Looking with a historical perspective at river running it's astonishing just how far we have come in such a short period of time. 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. Let's start by defining two important terms: "tensile strength" and "working load". 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.

It may surprise you to find out that the working load for most kinds of rope is between 15% and 25% of the tensile strength. Now consider the fact that any time you tie a knot in a rope you effectively cut the tensile strength in half. The knot when tensioned cuts the line. While certain kinds of knots damage the line less than others, the 50% loss of tensile strength is a good general rule to live by. Our research has shown that the figure 8 knot reduces the tensile strength by approximately 35% instead of 50% for other common knots we tested.

What does all this mean to a river rat? Basically it boils down to this; use the right rope for the job. While it has been done, don't always expect to unwrap a seriously pinned raft by using a throw line, or worse, applying mechanical advantage to a throw line. The recoil forces can and have caused serious injuries when the line or some other portion of the system (like D-rings) have failed. Likewise, its not healthy to use throw lines for logging, mountain climbing or towing cars.

Aside from special training and practice, serious rescue work requires high tensile strength static line. Mountain climbers use high strength dynamic line that stretches when shock loaded i.e. when they fall. Rescue rope should always be static line that is designed to have very little stretch.

Now lets review a few types of ropes pertinent to river people. The only kinds of synthetic fibers that float are polypropylene and polyethylene. Nylon and dacron sink but are substantially stronger. Up until a few years ago and still today, nearly all commercially available throw bags were made of solid braided polypropylene, typically 3/8" diameter with tensile strengths of 900 to 1200lbs. The newer kernmantle-polypropylene lines with linear solid strands have tensile strengths between 1600 and 2000lbs. The most recent innovation is "spectra core" which has a polypropylene kernmantle and a polyethylene core. While much more costly, spectra core lines have tensile strengths of 2200lbs for 1/4" line and 4500lbs for 3/8" line.

Working closely with a braider right here in Seattle, Downstream Products, Inc. has developed new "yacht braid" poly and spectra lines with tensile strengths of 1940 and 6300 pounds respectively for 3/8" line. These lines have better grip, strength and are very supple to the hand. While I'm not advocating everyone go out and buy spectra core throw bags, having one or two in the general trip inventory is not a bad idea. Standard throw lines are perfectly acceptable for what they are designed to do and that is primarily to retrieve swimmers or assist boats in getting to shore. While working loads for these lines may only be a few hundred pounds, its doubtful that a rescuer(s) or victim(s) could actually hang on to loads over 200-300lbs.

Since every rescue situation is different its important not to get locked into any one particular mind set or approach, however a few guidelines with respect to ropes seem reasonable. If you are using a highline for a Telfor lower over ground or greater than 40 verticle feet to the water, or any situation where extreme loads can develop and rescuers are in high risk scenarios and dependent upon rope, it is advisable to be using 12mm (1/2") static line with a tensile strength between 9,000lbs and 11,000lbs. For less dramatic loads like tension diagonals or unwrapping pinned rafts, the 3/8" spectra core is an excellent choice.

How do you know if your rescue line and throw ropes are still in good condition? It certainly helps to know their history. Have the line been subjected to sustained loads, shock loads or loads over three times the recommended working load? Is the line unusually stiff in certain areas? This symptom suggests the line has been overloaded or subject to excessive heat. Are there substantially worn or cut strands in the outer construction? Has the line been exposed to prolonged periods of direct sunlight or used often in mud, sand and dirt without being adequately washed off? If any or these symptoms are present, downgrade the line to less demanding applications or get rid of it.

Casey Garland is the NW Regional Director for Rescue 3 and owner of Downstream Products, Inc. and Downstream River Runners, Inc. in Washington.

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