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Messages 1 - 34 of total 34 in this topic
Gorgeous George

Trad climber
Los Angeles, California
Jul 10, 2014 - 09:27am PT
I never liked the loop, preferring the single strand with a small loop tied at each end. Assuming three placements (or fixed anchors) you clip the loops into the outside anchors, and clip the middle of the strand into the middle anchor. Then you equalize and tie a figure-eight at the natural fulcrum. The knot is easier to tie and creates less bulk.
Texplorer

Trad climber
Sacramento
Jul 10, 2014 - 09:29am PT
I would use these if we changed the name to Americord.
Ed Hartouni

Trad climber
Livermore, CA
Jul 10, 2014 - 09:31am PT
http://www.supertopo.com/climbing/thread.php?topic_id=307091&msg=309947#msg309947

I hesitate to post this because of the prevailing "wisdom" that theory can't inform practice (at least in rock climbing)


bottom line is that cordelettes with unequal length "arms" to anchors transfer an unequal distribution of forces to those anchors (the shorter arms transfer more force). The force on the master point is not equalized.

second bottom line: all such equalization schemes are some combination of the sliding-x and the cordelette.

Vitaliy M.

Mountain climber
San Francisco
Jul 10, 2014 - 09:41am PT
I like a double length dyneema sling which I usually use with a sliding x set up and a lightweight phantom locking biner for my masterpoint. Saves a lot of weight. If you use dyneema don’t tie knots in it. I tie myself in to the locker with the rope (strongest possible link) using a clove hitch. So basically I save weight by not bringing a heavy ass 8mm cord and not needing the bulky daisy chain.
7SacredPools

Trad climber
Guelph, Ontario, Canada
Jul 10, 2014 - 09:46am PT
Double length sling works fine for a 2 bolt anchor but for trad I like to be able to place 3 pieces and I use a 7mm cord loop. I'm open to suggestions however, and have never thought of the cord with a loop on each end.
j-tree

Big Wall climber
Typewriters and Ledges
Jul 10, 2014 - 10:03am PT
I started using Yates Dynema rabbit runners for my anchors and never looked back. Even lighter than similar sized looped Dynema runners.

The only downside is you need to make sure your partner who has never used a rabbit runner before knows that you can't use them in a normal sliding X set-up, otherwise you get to the anchor with your eyes wide and happy you didn't try the harder variation while following.
apogee

climber
Technically expert, safe belayer, can lead if easy
Jul 10, 2014 - 10:52am PT
"The force on the master point is not equalized."

"SRENE is a lie."


And yet...there still doesn't seem to be any kind of trend of catastrophic anchor failure attributed largely/solely to an unequalized anchor.
couchmaster

climber
Jul 10, 2014 - 11:28am PT


I tie in with the rope 95% of the time and regular multipitch swinging leads. Everything else could be called a clusterfukolet.....
LEG

climber
Jul 10, 2014 - 11:34am PT
I like 22 ft of 7 mm cord - no loops, no knots pretied. Leaves me open to options.
rgold

Trad climber
Poughkeepsie, NY
Jul 10, 2014 - 12:05pm PT
Some remarks about the rabbits of a theoretical nature that I think is still worth at least thinking about.

The standard configuration for three anchors will have two single-strand arms on the outside and a double-strand arm in the middle. We already know that the shortest strand will develop the highest tension, and if that strand is the middle strand (eg anchors in a horizontal line), then doubling it will increase its "modulus" and result in an even higher tension. The result will be a more extreme inequality in arm tensions and so a more unequal load distribution to the anchor.

Does this matter? Anchors so rarely get loaded with significant loads that there is really no data from the field on any aspect of load distribution. This absence of data makes it possible to dismiss any discussions with the observation that none of the issues under discussion actually ever happen. This is, of course, false, but the occurrences are very rare. In my 57 years of climbing, I've read about a total anchor failure about once every ten years, and I have no idea how much if at all bigger the actual frequency might be.

So all we really have is some extremely simple basic theory, which is roughly confirmed by tests that may or may not be "realistic." Add to this the very substantial variation in arm loading due to variations in the tying of the power point knot, and even the theoretical predictions about loading can be obscured.

In the face of all this uncertainty, it is easy to throw up your hands and go with the whatever ploy, but I don't think that is the most rational approach to the issue. We do have some sense of what should be best in theory, and we know that a host of variables may intervene to undermine those conclusions, but in the absence of anything else, it seems to be that one might at least strive for a theoretical optimization, understanding fully that reality is going to have its own say on the outcome.

Testing suggests that, if the cordelette is knotted with care, the piece on the shortest arm is quite likely to get more than half the total load. Using the rabbit configuration can only exacerbate that result for certain common arrangements. Whether or not one is ok with that as a likely feature of their anchors is a matter of psychology, not physics or testing.
Ed Hartouni

Trad climber
Livermore, CA
Jul 10, 2014 - 12:17pm PT
To boil it down, what are you utilizing in such a scenario? A series of Xs?

No, but I do make use of the analysis, theoretical as it is.

Because it is easier to arrange a cordelette with "two equal legs" my three point anchors are built by, first, placing a single bomber anchor and using the rope to connect to that anchor with a clove hitch (which can be adjustable)

then placing two additional anchors, making sure not to share the same mechanical features where there is some uncertainty of the strength of the features (e.g. don't put all three anchors in the same flake)

equalizing the cordelette on the two pieces, then adjusting the the rope to be roughly the same length and tension when I weight the total anchor.

