Hedderwick: Marine Architecture (1830)



Whole-Moulding is a method of drawing the rounding part of all the square-frames by a sweep of the same radius, or with a mould formed to answer this purpose, called the Bend-mould. This method of moulding was formerly much used for constructing boats or ships which were narrow abaft, and had a considerable round on the side; but it is quite inapplicable to the draught of ships on the present construction. In whole-moulding, the sheer-draught and floor-plane is laid down in the common way, only that the rising-line is drawn in the same manner as a buttock-line, being a vertical longitudinal section representing the lowest part of the curves by which the bilge and rounding parts of the bottom are formed. The rising-line and lower height of breadth line should run parallel to each other, and be perfectly fair. The bend-mould is made to answer the round of the midship-frame from the lower height of breadth downwards, forming the round of the bilge; from which part it must be perfectly straight, similar to a futtock-mould, only the straight part of the mould is made to extend from the lower part of the curve straight across on a level, in place of pointing to the upper edge of the rabbet of the keel; it is also as long as to reach considerably past the other side of the keel.

The bend-mould being constructed, and laid in the position for drawing the midship-frame, the lower height of breadth is marked on its upper end, and the centre-line of the vessel for every frame on the lower end, which is lying across the keel on a level, and as far above it as the rising of the midship-floor. This mark is drawn across the mould with a square, also the centre-line of all the other frames outside of it, according as the ship diminishes in breadth. The next thing to be provided is called the hollow-mould; it is made nearly in the same form as the other, but applied in a reverse manner. It is made straight for about half of its length, or so as to reach from the keel to the round of the bilge; and towards the other end, it is made to diverge from the straight into a regular curve, so as to form the hollow part of the frames in the runs of the vessel. A square or board is also required, which should be as broad as the siding of the keel, and as long as will take on the greatest rising of the floors, cut perfectly square on the upper end, with the middle-line drawn on it, and the rising of every floor squared across. When the frames are to be laid down by this method, the rising-line and lower height of breadth line being drawn, the base-line, side-lines, and middle-line for the body-plan, may all be erected in the common way. The lower height of breadth line is then taken from the sheer-plan for every frame, and set up from the base-line, and squared across in the body-plan; also the height of the rising-line for each frame, in the same manner.

When every thing is thus prepared, and a frame to be laid down, put the lower or straight part of the bend-mould with its lower edge fair with the rising-line, as drawn across the body-plan, and the upper end out to the breadth mark, on the lower height of breadth line; the middle-line mark on the mould will then be on the centre-line of the body-plan. Draw round by the outside of the mould; and if the floor is to have no hollow on the lower part, strike a straiht line from the back of the round of bilge to the upper edge of the rabbet, and the frame is finished from the lower height of breadth to the keel; but if you intend to have a hollow in the lower part of the floor, lay on the hollow-mould, with the round side upwards and the straight end out, so as to touch the back of the sweep or bend-mould; shove out the hollow-mould, keeping the upper edge of it fair with the rabbet, until you have the hollow required; draw it in by the upper edge of the mould, and the form of the floor is completed. Then, with the mould in this position, mark the side of the keel or edge of the rabbet on it, and annex the character of the frame.

To draw in the other square-frames in the after-body, begin at the aftermost, and lay the bend-mould right to the rising-line and lower height of breadth, as before; then place the hollow-mould with the round edge upwards and the straight end out, touching the back of the bend-mould; push the lower mould outwards, keeping its upper edge fair with the rabbet, until you have the intended hollow on the lower part of the after frame. Draw round the outside of the bend-mould and upper side of the hollow-mould, and mark the edge of the rabbet on the lower end of the mould, — you will then have the extent of the hollow contained between the midship and aftermost square-frame, by the rounding and distance betwixt the marks on the hollow-mould. This distance between the marks must then be divided by the number of frames, and the spaces betwixt them graduated in proportion to the heights or rising of the frames, as measured from the rising-line, with the number or character of each frame annexed.

The moulds being thus prepared, in laying down any of the frames place the bend-mould to the height and breadth as before directed, with the mark on the hollow-mould for the intended frame laid to the rabbet, and its outer end touching the back of the bend-mould. Draw round by the outside of the upper one and inside of the lower one, and so complete the frame from the main-breadth to the keel. The frames in the forebody may be drawn in the same manner.

Although the lines for every frame laid down in this way may appear fair, when considered by themselves, they may not produce perfect fair lines in a fore-and-aft direction; but this may be easily corrected by forming some ribband and water-lines, which will be otherwise useful in laying off the cant-timbers and fashion-pieces, and by which the bevellings may be taken. The timbers for all the square-frames may also be moulded in the same way by the bend and hollow-mould, by applying the rising square or board to the bend-mould, and laying the hollow-mould to the proper mark and rising marked on the board.

Peter Hedderwick: A Treatise on Marine Architecture, containing the theory and practice of shipbuilding, with rules for the proportions of masts, rigging, weight of anchors, &c including Practical Geometry and the Principles of Mechanics; observations on the Strength of Materials, Hydrostatics, &c. with many valuable tables calculated for the use of shipwrights and seamen; also the proportions, scantlings, construction, and propelling power of steam-ships. Illustrated with twenty large plates, containing plans and draughts of merchant-vessels from fifty to five hundred tons, with mast and rigging plans; plans and sections of a steam-boat of eighty-horse power; and eight quarto plates of diagrams, &c., by Peter Hedderwick.
Printed for the Author, Edinburgh, 1830. pp 221-223.

Transcribed by Lars Bruzelius

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