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Re: [sterlingjim] Doubles, rope stretch and a sore tail bone:
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billl7
Aug 17, 2008, 9:22 PM
Views: 15027
Registered: Oct 13, 2005
Posts: 1890
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sterlingjim wrote: gblauer wrote: [..]Anyway, my friend came off and watching the rope and my friend, it looked as if the belayer (who had set up the belay using an autoblock) let her zing through the belay device. My friend hit the ground at what looked like full force, as if she was not roped up at all. I'm not sure I understand how rope elongation came into play here. Given the part I highlighted above in particular. Also, It should be pointed out that a single strand of half (double) has, on average, no more static elongation than a single strand of single rope. Maximum allowed for certification for half is 12% and 10% for singles. Even though 12% is allowed for half ropes the average on the market is 10% or less. My point being that, in general. half ropes have little if any more elongation than singles ropes.
160 foot route. 10 foot fall. Three-plus extra feet of stretch (i.e., 2%) could make a very huge difference in this case.
So how much tension can a belayer from above realistically apply? Normally 35 pounds or about 1/4 of body weight at best in most cases? I think I'd still deck in this case but I'd be thankful for a pre-tensioned rope.
As a belayer, this kind of situation is when I most usually appreciate belay gloves since with them I can stand pulling harder before locking off ... and repeating ad nauseum.
Great point, Gail.
Bill L
Edit: Was going to edit to mention considering an intermediate belay if possible but goth beat me to it. 
(This post was edited by billl7 on Aug 17, 2008, 9:25 PM)
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Edit Log:
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Post edited by billl7
() on Aug 17, 2008, 9:24 PM
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Post edited by billl7
() on Aug 17, 2008, 9:25 PM
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