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#25247 - 10/29/06 05:29 AM Re: Harness Safety [Re: Julie]
rg@ofmc Online   content
Pooh-Bah

Registered: 12/25/99
Posts: 2467
Loc: Poughkeepsie, NY
Julie, read through this article on prusik rappel safety and see what you think. The failures described happened to experienced cavers.

Please, I'm not trying to start up the arguments about whether to use rappel back-ups or not, just observing that the chance they would have prevented the recent tragedy is minimal.

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#25248 - 10/29/06 02:33 PM Re: Harness Safety [Re: rg@ofmc]
fallenglass Offline
enthusiast

Registered: 08/01/03
Posts: 276
Loc: cornwall
i wonder if skinner was rapelling from a static line and whether that added any extra force to the belay loop, if the rappel was at all bouncy?

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#25249 - 10/30/06 02:43 AM Re: Harness Safety [Re: Aya]
Steven Cherry Offline

veteran

Registered: 12/23/99
Posts: 1300
Loc: New York, N.Y.
I think I'm going to go buy a new harness just because this makes me worry a little bit. My harness is in fine shape visually, but it's older...

There's a dozen things we can all think of that would have seen Todd alive today, though I don't think a prussik backup would have been one of them. (Extending the device, with or without a prussik, would have, because then the primary attachment would have been the harness, not the belay loop.)

With two extra seconds, he could have put a biner around the harness, paralleling the belay loop, and then the rappel biner could have been through it and the belay loop. Or he could have taken a 18 inches of webbing and with a water knot made a second belay loop (or with 12 inches of cord and a double fisherman's). And that could have been done back at home, right after ordering that new harness.

If there's a lesson in this, it's not to get a new harness. It's this: when a little voice says, hey, this is 0.01% unsafe, in a way that can be made safe in a few seconds, take the few seconds.

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#25250 - 10/30/06 02:21 PM Re: Harness Safety [Re: Steven Cherry]
Chas Offline
Pooh-Bah

Registered: 03/22/01
Posts: 1754
Loc: Flagstaff
Static line or notrussik or not, he would still be dead, unless he extended the rappel as Steven suggested. Adding a nylon sling loop may have helped but a biner is too rigid. You will always get multi-axial loads with a biner placed parrallel to the belay loop and asx stated on the Petzl website, it severely compramises the biner, whereas a piece of webbing can adjust to those multi-axial loads.

As his friend Paul said, after designing harness h knew what the safety factor is in the harness and it probably made him a bit complacent. That piece (the belay loop) is by far the strongest place on the harness but as a few others have said, I have found the loop on some of my friends harness's to be partially worn/ burned/ what-have-you, through (I tend to change out my harnesses more often). Now its a different story.

There is a time you just say, f$&% it and dole out some money for a new piece of gear.

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#25251 - 10/30/06 04:33 PM Re: Harness Safety [Re: Chas]
Steven Cherry Offline

veteran

Registered: 12/23/99
Posts: 1300
Loc: New York, N.Y.
Adding a nylon sling loop may have helped but a biner is too rigid. You will always get multi-axial loads with a biner placed parrallel to the belay loop and asx stated on the Petzl website, it severely compramises the biner

Let's just remember we're talking about body weight here. Even with some crossloading, a locking biner should hold 200 or 300 lbs of force. By the way, Petzl has a specialty biner designed for multi-axial situations.

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#25252 - 10/30/06 08:56 PM Re: Harness Safety [Re: Steven Cherry]
rg@ofmc Online   content
Pooh-Bah

Registered: 12/25/99
Posts: 2467
Loc: Poughkeepsie, NY
Let's just remember we're talking about body weight here. Even with some crossloading, a locking biner should hold 200 or 300 lbs of force. By the way, Petzl has a specialty biner designed for multi-axial situations.

Rappel loads are typically quite a bit more than body weight. Any time you weight a rope, the maximum tension is twice body weight , therby achieving or exceeding the 200-300 lbf figure. Various things that happen during rappelling can raise the load considerably beyond double bodyweight, and certain rappel devices (figure eights) can pry open locking biners when loaded with just body weight.

The best you can say about replacing the belay loop with a locker through both tie-in points is, "out of the frying pan, into the fire."

