Such a disposition of this most important problem of furnishing a ship with her propulsory elements, does not always secure a profitable character, but often militates against the credit of the model -- the fault, if any, being naturally laid at the door of him who is never present to speak for himself. Our experience has demonstrated to ourselves, that it is always best to locate the effort of sail in strict antagonism to the various resistance that will be encountered from the sea, to the progress and flotative properties of the ship. This cannot be done, except we know the elements of the model, and how to proportion the forces of propulsory power in each particular case required. The mode of making calculations for sail from the model of a ship, and from the science of forces, may be found in the Ship-Builders' Manual, published by Mr. Griffiths, of this magazine, to which we would refer the reader, if interested in these problems.
In this article we propose to furnish the diameters and forms of masts and spars which are generally recognized by spar-makers in this country and in England. In ascertaining what strength ad form should be given to the several spars of a vessel to secure a proper resistance to the strains which they wil be subjected to, we have no benefit of any means, except what experience and service have furnished, and which appear to have been all that spar-makers have ever required. Although it should be well known that the various kinds of timbers used in different parts of the world, for masts and spars, differ greatly in strength of fibre; in practice, we find little or no attention paid to the fact, perhaps because spar-makers do not know the precise ratios of strength. It is plain enough that some discrimination should be used in the application of "rules" to the diameter of spars -- that the stronger kinds of timbers require less size than those of inferior strength. Also, in the selection of trees for masts and spars, it is of very great importance that the timber be sound and fit to be used.
From observations that the spar-maker has been enabled to make, his judgement has been formed respecting the strength and diameters that are requisite for all masts and spars, and the following rules ascertained by experience to be pretty correct and easy of application have been given.
The largest diameter is fixed in proportion to the length, and is given thus: At the partners of lower masts; at the caps, in top-masts and top-gallant-masts; at the bed of bowsprits; at the slings of yards; at the bowsprit cap of jib-booms; at the middle of driver-booms; at the sheet of mainsail-booms; at about four feet from the ends of gaffs; at one-third from each end of top and top-gallant-studding-sail-booms; and at one-third from the inner end of swing or lower studding-sail-booms.
The diameters of masts and spars generally follow some proportion to their length, thus: main and foremasts of ships, one inch for every three feet of the length; mizen-masts, two-thirds of the diameter of the mainmast.
Main-mast of brigs, one inch to every three feet of length; and the foremasts, nine-tenths of the size of main-masts.
Masts of cutters and schooners, one-quarter of an inch in diameter to each foot of length. (If of white pine the mast should be larger, and the foremast of schooners should be larger than the main-masts.)
Main and fore-topmasts, one inch to every three feet in length; mizen-top-masts, seven-tenths of the diameter of the main-topmast.
Top-gallant-masts, one inch to every three feet of their length.
Royal-masts, two-thirds the diameter of their top-gallant-masts.
Bowsprits, the same diameter as the main-mast.
Lower yards, seven-tenths to seven-eights of an inch to every three feet of length.
Topsail yards, five-eights to seven-eights of an inch to every three feet of length.
Top-gallant yards, six-tenths to five-tenths of an inch to every three feet in length.
Royal yards, one-half the diameter of their topsail yards.
Studding-sail yards and booms, one inch in diameter to every five feet in the length.
Jib-booms and flying-jib-booms, seven-eights of an inch to every three feet in the length.
Driver-booms and gaffs, the same proportion as the topsail yards.
The intermediate diameters may bear the following proportion to the given diameter. Lower masts for ships and brigs 60/61 of the diameter at partners for the size at the first quarter; 14/15 at the second quarter; 6/7 at the third quarter; 3/4 at hound; 5/8 at cap, and 6/7 at step. For schooners, heel 5/6 of partners; tressle-trees, 3/5 of partners; cap, 1/2 of partners. Large schooners or sloops require greater proportions -- say, tressle-trees, 4/5 of partners; cap, 3/4 of partners.
Topmasts, top-gallant-masts, and royal-masts have the same proportions as lower masts, except that the hounds and head are larger -- say, hounds 9/13 or 4/5 of given diameter; head, 6/11 of same. For schooners and sloops, hounds 10/13 of given diameter; head, 1/2 of same.
Bowsprit, 60/61 of given size, at first quarter; 11/12 at second quarter; 4/5 at third quarter; 2/3 at cap, and 6/7 at heel.
Yards, 30/31 of sling diameter at the first quarter; 7/8 at second quarter; 7/10 at third quarter; at arms, 3/7; lower and topsail yards may be 1/2 of slings at the arms.
Jib and driver-booms, 40/41 of given diameter at the first quarter; 11/12 at the second quarter; 5/6 at the third quarter; ends, 2/3. For schooners outboard end, 3/4; inboard end of jib-booms also 3/4.
Or, main-booms may be 40/41 at first quarter; 12/13 at second; 7/8 at third; fore end, 2/3; aft end, 3/4, and middle, 11/12 of diameter at sheet.
Gaffs, 40/41 at first quarter; 11/12 at second; 4/5 at third, and 5/9 at end. The heeling of standing masts and bowsprit are sometimes after the following proportions: masts, 2/3 of given diameter athwart-ship, and 1/2 fore and aft; bowsprit, 7/12 athwart-ship, 2/3 up and down.
There is a certain fitness of proportion in the preparation and finish of masts and spars, which causes a vessel to display to advantage. This quality in sparring, so far as outline of masts and spars are concerned, will be found to consist in neatness of extremities. A clumsy appearance in a yard or boom, &c., is due to an insufficiency of contrast between the diameters of the middle and the ends. Proportions that give strength to a spar will at the same time endow it with the elements of beauty. It is the rake and taper that give life to spars.
On the finishing and fitting of masts and spars we remark in a future number. This principle should be kept in view by the spar-maker, viz.: a sufficiency of material for strength, with the least weight and bulk possible. Wire rope has been successfully introduced for rigging, and a patent has been taken in England for making the trunks of masts and the middle portions of yards, &c., of sheet-iron. As it is important to reduce the weight and bulk of spars and rigging for ships, we are prepared to expect many improvements will be made in the application of sail power to marine propulsion.
Transcribed by Lars Bruzelius
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Copyright © 1996 Lars Bruzelius