Author Topic: Which knots for Y hangs?  (Read 2553 times)

Offline tobyk

  • Newbie
  • *
  • Posts: 5
Which knots for Y hangs?
« on: January 11, 2019, 10:35:07 pm »
This has probably been discussed over and over a thousand times on here, but would like some enlightenment on which knots to use on Y hangs.
I’m currently in favour of using a double bowline on the bite, rather than double figure 8 on the bite, as it’s easier to adjust and uses less rope, but i’ve read about the dangers of only clipping one loop. I’ve also noticed with the figure 8 on the bite, it can slip dramatically if not dressed correctly.
Also what are people’s thoughts on a figure 8 - butterfly set up. I’m tempted in using the cavers (false) butterfly here, as it’s just so easy and quick to equalise, but have heard this knot can also slip, so is it generally recommended to use an alpine here?
Any comments will be much appreciated,
Toby

Offline Jon

  • menacing presence
  • **
  • Posts: 197
    • My blog
Re: Which knots for Y hangs?
« Reply #1 on: January 11, 2019, 11:02:19 pm »
I currently use a fusion knot as it's safe to clip one loop, only uses a bit more rope than a double bowline on the bight as is still easy to adjust once you learn how.

It's also possible to use it in a minimal rope configuration - instead of using the two loops for each part of the y hang, make one loop very short and use this as the central belay point. The other long loop goes to one of the y hang bolts. There will be some minimal shock loading if an anchor fails but if you keep that loop small I think it's acceptable. Once dressed properly I've not had any slippage on any of the loops.

I've not seen any tests or literature to back up this approach though.

Sent from my SM-G930T using Tapatalk


Offline JasonC

  • forum hero
  • *****
  • Posts: 1033
  • KCC
Re: Which knots for Y hangs?
« Reply #2 on: January 11, 2019, 11:13:34 pm »
This has probably been discussed over and over a thousand times on here, .....

You're not wrong :)

https://ukcaving.com/board/index.php?topic=14602.0

But personally I prefer double-fig8-on-the-bight, aka 'Bunny Ears'.  First one I learnt, and still the only one I can reliably tie without thinking about it...

Online Mark Wright

  • forum star
  • ****
  • Posts: 697
  • NCC, BBPC
Re: Which knots for Y hangs?
« Reply #3 on: January 12, 2019, 01:30:50 am »
I usually always tie a Bunny knot when 'Y' Hang anchors are reasonably close together and a Fig. 9 and Alpine Butterfly when they aren't.

I've never had any problems adjusting a Bunny knot. It is important the knot is dressed to ensure the common loop always sits at the top and be sure to set the knot before use.

It takes only seconds to dress and set knots neatly and this helps others easily identify they are safe as well as ensuring the rope's maximum knotted strength is maintained. It's unlikely a properly dressed and set knot will slip dramatically. It might slip a bit after some use.

They say (whoever 'They' are), you should have a fist-sized tail on all knots to allow for such slippage.

I don't think I would choose a particular knot because it saved just 100mm of rope but I would certainly choose a Fig. 8/9 and an Alpine Butterfly over a Bunny knot when tying a particularly wide 'Y' Hang where it could save well over 1m. This can be an important saving on expeditions when exploring deep caves with lots of re-belays. 

Most knots will deform slightly under load but I have seen a lot more seriously deformed Bowline on the Bight knots than any other. I remember re-rigging someone's Bowline on the Bight knot at the top of Elizabeth Shaft in Nettle Pot many years ago. It had deformed so much that none in our party could confirm what it actually was and we weren't prepared to commit to it. 

The danger of clipping only 1 loop is easily remedied by clipping, e.g. a HMS carabiner into both loops and subsequently clipping cow's tail carabiners into the HMS when passing the re-belay. This method is commonly used in the Alps.

Fig. 9's are marginally stronger than 8's but, more importantly, they are usually easier to untie after heavy loading. They aren't very practical for re-threading so I would use a Fig. 8 in these cases. 

