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#27890 - 03/27/07 10:02 PM Re: cordelette-attention RG [Re: chip]
rg@ofmc Offline
Pooh-Bah

Registered: 12/25/99
Posts: 2454
Loc: Poughkeepsie, NY
I think at one point I counted four or five cases I had read about involving a catastrophic anchor failure in the last ten years. Since no one is left to tell the tale when this happens, we have virtually no information about how these failures happen. Typically, the bodies and the gear are found at the base of the rocks and what happened and how it happened are matters of conjecture.

Dawn has described what I have understood about the Tahquitz accident. I don't know anyone familiar with the rock and the details of the accident who think the official S & R report is right, and there is a climber witness who heard a distinctive series of plunks that would be consistent with a sequential failure. But still, we just don't know.

In any case, the sequential failure hypothesis is almost unavoidable, since it seems extremely unlikely that all the pieces in a multi-piece anchor would be so bad as to fail at the the low loads that would occur if the impact was truly equally distributed to three or four anchor points.

As for the need for better distribution than you can get with a cordelette, we are speaking of highly unlikely scenarios and individual comfort levels with those levels of probability. I think that both Dawn's reasoning and her analogy to the EDK situation are flawed, however. The fact that there have been only a handful of catastrophic anchor failures may simply be a measure of how rare such occurrences are, rather than any indication of the adequacy of traditional cordelette rigging practices. The EDK is used worldwide and is tested almost continuously on a daily basis. Belay anchors are almost never put to the test anywhere.

My personal bet is that a significant number of belay anchors wouldn't survive, but I am not arguing that folks should throw out their cordelettes and start using any of the weird equalizing setups that have cropped up as a result of the Sliding-X thread. There are various uncertainties in climbing, and ultimate belay anchor strength is one of them.

John Long is, however, in a somewhat different position. If you are going to write for the world on what the best practice is, you have to devote some serious attention to divining what to do. It isn't enough to say, "I'm comfortable with this," you have to do better and say that, within the bounds of our still very limited knowledge, this is the best strategy for anchoring, one that will give you the best chance of surviving even those incredibly unlikely scenarios. From that perspective, it seems that cordelette-based anchoring techniques fall far short of what is ideal.

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#28088 - 04/04/07 09:43 PM Re: cordelette-attention RG [Re: rg@ofmc]
Julie Offline
Pooh-Bah

Registered: 01/16/00
Posts: 2082
Loc: SoCal
I only know what the rest of anyone knows from the SAR report about the Tahquitz accident. However, I've been to the spot(s) that the climbers are thought to have fallen from, and know the rock and area there. From the gear left on the climbers, and knowing the rock, I have two hypotheses about what might have happened.

First, there's a spot where the route they were on shares a belay with several other converging routes. One obvious place to plug gear is a horizontal crack that's about waist height, and quite varied in its size and inner geometry. It's not comfortable to sit or stand right at the gear, but a good seat/stance is a few feet directly right of that. My hypothesis in this case is that the 2nd took a (relatively) hard and/or swinging fall, and the gear in the crack rotated and pulled.

Second, above that point it's a pitch or two of mostly easy 5.0-5.3 climbing to the summit. Some climbers do simul past this point. Then once you get to the top, depending on rope drag, it's tempting and easy to put in a sub-optimal anchor ... or even hip-belay. The hypothesis here is that one of them fell and took both of them down, in the very last stages of finishing the route.

My point in writing this out is not to establish what happened; rather, to point out that we don't and can't know. What we do know is that the two climbers were experienced and able, and yet somehow, gear &/ anchor indeed failed.

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#28152 - 04/08/07 03:47 PM Re: cordelette-attention RG [Re: Julie]
Dillbag Offline
old hand

Registered: 05/02/06
Posts: 1130
Loc: "The Town"
 Quote:
gear & anchor indeed failed


Wasn't the paragraph just before this statement kinda saying... it couldn't be sure if the anchor or gear pulled?

From all the reports and conjecture that was tossed around on that accident, there are just too many different scenarios that could have played out for anyone to definitively say what happened.

Of course this doesn't mean that if testing was done on cordalettes after this and they aren't as safe as was initially thought... Well of course we should all pay attention to the new information. It's like everything with climbing, you make a choice...
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#28291 - 04/15/07 11:51 PM Re: cordelette-attention RG [Re: Dillbag]
rg@ofmc Offline
Pooh-Bah

Registered: 12/25/99
Posts: 2454
Loc: Poughkeepsie, NY
I think most people will still be using traditional anchor techniques at least some of the time. Some of the recent work on anchors provides useful practical information about strategies for anchoring with a cordelette (or tying in with the rope). I posted this advice on SuperT but is also seems to fit well in the context of the present discussion here. The assumption is a 3-point trad anchor rigged with a cordelette.

1. Use a cordelette of 7mm nylon rope. The stretch plays an important equalizing role. (But see item 5.)

2. Don't be sloppy. Slack in the arms and/or knot slippage makes a significant contribution to load inequality in the strands.

3. The strength of placements is much more important than achieving small arm angles (stretch in 7mm nylon cordelette will decrease the arm angles).

4. The shortest strand will bear the highest load. Expect it to get half the impact, so if possible the piece on the shortest strand should be the best piece, and if possible it should be the middle piece.

5. Use a low-stretch sling on an anchor piece to equalize nylon arm length if there big differences in arm lengths (otherwise the stretch in a much longer nylon arm will end up transferring most of the load to the other arms).

