Todd Skinners failed harness - update

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AE

climber
Boulder, CO
Mar 10, 2014 - 02:11pm PT
Interesting capsule history of harnesses, seasoned with light flaming. Forrest used bartacks, likely as that machine was available; seems there was a famous incident which revealed an inherent weakness in bar tacks, when a biner clipped into a leg loop for a belay (maybe the CMC belay tower?) ripped the thing apart. Turned out the bar tack was fine in-line, but awful when pulled to separate two layers. Of course, making micro-light harnesses has the advantage that no one would trust a leg loop for an anchor point, now?
I used 2" tubular web, wrapped twice, tied with water knot, for a swami - would have likely broken most test machines of that era. Point missed by many here is safe equipment outside the climbing bubble specifies "safe working load" which typically is no more than 10 - 20% of the maximum test. Climbing gear generally leaves much narrower margins, especially when worst-case scenarios add multiple factors all conspiring to weaken the critical link further. Wet/frozen ropes are weaker than clean dry ones, then run it across a sharp edge, then drag it sideways, under factor 1 fall load, on the one occasion in your life when you have one second to think gee, maybe this rope should have been replaced 5 years ago. . .
In regard to harness design, one gripe I have is, why is the actual final waist webbing a single flat piece usually only 1", weakened further by a tight buckle pass? Where's the redundancy there? Suppose one is belaying off the discussed belay loop directly, the leader climbs ten feet above your belay without clipping anything first, then falls, that is a factor 2 fall directly onto same belay loop and lonely 1" waist web. Amazing more incidents like this don't occur with disastrous results.
Most climbers don't think like scientists, and the few who do behave as everyone else, i.e. familiarity breeds contempt - this marginal jury-rigged system worked last week, or last year, so it most likely will work one more time. Until it doesn't.
Ratagonia

Social climber
Mt Carmel, Utah
Mar 31, 2014 - 12:39pm PT
Werner - I am honored to be spoken of well by you.

AE: Forrest used bartacks, likely as that machine was available;

Tom: Forrest used Box-Xs, as that was the cam on his 'bartacking machine'. That machine then went to the Boulder Mountaineer and got a bartack cam, then came to Jrat under the watchful eye of person-extraodinaire Kyle Copeland.

AE: seems there was a famous incident which revealed an inherent weakness in bar tacks, when a biner clipped into a leg loop for a belay (maybe the CMC belay tower?) ripped the thing apart. Turned out the bar tack was fine in-line, but awful when pulled to separate two layers.

TOM: speaking as a scientist, I think you are drawing the wrong conclusion. The problem is not with the bartack, per se, but with pulling on ANY assemblage with big forces in an unanticipated way. Are you talking the REI-harness blowout under a bridge in Oregon? Tied off to one ear of a two-ear type harness? Sad case but...

AE: Of course, making micro-light harnesses has the advantage that no one would trust a leg loop for an anchor point, now?

TOM: Good. On any harness, you should not trust the leg loop as an anchor point, period.

AE: I used 2" tubular web, wrapped twice, tied with water knot, for a swami - would have likely broken most test machines of that era.

TOM: do you have the disc and back problems that many experienced as a result of taking falls on a swami? A very dangerous way of attaching a human body to a rope!

TOM: (snarky) - Tensile Test machines come in many different flavors, from ones designed to test thread (max = 20 lbsf) to ones designed to test crane parts (max = 100,000 lbsf). Since the human body is capable of taking about 10kN max (2250 lbs), that your swami can take 15,000 lbsf is rather a non-sequitor. Thinking like a scientist includes identifying what is important and what is irrelevant. (/snark)

AE: Point missed by many here is safety equipment outside the climbing bubble specifies "safe working load" which typically is no more than 10 - 20% of the maximum test.

TOM: SWL / Safe Working Load is a different system for stating the same thing - how strong something is. It is a system used in construction based on protocols for how cranes n sh#t are used. The SWL is calculated by taking the minimum breaking strength and dividing by 5 (though the factor might vary for different pieces of equipment). In climbing we use a different system where we just report the minimum breaking strength. Your point shows a misunderstanding of what SWL means.

AE: Climbing gear generally leaves much narrower margins, especially when worst-case scenarios add multiple factors all conspiring to weaken the critical link further. Wet/frozen ropes are weaker than clean dry ones, then run it across a sharp edge, then drag it sideways, under factor 1 fall load, on the one occasion in your life when you have one second to think gee, maybe this rope should have been replaced 5 years ago. . .

TOM: not really. For evidence I provide ANAM which shows many people dying from many factors, but equipment failure is extremely rare. My climbing system is good for 2500 lbs, yet, even if I have that fourth doublebock and balloon up to 250 lbs, I still have a 10:1 safety margin. The safety margin in climbing and in the SWL system ACCOUNTS for all those crazy normal things that happen - that why both systems HAVE a safety margin built in.

But at least we agree that that rope should have been tossed out 5 years ago!

AE: In regard to harness design, one gripe I have is, why is the actual final waist webbing a single flat piece usually only 1", weakened further by a tight buckle pass? Where's the redundancy there? Suppose one is belaying off the discussed belay loop directly, the leader climbs ten feet above your belay without clipping anything first, then falls, that is a factor 2 fall directly onto same belay loop and lonely 1" waist web.

TOM: Because it works?

AE: Amazing more incidents like this don't occur with disastrous results.

TOM: Can you pull out ANAM and point to a single incident??? This is the data that shows that it works.

AE: Most climbers don't think like scientists,

TOM: perhaps I think more like an engineer. We have a huge supply of data that shows that this system works quite well; therefore we have proved scientifically that your hypothesis is not true. Publish, go find another grant...

AE: and the few who do behave as everyone else, i.e. familiarity breeds contempt - this marginal jury-rigged system worked last week, or last year, so it most likely will work one more time. Until it doesn't.

TOM: "jury-rigged" - You Keep Using That Word, I Do Not Think It Means What You Think It Means

Yes, it is good for people to think and understand about the systems that protect their lives when we go climbing. But, quite frankly, the UIAA and climbing manufacturers recognized, quite some time ago, that having everyone jury-rig their own systems, everyone be their own engineer, was not a good idea. The ultimate end of this is Sport Climbing, of course, but that is not my point. The point is that the system of engineering and standards (with the help of Zeus and Ba'al looking after fools and drunks) has been successful at creating a gear system that is pretty darn safe!

Despite the tendency of the climbing community to cling to 'it worked before' thinking, and to latch onto erroneous rumors about how to use gear, such as the one about not trusting your belay loop. So please, stop promoting rumors. Please, promote understanding and knowledge based in actual testing and engineering.

Thanks for the soapbox. Back to you, Coz...
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