One way to eliminate some of the fear and to build a more secure anchor is to build anchors "In Series."
In the past we've discussed SRENE and ERNEST anchors. The standard is that these anchors are built off of three or four pieces with a cordellete as in the following picture.
A Standard Pre-Equalized SRENE AnchorThe angles on this particular anchor are a bit wide between each of the outside pieces.
But what if it can't?
When the pieces aren't solid, you have to add more. To keep it simple, the best way to add more pieces is to add them in series. This is a method wherein one SRENE anchor is stacked on top of another SRENE Anchor. This system allows a climber to do a couple of things. First it allows one to add more pieces to the anchor. Second, it allows those pieces to be added in a simplistic way that makes sense with a cordellette or an extra sling. And third, it spreads out the weight at the powerpoint into more equalized pieces.
An Anchor In Series with a Magic X on the Left-Hand Leg
While the preceding picture may seem to tell the whole story, there is one thing to consider when building an anchor in series. One element that is terribly important to be aware of is that if a magic x (self-equalizing twist) is used in the system, it may not be as effective as a pre-equalized knot in the system.
In the picture above, the left hand leg of the cordellette terminates in a sling clipped to two pieces and equalized with a magic x. The problem with a magic x in this kind of system is that if one of those left hand pieces blows out, the sling will become limp and the weight will not automatically transfer to the other piece in the magic x. If this happens, then all of the weight will be placed on the two pieces on the right.
It's better to build two pre-equalized anchors on top of each other when working in series. However, occasionally this isn't possible and you're forced to work with a magic x. When that happens, make sure that the pieces that are not a part of the x are extremely strong.
An Anchor In Series with a Pre-Equalized Knot on the Right-Hand LegThis anchor is essentially a three piece anchor that was linked together in series
because the climber only had two double-shoulder length runners to build an anchor.
It is quite possible to build a vast anchor with codellettes and slings in series. And sometimes -- when the rock is very bad -- that is exactly what you have to do.
There are many other ways to add additional pieces to an anchor and to keep it SRENE, but for many who are just dipping their toes into the world of leading, anchors in series make a lot of sense. Most guides recommend that beginning level leaders work with anchors in series for a significant period of time before experimenting with other systems. This will help lay a solid intellectual framework of what an anchor is supposed to look like and what it is supposed to do.
--Jason D. Martin
9 comments:
Hey Jason - how about another post that combines this one and the previous one: where to use lockers in a trad anchor? When I started leading, I used lockers everywhere. Now I tend to just use a locker at the master point, and maybe on one piece of gear. It just happened slowly, but I can't really justify either way, except weight savings. Discussion would be welcome!
Chris,
Generally lockers are only required at locations where someone's life is at stake that doesn't have redundancy.
If you build a trad anchor and you have three or four pieces in the anchor, non-lockers are okay for connecting your cordellete to the pieces. This is because you have one in the system for each piece, which creates redundancy.
But a full post on this topic is a good idea!
Thanks,
Jason
Thanks for the food-for-thought on the failure mode of the magix x. Previously, I would have gone to using it on an upper segment of an anchor in series like this. Now I will give it some more consideration.
A cordelette or other "preequalized" setup is NOT the setup to use when dealing with sub-optimal placements. The lack of actual equalization makes this setup prone to sequential ripping of pieces. Much better to not let anything rip in the first place by truly equalizing the pieces. Limiter knots on the sliding X may be used to minimize "shock-loading" if any single placement fails.
See the latest edition of John Long's book "Climbing Anchors" for dynamic, real tests of anchor setups. At least two total anchor failures with cordelette setups have been reported; nobody of course knows exactly what happened, all involved climbers are dead.
@Unknown
Much of what John Long wrote in the latest installment of the Climbing Anchors series was refuted by Craig Lubben in his anchor book which came out a year or two later. Indeed, he has a chapter in the book entitled, "cordellete shit," which deals with this issue.
