ロープの結び方とその強さについて

Abstract

To obtain a standard for rope usage, the tensile breaking strength of various ropes tied in ten different kinds of knots has been tested in both dry and wet conditions. The ropes tested were a polyethylene, a polypropylene, a mixed one consisting of polyethylene and vinylone which comprised a 3-strand laid rope, and a polyethylene 8-strand braided rope. The commercial size was 9mm in diameter for all ropes. “Dry condition” means that the knot samples were stored at normal temperature of a room, and “wet condition” means that the knot samples were soaked in water applying a pressure of 2.0kg/cm2 for 12h. Results of tests for tensile breaking strength indicated that the optimum number of tucks in an eye splice was 4 tucks for the laid ropes, and 3 tucks for the braided rope. Percentages of the knot strength to the dry one of the eye splice although being somewhat different for both sample conditions and among the kinds of ropes tested, were roughly estimated as follows: 50% for the overhand knot and the single-sheet bend with end return, 55% for the double-sheet bend, 60% for the bowline knot and kakine-musubi and 95% for the short splice. Furthermore, percentages of the knot strength to the dry strength of the unknotted rope, if estimated as 90% for the eye splice, become 45%, 50%, 55% and 85% respectively.