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Rope sheath for aid webbing?
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Aug 24, 2005, 3:36 PM
Post #1 of 3 (1025 views)

Registered: Aug 24, 2005
Posts: 37

Rope sheath for aid webbing?
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There was a thread a few weeks back that discussed the pros and cons of various webbing diameters for aid climbing. When reading it, I remembered in Twight’s Extreme Alpinism he mentioned using rope sheath material as sling material for alpine rap anchors. That got me thinking . . . the retired 10.5mm rope in my basement could be 50 meters of aid runners! I cut off a few feet of an old rope, pulled out the core with some pliers, and tied it into a 2-foot loop with a double fisherman’s knot. I even did some rudimentary drop tests off a deck, giving it a few factor 1.5 falls (approx) with a haulbag loaded with about 100 lbs.

Now it’s pretty tempting to tie up a few of these for easy aid climbing, but I need to hear from Those Wiser Than Myself before I do.

So, you engineer folks (and those who like to break gear and find out what it can really hold), a few questions for you.

1 – Is using a tied rope sheath reasonable for aid runners? (I still am not confident enough in the sheath that I would place it where I could take a real fall onto them, but alternating them with “real” runners for C1 placements seems pretty reasonable.)
2 – Has anyone done this? If yes, any problems/breakage stories?
3 – What kind of knot would people recommend for tying rope sheath into a loop?
4 – For the gear breakers: Can you test some loops of tied 10.5 mm rope sheath and report here what the average break rating is?



Aug 24, 2005, 4:14 PM
Post #2 of 3 (1025 views)

Registered: Jan 15, 2003
Posts: 1277

Re: Rope sheath for aid webbing? [In reply to]
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If you feel confident skipping placements on C1 terrain, why bother putting a sling n them. Backclean.


Aug 26, 2005, 3:26 AM
Post #3 of 3 (1025 views)

Registered: May 28, 2003
Posts: 471

Re: Rope sheath for aid webbing? [In reply to]
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unless I am mistaken, it is not about using just the sheath, it is rather about using more supple material, which may be helpful for tie-offs.

using sheath material for rappel anchor may be appropriate because of low max force. Using it on pro where it is girthitched to a sharp-edge piece of metal and terminated with a double fisherman knot is something different. You are probably in the right direction trying to test the thing, but you are probably weighting 2x you test bag.
I believed I have read that 30-40% of the strenght of a new dynamic rope comes from teh sheath. I can not vouch for that figure.
computation show that if you weight 90kg and fall with ff 1.5 with a 10.2 rope belayed on a grigri, the anchor point would see more than 1100 DaN

2 points to consider:
- a sheath without a core ought to be similar to tubular webbing, check out the strengths published by manufacturers .
- why did you retire your rope if you consider that is is safe enought to use the sheath ???

I have seen guides using sling made of thinned 8mm rope instead of 6 mm nylon. They would remove some of the core strands from 8 mm rope and pull back the sheath before melting the ends. This produce a very loose/supple piece of material which you can thread more easily or use as prussik.

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