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Climbing Anchors: Evidence-Based Practices, Myths, and Assessment Tools
This blog post is intended to supplement our Three-Piece Anchors video, in which we demonstrate three different three-piece anchor configurations: what we call the “W,” the “V-Clove,” and the “Quad.” These are just a few ways to build three-piece anchors, and our video and this post are certainly not comprehensive. That being said, we want to further address some important considerations when building these specific anchors as well as principles that apply to most other anchor configurations.
First, the foundation of any anchor is a well-placed piece of pro. Strong, bomber pieces are really, really important. Nothing else matters if your pieces are junk. Take the time to practice (on the ground, mock-leading, etc) and seek professional instruction in order to competently place and assess bomber gear.
Second, it is nearly impossible to truly equalize anchors in most climbing scenarios. So- called “pre-equalized” anchors, (e.g. the W and V-Clove), are almost never truly equalized (M. Beverly). And, contrary to popular belief, neither are “self-equalizing” anchors (e.g. the Sliding-X and Quad).
Research conducted and compiled by Thomas Evans shows that with static loads, LD anchors (LD= load distributing, AKA “self-equalizing” anchors) don’t distribute the load equally between legs. This is often due to friction in the system, particularly with the Sliding-X, and is dependent on the lengths of each leg.
With static loads, Evans’ data indicates that the “load sharing behaviors of LD [self-equalizing] and LS [pre-equalized] anchors are more or less overlapping…” However, “LS [pre-equalized, e.g. the W] anchors experience higher peak loads during dynamic events.
The take away from this is that if you’re going to have a dynamic load, an anchor configuration such as the Quad will distribute the load better than something like the ‘W’. But we can’t rely on either system to equally distribute the load to each leg.
Ron Funderburke reiterates this in the Anchors blog post he wrote for the American Alpine Club (AAC, 2017);
“Anchors are never really equalized. That is to say, they never manage to equally distribute the total load of the climbing team equally to all the components in the anchor… In experiment after experiment, the most carefully constructed anchor, with the most meticulous care taken to ‘equalize’ all the components, will demonstrate that part of the anchor is holding most of the weight, most of the time. This is especially true if:
- The direction of the load alters in any way
- Any knots in the system tighten
In short, anchors such as the Quad and the Sliding-X are frequently referred to as “self-equalizing” anchors, which is not entirely accurate. As stated above, they generally don’t distribute the load equally, although research performed by Evans demonstrates that under a dynamic load, they distribute the load better than so called “pre-equalized” anchor systems, such as the W or V-Clove. It is also notable that the Quad seems to distribute loads more effectively than the Sliding-X.
Third. Despite the research, and particularly in the United States, there is much attention and effort given to “equalizing” pieces in our anchors, especially in the instructional and educational sides of climbing. We encourage the climbing community to shift away from using acronyms such as “SERENE” and “ERNESTA,” which both include “equalized” and other principles that are outdated.
STRADS
In light of the above, we propose using the acronym “STRADS”: think “trad” with an “s” on either end. STRADS stands for Solid, Timely, Redundant, Angle, Distribution, Simple. We developed STRADS in an effort to prioritize the principles it covers, with “solid’ being the first priority. The acronym also addresses old school concepts such as “equalization” and “no-extension” with more accurate terminology that reflects modern data. Let’s have a closer look…
Distribution instead of Equalization:
With Distribution, we aim to highlight the importance of giving thought to equitable distribution, instead of promoting the false assumption that we can truly equalize the load on the components in our anchor. This concept is thoroughly addressed above.
No Extension?
While “No-extension” is found in both EARNEST and SARENE, we have omitted it from STRADS for two reasons:
- Putting thought into load distribution includes taking into account the consequences of extension. That is, we should consider how the load will be redistributed if one piece fails (which it should not in the first place!).
- More importantly, data suggests that the phenomenon of extension and so called ‘shock-loading’ is not the enemy we once thought it to be. It is true that one potential drawback to ‘self-equalizing’ anchors is that there is potential for shock-loading (extension) of the remaining leg(s) if one piece fails. Though it is unlikely, this could have catastrophic consequences, especially if a dynamic rope is absent in the system. However, the shock-loading event that many of us have been concerned with for years, is probably not a major factor in most situations. This is evidenced by Evans’ tests that demonstrate that extension could result in an increased load of about 2kn when one leg fails. This type of shock-load should not make or break you (corny pun intended).
- With that being said, it is important to note that a dynamic rope was not incorporated in Evans’ experiments. Other tests have shown that if there is adequate dynamic rope in the system (3-4 meters), the force on the anchor does not increase (does not shock-load) when one leg fails. It is assumed that this is a function of the forces created by the falling mass being absorbed by the dynamic capability of the rope. Stay tuned for a blog post and accompanying video of the aforementioned test results.
In short, extension of a few inches should not matter if your pieces are bomber and there’s a dynamic rope in the system to absorb the energy.
Lastly, we believe that climbing practices should be evidence-based whenever possible. Unlike other high-risk industries, the climbing community doesn’t have ample economic resources to test each hypothesis that is proposed by practitioners, thus it is sometimes difficult to make decisions based on substantial evidence. However, an increasing amount of data is becoming available and accessible. We encourage the climbing community to question what they’ve assumed or been taught over the years and seek data to back up critical decisions. What we do while climbing, guiding, and instructing should reflect research that either debunks or confirms assumptions, instruction, and guesswork. As technology and research progresses and evolves, so should our practices.
References:
Beverly Mountain Guides:
http://beverlymountainguides.com/wp-content/uploads/2016/02/Multi_point-pre_equalized-anchors.pdf P.4, See graphs
AAC link to Anchors post:
https://americanalpineclub.org/resources-blog/2017/7/31/anchors
Thomas Evans article:
https://app.box.com/s/grcnlw1myjzzmta1q5gem7m5dugupprv