New technology and design of boats and accessory equipment has enabled us to expand not only the variety and difficulty of the rivers we descend, but also the ability of the participants as well. While commitment to rescue training and equipment has lagged behind equipment developments, it's gratifying to see the trend toward rescue consciousness is finally emerging. One area of misunderstanding that needs to be brought to the surface is the proper interpretation of rope strength, appropriate usage and care.
Tensile strength is the average strength of new rope under laboratory conditions.
This is determined by wrapping the rope around two large diameter capstans and slowly tensioning the line until it breaks. The manufacturer's recommended working load is determined by taking the tensile strength and dividing it by a factor that more accurately reflects the maximum load that should be applied to a given rope to assure a comfortable safety margin and longevity of the line. Of course that factor varies with the type of fiber and the weaving construction. There are however always exceptions, most notably the fact that rope is susceptible to degradation and damage in numerous ways that are not controllable by the manufacturer. Now consider the fact that any time you tie a knot in a rope you effectively cut the tensile strength in half.