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Topic - Dyneema Slings Problem?

Rob Naylor - on 09 Apr 2006
In the past we've discussed the potential failure of dyneema slings when larksfooted (heat/sawing action if the sling edge on the flat tape as the larksfoot tightens) and the tests Chris Harmaston (formerly of Black Diamond) did some years ago, larksfooting (girth-hitching) dyneema and nylon slings together.

However, last weekend when climbing in Wales I heard some disturbing news about tests recently carried out, I think at Plas y Brenin.

As I understand it, a dyneema sling was clipped into solid gear, an overhand knot tied in it, and an 80 kg weight applied to the other end. the sling was then set up horizontally from the gear, and the weight released.

The test was repeated a number of times and every time the dyneema melted through at the overhand knot, depositing the weight on the floor.

Now I appreciate that we've discussed not climbing above the belay point on a sling before (I believe someone died last year or the year before, climbing above their first anchor when clipped in on only a sling to set another anchor for the stance). It's probably quite rare for people to do that, but I reckon it'd be quite common for someone anchored with a dyneema sling to be placed with the sling coming at a horizontal angle off the anchor. I've also seen knots tied in slings quite frequently to either shorten them or to create 2 independent sets of loops.

Apparently the dyneema in the above tests failed due to its significantly lower melting point than nylon. Nylon slings don't fail in this manner.

Now admittedly I heard of these tests second hand, but from someone very close to the people who'd done them. I'd be interested to hear from anyone who has any more information on this. When I left Wales on Monday, I left a very experienced climber and former long-standing instructor at PyB so worried about what we'd heard the night before that he was systematically going through his gear removing all dyneema slings and putting them on one side pending more information.

Was he adopting "bird flu-itis" or being sensible?
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