Knots, Libri GmbH Knots, Splices and Rope Work

efore taking up the matter of knots and splices in detail it may be wellto give attention to cordage in general. Cordage, in its broadest sense,includes all forms and kinds of rope, string, twine, cable, etc., formed ofbraided or twisted strands. In making a rope or line the fibres (A, Fig. 1)of hemp, jute, cotton, or other material are loosely twisted together to formwhat is technically known as a "yarn" (B, Fig. 1). When two or more yarnsare twisted together they form a "strand" (C, Fig. 1). Three or more strandsform a rope (D, Fig. 1), and three ropes form a cable (E, Fig. 1). To form astrand the yarns are twisted together in the opposite direction from that inwhich the original fibres were twisted; to form a rope the strands are twistedin the opposite direction from the yarns of the strands, and to form a cableeach rope is twisted opposite from the twist of the strands. In this way thenatural tendency for each yarn, strand, or rope to untwist serves to bind orhold the whole firmly together (Fig. 1).Rope is usually three-stranded and the strands turn from left to right or"with the sun," while cable is left-handed or twisted "against the sun" (E,3 A. HYATT (ALPHEUS HYATT) VERRILLFig. 1). Certain ropes, such as "bolt-rope" and most cables, are laid around a"core" (F, Fig. 2) or central strand and in many cases are four-stranded (Fig.2).The strength of a rope depends largely upon the strength and length of thefibres from which it is made, but the amount each yarn and strand is twisted,as well as the method used in bleaching or preparing the fibres, has much todo with the strength of the finished line.Roughly, the strength of ropes may be calculated by multiplying the circum-ference of the rope in inches by itself and the fifth part of the product will bethe number of tons the rope will sustain. For example, if the rope is 5 inchesin circumference, 5 X 5 = 25, one-fifth of which is 5, the number of tons thatcan safely be carried on a 5-inch rope. To ascertain the weight of ordinary"right hand" rope, multiply the circumference in inches by itself and mul-tiply, the result by the length of rope in fathoms and divide the product by3.75. For example, to find the weight of a 5-inch rope, 50 fathoms in length:5 X 5 = 25; 25 x 50 = 1,250; 1,250 / 3.75 = 333-1/3 lbs. These figures apply toManila or hemp rope, which is the kind commonly used, but jute, sisal-flax,grass, and silk are also used considerably. Cotton rope is seldom used savefor small hand-lines, clothes-lines, twine, etc., while wire rope is largely usednowadays for rigging vessels, derricks, winches, etc., but as splicing wire ropeis different from the method employed in fibre rope, and as knots have no