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Gorgeous George
Trad climber
Los Angeles, California
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Jul 10, 2014 - 09:27am PT
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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.
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Texplorer
Trad climber
Sacramento
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Jul 10, 2014 - 09:29am PT
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I would use these if we changed the name to Americord.
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Ed Hartouni
Trad climber
Livermore, CA
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Jul 10, 2014 - 09:31am PT
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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.
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Vitaliy M.
Mountain climber
San Francisco
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Jul 10, 2014 - 09:41am PT
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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.
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7SacredPools
Trad climber
Guelph, Ontario, Canada
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Jul 10, 2014 - 09:46am PT
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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.
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j-tree
Big Wall climber
Typewriters and Ledges
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Jul 10, 2014 - 10:03am PT
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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.
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apogee
climber
Technically expert, safe belayer, can lead if easy
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Jul 10, 2014 - 10:52am PT
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"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.
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couchmaster
climber
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Jul 10, 2014 - 11:28am PT
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I tie in with the rope 95% of the time and regular multipitch swinging leads. Everything else could be called a clusterfukolet.....
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LEG
climber
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Jul 10, 2014 - 11:34am PT
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I like 22 ft of 7 mm cord - no loops, no knots pretied. Leaves me open to options.
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rgold
Trad climber
Poughkeepsie, NY
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Jul 10, 2014 - 12:05pm PT
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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.
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Ed Hartouni
Trad climber
Livermore, CA
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Jul 10, 2014 - 12:17pm PT
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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...)
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Ed Hartouni
Trad climber
Livermore, CA
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Jul 10, 2014 - 12:29pm PT
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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)
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Studly
Trad climber
WA
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Jul 10, 2014 - 12:41pm PT
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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.
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overwatch
climber
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Jul 10, 2014 - 12:53pm PT
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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
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overwatch
climber
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Jul 10, 2014 - 01:08pm PT
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That is a good one too. More tools in the tool box to quote an overused phrase
Referring to the Fet of course
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overwatch
climber
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Jul 10, 2014 - 01:10pm PT
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although that is a tool in a tool's box also
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overwatch
climber
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Jul 10, 2014 - 02:10pm PT
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I don't know, I am just a dumb door kicker...marriage?
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JEleazarian
Trad climber
Fresno CA
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Jul 10, 2014 - 02:57pm PT
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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
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SuperTopo on the Web
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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
Let us know!