Anchors: No extension vs. equalization

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David p

Trad climber
Mountain View, CA
Topic Author's Original Post - Sep 12, 2014 - 12:37pm PT
I've been climbing a good many years, but have been on hiatus the last few. I recently took a trip with a friend and he questioned an anchor I did and I wanted to see what the general wisdom on the matter is.

We had a simple enough 2 bolt anchor above 3 climbs we were going to be top roping (left, right, and center). I did an anchor with 2 extra long double length slings (each attached to both bolts the same), twisting one strand of each for the sliding X (two lockers on the end and all that).

My friend pointed out the that there would be a slings length worth of extension if one bolt failed, putting a shock loading on the other and called that risky. I countered the debate by pointing out that a cordelette or the like (no extension) would provide poor equalization across the 3 routes we were doing.

The last time I put much time into analyzing these kinds of things this was a tradeoff, but I vaguely recall there being some talk of an alternative to cordelettes that provided equalization and no extension, I also vaguely recall there being some talk of shock loading being a lesser evil than was previously thought.

I'd love to hear what others have to say here. Is there a better option for anchoring 2 bolts for the 3 climbs? Is the tradeoff of one over the other preferable, no extension vs. equalization?

An alternate arrangement we discussed might have been individual slings on each bolt joined to a couple half slings with a "sliding X" for equalization. This way the extension would have been only as much as a half sling allows for rather than the double sling.

David
G_Gnome

Trad climber
Cali
Sep 12, 2014 - 12:48pm PT
Clip one runner into each bolt and the rope into the other end of each.
Tvash

climber
Seattle
Sep 12, 2014 - 01:34pm PT
If one anchor point is notably mankier than the other - a non-dynamically equalized (figure 8) tied sling(s) - slightly favoring the better of the two anchors, might be better, but with two decent bolts? You're fine. You can always backup the 'mankier' anchor point with an extra sling if you've got one, too.

Cordelletes are not full strength as compared to slings or a rabbolet - not even close. Plus, they're more time consuming. I never use them.





David p

Trad climber
Mountain View, CA
Topic Author's Reply - Sep 12, 2014 - 01:35pm PT
My partner is fantastic, I trust him with my life, in large part because he asks questions like this, and certainly appreciate that he does. I would have it no other way.

I haven't heard of a rabbolet (nor has google it seems). Do you mean equalette? They were both solid bolts, I wouldn't anchor to anything less to be sure.
Aaron Johnson

climber
Bear Valley, CA
Sep 12, 2014 - 01:40pm PT


don't get hung up on the webbing anchor points
the Fet

climber
Tu-Tok-A-Nu-La
Sep 12, 2014 - 01:47pm PT
Yeah the good news is with 2 good bolts any decent setup will work fine.

For 3 climbs on 1 set of bolts I would use something that equalizes if only for the fact that the anchor point will move and the climber will be looking at less swing if they fall near the top.

You won't get equalizing and non extending. But you can minimize the extension but 1. using sliding Xs with limiter knots (I carry two, pre-tied with unequal length arms that work on 90%+ of all two placement anchors, they are tied so little binding occurs on the powerpoint biners which limits how much they equalize, I use 1 on trad anchors where I can see them or two on top ropes where I can't see them) or 2. using an equallette, something developed for John Long's latest anchor book, perhaps this is what you were thinking of. For sport anchors it's really slick.

Both of those options will limit extension to maybe 6". With all the rope in the system during a top rope that's minimal. Hell even the extension of a full length runner extending with all the rope out in a TR situation I bet the shock forces would be low.

Edit; haha as I posted this Aaron posted some great photos of those two options. Sliding X with limiter knots above and quad (which if I remember correctly is a variant of the equallette) below.

Edit 2: there's how you tie it and there's material used. Cordelletes usually use cord and Runners webbing but you could go either way. However it is best IMO to use Nylon not spectra because Nylon holds up better over time and has a tiny bit more stretch.

Rabbit runners perhaps that what was meant are a single strand runner with loops on the end, I never saw the point in them.

The sliding X photo above it extra long IMO, I use 48" sewn runners and just leave them tied all the time.

On the sliding X you can see the strand of runner that has the X in it that goes around the biners, I tie it so that's a little longer than the other strand that goes straight thru the biners to reduce binding so it equalizes better.

BTW that's what I like for biners for top ropes too. Two reversed and opposed ovals. Low friction, very unlikely to get unclipped or hung up in any way, no gates to bang against the rock.
David p

Trad climber
Mountain View, CA
Topic Author's Reply - Sep 12, 2014 - 01:52pm PT
Yeah, both of those look like the options I should be thinking of, thanks for the pictures and good discussion both Aaron and Fet!
Big Mike

Trad climber
BC
Sep 12, 2014 - 03:09pm PT
Shouldn't the real question be: will you ever generate enough force in a toprope situation to worry about it?
neversummer

climber
30 mins. from suicide USA
Sep 12, 2014 - 03:35pm PT
couchmaster

climber
Sep 12, 2014 - 03:41pm PT
Time to embrace the Clusterf*#kolette™ ™ ™ ™ or the sucko-lette™ ™ ™ ™ I guess.

I'd climb on your rig all day long. 2 slings -one from each bolt wou;d be much better than Neversummers abortion-o-lette™ up there but that wouldn't fail either.

skcreidc

Social climber
SD, CA
Sep 12, 2014 - 03:44pm PT
I like the quad too. As long as you have 2 bolts it works great for lead or following. Have it pre-rigged and its very fast and flexible; becomes an equalette with no problem. But there are endless solutions.
neversummer

climber
30 mins. from suicide USA
Sep 12, 2014 - 03:46pm PT
Better yet...explain what the issue is again with my abortionlette??
JonA

Trad climber
Flagstaff, AZ
Sep 12, 2014 - 04:29pm PT
You guys are seriously arguing about how to rig a TR anchor off two bolts that were installed for that purpose? God the Internet has made us dumb.
Vegasclimber

Trad climber
Las Vegas, NV.
Sep 12, 2014 - 04:43pm PT
No, people are actually having a discussion about climbing content so take the trolling to the political stuff.

