abseil

Required strength of belay anchors

A rigging example by Nick Bullock [©Will Sim (2014)]

There was a fatal accident in Yosemite — the circumstantial evidence implies the party placed 4 pieces of gear for the belay, then the leader took a factor-2 fall on the belay, all the gear of which ripped, and as a result the entire party was perished. In that particular case, clearly the belay was not strong enough despite 4 pieces of gear…

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Force and gravity

Ruler.  (Cropped from the original image by Ejay in http://commons.wikimedia.org/wiki/File:Steel_ruler_closeup.jpg . License: CC Share Alike 3.0)

In this world, the unit is often the source of confusion. Climbing is no exception. As an example, here is an extract from Andy Kirkpatrick's solo attempt in Troll Wall, where he had a hard time as vividly described in his own words:

[After hand-drilling a hole to place a bolt:]

I slid the bolt onto the hanger, then pushed it into the hole, but found it was a little too big to fit easily, so tapped it in with my hammer. I felt it trying to resist, but eventually felt it begin to give way. Then, after only a centimetre, it started to bend.

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