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veganboyjosh
Mar 10, 2004, 3:46 PM
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Registered: Dec 22, 2003
Posts: 1421
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hey kids...
i've been reading up on some knots, and i understand the prussik, how to tie one, how it works, etc. but i have one question about it's use. when using it (or an autoblock knot) for a rappel backup, doesn't the rope's sliding thru the knot create lots of friction on it and the rope? i thought this was to be avoided.
thanks in advance.
josh
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escale
Mar 10, 2004, 4:25 PM
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Registered: Sep 10, 2003
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For rappel backup, I put the prussic above my belay device and keep it firm but loose enough that it doesn’t “warm up” as you are rappelling. I am right handed so I keep my left hand on it loosely so that it will not set on a normal rappel. If you are rappelling so fast that either hand is getting too warm from rope sliding through it either your controlling or free hand then you are rappelling too too fast and running the risk of letting go due to burns. Stop the rappel and let things cool down.
The idea for a backup up is that if you hit your elbow or your control hand hits something that causes you to let go of the controlling end, your sudden fall will be pulled by the end of the prussic that is tied to your tie-in point on your harness and it will lock up. I have had this happened and my prussic cord got slightly melted, but it held. I retired that cord and now it is used to tie stuff to my pack.
But now, I use a shunt as a rappel backup because it is easy to unset after locking up. I still carry two cords long enough on my harness just incase I need a prussic to do some self-rescue or ascend rope or if I just stupidly drop my shunt down the mountain.
---Escale
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j_ung
Mar 10, 2004, 4:41 PM
Post #3 of 3
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Registered: Nov 21, 2003
Posts: 18690
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In reply to: hey kids... i've been reading up on some knots, and i understand the prussik, how to tie one, how it works, etc. but i have one question about it's use. when using it (or an autoblock knot) for a rappel backup, doesn't the rope's sliding thru the knot create lots of friction on it and the rope? i thought this was to be avoided. thanks in advance. josh
I retire the loops I use for autoblocks on a semi regular basis. No biggie, they cost about 60 cents.
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