To evaluate the effect of sunlight and weather on nylon cordage, Practical Sailor, with the help of New England Ropes, tested several weathered 10- to 12-year-old dock lines to destruction. The New England Ropes testing lab contained a large, dual vertical-piston hydraulic ram with a jig arrangement that allowed a line to be positioned between two attachment points that moved apart at a slow and uniform rate. Because we had a variety of lines, some with spliced ends and others with free ends, we used two differing pieces of termination hardware. The free ends were given a single turn around a large winch like drum (right, below) and made fast to a conventional cleat. Through the use of the unit’s spacing adjustment, we were able to keep the chafed ends of each line out of the test. When securing a line with an eye splice, the drum and cleat fitting on the jig were replaced with a piece of hardware that allowed the spliced loop to be held on a smooth, cylinder-shaped attachment (far right).

A load cell linked to a computer tracked the strain imposed by the jig. The amount of elongation in the tested ropes prior to destruction was impressive, but it was still shorter than the 25-percent maximum elongation that new nylon cordage will exhibit prior to failure.

Nylon Dock Line Breaking Strength