CORDAGE.

Ropes, cables, and all other descriptions of cordage are distinguished by their circumference, thus a two-inch rope means a rope two inches in circumference.

To find the weight of a rope.

First method.—Multiply the length in fathoms by the square of the circumference, and divide the product by 480 for the weight in cwts.

Example.—Required the weight of 110 fathoms of 3-inch rope.

3 × 3 × 110 = 990, which divided by 480, gives 2 cwt. 7 lb. Weight required.

Second method.—Divide the square of the circumference by 4, the quotient will give the weight, in pounds, per fathom.

Example.—What is the weight of a 3-inch rope per fathom?

32 ÷ 4 = 2¼ lb. Weight required.

To find the strength of a rope, or the weight it will support.

First method.—Square the circumference, and divide by 5, for the number of tons which it will bear suspended from it.[46]

Example.—What weight will 3-inch rope of the best description support?

(3 × 3) 5 = 9/5 = 1⅘ ton, or 4030 lb. Weight required.

Second method.—Multiply the square of the circumference by 2, the product will give the practical weight in cwts. that may be lifted by it, or about half the breaking weight.

Example.—What number of cwts. may be lifted by a 3-inch rope?

32 × 2 = 18 cwts. Weight required.

The strain,in pounds,a ropewill bear safely= girt2 × 200}nearly.
””a cable” ”= girt2 × 120}