LONGITUDINAL SECTIONS OR BUTTOCK AND BOW-LINES.
20. The method of setting off these lines upon the sheer-plan is, by taking off the heights from the base-line in the body-plan, on a batten where the lines drawn for the sections intersect the transverse sections or frame-lines, and transferring these heights to the corresponding stations in the sheer-plan, setting them up from the base-line. Other points may be obtained for running this curve from the half-breadth plan, by squaring up the intersection of the water and sheer-lines with the section-lines on to their corresponding lines in the sheer-plan; and, if correct, the same water and section-lines will be found to intersect on the sheer-plan in that perpendicular.
ENDING OF VERTICAL LONGITUDINAL SECTIONS OR BUTTOCK AND
21. The ending of these lines is obtained by squaring up from the half-breadth plan the intersection of these lines with the halfbreadth of rail on to the corresponding line in the sheer-plan, and ending the battens at that point. Now pin battens to the spots before set up, and to the last squared up as the ending, which should produce fair curves representing the body cut in that direction in the sheer-plan. Then, if these lines prove fair, the frame-lines in the body will be fair, and, likewise, the waterlines in the half-breadth plan; but if these lines to be made fair curves require alteration from the spots before set off, then the frame-lines in the body-plan must be altered accordingly, and, consequently, the water-lines.
The rising or height of these section-lines appear in the Tables having been obtained from the draught, no such measurements can be got direct from the model.
We will now proceed to prove the correctness of the body for the second and last time, by diagonal lines.
(Plates I. and II., Fig. 2.)
22. A diagonal-line is a curved line bounding a section or area of the body in an oblique direction, passing through the vessel longitudinally, and meeting the centre-line its entire length, parallel to the base-line. They are usually drawn in red on the bodyplan of the draught where they are made to denote the lengths of
the timbers forming the frame of the vessel, and by projection they are in that plan represented as straight lines running in an oblique direction from the centre-line, each line crossing the forward and after body at a corresponding angle with the centreline marking the heads and heels of the frame timbers. These lines are considered the most effectual towards fairing the body of the ship, or making the one portion of her assimilate with the other. It may here be observed that the diagonal-lines standing square to the frame-lines, or nearly so, upon the body-plan, are the least to be depended upon for pointing out any unfairness in the formations of the frame-lines, because they may really appear as fair lines on the half-breadth-plan, while the body itself is unfair. Therefore the diagonals can be first struck in at the discretion of the draughtsman, and after taking them off and proving the fairness of the body, these lines may be erased, and the diagonals drawn in red ink on the draught, or red chalk or pencil on the floor, strictly adhering to what has been said on this subject. Between the diagonals drawn at the heads and heels of the frame timbers, draw other diagonals for the sirmarks or stations of the ribbands which are placed between the heads of the respective frame timbers, in order to give support to the ship whilst in frame. A diagonal should also be marked between the floor-sirmark and keel for the floor guide. The diagonals are distinguished as 1st, 2d, etc., diagonals. The sirmarks are distinguished as floor-sirmark, 1st, 2d, 3d, etc., sirmarks. Having explained the nature and use of the diagonals, I will now proceed to explain the method of taking them off from the bodyplan, and developing their curves in the half-breadth-plan.
METHOD OF TAKING OFF DIAGONAL-LINES.
23. The diagonals are taken off from the body-plan, for the form of the diagonal section to be shown on the half-breadth-plan, where it will be developed as a curve; by taking on a batten in the direction of the diagonal, the distances or intersections of each frame line with the diagonal from the centre-line, and setting them off from the centre-line of the half-breadth plan on their corresponding stations, and pinning a batten to these spots.
TO END THE DIAGONAL-LINES.
24. Diagonal-lines may be ended on the bearding-line, as the harpins, the form of which the diagonals are intended to de