Edit: But...Steve's 200-300 lbf for minor axis strength is way off. Typical minor axis strengths are 7 kN or more, which is a bit more than 1500 lbf. The fact that this is still 1/3 the strength of a properly maintained belay loop remains.


Edited by rg@ofmc (10/31/06 07:29 PM)

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#25253 - 10/31/06 12:29 AM Re: Harness Safety [Re: rg@ofmc]
tls Offline
journeyman

Registered: 07/24/00
Posts: 54
Heh. Don't say that on rec.climbing, I just got torn a new one for calling carabiner-paralleling-belay-loop "notoriously unsafe". Well, that's as may be; you still won't find me using such a rig in preference to my belay loop, which presents no risk of multi-axial loading.

But you can bet I checked all the webbing on and around the belay loops on every harness in our gear room this past weekend. It's worth checking the corresponding webbing that the loop is threaded through on both parts of the harness, too; a failure of either the leg loop or waistband connection to the belay loop would not necessarily be fatal, but it sure could be highly uncomfortable and frightening.

When enough time has passed that people close to the action can talk about this more comfortably, I hope they will give a better account of just how Skinner's belay loop "looked scary". I too am remembering the BD tests of belay loops that were more than 3/4 cut and held 700 lbf; Skinner was not a big guy and generating loads higher than that on rappel seems unlikely, even as he swung under a roof, which was what evidently happened. Did that loop "look scary" in some way that would make us all wonder if our own harnesses were safe, or did it just "look scary" in a way we'd be unlikely to consider serious? Maybe next year's ANAM will let us know.

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#25254 - 10/31/06 03:45 AM Re: Harness Safety [Re: tls]
rg@ofmc Online   content
Pooh-Bah

Registered: 12/25/99
Posts: 2467
Loc: Poughkeepsie, NY
Heh. Don't say that on rec.climbing, I just got torn a new one for calling carabiner-paralleling-belay-loop "notoriously unsafe". Well, that's as may be; you still won't find me using such a rig in preference to my belay loop, which presents no risk of multi-axial loading.

Heh indeed. Funny that you woke those old mummies up for yet another round of gratuitous insults---but you knew what you were doing. By the way, I didn't say the biner through the tie-in points was worse (or "notoriously dangerous"), I just suggested that as a "solution" it is no better. ( Why replace something that---when treated properly---is 25 kN in all directions with something that has only 1/3 the strength in some directions? A backup belay loop makes more sense then that...)

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#25255 - 10/31/06 06:13 AM Re: Harness Safety [Re: Kent]
fear Offline
enthusiast

Registered: 06/27/03
Posts: 221
Loc: New England
I've just about always used a big 'ol Pear shaped locker through my leg and waist loops. Seems to keep everything oriented just right. Rated at ~28kn or somesuch closed and locked.

I'm still not clear how I can ever break that in a rap or belay with a tube-type device. I'm currently using the BD XP/Jaws-like thingy... What's the maximum clamping force I could ever hold?

Or rather, has that failure ever happened?

Please bear with me, I also have been know to run with scissors / exceed the speed limit / drink from streams / etc..

-Fear

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#25256 - 10/31/06 07:51 PM Re: Harness Safety [Re: fear]
rg@ofmc Online   content
Pooh-Bah

Registered: 12/25/99
Posts: 2467
Loc: Poughkeepsie, NY
Good question---the fact that the rope will run through the ATC at lower forces than 7 kN does make it seem unlikely that minor axis loading could break the biner.

The things we know have caused failures in this situation are figure-8 type devices levering open the gate. The same problem seems possible with Gri-gris or any device whose connection to the carabiner is, for some reason, inflexible and whose hole is large enough to allow the device to slide over the screw lock and onto the gate.

Minor axis loading is known to have caused other problems. One is the screw gate being opened by rope and ATC wire motions, and the other is the stripping of the sheath when the rope runs under tension across the region near the gate and screw.

We do not know , however, that minor axis loading is more likely with the biner through the tie-in points than it is with the biner through the belay loop---such loading is possible with both methods, and although it does seem intuitively that fixing the biner in position by putting it through the tie-in points will greatly increase the possibility for a bad outcome, I don't think anyone has studied the two alternatives statistically.

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