In an industrial environment the IRATA syllabus recommends Bunny Knots when anchors are close together and either a Fig. 8 or Fig. 9 (slightly easier to untie after loading) in conjunction with an Alpine Butterly.
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In an industrial environment it would generally be considered as poor rigging if any type of knot could rub an abrasive surface during use.If you have a rub point on the knot itself then bunny ears could totally fail, but if that's the case you wouldn't be using it!
Most knots are a pain to untie after being loaded by a large group. When we de-rigged the Berger in 2012, after over 200 people had been down and back up the ropes, we had to cut a large number of the knot loops from a whole range of knot types.Bunny ears are a right pain to untie after being loaded by a large group. Bowlines on the bight and alpines are much nicer to undo afterwards. And bowlines don't require lots of dressing to appease people like Bunny ears do.
Referring to the OP and the use of two alpines for the Y. You may want to leave your last section of traverse line slack or slightly looped. This, so that you can easy reach it and clip in when you have prussiked up to the Y hang knot. You can often pull yourself up with it. In this case it is worth remembering that an alpine is intended for three way loading where the loop and both ends are loaded tight. This is fine if your traverse line is tight all the way, but if it is slack then use a fig8/9 for the first bolt of the Y. I hope that makes sense.
I do dislike seeing alpines that are only loaded in two directions and slack in the third. It's not unsafe, no ones going to die, but it isn't the best choice of knot for the situation. You do see some rigging where alpines are used for everything.
I can't agree. Alpines used on Y hangs are the hardest of all to undo, so much so that I consider it last resort/special circumstances only. Easiest to undo is bowline bunny followed by fusion.Bunny ears are a right pain to untie after being loaded by a large group. Bowlines on the bight and alpines are much nicer to undo afterwards. And bowlines don't require lots of dressing to appease people like Bunny ears do.
In my experience, a badly dressed Alpine is a right pain to untie. I guess that's true of all knots, but it seems particularly bad with Alpines.Alpines used on Y hangs are the hardest of all to undo, so much so that I consider it last resort/special circumstances only. Easiest to undo is bowline bunny followed by fusion.
Frowned upon by whom?If one, or both of the anchors are so marginal that you are worried they won't take more than half the load, you probably wouldn't want to use them anyway. I'm usually more concerned with positioning the Y so the rope is going to miss any rub points. If that loads one side, more than the other, that is fine by me. If the more heavily loaded side were to fail, the load would transfer to the other with a minimal shock to the anchor, rope, or caver, which is the primary purpose of a Y hang.
Two butterfly knots, close together would work fine, but be harder to adjust, if you need to feed rope through both knots to get the hang to your satisfaction. A fusion knot, in particular is much easier to adjust than other bunny ears style knots. Bowline on the bight was easier still, but they are frowned upon now.
https://www.peakinstruction.com/blog/testing-a-method-of-failure-with-a-bowline-on-the-bight-knot/ and https://www.peakinstruction.com/blog/2nd-round-of-testing-on-the-bowline-on-the-bight-knot/Frowned upon by whom?
Only way you can deck is if the only place you’re clipped into is this one loop, no second cowstails, no jammers, no descenders AND it actually slips.https://www.peakinstruction.com/blog/testing-a-method-of-failure-with-a-bowline-on-the-bight-knot/ and https://www.peakinstruction.com/blog/2nd-round-of-testing-on-the-bowline-on-the-bight-knot/
Originally publicised by the French national federation, but don't have their link. Don't know of any instances of some one actually decking out from this, but since other knots are available that don't have the risk, this was enough for me to remove it from my repertoire and use bunny ears and fusions instead. Especially since I regularly cave and rig for mixed experience level groups, who can't be relied on to clip in to both loops if told to.
Having a rebelay below will limit the drop to a couple of metres too. All these reduce the risk, but don't eliminate it. I used bowline on the bight for decades and still would with an expert team, but a fusion is almost identical in speed to tie adjust and dress, with just another turn in the rope to make. Easier to use another knot that doesn't have the risk at all than be explaining to a coroner why you tied it and some one else hit the ground.Only way you can deck is if the only place you’re clipped into is this one loop, no second cowstails, no jammers, no descenders AND it actually slips.
Can be mitigated with groups with a ‘king crab’, and if anything actually makes life waaaay easier for non-novices as well.
There are limits to all knots, and so all should be frowned upon in different ways…
Could we all just agree to use a bunny knot on any not too wide Y hangs and an alpine butterfly or two (maybe even an 8 at the start) on a few anchors leading up to the drop.