The Alpine Butterfly is the only true multi-directional, mid-rope knot with pretty much the same strength regardless of the direction of loading. The 'Cavers', 'False' or, as I call it, the 'Incorrectly Tied' Butterfly does not fit into this category.

Again, I have never had any problems adjusting them. If ropes are thick and particularly stiff then all knots are going to be harder to tie correctly. Running your ropes through the washing machine with some softener will make knot tying much easier. 

The Alpine Butterfly knot is regarded by the International Guild of Knot Tyers as the 'Queen' of knots. The title could well relate to the Queen in a Chess game being able to move in any direction.

Mark

 
« Last Edit: January 12, 2019, 01:50:39 am by Mark Wright »

Offline The Old Ruminator

  • forum hero
  • *****
  • Posts: 3074
Re: Which knots for Y hangs?
« Reply #4 on: January 12, 2019, 07:42:05 am »
Can you tell from this ?

Vurley by Nicholas Chipchase, on Flickr

Offline Pitlamp

  • forum hero
  • *****
  • Posts: 4526
Re: Which knots for Y hangs?
« Reply #5 on: January 12, 2019, 08:10:38 am »
This has probably been discussed over and over a thousand times on here, .....

You're not wrong :)

https://ukcaving.com/board/index.php?topic=14602.0

But personally I prefer double-fig8-on-the-bight, aka 'Bunny Ears'.  First one I learnt, and still the only one I can reliably tie without thinking about it...

I have a similar attitude to Jason C on this. Before I comment though, People like Mark Wright will have far more experience and knowledge than me on rope work, so their advice is probably far better than anything I can offer.

However, FWIW, I like the double figure of 8 because (like Jason) it's the first knot I learned but also because it's so simple to tie (i.e. less likely to get wrong when you're tired on a very long trip). I find bowline on the bight very easy to get wrong (maybe I just need to practice more?) The person who first showed me the double fig 8 knot, back in the day, told me that it allows a bit of slippage which (almost automatically) helps load both belays equally. It's certainly very easy to adjust. None of the info in this paragraph is evidence-based though, so trust people like Mark rather than me!

Offline MJenkinson

  • obsessive maniac
  • ***
  • Posts: 473
Re: Which knots for Y hangs?
« Reply #6 on: January 12, 2019, 08:48:25 am »
Most of the time I use a fig 8 and a cavers butterfly as it’s quick. I’m not that fussed about various strength values for knots as I just don’t think it matters enough in the grand scheme of things. You do have to watch the cavers (or incorrectly tied butterfly as per earlier post!) because it can go a bit pear shaped if you don’t dress it properly.

Offline Bob Mehew

  • forum hero
  • *****
  • Posts: 1147
  • breaking knots is fun
Re: Which knots for Y hangs?
« Reply #7 on: January 12, 2019, 09:01:02 am »
As back ground, see http://british-caving.org.uk/wiki3/lib/exe/fetch.php?media=rope_testing:initial_results_from_a_preliminary_investigation_into_y_hang_knots.pdf and note the observation at the end of the report namely  “Cavers should be aware that the loading of parts of ANY KNOT other than via the designed load points (active ends) MAY result in the failure of the knot to hold the caver’s weight.”.  (I note the link in the document nol onger works as do some of those in the other thread.)

Online ChrisJC

  • Funky
  • forum hero
  • *****
  • Posts: 1207
    • http://www.cowdery.org.uk
Re: Which knots for Y hangs?
« Reply #8 on: January 12, 2019, 01:04:39 pm »
For me, Figure of 8 on the first anchor point, then an Alpine Butterfly for the Y hang and 2nd anchor point.

I do that because I believe the Figure of 8 is one of the strongest knots of that type, and the Alpine Butterfly because if one anchor fails or the rope snaps, the other anchor is still perfectly safe...