First off, welcome back to climbing!

Like a few of the posters here, I have no issue with the sliding X and unless the bolts are manky as hell the chance of shock loading the other bolt to failure on TR is minimal with that setup. Maybe one of our residents experts that have done some actual testing on that could chime in here. When I use a sliding X I usually back up with a second sling and run the biner(s) through both.

I have been using the quad almost exclusively for the last 4 years or so. Limiting knots, equalizing, bomber and usable in many ways.
ruppell

climber
Sep 12, 2014 - 04:46pm PT
Didn't John Long do some tests for the last climbing anchors book that prove shock loading does not exist? SO that debate is way last year. As long as the anchor is redundant rig it however you want. I just clip a couple runners or draws to each bolt and call it good. For multi-pitch I use the sliding X without limiters. To each their own.
BG

Trad climber
JTree & Idyllwild
Sep 12, 2014 - 08:57pm PT
Here are a couple of self-equalizing rigging methods I often use when I know the anchor will be loaded in different directions.

Just finished a new anchoring book (with John Long): Climbing Anchors Field Guide, 2nd edition. Publication date set for Nov. 6. This is the latest in the Climbing Anchors series, featuring all-color photos and detailed analysis of state-of-the-art rigging methods including: magic X's, stacked X's, the QUAD, the equallette, the double equallette, the Joshua Tree System for rigging TRs with an extension rope, and much more.

Available right now for a pre-publication discount at amazon.com
ms55401

Trad climber
minneapolis, mn
Sep 12, 2014 - 10:00pm PT
how many climbers are going to die driving to and from the crag? I'd worry about that more than worrying whether something is five- or six-sigma, because five and six sigma isn't going to be tested in the field
ryankelly

Trad climber
el portal
Sep 12, 2014 - 10:09pm PT
is that Bill Murray of CaddyShack fame tossing his club up thread?
rgold

Trad climber
Poughkeepsie, NY
Sep 12, 2014 - 11:49pm PT
Lots and lots of testing as well as theorizing has been done on sliding X's by now. I think it fair to say that the results suggest that you cannot, in general, count on any equalization advantage from a sliding X over some fixed system, and when you get to three-anchor situations the sliding systems can be far worse than fixed ones. This means that the only advantage of a sliding X might be convenience of installation.

Shock loading. The first problem is that people use this term without having any plausible definition for it. There is in fact no reasonable definition that would not classify all climbing falls as shock loads, except perhaps for certain tightly-belayed top rope falls. So the idea that you will or will not avoid shock loads with this or that rigging is fundamentally nonsensical.

So if we can manage to forget that term, there is a question whether the extension in a sliding anchor that occurs when a piece fails will produce a bigger load on the remaining piece(s) than they would have felt had some sort of fixed rigging been used and the same piece failed. The answer is, it depends, and significantly elevated loads are most definitely possible.

The tests on "shock loading" done, I think, by Jim Ewing of Sterling Ropes for Long's anchor book only considered one of several scenarios of importance to climbers, essentially a leader fall onto a two-piece sliding X anchor. It would have been easy to predict from strictly theoretical considerations that the scenario tested would show only a neglible extension effect, because in the situation tested, the anchor extension only made a tiny change in the fall factor.

The DAV in 2009 found a 40% increase over what would have happened with fixed rigging when a sliding X failed, for example. The reason their results are so different from the ones reported in Long is, I think, because of varying relations between the actual extension and the fall height. The bigger the extension relative to fall height, the bigger the increase in fall factor due to extension and so the more effect on the remaining pieces.

A scenario of some interest to climbers that Long/Ewing did not consider is what happens in a factor 2 fall onto the belayer if the impact pulls the belayer off. In that case, the fall energy of combined leader and belayer has to be absorbed by the belayer's tie-in, and for this the anchor extension could be relatively quite large and so lead to a very high fall factor with a load of not one but two body-weights. In this case the effect of anchor extension will be enormous.

The upshot of all these considerations is that there doesn't seem to be any simple mantra to be uttered about the performance of a sliding X. Extension could matter---in some cases a lot---and the variation in performance in any one situation makes it impossible to count on a level of equalization better than one gets from fixed rigging. Although there is some room for debate when there are two anchor pieces, the performance of sliding systems for three pieces is in general bad enough that there is no reason to prefer them over fixed rigging, imperfect as it is in equalizing.

Perhaps it is worth concluding with the fact that equalization has been oversold. It is based on an assumption that the pieces themselves are more or less of the same strength. When this is not the case, equalization makes little sense, and one can even describe hypothetical situations in which equalization causes the failure of two pieces which would, however, survive sequential loading.

When two good bolts are involved, there is virtually no good case for equalization, most especially for top-roping. It makes perfectly good sense to rig so that all the load goes to one bolt with the other one as a backup in case the first one fails. Rigged this way, you get a multi-directional anchor as well.

bhilden

Trad climber
Mountain View, CA/Boulder, CO
Sep 12, 2014 - 11:55pm PT
When two good bolts are involved, there is virtually no good case for equalization, most especially for top-roping. It makes perfectly good sense to rig so that all the load goes to one bolt with the other one as a backup in case the first one fails. Rigged this way, you get a multi-directional anchor as well.

^^^^^^^^^^^^^
What he said!
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