RAPPEL SAFETY HITCHES REVISITED
By Brady Robinson
Dr. Gary Storrick made a compelling case against the conventional use of the prusik as a rappel belay method in his article "Prusik Rappel 'Safety'" in the No. 42 issue of Nylon Highway. While citing an impressive array of accident reports, Storrick argued that when something goes wrong with a prusik belayed rappel, the natural human reaction is to grasp the prusik knot ever more firmly - exactly the wrong thing to do. The "negative action" required to effect the prusik belay is completely counter-intuitive. Even experienced cavers were largely unable to force themselves to let go of the prusik in a simulated out of control rappel.
I agree with Dr. Storrick on many of his points. Clearly, placing a prusik above the rappel device provides a marginal backup at best. However, there are other options. Dr. Storrick described the use of a friction hitch below the rappel device, but then rejected the idea, since there is a possibility that the hitch could enter the rappel device, rendering the backup ineffective. While no technique is foolproof, I think this latter, "friction hitch below" method deserves some more attention before we categorically reject all forms of friction hitch rappel backups.
To set up this type of backup the rappeller clips the friction hitch onto a leg loop of the harness, so that the friction hitch is below the rappel device, right near the brake hand. As the rappeller descends the rope, he or she must keep the brake hand on or just above the hitch to keep it from grabbing. This method is superior for several reasons. If the rappeller loses control, the friction hitch only needs to apply the same amount of friction as the brake hand, since the brunt of the friction is still provided by the rappel device. This greatly reduces the risk of the hitch melting out. Another advantage is that the hitch keeps the rope on the rappeller's brake side, so the rope can't easily get away from the rappeller's brake hand. This seems to have been a contributing factor in a number of rappel accidents. And perhaps most importantly, grasping the knot tighter - the very action that was so disastrous in the old method - will stop the rappeller. If you panic and hold the hitch really tight, your hand provides friction, and you stop. If you let go, the hitch provides friction, and you stop. Idiot proof, right? Well, not exactly.
In the December 1997 NSS News, American Caving Accidents (p414-5), there is an account of an accident involving the use of the "friction hitch below" method. The group involved had marked their ropes at various intervals with duct tape. As one man descended, his prusik caught on the tape and became stuck. The man was unable to rescue himself, and a dangerous hour long epic ensued. Clearly, this man's inability to rescue himself from such a relatively benign predicament was a contributing factor. However, had the prusik (or the tape!) not been there in the first place, this incident wouldn't have happened. There is a solution. Aside from removing any globs of tape from your rope, it's a good idea to use a Penberthy or an auto-block instead of a prusik. The prusik provides too much friction and can lock up, causing unneeded hassles. A Penberthy or auto-block with several wraps provides adequate friction and is easy to release, even when weighted. Experiment and see how many wraps work best for you. (To make a Penberthy, take a strand of cord (5- 7mm), tie overhand bights on both ends, wrap the cord around the main rope in a flat spiral several times, and clip both overhand loops to a carabiner. To make an auto-block, take a closed loop of cord, wrap it around the main rope several times in a flat spiral, and clip both bights of the looped cord to a carabiner.)
Another concern is the length of the safety hitch. It should be short enough so that there is no way it could get pulled up to the rappel device. Obviously a Penberthy sucked into a rappel rack isn't going to do anybody any good. So either make your friction hitch cord short, or do what a lot of AMGA (American Mountain Guides Association) guides do and extend your rappel device. To do this, take a standard 1 1/2 ft loop of webbing, pass it through your harness, and clip it into your rappel device, doubled up. In addition to keeping your device clear of the friction hitch, some people appreciate being able to get their brake hand further underneath the rappel device to create more friction, since their hip is no longer in the way. Try it.
The "friction hitch below" technique isn't perfect, but I have found it to be a valuable tool, especially on exploratory rappels. As I'm descending, looking for another station, or perhaps just enjoying the view, I can stop at any time with my hands free. It is also an effective backup to the brake hand. The consequences of losing control on a rappel can be dire. It only has to happen once in your career to be significant. Rocks can fall and experienced people can make mistakes. There is no shame in redundancy when your life is on the line, be it a friction hitch, a fireman's belay, or a friend checking your harness.
I believe the "friction hitch below" technique is a useful tool, but like any tool, it has limitations and can be misused. Experiment with it and make your own judgments. As Dr. Storrick wrote, "safety is not given by any gadget but is the property of one's attitude and experience."
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