Chris.
--
http://www.cowdery.org.uk
Mines, caves,
Land Rovers

Offline topcat

  • obsessive maniac
  • ***
  • Posts: 365
Re: Which knots for Y hangs?
« Reply #9 on: January 12, 2019, 04:32:56 pm »
 Consideration should also be given to the ease of accessing the traverse rope, esp.  for inexperienced folk.

The fig.8 bunny has the traverse rope coming from the Y hang knot, the standard fig.8 and alpine combination does not.  This can make a big difference .  Like others, I also use this latter system when bolts are far apart, but sometimes will make extra effort and rope and use a bunny when needed.

I invariably use a bowlin on single point rebelays, especially with 9mm rope.

Offline Pitlamp

  • forum hero
  • *****
  • Posts: 4526
Re: Which knots for Y hangs?
« Reply #10 on: January 12, 2019, 05:13:50 pm »
That's a fair comment Topcat.  I also use the normal fig 8 loop followed by a butterfly sometimes for the same reason.

Regarding the strength of knots - is this actually a problem in practice? What I mean is - how often have accidents been caused by this? (I do realise that a sparsity of accidents is no excuse for ignoring good practice, of course.)

Online Mark Wright

  • forum star
  • ****
  • Posts: 697
  • NCC, BBPC
Re: Which knots for Y hangs?
« Reply #11 on: January 12, 2019, 08:18:47 pm »
Rigging to allow easy access to and from the pitch head is really important, particularly when less experienced cavers are on their way out carrying a heavy bag after a long and hard trip and feeling like their arms could drop off at any point. My arms felt like that last weekend getting out of the entrance hatch in Rowter Hole after a 7 hour digging session!

In practice, the strength loss in a knot isn't worth worrying about. Even a badly tied Bowline, which is probably the weakest of all the knots we use in caving, is still going to be twice as strong as the maximum force that could be applied in any likely caving scenario on a typical 9mm rope. I'm not aware of their being any rope failures in caving or in the rope access industry due to the weakening effect of a knot.

As Pitlamp agrees, this lack of any reported accidents shouldn't excuse following best practice. Industry best practice suggests neat and tidy 'Y' Hang rigging with appropriate angles and correctly dressed and set easily identifiable knots. There is no logical reason why this same level of good practice shouldn't be adopted in caving. Any extra time it might take to tie neat and tidy knots is negligible.

Mark

Offline tobyk

  • Newbie
  • *
  • Posts: 5
Re: Which knots for Y hangs?
« Reply #12 on: January 12, 2019, 08:43:28 pm »
Completely contradicting what I initially said, after watching the video on bowline slippage, I think I might pursue the double figure 8 on the bite. Had a practice earlier and it is very straightforward to adjust and easy to tell if it’s dressed correctly.
The fusion knot does look and sound brilliant, although at this stage the fusion knots I’m producing I have no idea if they’re right, and think I need to be shown properly without winging it, so something for the future maybe!
Still undecided on which butterfly to use for y hangs. I’ve had comment previously the cavers is a bit of a pig to untie once loaded, so will probably opt for the alpine for regular use. As I’m still at the start of my rigging career, I just want to make sure my habits are sound.
Thanks for everyone’s comments, very useful!
Toby

Online ChrisJC

  • Funky
  • forum hero
  • *****
  • Posts: 1207
    • http://www.cowdery.org.uk
Re: Which knots for Y hangs?
« Reply #13 on: January 12, 2019, 09:17:40 pm »
In 25 years of SRT, I've never needed anything other than a Fig8 and an Alpine Butterfly.

Chris.
--
http://www.cowdery.org.uk
Mines, caves,
Land Rovers

Online Mark Wright

  • forum star
  • ****
  • Posts: 697
  • NCC, BBPC
Re: Which knots for Y hangs?
« Reply #14 on: January 12, 2019, 09:25:30 pm »
You could ensure 100% rigging safety with just an Alpine Butterfly.

