Hedderwick: Marine Architecture (1830)



There is a little variation in the lengths of the yards of ships of nearly the same dimension, according to the particular rigg or trade for which they are adapted.

Ships employed in the foreign trade have commonly longer yards than those of the same size that are employed in the coal and coasting trade; yet both have their particular advantages, being properly adapted to the build of the vessels, and the trade in which they are employed.

Vessels in the coal and coasting trade are generally of a broader and lower construction than those in the foreign trade, on account that a greater stabilty is required, these having often to perform one half their passages in a ballast-trim; also, as they are more frequently beating to windward in narrow channels, in which case narrow sails are found to answer best, as the ship will lie closer to the wind, and sail faster, than with the same quantity of canvas in a broader sail, when laid with the same angle to the wind; also the yards being shorter, are lighter and easier braced round, which is a great advantage in navigating narrow channels.

Ships for the foreign service are commonly built deeper in the hold, to give room for same particular stowage, and in general they have less stability than coasting vessels of the same size; therefore their masts are rather shorter, and their yards longer, by which they are enabled to spread an equal surface of sail in proportion. The leverage power of the masts and sails being reduced in proportion to their stability, they are also found to answer their purpose equally well; for as they are more in the open ocean, where the swell of the sea runs longer and higher (they are also seldom steered so close to the wind), although their sails are of a broader form, they stand with a good effect. In general, when the topsail is as broad at the lower reef as the depth between the main and topsail-yard, it is considered to be in the best proportion.

To Proportion the Yards of Ships to be employed in the Foreign Trade.

25ths, To find the length of the Main-Yard, from which all the others are generally proportioned. — Rule. To the length of the load-water line, including the breadth of the main-stem and stern-post (which in most vessels is equal to the length taken for tonnage),* add the ship's extreme breadth in feet and inches, and from this sum as a momentum, the length of the yards must be calculated; accordingly, to find the length of the main-yard, take 4-11ths of the length of the load-water line and extreme breadth added together, for the main-yard.

26th, Main Topsail-yard, 7-9ths of the main-yard.

27th, Main Topgallant-yard, 3-4ths of the main topsail-yard.

28th, Main Royal-yard, 2-3ds of the main topgallant-yard.

29th, For the Diameter of the Yards. — The diameter at the middle, or place of the slings of all the yards, is 1 inch for every 4 feet of their whole length. The outer ends are half the diameter of the slings or centre of the yard.

30th, That part of the yard without the cleats, called the Yard's-arm, is commonly about 1-20th of the full length of the yard.

Observation. — It was formerly the custom to have all the fore-yards about 1-20th or 1-18th part shorter than the main-yards, and the fore-top, and top-gallant masts in the same proportion; in which proportion it was considered that the head-sails were more easily managed, and also lighter on the fore part of the vessel. But it is now found to be a little more convenient to have the main and fore-top and top-gallant-sails of the same size, by which three topsails may often answer the purpose of having four, as required when the yards are of different lengths. The fore-mast is now set a little farther aft, which makes the vessel equally easy in the sea, and the only difference in the size of the sails by this arrangement is in the fore and main courses. Many shipmasters approve of the old method of having the fore-yards and fore-topmasts 1-20th shorter than the main-yards and top-masts. The main and fore-yards being of the same length and diameter, we have only to state, that

31st, The length of the Mizen-yards is 3-4ths of the length of the main-yards, and their diameters are in the same proprotion, except that the lowest yard, commonly called the

32d, Crossjack-yard, is considerably smaller in proportion to its length, being only 1 inch in diameter for every 4½ feet of its full length.

33d, The Spritsail-yard is made the same, or 7-8ths of the length of the fore-top-sail-yard, and its thickness is in the nearly the same proportion, only a little lighter. This yard is used in small ships as a flying jib-boom, and may occasionally answer for a topsail-yard, if required.

34th, Studdingsail-booms. — The studdingsail-booms are about 2 or 3 feet longer than the half length of the yards to which they are fitted. Their diameter at the outer boom-iron is 1 inch for every 4 feet of their whole length, and the outer end 2-3ds of the thickness at the boom-iron; lined rounding the same as the yards, from the boom-iron to the outer end.

By the foregoing rules, the dimensions of all the principal spars, &c. of any ship may be calculated in a few minutes, and their simplicity and correctness is illustrated by the following example, and a reference to the mast and rigging-plan of the ship, see Plate XXVII.

* If the vessel has an upright stern-post and a raking stem, the length taken for register will exceed the length of the load-water line, by as much as the stem rakes-out above the load-water line; in this case, one-half of this rake must be added to the length of the load-water line, for the medium rake, and proceed as above stated.

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 355-356.

Transcribed by Lars Bruzelius

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