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One important thing to keep in mind when rappelling is that each rappel setup is different and results in different rappel speeds and friction amounts. To compensate for this, you may need to adjust your rappelling setup for different rappels.
After you've been rappelling several times with different setups, you will develop a feel for how much friction you prefer and what setup will generate that amount of friction. However, it is important to know how to add or remove friction mid-rappel so that if you unintentionally go over the edge of a cliff without enough friction you will be able to fix the situation rather than careeen out of control.
Factors that Affect Friction
Following is a partial list of factors that affect how fast you rappel and some rules-of-thumb on how the factors influence rappel speed.
- Rope diameter (large = slow, small = fast)
- Rope stiffness (stiffer = slow, more flexible = fast)
- Rope condition (dry = slow, wet = fast)
- Rope condition (sandy = slow, clean = fast)
- Rope condition (icy = could be slower or could be faster)
- Person + gear weight (light = slow, heavy = fast)
- Height of rappel (slower at the top of the rappel where the brake strand is pulling itself down, faster at the bottom)
- Type of rappel device (too complicated to give generalizations)
- Age of rappel device, annodized coating (new = slow, old = fast)
- Friction mode of rappel device (see following sections for details)
- Rappel method (double strand = slow, single strand = fast)
- Angle of rappel (flat = slow, steep = fast)
The Rappel Z