1st, To find the Length of the Main-mast. — Rule. To three times the breadth of the beam per register, add one-third of the length of the load-water line, including the breadth of the main stem and stern-post, and 4-7ths of the sum is the length of the main-mast.
2d, The Length of the Mast-heads, from the lower part of the trestletrees to the top, is 5 inches for every three feet of the whole length of the mast; or — Rule, multiply the full length of the mast by .14 for the length of the head.
3d, To find its Diameter. — Rule 1st, Make the diameter at the partners of the main-deck, for Riga timber, 1 inch for every 3½ feet of the full length of the mast. Rule2d, Make the diameter at the partners 2-7ths of the length of the mast, taking inches for feet. Rule 3d, Multiply the ship's extreme breadth, feet and inches, by .68; cut off the decimal, which multiply by 8 for the diameter in eighth parts of an inch. Rule 4th, For American yellow pine mast, multiply the ship's extreme breadth by .72 for the diameter at the partners.
Another method for finding the length of the main-mast, either for brigs or ships, which I have found to be very correct in almost every case, is as follows:—
For a Ship's Main-mast. — To one-third the length of the load-water line, including the main-stem or stern-post, add three times the breadth of the midship-frame, exclusive of the plank and the housing of the mast from the main-deck to the kelson, and half that sum will be the length of the main-mast in feet and inches. To find the diameter, multiplying the length by .3 gives the diameter for American pine; or 2-7ths of the length, taking inches for feet, gives the diameter for Riga timber; or, what is the same, make the diameter 1 inch for every 3½ of its length.*
4th, For the Diameter at the Top. — Rule. Make the diameter at the top 2-3ds of the diameter at the partners. When the mast is to this size at the top, and lined to the regular sweep, you have the diameter at the hounds, at which place it is left square and finished off with the cheeks.
5th, Size of the Trestletrees is 7-8ths of the diameter at the partners, at least not less than 3-4ths of the same.
6th, For the Main Top-mast. — Rule. Make the length of the main top-mast 4-7ths of the length of the main-mast.
7th, Diameter of the main top-mast at the cape, 1 inch for every three feet of the full length.
8th, Do. the size of ditto at the top, 2-3ds of the diameter at the cape.
9th, For the Main Top-gallant Mast. — Rule. Make the length of the main top-gallant mast 5-9ths of the main top-mast, and its diameter 1 inch for every yard of its length.
10th, The Length of the Main Royal-mast, from heel to pole, is 4-7ths of the main top-gallant mast, and its diameter 5-8ths of the main top-gallant mast. 11th, Length of the pole is 3-5ths of the length of the mast from heel to the rigging; diameter at the same 2-3ds of that at the cap; at the truck, 3-5ths of the diameter at the rigging.
12th, For the Fore-mast. — Rule. Make the length of the fore-mast 14-15ths of the main-mast, and its main and other diameters in the same proportions as the main-mast.
13th, Fore-top and Top-gallant Masts. — Rule. These masts are generally 19-20ths of the length of the main-top and top-gallant masts, and their diameters in the same proportion.
14th, To find the length of the Bowsprit without the Knightheads. — Rule. To 1-3d the length of the load-water line, add the ship's extreme breadth, and half this sum will be the length of the bowsprit without board.
15th, The diameter of the Bowsprit at the Stem-head is equal to the diameter of the main-mast at the partners.
16th, And its diameter at the outer end 2-3ds of the diameter at the stem,
17th, The Cleats left on for the heart of the Fore-stay are 4-7ths of the length from the knight-heads, or 3-7ths of the length of the bowsprit set in from the outer end.
18th, The Jib.boom. The length of the jib-boom is 1 1/6th the length of the bowsprit without the knight-heads; its diameter at the cap 1 inch for every three feet of its length; the diameter at the outer end 2-3ds of the diameter at the cap.
19th, For the Mizen-mast. — The length of the mizen-mast (when set on the same level as the main-mast**) is 9-10ths of the length of the main-mast, and its diameter at the partners 3-4ths of the diameter of the main-mast at the same.
20th, The length of the Mizen-topmast, Top-gallant, and Royal-masts, are 3-4ths of the length of the main-topmast, main-top and gallant, and main royal-masts, and their diameters in the same proportions.
21st, Mizen-boom and Gaff. — The length of the boom may be found by multiplying the ship's breadth by 1.2; or make it such as to be 1-3d of its length over the taffrail. Its greatest diameter should be at 1-3d of its length from the end; but if the sheet is within that distance, it must nevertheless have its greatest diameter at the sheet, which should be 1 inch for every 3½ or 4 feet of its full length; or if we multiply its length in feet and inches by .23, the product is the diameter at the sheet in inches and parts. Its diameter at the mast or cheeks is 2-3ds of the diameter at the sheet; and its diameter at the outer end is 3-5ths of the diameter at the sheet. It is lined with a rounding-sweep, the same as a yard, having its greatest diameter at 2-3ds of its length from the mast.
The Gaff may be made about 2-3ds the length of the boom, and ought to have its greatest diameter at the tail of the cheeks, or at 1-7th of its length from the mast. The diameter at this place is one inch for every 4 feet 4 inches of its length; or for the main diameter — Rule, multiply the length by .24 for the diameter in inches and eighth parts. The outer end is half the main diameter, and is lined with a rounding-sweep, the same as the boom.
22d, Of the Tops, &c. — The breadth of the main-top is half the extreme breadth of the ship, adding the diameter of the mast; or. 2d, make the breadth of the top 5-9ths of the extreme breadth of the ship.
The depth of the Trestletrees is 5-6ths of the diameter of the mast at the top of the cheeks, and their thickness 3-7ths of their depth. Their length 5½ or 6 times the diameter of the mast; or, 2d, their length half the breadth of the top.
The Crosstrees are in length equal to the breadth of the top; their siding dimension equal to half the diameter of the topmast at the cape, their depth 5-6ths of their breadth.
The length of the Cap is 3½ times the diameter of the mast-head; their breadth 1 and 3-4ths the diameter of the topmast; their depth from the 3-4ths to 7-9ths the diameter of the topmasts, which pass up through them.
23d, The Topmast Trestletrees are half the length of the main trestletrees, and bear the same proportion to the topmasts as the main trestletrees to the main-mast.
24th, The Topmast Crosstrees are half the length of the main-crosstrees, and in the same proportion of thickness.
The Cap of the Topmast is the same proportion to the top-gallant mast as the lower cap is to the topmast. Thus all the tops, caps, and crosstrees are made in proportion to the masts or jib-booms they have to support.
* The reader is requested to contrast the above rule with the following for a brig's main-mast. To 1-3d the length of the ship at the load-water line, including the main-stem and stern-post, add three times the extreme breadth per register, also the depth of the hold from the upper part of the main-deck to the top of the floor-timber, and half that sum will be the length of the main-mast in feet and inches. The diameters are found as for a ship.
** When the step of the mizen-mast is higher than that of the main-mast, such additional height must be deducted from the length of the mizen-mast, as given by the above rule.
Transcribed by Lars Bruzelius
Sjöhistoriska Samfundet | The Maritime History Virtual Archives | Masting & Rigging.
© Copyright 2000 Lars Bruzelius.