The American Mountain Guides Association currently accepts the cordellete as an acceptable alternative for pre-equalized anchors. There are no confirmed fatalities or anchor failures due to the use of a cordellete.
Now that said, you're right. You can't truly equalize a cordellete. The shorter cord in the system will always take a bit more force than the longer cords and that piece will be stressed a bit more than the others.
The question then is, "does it matter?"
The answer -- at least as far as most certified guides are concerned -- is that it doesn't matter enough to truly impact the system to the point of failure...
Jason
There is one other thing I'd like to address concerning your post. I'm not super-psyched about using a magic x with load limiters to equalize sub-optimal pieces. The problem is that there will be extension EVEN if you have load-limiters. This could result in failure of a second piece that could lead to a domino effect of failures.
Certainly using a magic x with load limiters to equalize two sub optimal pieces could work and isn't wrong. But as AAI's technical director likes to say, "in the mountains everything costs you something." A magic x with load limiters gives you better equalization, but could result in multiple failures. A pre-equalized cordellete doesn't give as much equalization, but isolates the pieces in a way that decreases the potential of shock-loads.
This is a great conversation and probably worthy of a blog in and of itself...
Jason
I will check out the Luebben book, maybe you can also briefly summarize his arguments here or in a separate post?
The question "does it matter" of course also applies to the oft-cited but never (as far as I've seen) quantified, field-tested or actually occurred (as a failure mode for anchors) "shock loading" with a magic x. Here is how I think about it for a sketchy anchor: if you feel that none of the pieces by themselves would be sufficient to hold a maximum impact, why wouldn't you want to equalize them as much as possible to minimize the chance of failure? In that scenario, once a piece rips, the pseudo-equalized cordelette is not going to help because of the low holding power of each piece. In the end of course, those discussions remain very theoretical because such scenarios are very rare, as are falls that would require an anchor to hold a very large load, so the combination of those events is extremely rare. The cordelette's simplicity and efficiency have me feel good enough about it in standard anchor situations, but for the most likely setup involving sketchy pieces in an anchor, I'd equalize them with a sliding x with limiter knots and use that combined point as one of the (three) legs of my cordelette.
BTW the anchor failures I am referring to were on Super Pooper in Tahquitz (with tons of info/speculations available online) and an earlier one on the DNB i believe. Of course nobody knows the details and the failure mode and whether that involved the anchor setup or its failure, but both times a cordelette setup was recovered. Of course, given that just about everyone always uses a cordelette, that is what one would suspect to find no matter what the actual cause of the accident, as long as the anchor was set up when the accident occurred...
My understanding -- without having done the route -- was that the catastrophic anchor failure on Super Pooper was due to the combination of the flaring nature of the crack the anchor was built in and a factor 2 fall.
Now I haven't reread everything from a few years ago, so I may be thinking of a different incident.
Another element to consider is the "12 Point System." In essence the idea behind this is that each good piece is worth four points and that your goal is to achieve 12 ponts in an anchor. When you can't get 12 points, you keep adding pieces until you can get it.
If you're thinking in the 12 Point worldview and have some weaker pieces, you're regularly putting things into a series and equalizing pieces on top of pieces. The more pieces you have, the more points of potential failure and when you get some really weak points (1 point pieces and 2 point pieces), I believe that keeping them isolated is a much better way to go.
But as you stated, it's all theoretical. And even if we were to do some experiments with a drop-tower, they too would be somewhat theoretical because of the fact that the biggest variable is the weakness of the pieces in the rock...
Anyway, thanks for your comments.
Jason
From what I remember re Super Pooper was that the official conclusion was that the party dismantled the anchor by taking the pieces out of the rock, stayed roped up though and slipped while walking, while people on the rockclimbing.com forum thought it more likely that a fall of the second with some slack occurred which sequentially ripped the pieces in the flared crack. The route traverses strongly at top, which would have made good equalizing with a cordelette impossible, one of the several contributing factors in this scenario.
Post a Comment