Self-Equalizing Figure 8 with rope anchor--correct tying method?
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Hi All: I have used the self-equalizing figure 8 tie in at 2-bolt anchors, by tying the 8-on-a-bight and then wrapping the loop over and through the knot a second time, and collapsing the extra strand: But I frequently see instructions online that instead of looping over and through again, you should rethread the loop through the knot like this: These come up at the top of the list when you google "using rope for climbing anchor" Climbing.com equalizing figure 8 thoughtco.com equalizing figure 8 Someone actually pointed out in the comments on the climbing.com entry that if the gear on both loops on the left pull (or if you collapse the 2nd left loop, and the remaining left loop fails), then the entire knot comes undone. I think this is easy to see in the 2nd pic, although in reality the 'biners and/or gear might prevent the loop to get pulled through the knot. But this can't happen with the first method, which I learned from a book, although I don't remember which one at this point. Even if the left loops slipped through the knot and it untied, you would still be held by the last piece, although if you're the belayer you would likely get pulled into it and at best, bad things would happen. My question is, am I tying it correctly, and the other method is wrong? And if so, why is it commonly shown this way? Or will it work either way and I'm overthinking the problem? |
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I see potential for FUBAR here. Just learn the super 8. |
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Climbing .com don´t know the difference between equalising and equalised. |
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John Wilder wrote: Thanks John...the method I use works for 2- or 3-piece anchors, but is also vulnerable to the rope getting cut...but I'm not sure the bunny ears 8 is any less vulnerable to the rope getting cut? |
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Never seen it tied like that... for 2 bolt anchors my partner and I always just use the "bunny ears 8" you can equalize buy tying is loose and clipping it to both bolts then snuggin everything up. Off belay pull up the slack and clip a quick draw through the shelf and put your partner on belay in less then 2 mins... sure speeds things up!! Here is a pretty good thing on back country how to tie it. Animated knots also has it. |
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You're tying it correctly. You can verify that in Craig Luebben's excellent book "Rock Climbing Anchors", it's in the appendix. |
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John Wilder wrote: Have pull tests been done to determine the affect on knot strength if one loop is cut? Intuitively, I don't buy the it won't fail if a loop is cut, since both loops are connected in the bight that's passed over the ears, but I don't have an intuition for the internal friction of the knot. |
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Nathan Hui wrote: I get the same iffy feeling when looking at it. The guy at RopeLab has pull-tested the figure eight bunny ears, and it seems to hold: |
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John Wilder wrote: I don't get too worried about that either, although there was a story last year in AAJ about a trade route in Little Cottonwood Canyon where the leader set off from a two-bolt anchor and pulled off a large block, shearing through the left arm of the sling that had been tied into a cordelette, leaving them hanging off one bolt. If it wasn't FF2 onto a single bolt/sling it was pretty close. |
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Nathan Hui wrote: It's been tested a few times that I'm aware of. It holds on just one loop. This is super easy to replicate yourself BTW. Just tie the knot and pull one loop. The only mode for total failure would be to cut the exact spot where the "over the top" bight passes around the base of the knot - not that likely, and not something I ever worry about. |
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If the rope gets cut in one of the loops, I've very little faith in either of those knots, but it's not something I'm particularly concerned about. Aren't you trusting the rope not to get cut below this anyway? The second knot seems pretty sketch in the case where the left anchor blows. That seems only marginally better than having no redundancy at all. |
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I've never found any use for any of the bunny ears knots. Clove hitch "technology" is better because it is quickly and easily adjustable. I'm already belaying while the bunny-ears user is still fiddling with the lengths of the ears and the tie-in. |
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rgold wrote: I agree, finding it at least as fiddly as an "auxillary cord" method (e.g. cordelette, quad) with none of the advantages (ease of escape / block leading without untying). However, the bunny ears / super figure 8 has become my "go-to" anchor setup for toprope soloing from a two-bolt anchor (pretty common at the crags where I do toprope soloing). |