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#28447 - 04/20/07 02:48 PM Re: cordelette-attention RG [Re: rg@ofmc]
chip Offline
Carpal Tunnel

Registered: 10/06/01
Posts: 2674
Loc: Sittin' Pretty in Fat City
I've been using an equalette, as outlined in JL's new book and find it just as fast and more forgiving than the cordelette. The cordage can always be tied as a cordelette if you see this as a better option for a given situation. Thanks everyone, especially RG.

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#28467 - 04/20/07 09:10 PM Re: cordelette-attention RG [Re: chip]
empicard Offline
Carpal Tunnel

Registered: 08/29/01
Posts: 2952
Loc: LI, NY
can we see some pix of an equalette, or is it the same as the trango thingamabob?
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#28473 - 04/21/07 01:41 PM Re: cordelette-attention RG [Re: empicard]
chip Offline
Carpal Tunnel

Registered: 10/06/01
Posts: 2674
Loc: Sittin' Pretty in Fat City
I don't have a pic, but there is a nice one and description in JL's new version of Climbing Anchors.

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#28476 - 04/22/07 04:16 PM Re: cordelette-attention RG [Re: rg@ofmc]
paulraphael Offline
enthusiast

Registered: 01/22/02
Posts: 321
Loc: New York, NY
 Originally Posted By: rg@ofmc
4. The shortest strand will bear the highest load. Expect it to get half the impact, so if possible the piece on the shortest strand should be the best piece, and if possible it should be the middle piece.


RIght. And what seems strange to me about Mr. Long's solution (equalette) is that it automatically puts 50% of the load on the single arm of a three piece anchor.

I think there are better solutions out there ... none perfect, but ones that approach the simplicity of a cordelette, limit extension (at least to the point where the belayer won't get ripped from the ledge), and distribute loads dynamically and efficiently. I have one solution that I'm getting ready to post pictures of; I'm sure many others have yet to be discovered.

In the mean time, I'm not too concerned about these problems with the traditional cordelette. Craig Conolly's testing suggests that the maximum possible impact in a real world factor 2 fall is under 4 kn. If each individual piece in your anchor can't handle 4kn with ease, then you have serious problems: the rock is bad, the placements are bad, or the load direction is way out of line with what you predicted. In any case, this means you have no actual redundancy whatsoever, because the soundness of the anchor depends on no piece failing. If you know you have placements this weak, then you're going to need many of them, and you may to engage in elaborate equalizing to make them safe (numerous sliding Xs, etc.).

With more reasonable placements (each able to hold well over 4kn), a standard cordelette is pretty good. Each of the three arms can individually hold the fall. If a piece fails for reasons you couldn't predict, you still have double redundancy. Efficiency of distribution and sequence of loading are just not a big deal. Direction of loading is always a big deal, but more from the perspective of the individual placements than the rigging.

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#28478 - 04/22/07 07:01 PM Re: cordelette-attention RG [Re: paulraphael]
dalguard Offline
veteran

Registered: 03/22/00
Posts: 1515
Loc: CT
So I was hanging off my anchor yesterday. It wasn't a hanging belay, I was just leaning back against it while belaying, like you do, and all three arms looked quite weighted to me. They were all taut anyway. I could even shift somewhat from side to side without that changing - not a lot but say 6 inches to each side. What gives? Is that imaginary weighting? Does it not count?

I almost always, and was at that time, ledged (clipped above the knot). Does that make a difference?

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#28479 - 04/23/07 01:45 AM Re: cordelette-attention RG [Re: dalguard]
rg@ofmc Offline
Pooh-Bah

Registered: 12/25/99
Posts: 2454
Loc: Poughkeepsie, NY
Craig Conolly's testing suggests that the maximum possible impact in a real world factor 2 fall is under 4 kn.

If this were true a single black alien could withstand a factor two belayed fall. Do not try this at home folks. Think about the anchor failure that caused a fatality on the DNB a few years ago. Four pieces, none of them capable of holding 4 kN either separately or in combination. Thinking about anchoring with a 4 kN max as a guiding principle is not a good idea, in my opinion.

Look, I've never said cordelette anchoring isn't good enough for most situations, I've only pointed out, back when most people were chanting the srene mantra, that equalization part of that refrain is a myth, a fact that has now has had some experimental confirmation.

All three arms looked quite weighted to me. They were all taut anyway. I could even shift somewhat from side to side without that changing - not a lot but say 6 inches to each side. What gives? Is that imaginary weighting? Does it not count?

The fact that all three arms are under tension does not mean they all have the same tension. Failures of equalization, which can be substantial, occur because the tension in the arms isn't equally distributed, not because there isn't any tension. A properly rigged cordelette on three pieces in a horizontal crack will, if loaded in the direction it was tied for, probably distribute about half the load to the center piece and the rest to the sides arms. This seems pretty acceptable to most people, except perhaps the rescue folks, and the equalette doesn't seem to be any better for three-piece anchors. Off-axis loads on a cordelette will typically weight only one arm and set the scenario for a cascade failure if the individual pieces aren't good enough.

As for the 6-inch horizontal shift having no effect on arm tension, I don't know what the configuration was and how the shifting was measured, but if you put three pieces in a horizontal crack, rig a cordelette, and contrive to shift the power point 6 inches to the side in the plane of the rock, only one arm will be weighted. i'm not sure what the effect of "ledging" is; it doesn't seem to me that it would make any difference. Perhaps a shift could pull slack out of the cordelette power point knot and thereby maintain tension in the other two arms, but if this happens, only the center strand will be weighted by a straight-down load.

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