Hedderwick: Marine Architecture (1830)


Channels. — The channels are a kind of projecting platform fixed to the side of the ship, for the purpose of giving the shrouds more spread than the bare breadth of the vessel, that they may the more powerfully support the side-strain of the masts. The channels, also, by projecting beyond the side, prevent the shrouds or lanyards from chafing or rubbing against the rails or upper works of the vessel. They are commonly made of 3, 4, or 5 inch plank, according to the size of the ship, and of sufficient breadth to keep the rigging clear of the rail, say 14, 16, 18, 20 inches, or two feet, according to the size of the vessel, and tumble-home of her top-sides. On smacks, in the Leith and London trade (vessels of about 180 or 200 tons register), the channels are commonly 7 to 8 inches thick, and from 10 to 12 in breadth; their length from one-half to 5-9ths of the ship's extreme breadth. The greatest spread of the rigging should not exceed one-half the ship's breadth, nor be closer than 4-9ths of the same. The dimensions of the channels for all kinds of smack or sloop-rigged vessels are made in a similar proportion.

The channels of ships of about 300 tons are generally about 4 inches thick at the inner edge next the ship's side, and thinned off to about 3 inches at their outer edge, or to the size of the moulding on the lower part of the sheer-plank on which they are often placed. Their length for brigs, and the main and fore masts in ships, requires to be about 2-3ds of the extreme breadth of the vessel, and fitted with a cant down at the outer edge of one inch to a foot of breadth. They are fastened to the side with 3-4th or 7-8th inch bolts, one every 2½ or 3 feet, these bolts being placed clear of the chains.

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. p 324.

Transcribed by Lars Bruzelius

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