Should I let my rope "rest" between falls?

1:09 p.m. on January 4, 2012 (EST)
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The advice to let the rope "rest" between holding falls has been around for a while, and is mentioned in that "bible" of the outdoors, M-FOTH. From personal experience with the climbing instruction programs I run, the ropes at the indoor climbing wall tend to stretch and "flatten" after a full day of practice, then recover somewhat after "resting" overnight.

Black Diamond has several folks in their Quality Control group who investigate questions like this. They conducted some tests and posted a write-up on it here. The brief conclusion is that, yes, letting the rope "rest" between loading it by a fall does reduce the impact force somewhat. Their tests raise other questions that are mentioned and discussed in the writeup.

The link I gave contains links to other discussions of equipment, its proper use, and modes of failure, such as runners dry and frozen, as well as tests of old, worn gear.

1:41 p.m. on January 4, 2012 (EST)
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Thank you, Bill!

11:08 a.m. on January 5, 2012 (EST)
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I just read that BD QC Labs article the other day. Its a really huge benefit to us that BD has that and publishes its results. The academic freedom to try things on a whim or suspicion in a controled lab is awesome. Sort of like Mythbusters with the scientific method. I am always thankful for BD for doing this! It makes sense though, to rest a rope. The part about the knot tightening adding a little bit of shock absorption is what surprised me though. A looser knot isn't something I ever really thought about. I have thought about how hard it can be though to un-tie a figure eight on a 9mm (skinny) rope after falling on it; that can be a pain.

7:09 p.m. on January 5, 2012 (EST)
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how many hard falls can a modern rope take before you consider retiring it? 

8:45 p.m. on January 5, 2012 (EST)
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Depends on (1) what you mean by hard (Factor 1? Factor 1.5? Factor 2?), (2) whether it is a single, double, or twin, and (3) was it over an edge?

The UIAA ratings are as follows:

Single ropes 10.1-11mm are rated at 10-17 UIAA falls

Single ropes 9.5-10mm are rated at 7-9 UIAA falls

Skinny single ropes 8.9-9.4mm are rated at 5-6 UIAA falls

Half ropes (aka "double", alternating clips) 8-9mm are rated at 6-16 UIAA falls

Twin ropes 7-8mm (both strands through every clip) are rated at 12-19 UIAA falls

Static ropes should not be used to hold falls, since they provide no dynamic braking.

The UIAA rating test is pretty idealized - fall factor (1.77 IIRC), diameter of the rod over which the rope passes (supposed to be the same as a carabiner, but which carabiner??? used to be 5mm, but I think it got changed recently), the weight used, etc. And it is done with a brand new rope in a clean fall (no drag over a sharp edge). Add in the wear, how much time sitting in the sun, whether your cat relieved itself on the rope, what else was in the trunk of the car (like the old battery you intended to take to recycling), how many times your bud walked on it in the sand and dirt, etc.

With all those factors, it is best to know the history of the rope. Which means, don't buy a used rope, and be hesitant about loaning the rope to your bud, unless you really know his climbing habits well.

In the end, it is your call based on what you know about the history of the rope.

1:31 p.m. on January 16, 2012 (EST)
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coil and rest

July 24, 2014
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