In reply to John Kelly:
> < a practice that has led to anchor failures and fatalities>
> Is that true, I don't know of an instance
> the risk as far as I'm aware appears to be theoretical..
Unfortunately yes, there have been fatalities due to this. https://www.ukclimbing.com/forums/expedition+alpine/fatal_accident_-_shock_...
I'm aware of one other, in Canada, where the anchor sling failed under a FF2. If you search the journals of the various European and North American alpone federations you may find more.
Near misses also. http://www.neclimbs.com/SMF_2/index.php?topic=2565.0
That one involving John Sherman - another one who you could point out has 'done a bit'!
Following that incident Black Diamond ran tests on slings girth-hitched to slings.
https://eu.blackdiamondequipment.com/en_GB/qc-lab-connecting-two-slings-tog...
Result of girthing an 8mm dyneema to an 8mm dyneema sling - 57% reduction of ultimate strength from 22kN (brand new sling) to 10kN.
My point about House falling IS irrelevant to the topic, as you say. I made it to illustrate how your raising his experience level is an irrelevant response to me pointing out that slings are a weak link worth highlighting in House's anchor video. Hoped that would be obvious.
It's interesting if you analyse the video for the weakest link in the chain and the most probable point of failure:
- Ice screw belay - each around 10kN assuming good ice. Less in poor ice and hard to know for sure. The video shows the norm of 2 screws equalised as a minimum for a belay.
- V-thread anchor - again around 10kN ultimate strength depending on ice quality. The vid shows the v-thread being backed up with a screw, again the norm you'd expect.
- Sling girthhitched connection. Maximum strength of 10kN if brand new. Good probability of this being lower than 10kN if a couple of years old, wet, frozen etc. No back-up. Slack in the system and the potential - not in this video perhaps but certainly in the real world involving the hundreds-thousands of people who will do this exact same thing - for a shock load in excess of the weakest link.
He has to show the ice-screw belay and the v-thread anchor, as these are what you do when ice-climbing. He doesn't 'have' to show girth-hitched slings, which is less than good practice and many people aren't aware of the strength limitations (combined with potential for high shock-load) it introduces.
Not blanket condemnation is it? Just saying it isn't always clear what the biggest risks are in the mountains and there are lots of ways to kill yourself that aren't immediately obvious. The video overlooks (in a way encourages) a big one.
Post edited at 21:07