Photo Credits

Climber Jamming Bloody Fingers

Eve Preus jams her way up Bloody Fingers (5.10a) at City of Rocks, Idaho.

© Alex Kosseff/Outdoor Safety Institute

Trouble With Tethers (Climbing)

Metolius PAS Tether Spectra and NylonClip yourself into a bomber anchor with a safety tether and relax, right? Not quite. Slip off that ledge you are on and a fall of 18 inches (46cm) or less has the potential to snap many of the slings and purpose designed tethers on the market. Such an accident took place on the Grand Capucin in France when a climber fell less than two feet onto his rappel anchor while waiting for his partner. The risk of tether failure is exacerbated by two common factors: the first is slack in the system and the second is the use of Spectra (or Dyneema) tethers.

It gets worse. Even if your tether holds, the force on your body (over 10kn/2400 pounds of force) may be enough to cause internal injuries and break trad pro. Unlike a lead fall, a tethered climber is falling onto a fairly inelastic system that has limited ability to stretch and absorb shock. Tethering yourself in with inelastic Spectra is close to attaching yourself to the rock with a steel cable. There are better options but they aren't the ones getting the most hype. This is not news, much of the testing was done years ago, but tethering remains an area where it’s possible for our gear to be pushed beyond its limits.

I encourage you to read the whole article and watch the video, but here are some quick guidelines for increased safety when tethering:

1) Don't use tethers with Spectra or Dyneema components
2) Keep slack out of the system (avoid potential shock loading)
3) Never use a daisy chain for tethering (more on this here»)
4) Consider tying in with the rope when feasible, especially when belaying directly off of your harness

Watch the video to see lots of slings breaking under the impact of an 80kg (176 pound) falling object simulating a falling climber. Yes, it is true that there would likely be some more give in the system if we did drop tests with real climbers (obviously not possible). Yet other factors may increase the forces including climbers who, with all their gear, weigh a lot more than 80kg. Why push the limits of climbing gear so far? We typically have a greater margin of safety in our climbing systems than we do with commonly used tethers.

 

 



Perhaps most relevant is at 10:00 when they run some tests with shorter falls more typical of a tethering situation. This video alone is an argument against the use of Spectra in any safety tethering system. This includes Spectra-nylon combinations, which all products on the market are to some degree (Spectra can’t be dyed, so any fibers that aren’t white are nylon). View DMM's original post»

Head to the Rigging for Rescue website for more technical details on tethers. This includes their "Daisy Chains and Other Lanyards" and "An Examination of Purcell Prusiks as Personal Restraint Lanyards" with downloadable reports plus testing video featuring a variety of tethers. Also visit our article about traditional daisy chains—even if you don't use one it is important to be able to explain the concerns to your less informed friends.



guided rock climbing in city of rocks idahoClimbing instructors and guides tend to use tethers even more than recreational climbers, which is smart. Still, I've seen instructors using some questionable tethering practices. Ever see anyone clip fixed anchors on a face from above and then climb down to them? They might be facing up to a 72 inch (183cm) fall onto their 36 inch (91cm) tether. No tether or climber is going to make it through that intact.



When properly selected and used tethers can be invaluable safety tools at rappel stations, while cleaning sport anchors, or for setting up topropes. Their appropriate use for anchoring at a belay (especially when you'll be belaying the leader off your harness) is more problematic, and clove hitching in with the rope is always preferable.

Nothing in this post has any direct bearing on use of Spectra webbing in your overall climbing system. The more of your dynamic rope that is part of your safety system, the less the relative inelasticity of Spectra versus other materials is of concern. There is already misunderstanding of the issues involved floating around on internet forums and OSI does not want to add to that.

Below are OSI's recommendations for tethers (you can also grab a simple nylon runner). What do you use?


 

Purcell Prusik

Why do we like the Purcell Prusik at OSI? First of all it is convenient and inexpensive. Mostly we like it because absorbs more shock in case you slip off a ledge. Still, if you’re anchoring yourself to belay off your harness, back it up by tying in with your rope. OSI's feature on how to tie one»

 


sterling rope chain reactorSecond choice is the Sterling Rope Chain Reactor, which we like for it’s full strength loops and the fact that it is made of nylon webbing. While a little heavier and bulkier than similar spectra offerings, nylon will stretch to absorb a little more fall force. Buy it on Backcountry.com»


 


This article relies extensively on testing data from training pros Rigging for Rescue and climbing gear manufacturer DMM. These organizations deserve our thanks and support.

Visit our article on daisy chains» (the Black Diamond video is eye opening if you haven't seen it)

Posted by

Alex Kosseff

on 5/14/12
Categories: 
Field SafetyTools & ToysResource

Comments

I would like to see the same test with Sterling Rope Chain Reactor vs a Spectra Chain PAS,
Queastin : with 6” loop is there the same loads or not? Nylon will have less chance to elongate.

By Rick Krause on 06/14/2012 at 03:14 PM

Rock & Ice has a new article by Duane Raleigh on the dangers associated with short, static falls. Just be aware that the captions on the illustrations are accidentally reversed-you don’t want to fall onto your tether, but rather onto your rope! http://bit.ly/UocJNu

By Alex Kosseff on 02/04/2013 at 11:29 AM

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