Babyhagrid
Well-known member
I find a bowline on the bight works much better than a fig 8 for each of use and for undoing. Not sure if there's a disadvantage I don't know of yes
Relative knot strengths
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andrewmcleod
Well-known member
The minor possibility of theoretical death in highly unusual circumstances, hence a preference amongst some for the Fusion which maintains the easy-to-untie nature of Bowline-on-the-Bight (search this forum for details somewhere).
This summer I successfully untied, in a reasonable time, fusions knots that had been on the main trade route of WUG Pot in the Dachstein for probably around 12 years and would have had hundreds of trips loading it. Try doing that with an Alpine Butterfly or a Fig 8 bunny ears.
Babyhagrid
Well-known member
Yes , fusion knots are much nicer for Y hang rigging
Babyhagrig: 'I find a bowline on the bight works much better than a fig 8 for each of use and for undoing.'
I assume that you mean here that you would use a B-o-B in a single bolt rather than as a Y-hang, if it's to replace a figure-8?
whereas when andrewmcleod says: 'The minor possibility of theoretical death in highly unusual circumstances' I assume that he's referring to its use as a bunny's-ear knot and you clip into one of the loops.
So – that's 2 different uses for the same knot, both (in my opinion) perfectly OK. I sometimes use a B-o-B to tie into a single bolt as it's easier to untie than is a figure 8, while I now tend to use a Karash knot (fusion knot) for Y-hangs.
I assume that you mean here that you would use a B-o-B in a single bolt rather than as a Y-hang, if it's to replace a figure-8?
whereas when andrewmcleod says: 'The minor possibility of theoretical death in highly unusual circumstances' I assume that he's referring to its use as a bunny's-ear knot and you clip into one of the loops.
So – that's 2 different uses for the same knot, both (in my opinion) perfectly OK. I sometimes use a B-o-B to tie into a single bolt as it's easier to untie than is a figure 8, while I now tend to use a Karash knot (fusion knot) for Y-hangs.
Babyhagrid
Well-known member
Yes I agree, BoB for single bolts hangs and "fusion" knots for Y hangs.
And as I learned this summer, no alpines for Y hangs
Cantclimbtom
Well-known member
What did you learn this summer that means you no longer use alpine (butterfly?) on Y hangs?
I understand the arguments (e.g. andrewmcleod post above) that fusion may be better, but is there something that now makes you think alpine butterfly can be bad?
Mark Wright
Well-known member
I've been expedition caving for nearly 45 years and never once come across an Alpine Butterfly knot that has locked tight over long periods of use.
During the first of the Gouffre Berger clean-up trips in 2012, around 200 people made at least 200 descents and ascents (probably double this figure) of the ropes in the entrance series and we managed to untie all the knots when we de-rigged it and got the ropes back to the campsite. I think our photographic team alone made over 30 descents and ascents of the ropes in that year.
By its very nature of being a 'mid-rope knot', there should never be a situation where it receives 'heavier than normal loadings' as the load is usually being shared with a suitable 'end of rope knot'.
The Alpine Butterfly is regarded by the IGKT as being the 'Queen of Knots'
Babyhagrid
Well-known member
Had to be undone with a knife as it had cinched tight after 5 weeks of use.
I think that the original article was written in about 1968 and that it refers specifically to nylon rope. The section on prussic loops is a classic bit of understatement. If a prussic loop slips, it will almost certainly fail due to melting of the rope surface which will rapidly cut through the loop. Back in the late 60s climbers occasionally used prussic loops for self lining, resulting in a few unfortunate accidents.
Not due to rigging, but carrying multiple bags back up at end of expedition, or having more than one person at a time on really long pitches.
Loki
Well-known member
Like to see him tie that over the second pitch in large pot.
Space Doubt Caver
Active member
This is a fun video to watch
JAshley73
Active member
Perhaps I'm just tapped out of bandwidth, but if I can't get it done with a Figure-8, or Alpine Butterfly, I'm probably not interested...
Even my "loops," I join with a F8-follow-through, as opposed to the "Correct" way of using fisherman's knots. One advantage, is they're relatively quick to adjust the length. And untying hasn't been a pain, yet...
Maybe one of these years, I'll attempt to learn a bowline...
(I know, I know, my namesake would be ashamed of me...)
Even my "loops," I join with a F8-follow-through, as opposed to the "Correct" way of using fisherman's knots. One advantage, is they're relatively quick to adjust the length. And untying hasn't been a pain, yet...
Maybe one of these years, I'll attempt to learn a bowline...
(I know, I know, my namesake would be ashamed of me...)
JAshley73
Active member
On a slightly more related note, I seem to remember YouTuber "HowNot2" concluding that all common knots, the "strength reduction" was so nearly equal among knots/bends, that it was 'near as makes no difference.
Given the MBS of our caving ropes - 2-tons or more on anything I can think of - does it practically matter for us? Reckon' two cavers, tandem-climbing on some 4,500lb MBS rope, we're still only using 10% of the rope's MBS. So if the knot has reduced the strength of the rope by 50%, then those tandem climbers are still only using 20% of the available strength...
Given the MBS of our caving ropes - 2-tons or more on anything I can think of - does it practically matter for us? Reckon' two cavers, tandem-climbing on some 4,500lb MBS rope, we're still only using 10% of the rope's MBS. So if the knot has reduced the strength of the rope by 50%, then those tandem climbers are still only using 20% of the available strength...
Jim MacPherson
Active member
The one-handed version is quick, easy and moderately memorable ( as in ... over, under, round and through)
Sorry it's facebook but a clear enough example.. Think I was taught it climbing on the Wainstones 50/60 years ago, ends up a bit like an earworm but useful nonetheless.
Jim
Loki
Well-known member
One thing to note is that when ascending or descending for that matter you are totally reliant on the sheath strength, rather than cowstail when you’re attached to the knot.
I did some work on this a while back into fall arrest device performance on used worn ropes. Let’s just say the results weren’t pretty and the sheath is not as strong as you might assume!
JAshley73
Active member
HowNot2's videos show a pretty consistent around-4kn before the sheath "fails" on a lot of ropes, with a toothed-ascender. About double the weight of the two combined tandem-climbers. Granted, that's usually on a slow-pull machine. Yes, results may vary when compared to drop-tests. However, he also has a lot of drop-tests where ropes de-sheath, and the "load" does not plummet to earth. (er, beneath the earth for us?)
I'm not sure how that translates into a caver taking a FF1 or FF2 onto a toothed ascender. My guess is that's a pretty unlikely scenario.
We were talking about knot-strength(s) though. Surely the issue of rope-sheath(s) strength is a different issue...? My guess is the knot will always be stronger than the sheath under a shock load - any kind of load really.
I'm not sure what we're supposed to do with that "information" though...? Just use a "bigger" rope, and replace it more often?
I may have misunderstood your point, but that's not my experience. When practicing SRT rescues using a spare rope, clipping the rescuer to the casualty then cutting the casualty's rope, the weight wasn't transferred until the last strand of the core was cut. There was movement when the sheath was cut but the core was more than adequate.
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