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Topic Date User

double ropes 9-Jun-2008 At 11:38:36 PM Andrew_M

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On 9/06/2008 gfdonc wrote:
>
>With ropes of unequal diameter I believe the overhand knot is "less safe"
>but can't contribute any factual information. But the punch line that
>I recall was "don't use it". This, plus the consideration that the knot
>might fail if badly tied, makes me wonder why you'd risk it?
>
>By choice I only ever rap on double-fishermans, which works in all situations,
>very safely, and I can tie it blindfolded. And I've never got a rope stuck
>because of the knot. Why shop anywhere else?
>

Because sometimes, rarely, getting a rope stuck is likely to more than just being very unpleasant... couple of examples: in a cold wet canyon under high water conditions, or in an alpine retreat with a storm brewing...

Another interesting link with actual data about pulldown...
http://www.bwrs.org.au/bwr/research/documents/1%20main%20paper.pdf

Also, another vote of confidence in abseiling with 2 ropes of different diameters, but with the note that some abseil devices with deep/grooved friction areas for use with smaller diameter ropes can sometimes cause a problem where the thin rope feeds through much faster than the thick, causing the thick rope to start doing an interesting pulley thing on the anchor sling (which can get the heart going as you imagine the sling burning through). Alpine butterflies and a biner joining the strands, all removed for the second down using a different device, will stop this.