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j-tree
Big Wall climber
Typewriters and Ledges
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Jul 10, 2014 - 06:17pm PT
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Checking out the rabbits. I'm assuming you'd clip the ends to the outside two pieces, clip the center to the third, overhand the bottom of the W you create and call it good?
That works. From above, there's obviously issues with the third arm. I find myself equalizing two pieces into one and creating a rabbit runner to two points, but even then you end up looping extra webbing to one of the two points so *throws hands in the air* I usually say whatever and keep climbing. I've gotten so used to ridiculous anchors on bigwalls (none of that tradewall three bolt fun) that when I'm freeclimbing I look at my two to three C1 pieces and am happy.
Never had a problem with untying the master point in Dynema (and you can always toss a biner into the knot if you're expecting a lot of force to hit the anchor) and the issue of knots in Dynema is another hands in the air situation for my personal comfort with safety.
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jstan
climber
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Jul 10, 2014 - 06:33pm PT
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I have had few memorable climbing events. I'll repeat a prior discussion of THE most memorable.
PT was going to participate in a rappelling class with twenty other people. I saw a single sling sliding X( I guess) being used to anchor to three trees the smallest of which had a three inch diameter. As I have said before, I would have trusted my truck on any one of those trees. (Mind you that is my truck.)
No redundancy for a class of twenty people.
I strongly suggested to her that we should make tracks, which we did.
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ruppell
climber
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Jul 10, 2014 - 06:42pm PT
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I use a 4' length of webbing. With a sliding X and a clove. lol If you need to extend a piece just use a two footer to do it. I never understood the cordelette and most likely never will. For those worried about redundancy in the system just clip into one of the anchor points with the rope. Now you're redundant. Unless the rope fails. Hence why I climb om doubles.
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Ed Hartouni
Trad climber
Livermore, CA
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Jul 10, 2014 - 06:46pm PT
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I pretty much enjoy climbing, not sure why you might infer that I don't... part of that enjoyment comes from doing it safely.
There are no analyses of how good our belay anchors are, as many people have pointed out. So any discussion is basically "theoretical."
John Long advocated in some edition of Climbing Anchors the cordelette because it looked "equalized" but a simple analysis would have shown it was not. The analysis was done only after tests were performed and data crunched, the analysis agrees with the theory.
A single anchor is certainly possible of holding the most horrendous of falls. Judging whether any particular single anchor will hold a fall is difficult because of the number of variables involved, many are basically unknown (e.g. how good is the rock the anchor is placed in?)
So we mitigate the risk by putting in multiple anchors.
Since there is a probability that these anchors might fail sequentially we try to arrange a situation where the force of the fall is distributed over all the anchors under the assumption that if we reduce the force on any anchor it has less a probability of failing.
That is a largely untested assumption, certainly the force required to blow one of your anchors cannot be known in advance, so even if you put in 3 and connive some configuration that distributes the force so that 1/3 goes to each, you might still end up blowing one of them.
We argue that it is unlikely that we'd blow all three anchors, once again, this is an assumption that has no basis, since we cannot state what the probability of a single anchor failure is.
We also know that in some cases where the anchor is "challenged" in a fall it fails. We do not know what the likelihood of a anchor failure is when the anchor is not challenged.
So you can throw your hands up and decide that, most likely, this is not an issue, since it never happens. And you'd probably be safe throughout your climbing career doing so.
But you don't know if you would be or not... you might just be lucky. And you'd only really know that if you were unlucky once.
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rockgymnast
Trad climber
Virginia
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Jul 10, 2014 - 07:20pm PT
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I don't always use a cordalette. I often use the climbing rope. I try to use whatever system I think is best for the pro/belayer stance/who is leading the next pitch, etc.
For years I used a cordalette tied in a loop. I was exposed to using it in an open length (i.e. figure 8 knot tied on both ends) some years ago and I now keep my cordalette tied in this configuration.
Having it tied this way gives me more belay options without having to untie a loop cordalette and converting it to the open length and back again (a very time consuming number of steps).
I can use it as a "conventional cordalette" by clipping both figure 8's into the same biner and tying it as usual:
If I need more reach to get to more distant pro, I can tie it in a "webolette" fashion:
As some previous posters have mentioned, a webolette does not truly equalize (theoretically it is 25%/50%/25%). If that is a concern, this open length cordalette can be configured into all single strands very easily:
Having an open length of cord can also allow you to reach very distant pro locations (i.e. small tree 15+ feet away by girth hitching it) and incorporating it into a belay anchor with other gear pro closer to the belayer.
I just find having it full length gives me more options without any tying and untying of knots.
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ruppell
climber
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Jul 10, 2014 - 07:28pm PT
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We argue that it is unlikely that we'd blow all three anchors, once again, this is an assumption that has no basis, since we cannot state what the probability of a single anchor failure is.
But we can assume that it has basis. If not their would be bodies littered all over the base.
Total anchor failure is rare. Why?
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Ed Hartouni
Trad climber
Livermore, CA
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Jul 10, 2014 - 07:38pm PT
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total belay anchor failure is rare because there are few falls that actually load the anchors much beyond body weight. When was the last time you held a factor 2 fall?
the forces of falls are largely damped by the other parts of the system, the ropes and the anchors along the lead... which do blow occasionally.
