The Sea-Man's Vade Mecum, 1707.

Concerning the Masts of Ships.

From the Length and Breadth is gained the Main Masts Length, and all the other Masts; also the Yards are derived from thence, but there is different Proceedings in this case, according to the largeness of the Ships: Thus the Main Masts of small Ships are to be 3 times as long as the Ship is in Breadth; as a Ship of 20 Foot broad, by the same rule must have a Mast of 60 Foot long.

Others for greater Ships, add the Breadth to the Length, and to that the half Breadth, which Sum they divide by 5, and the Quotient is the number of Yards; as a Ship 114 Foot long, and 34 Foot in breadth, the Breadth added to the Length, and the half Breadth added together, make 165; that divided by 5, yields 33, and so many Yards is the length of that Mast; the Fore Mast must be a Yard shorter at the Head: that is to say, besides the height of the Step, which in most Ships standeth higher from the bottom of the Ship than the Step of the Main Mast; the Fore Mast must be shorter by that difference, and one Yard more; the bigness of the Ship considered, may be 4 Foot shorter at the Head, besides the difference following:

        5) 168 (33 Yards the Masts Length
The Top Masts two thirds of the length of the Lower Masts.

The Main Yard to be 2/3 and 1/12 of the Main Mast; as in the Mast aforementioned of 60 Foot long, two thirds of 60 is 40, and the 1/12 of 60 is 5, added to 40, makes 45, for the length of the Main Yard.

The Fore Yard to be 6/7 of the Main Yard; as the Main Yard being 45 Foot, divide 45 by 7, so cometh 6 in the Quotient, and a Fraction remaining of 3, signifying 3/7, so that the 1/7 of 45 will be 6 and 3/7; you must take 6 times so much, as 6 times 6 makes 36, and if you take 6 times 3/7 make 18/7, that is two whole Numbers and 4/7, which added to 36, makes 38, and 4/7 of a Foot for the length of the Fore Yard.

The Topsail Yard must be half the length of the Lower Yards; the Mizen Yard usually is made of equal length with the Fore Yard; the Crossiack Yard of equal length with the Main Topsail yard, and the Mizen Topsail Yard to be half the length of the Cross Jack Yard.

The Mizen Mast to be of the length of the Main Top Mast from the upper Decks, and so much longer as in the heighth of the Ship between Deck; and Boltsprit to be of length equal to the Fore Mast, from the upper Deck of the Fore Castle upwards.

Fore the bigness of these Masts, to a Yard in length ¾ of an Inch, or else ¼ of an Inch to the Foot; and so of Yards likewise, only the Boltsprit something bigger, would be the better, if he be made as big as the Fore Mast.

The Spritsail Yard in length 2/3 of the Boltsprit; the Spritsail Topsail Yard, as of the rest, to be ½ the Spritsail Yard; the Mizen Yard in bigness, but ½ Inch to a Yard.

[pp 131-133]

Transcribed by Lars Bruzelius

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Copyright © 1996 Lars Bruzelius.