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Fusion Knot

D

damian

Well-known member
I've just had an interesting conversation with a French person. It seems the French Caving School are now advocating using a "Fusion Knot" in place of a Bowline on the Bight because of their concerns over it slipping and coming undone. I've not yet played with the Bowline on the Bight to make it misbehave as described, nor have I tried the Fusion Knot, but I will be shortly. This is the first I knew of this.
A video of the problem is here and the solution (a Fusion Knot) is here. I don't think there's any need to understand the French in either to get the point.
 
Looks very much like a fig8-bight, not quite the same though - Damian beat me to it, it is a subtle difference!
 
In fact, now I've tied it, I can report it's a lovely little knot (and I've also managed to replicate the Bowline on the Bight problem). I have no doubt the French have done plenty of drop testing before The French Caving School has actually come out and recommended the Fusion Knot.
 
I think I have seen this before when teaching people to tie a Bowline on the bight.
If you tie a Bowline on the bight by forming an overhand loop first and then pass the loop over the knot, inverting it, to create the bowline then you'll know this 'Fusion Knot'.
Tie a figure of 8 on the bight and then invert this to form the knot in the same way as you would the bowline.
I've not got a bit of rope in reach now but I think that should give you the fusion knot.
 
As with any knot, there are alternatives.
With the BotB it is the case that in some applications, particularly SRT, it is simply the better knot to use over a bunny-ears fig 8.
 
Pete K said:
If you tie a Bowline on the bight by forming an overhand loop first and then pass the loop over the knot, inverting it, to create the bowline then you'll know this 'Fusion Knot'.
Click to expand...

I'm not sure that it is the same, Pete K. IF I have managed to tie the fusion knot correctly, it's got an extra layer of complexity so a little bit more effort is required to adjust the length of a loop.

It's certainly a robust knot, with no risk of slippage, and with the ability of adjusting the individual loop lengths, but I'm not totally converted.
 
Do you teach yosemite tie-off/backup for your bowlines? That's what we teach to prevent slipage (which we do see happen here).
 
Amy said:
Do you teach yosemite tie-off/backup for your bowlines? That's what we teach to prevent slipage (which we do see happen here).
Click to expand...

Very difficult to do a Yosemite tie off in the middle of a rope or indeed on a bowline on the bight.
 
I've noticed slippage on the BotB before but isn't only when the knot isn't dressed correctly?
 
Amy said:
Do you teach yosemite tie-off/backup for your bowlines? That's what we teach to prevent slipage (which we do see happen here).
Click to expand...

Not seen them used in the uk - anyone use it here?

i always finish a free end with a barrel knot, (of course at a pitch head 'Y' hang you wouldn't normally have a free end, as there's usually a traverse line/backup before the pitch).

Have also managed to replicate the problem in the video - but sometimes the rope pulls through, and sometimes it doesn't - not sure why at the moment.

Tried out the fusion knot and it seems quite good...
 
@Jon - I agree, with stiff rope or a poorly dressed knot the chances of slippage are far greater. The knot has to be tied correctly to function correctly. That said I have never seen the issue that the OP brings up with BotBs before. I will investigate.

@Langcliffe - You are correct but I am about there. Using the wiki images I have worked out that you tie it he same as a BotB but using a figure-8otB. The loop passes over the kn ot in one direction to form the knot I've seen before but if you pass it over the knot the opposite way you'd form a BotB than you get the Fusion Knot.

@Amy - Stopper knots are the preffered option in the UK where required.

Anyone know where any test date for the Fusion knot can be found?
 
Amy said:
Do you teach yosemite tie-off/backup for your bowlines? That's what we teach to prevent slipage (which we do see happen here).
Click to expand...

For a bowline-on-the-bight a Yosemite tie-off is impossible (I use a barrel knot tie-off).

I like the Yosemite tie-off for single bowlines (plus a final barrel knot, since I'm paranoid about bowlines). You can also use it with a double bowline, to create a foothold!

I don't think any kind of tie-off would help in this case, however. It's not the tail that slips through, but the main pitch rope! Look at the video.

A good caving knot should be secure. It seems our beloved bowline-on-the-bight is less secure than we thought. Time to use a different knot!
 
I can't in good concience continue to use a BotB until I have explored the problem personally and am satisfied, however that same thing applies to the Fusion Knot which I only tied for the first time today. I have my suspicions about the BotB problem and what the causing factor is but I need some practical evidence.
I'm not ready to leave my BotBs behind so I'm off to do some testing. Will return with results later.
 
Interesting find Damian.

I've never noticed slippage in a BotB, but I'm fastidious about tying the knots right and dressing them well (and quickly too - practice makes perfect). This isn't to say slippage isn't a potential problem.

Personally I've always clipped into the two sections of loops; probably because in the dim distant past I'll have said to myself "what happens if it slips?

This fusion knot took me one go to learn and fits the bill re: adjustability. Will view with interest.

A knot I can tie but have never used is this this. Would like to see someone throw a heavy item on to this to see how it fairs.

 
weird isn't it. they're not drop testing, they're just loading the loop with 100 Kg and the rope just pulls through in a manner I'd only expect to see on an incorrectly tied knot.

Its surprising that this hasn't been noticed before.
 
For clarity, as Cave_Troll says, the problem is slippage caused by the rope going down the pitch running through the knot when you clip your cowstail into one only branch of the knot and then fall. It does not matter whether or not there is a traverse line. Obviously a rebelay further down the pitch will prevent a major fall, but on free-hanging pitches you could fall all the way to the bottom.

I can't believe I haven't thought of this before! We knew we needed a stopper knot on the free end of the knot, so why didn't we think about the other end ... oops!
 
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