Moderator: Tim White
rebelfirefighter wrote:This might come down to preference but I'm gonna ask any way. Doing a multi drop I've seen people anchor to the bolts with a figure 8. Wouldn't it be better to use an alpine butterfly.
Mike Hopley wrote:An alpine butterfly is not meant to be loaded in that direction; a figure eight is. See Al Warild's Vertical for details.
In the event that the rebelay fails (abnormal loading), the alpine butterfly is actually better -- but the primary concern should be how it's normally loaded.
Jeff Bartlett wrote:rebelfirefighter wrote:This might come down to preference but I'm gonna ask any way. Doing a multi drop I've seen people anchor to the bolts with a figure 8. Wouldn't it be better to use an alpine butterfly.
Are you talking about rigging to a bolt pair with a double figure eight, or are you talking about watching people rig a separate figure eight to each bolt? IF you mean the latter, you are correct in that this is not the preferred way to rig a drop. But we need more info about the scenario you're describing.
Also, if you mean the latter, then it is correct a butterfly knot can be the best option for rigging a Y-hang with certain bolt configurations... but it's tricky. And if the bolts are close together, a double-figure-eight often works best.
rebelfirefighter wrote:In the scenario I'm talking about.... its one bolt, one knot
rebelfirefighter wrote:We were backed up.
rebelfirefighter wrote:Didnt have any trouble untying or other wise.
NZcaver wrote:Warild's book Vertical is a great reference (my first real caving book), but in my opinion the knot data section is misleading and some of the advice should be taken with a grain of salt.
Mike Hopley wrote:I don't think the relative strength is especially relevant, however. Our ropes and knots are almost always strong enough...
I would not worry about the breaking strength, so much as the behaviour of the knot under load.
Would an Alpine butterfly collapse and slide, when heavily loaded in the "wrong" direction?
NZcaver wrote:The difference comes down which is the slightly smaller knot, which is easier to tie/untie, which is more easily recognized as the regional norm when checked by other cavers in your party, etc. All ultimately more about ergonomics and personal preference.
Based on what I have seen during testing, no. A single bolt rebelay loaded 'normally' with the bight clipped in, no problem with either a Figure 8 bight or a Butterfly. Bolt fails, sudden abnormal loading across legs, I would still expect no great problem with either knot.
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