The climbing rope is what the entire safety system hangs from. Without a rope, all the other hardware is useless. Ropes are precisely engineered tools that allow people to safely push their limits, so understanding what makes them work is important.
Construction and Dimensions
Ropes are made of continuous nylon fibers and are constructed with an internal core and external sheath. The core accounts for most of the strength of the rope, whereas the sheath is woven to protect the core by providing abrasion resistance.
Single climbing ropes that are designed to be used with one strand between climbers range from about 9 millimeters in diameter to more than 11 mm, and from 150 feet (45 m) to more than 220 feet (70 m) long.
Other ropes of smaller diameters are designed to be used two strands at a time-the systems for double ropes are not covered in this hook, Some ropes are chemically treated to repel water, which is important for ice climbing.
Climbing ropes are strong because they stretch during a fall (“stain” topes, which do not stretch, arc applicable in some limited climbing situations, hut their use is not covered in this book).
By stretching, they absorb force so that when the fall is over, the load left on the system is less than the breaking strength of any of the equipment and low enough so that it will not injure the climber.
If climbing ropes did not stretch, climbing equipment would break and climbers would be hurt. When you buy a rope, it will have a tag on it with several numbers, often in unfamiliar units of measure. Do not worry; it is really quite simple. There are three important numbers:
- Maximum Impact Force – Expressed in units of force such as kilonewtons (kN). It means the maximum force that can ever he exerted by the falling climber on the rope-when the tall is over, this is the force that remains and must be held by the system and endured by the climber. The maximum impact force allowed by the UIAA is 2,680 pounds and is determined in its drop test (see the paragraph on UIAA test falls held, below). The lower the impact force number is, the more elastic the rope is, which makes for longer, but softer, falls. Most ropes have a maximum tensile strength of more than 5,000 pounds, so even under the most severe circumstances can only be stressed to about half their strength.
- Static elongation – The stretch of the rope under a body-weight load of 176 pounds (80 kg) expressed as a percentage of length. The higher the number, the more the rope will stretch when used for top-roping and rappelling.
- UIAA test falls held – The number of test falls held before failure. This is perhaps the most misunderstood number of all. A rope that is rated for eight UIAA falls does not have to be retired after you take the eighth leader fall. The number means that the rope held eight falls before failure in a laboratory test. The test fall involves dropping a 176-pound (80 kg) load 16.5 feet on 8.25 feet of rope with the rope running over an edge that simulates a carabiner. This short fall produces the highest impact force possible-there is plenty of air time to generate forces, and little rope in the system to absorb the shock.In addition, there are no knots to tighten, belayers to shift, or any other system adjustments that might mitigate the force. This test fall cannot be duplicated under normal climbing conditions. In the lab, the test fall is repeated over a short period of time until the rope fails. The rope is always stressed at the same place, and no time is given between falls for the rope to recover-a rope stretched in a fall will rebound if left without tension for a while. With each test fall, there is less elasticity left and the impact force rises; it eventually exceeds the tensile strength of the rope, and the rope breaks. The stress of these repeated falls never occurs in the real world. A climbing rope can hold dozens and dozens of lead falls and many more top-rope falls. Ropes are retired because their owners feel they are past the point of being trustworthy, not because they are no longer strong enough to hold falls.
The bottom line is that all ropes are designed to be more than strong enough. An undamaged rope can never be stressed enough to break while climbing. The most important numbers to look at when considering buying a rope are diameter and length. Once you have settled on that, then consider the ropes in that category and compare them.
If your primary use will be top-roping, then a rope with lower elongation and higher impact force may be fine; if you expect a lot of leader falls, perhaps the opposite would be better. If you are going to be hard on your rope, go fatter. If minimizing rope weight is important, go thinner. Ask the staff at retail stores to help you sort out the differences and make the best choice.
When using your climbing rope, keep it clear of sharp edges and avoid stepping on it, which can drive dirt through the sheath and cause core damage. Do not expose it to any liquid except water.
Use a rope hag to protect the rope during transport in your car and keep it clean when it is on the ground. Keep the rope away from all types of acids such as that found in car batteries, and jumper cables. Ropes should be stored in a cool, dark, dry place. Clean a rope by braiding it or putting it in a pillow case and washing it with mild, nonliquid detergents in a washing machine without any bleach.
Some manufacturers make special detergents for cleaning ropes-check the manufacturer’s tag for more information. Let the rope air dry. Always take a few minutes to check your rope before using it. Run your hand down the length of it, feeling for mushy spots, fuzzy spots, or any sheath damage. Do not gamble if you find a had spot-particularly if the core can be seen through the sheath. Cut any badly damaged sections off.
The remaining portion can be used as a short climbing rope or for building top-rope anchors. With proper use and care, a rope will last several years.