But we don't know about any anchor failure unless it is reported, and that is usually only for a serious injury accident.
most belay anchors never hold much more than body weight (aid anchors might hold static loads up to 500 lbs)
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ruppell
climber
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Jul 10, 2014 - 07:44pm PT
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Sure. How about the pieces that make up the anchor? I've fallen on a lot of gear. Well over 100 placements. I've only had two pieces ever fail. One broke the rock it was placed in and one was just a crappy piece. So my first hand observation is a 2% failure rate with normal forces. Assuming a factor two fall onto the anchor what is the probability that all three pieces fail?
We don't have that data but you'd have to agree the chances would most likely be pretty small.
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jstan
climber
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Jul 10, 2014 - 08:12pm PT
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Forces on the anchor are surprising. Everyone really should go out and measure this a few times.
As has been stated things like the length of rope in the system are critically important. Tie your swami into an anchor and drop six inches. Don't try dropping a foot.
Using a piece of perlon I made a device for measuring peak force, and then dropped a US army duffle bag filled with 165# of shale about 40 feet. Free fall. When a belay was given I got about 500# on the anchor. When I tied the belay to a big tree I measured about 1000#. There was about 100 feet of rope in the system.
I also set up to watch the failure of a nut from close by in the same kind of fall. I thought I might be able to see how it failed. I used a rusty old 1/2" angle as the backup. About all I saw was a big cloud of rust. The duffle bag was cool with the whole affair.
PS
Don't take anyone's word on this. Go measure.
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rgold
Trad climber
Poughkeepsie, NY
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Jul 10, 2014 - 08:20pm PT
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Ruppell, we're speaking about forces that might be triple the ones your "normal" falls engendered, so any attempt at extrapolation from that personal experience is going to be seriously flawed.
But that may not be the point. Suppose we stipulate that the probability of failure of your belay anchor under a severe fall (and factor 2 isn't the worst, the worst is factor 1.8 with the belay redirected through the belay anchor) "would most likely be pretty small." Of course we have absolutely no practical clue what "most likely pretty small" actually means. In a lot of statistical work, "most likely pretty small" means 1 in 20. That doesn't sound good to me for a belay anchor, although the owner of Metolius has stated that's about what you can expect from a cam placement. In high-precision manufacturing, "most likely pretty small" means "six sigma," or very roughly 1 in 300,000. BD rates its gear to "only" 3 sigma standards, meaning the probability of failure at a load below the given rating is about 1 in 770. So how does 1 in 1000 sound for a probability of catastrophic belay failure? Is that "pretty small?"
Part of this is to suggest that it doesn't matter that the probability of total failure is "pretty small." The smallness is certainly is of little consolation if you find yourself and your partner(s) plummeting to the ground. The question some folks find worth discussing is, "are there simple rational ways to make failure less likely?" The mindset is that we don't know what the odds are, and even though we believe them to be massively in our favor, we are not against trying simple things to make them a little better, and avoiding obvious things that will make them a little worse.
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ruppell
climber
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Jul 10, 2014 - 08:46pm PT
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You guys are the math wizards here. If you say a standard probability of a single cam failing is 1/770 I believe you. My carpenter brain says even with two cams that ratio goes way up. With three even higher. Also how is BD testing their cams? The point is anchors don't fail often. Hence the "small" chance. I'm all about climbing as safe as possible. I just don't worry about my belay failing.
In situations where a fall onto the anchor can occur I always have my belayer tie off at least ten feet down from the anchor. Then I clip a piece of the anchor and climb. Luckily, I can climb pretty well and have never actual taking that fall. If I ever do though it's at least reducing the fall factor significantly. It also provides an adding benefit of the belayer being able to get out of the way.
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Ed Hartouni
Trad climber
Livermore, CA
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Jul 10, 2014 - 09:45pm PT
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an anchor failed high on DNB, three pieces, leader on easy ground took a force 2 fall on it not too far out,
it is speculated that the three pieces were all behind the same flake, and the flake blew...
don't do that...
the party of two experienced climbers went all the way to the ground.
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rgold
Trad climber
Poughkeepsie, NY
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Jul 10, 2014 - 10:05pm PT
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Actually Ed, that was four pieces. The party was using 9mm half ropes and the anchor was constructed using both ropes. One rope has a blue Alien and a #4 BD stopper clove-hitched in series, the other rope had a purple and a green camalot clove-hitched in series. The leader had about 25 feet of rope out and no protection or carabiners were found on the rope, so possibly a 50 foot factor-2 fall. I don't think anyone knows for sure exactly where the fall happened or whether the leader was, in fact, on easy ground; the DNB is rather run out in some places. All we know for sure is that the four anchor pieces blew. These were very experienced climbers, by the way, and they had recently done a bunch of other hard Yosemite routes.
The AAC Accidents in North American Mountaineering 2002 has these details. The report mentions that "at least 5 other cases of complete anchor failure (protection pulling out---not breaking) have occurred in the last 30 years in the Park."
This means I have to substantially revise my "one failure every ten years" remark.
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