C_Claycomb said:
My knot book talks about prusiks needing the main line to be twice the diameter of the line you are tying the knot in...whatever relevance that has :?:
Hi Chris, what your book says is right.
As you know, Prusik, Klemheist and other similar knots loop around "fixed" rope, and slide easily easily along it when not under load, then lock tight when a load is applied along the direction of the fixed rope. One of their most valuable uses is for a climber who has fallen and is hanging from a rope to climb back up that rope. You can't do this hand over hand so you carry a couple of prusik loops ready made to give you a sliding clamp for your hands and feet.
If the prusik loops are made of cord with the same diameter as the fixed rope their tied around, they won't grip properly. They slide under load when they shouldn't. If you're climbing, they heat up and melt :yikes: To get them to grip, the cord used for the prusik has to be significantly thinner than the "fixed" rope. Half the diameter or less. Use 2 or 3mm prusik cord with a 5 or 6mm ridge cord. 5 or 6mm prusiks around a 10 or 11mm climbing rope.
Hope this makes sense of it. BTW here's the Kelmheist, an alternative to the prusik that some people find quicker to tie.
http://www.ozultimate.com/canyoning/knots/klemheist/
The loop in these demo photographs is made from cord that is much too thick - check out the words too because these are right.
Cheers, Alick