Hi there,
Hopefully someone on here can point me in the right direction.
I'm trying to find any data on the strength and especially the stability of common multi-loop knots under partial failure. Basically, which knots are still intrinsically stable if one out of two (or two out of three loops) are cut through whilst both standing ends are loaded and not parallel.
I'm trying to investigate what is the best multi-loop knot (if any) to tie to improve the abrasion resistance of an emergency mountaineering abseil anchor. For example, assume we have SINGLE loop of 5mm cord tied around a large spike (with a double fisherman's) and will be threading the abseil ropes directly through this.
It would seem sensible that tying a multi-loop knot in the loop and having the abseil ropes pass over multiple thicknesses of cord might improve the abrasion resistance in the case of untoward rope movement. However that obviously assumes that:
1) The knot doesn't significantly weaken the set-up.
2) In the case of a double loop knot, the knot doesn't still fail if one strand abrades.
[Obviously using thicker cord, multiple strands plus leaving behind a rap ring, maillon or karabiner is a better option, but in the real world that doesn't always happen.]
My gut feeling is that the Double Bowline might not be stable enough and I don't know whether other well known options (Double Figure of Eight Loop, Triple Bowline) are significantly more secure or whether other better options exist.
Many thanks in advance.
Mark