Kernmantle rope
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Kernmantle rope is rope constructed with it's interior core (the kern) protected with a woven exterior sheath (mantle) that is designed to optimize strength, durability, and flexibility. One or more of the characteristics may be altered somewhat, depending upon the ultimate use of the rope, at the expense of the other properties. For example, rope used in caving is generally exposed to more abrasion than other forms of recreation, so the mantle is woven more tightly than rope used in climbing or rappelling. However, the resulting rope is cumbersome and difficult to tie knots in.
Kernmantle rope is the development of centuries of rope development. Nylon ropes that were used in yachts for hauling were tested and found useful in climbing and caving, and are now the modern standard. Although there are occasional innovations, the type of rope used today is similar in construction, strength, and durability across manufacturers. There are several major manufacturers, including Pigeon Mountain Industries or PMI, Mammut, Edelweiss, Blue Water, Roca, and Maxim.
Typically, 7/16" rope has a minimum tensile strength of 7500 pounds; 1/2" rope typically holds 10,000 pounds; 5/8" rope is often rated at 12,700 pounds. Diameters and weights used in the United States are kept to English standards for ease of use, generally in the fire service.
Smaller kernmantle ropes are commonly used to make prusik knots and loops, used for ascending or belays.
Kernmantle construction may be used with both static and dynamic ropes. Static ropes are designed to allow relatively little stretch, which is most useful for hauling, rappelling, and other applications. Dynamic rope is used to belay climbers, and is designed to stretch under heavy load to absorb the shock of a fallen climber. Dynamic ropes are usually rated for a given number of falls, meaning the rope is to be retired after it has accumulated a certain amount of damage. The shock loading of a rope from a fall should be taken in context, so that a rope that has been used longer and harder should be retired sooner than the manufacturer suggests, based on the number of falls alone.
Kernmantle rope should be inspected after every use for any form of damage. "Boogers," which indicate internal damage to the kern, will appear as tufts of white threads poking out from the mantle. Ropes that have been severely stressed will have tapered sections to the rope, where it is visibly or palpably thinner. Rope that has been abraded or cut on sharp edges should be examined closely by an experienced user who may choose to cut the rope at that point, rather than risk it parting at that area.
Rope may be cleaned by chaining it, and washing it in a front-loading clothes washing machine with soap flakes. Strong cleansers, including bleach and detergent should not be used with life-critical Nylon components. Commercial rope cleaning devices are available from the climbing and rescue companies CMI and PMI. Directions for making a similar device can be found here.