Generally I try to make a system where any of the three anchors would be sufficient to hold a fall from a partner.

I might add additional 'biners for a second coming up so that they can tie off quickly without having to dink around with my connection to the anchors.

I might use a cordelette, or two nylon "daisy chains" like the one made by Sterling, a chain of sewn loops.

Cordelettes are nice because of the many different ways they can be used, other than setting up a belay anchor, in case the need arises (I also have a 6mm cord to secure my chalk bag, which I can use as a prusik in the event that I need one...)

Ed Hartouni

Trad climber
Livermore, CA
Jul 10, 2014 - 12:29pm PT
the major problem with the sliding-x is that it is a single point failure, if the sling fails for whatever reason you are no longer connected to the anchors.

knotting the sliding-x defeats its function, which is to slide to equilibrate the forces. you can do an analysis for mixed sliding-x and "cordelette" configurations, but once you know the basic idea, you realize there is no "right" solution combining knots and x's...

you do have an awareness of how the forces are applied to the anchors, and the need to build reliable single-point anchors, and finally, the possibility of an anchor system failure.

The more "what if" scenarios you have too use in the choices you make in building your anchors, the better off you are.

the only way I know to address the unequal arm lengths is to have a variety of slings where the young's modulus (the "stretchy-ness" of the sling) is inversely proportional to the length of the slings, so that the tension generated from the same fractional elongation was the same for different length slings. then you color code the slings...

but that is way to complex for climbers (apparently)
Studly

Trad climber
WA
Jul 10, 2014 - 12:41pm PT
I place gear for anchors and then use draws and runners to equalize the placements, or back up a cam placement with another cam placement. You can move gear in the cracks up or down to micro manage the tension. Saves having a cordellete along, and seems me to be more bomber because you can backup each piece with usually just the right amount of tension, so if something blows there is no shock loading the system.
overwatch

climber
Jul 10, 2014 - 12:53pm PT
I use a combination of the three basic possibilities for anchoring, on a situational basis.


on a separate note I must say I like the new less confrontational burchey
the Fet

climber
Tu-Tok-A-Nu-La
Jul 10, 2014 - 01:05pm PT
I use a sliding X with pretied limiting knots, with unequal length sides
 it does a pretty good job of equalizing if tied right (the side with the loop in it is longer than the side without). It probably equalizes better than a sliding X without limiter knots
 it limits extension if one piece blows
 it would need to break in two places for it to completely fail because of the limiter knots
 super fast to deploy, works on 95%+ of placements

If I want a third piece I'll use a runner to attach it to the powerpoint with as little slack as possible.

I use partners cordlettes sometimes but they take longer to setup and don't equalize.
overwatch

climber
Jul 10, 2014 - 01:08pm PT
That is a good one too. More tools in the tool box to quote an overused phrase

Referring to the Fet of course
overwatch

climber
Jul 10, 2014 - 01:10pm PT
although that is a tool in a tool's box also
overwatch

climber
Jul 10, 2014 - 02:10pm PT
I don't know, I am just a dumb door kicker...marriage?
JEleazarian

Trad climber
Fresno CA
Jul 10, 2014 - 02:57pm PT
Whether or not one is ok with that as a likely feature of their anchors is a matter of psychology, not physics or testing.

As usual, Rgold for the win. Although I have ten fewer years of climbing experience, my knowledge of incidents of total anchor failure is similar. Most of those cases involved only a single anchor (for example the tragedy for which Anchors Away is named), failure of a vegetable anchor, or something similar. Unfortunately, a total anchor failure leaves no survivors, so we cannot determine with certainty whether unequal loading was a cause in fact of the failure.

It all comes down to mollifying our fears.

John
labrat

Trad climber
Auburn, CA
Jul 10, 2014 - 03:29pm PT
I changed over to the equalette of 7mm nylon cord with limiter knots...

https://www.inkling.com/read/how-rock-climb-john-long/chapter-5/section-5-9
Texplorer

Trad climber
Sacramento
Jul 10, 2014 - 03:30pm PT
Pertinent
https://www.youtube.com/watch?v=Vrgadjo9niY
j-tree

Big Wall climber
Typewriters and Ledges
Jul 10, 2014 - 06:17pm PT
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.
jstan

climber
Jul 10, 2014 - 06:33pm PT
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.
ruppell

climber
Jul 10, 2014 - 06:42pm PT
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.
Ed Hartouni

Trad climber
Livermore, CA
Jul 10, 2014 - 06:46pm PT
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.
rockgymnast

Trad climber
Virginia
Jul 10, 2014 - 07:20pm PT
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.
ruppell

climber
Jul 10, 2014 - 07:28pm PT
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?
Ed Hartouni

Trad climber
Livermore, CA
Jul 10, 2014 - 07:38pm PT
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)
ruppell

climber
Jul 10, 2014 - 07:44pm PT
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.
jstan

climber
Jul 10, 2014 - 08:12pm PT
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.
rgold

Trad climber
Poughkeepsie, NY
Jul 10, 2014 - 08:20pm PT
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.
ruppell

climber
Jul 10, 2014 - 08:46pm PT
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.
Ed Hartouni

Trad climber
Livermore, CA
Jul 10, 2014 - 09:45pm PT
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.
rgold

Trad climber
Poughkeepsie, NY
Jul 10, 2014 - 10:05pm PT
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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