Mark

Offline andrewmc

  • forum star
  • ****
  • Posts: 621
  • EUSS, BEC, YSS, prov. SWCC...
Re: Which knots for Y hangs?
« Reply #15 on: January 12, 2019, 09:53:10 pm »
I've gone fusion. I was never convinced until someone showed me the 'other' way of tying a bowline on a bight (i.e. tie an overhand on a bight first, then grab the loops). Tying the fusion is exactly the same except you tie a Fig 8 on the bight instead of the overhand.

Having two loops, either of which can be clipped, stops people clipping onto the single leg you get from a fig 8/Alpine combination (although people can still fail to clip 'into' the loops).

More significantly for me, I much prefer having the incoming traverse line join the knot. This stops that awkward 'gap' in the rigging between the 'end' of the traverse line and the start of the down rope. On particularly poorly-rigged pitches, you can end up semi-prussiking up one leg of the Y-hang...

If there isn't a traverse line, rope is short, and everyone is fairly competent, then an end knot and an Alpine butterfly is fine for saving a bit of rope. Equally if the incoming traverse line is the long loop from a previous down rope and there is no trouble getting on/off the pitch down without it, then it's fine. But generally, I've greatly increased my use of double loop knots.

Offline Wardy

  • regular
  • *
  • Posts: 58
Re: Which knots for Y hangs?
« Reply #16 on: January 12, 2019, 10:34:12 pm »
seems to have been a problem loading this post, so apologies if my original attempt re appears.

When teaching rope access this topic seemed quite clear.

People generally find tying one knot easier and slightly quicker than two, so most people go for that and a bunny knot is a pretty good choice.
When the anchors were further apart, trainees or those less experienced always seemed to struggle getting the length right to achieve their desired angle, often underestimating the length of rope required by quite a way.
If they were using a bunny knot they then found it difficult to add more rope length into the knot and so started again, but then often struggled a second time.
I therefore encouraged them to use two knots for anchors further apart.
In industrial applications anchors can often be a long way apart compared to common caving situations and it was then obvious to configure it so that the longer leg of the y hang was made up of a single rope coming out of a fig 9 or 8 and the shorter leg was the loop often from an alpine butterfly.
It is however a matter of personal preference / convenience as there are not many examples of catastrophic failure, but best practice does help stack the odds in your favour.

Offline JasonC

  • forum hero
  • *****
  • Posts: 1033
  • KCC
Re: Which knots for Y hangs?
« Reply #17 on: January 12, 2019, 11:06:23 pm »
Just to add to the debate...
Not that long ago, I attended a SRT/rigging course where it was suggested that best practice was to tie alpine butterflies all along the traverse, including the 'last' anchor which was also one of the Y-hang anchors, and then do a BotB (or bunny-ears) so that one of the Y-hang anchors had two krabs hanging off it, one for the alpine butterfly and one for the double knot.

The argument is that this gives you a good solid Y-hang, and makes getting on/off the pitch easier.

Of course, it also uses more rope, more time and an extra krab, but may be worth doing if the pitch is awkward and/or the cavers are less experienced. 


Online PaulW

  • stalker
  • ***
  • Posts: 297
  • WSCC, WCC
Re: Which knots for Y hangs?
« Reply #18 on: January 12, 2019, 11:09:31 pm »
Just to add to the debate...
Not that long ago, I attended a SRT/rigging course where it was suggested that best practice was to tie alpine butterflies all along the traverse, including the 'last' anchor which was also one of the Y-hang anchors, and then do a BotB (or bunny-ears) so that one of the Y-hang anchors had two krabs hanging off it, one for the alpine butterfly and one for the double knot.

The argument is that this gives you a good solid Y-hang, and makes getting on/off the pitch easier.

Of course, it also uses more rope, more time and an extra krab, but may be worth doing if the pitch is awkward and/or the cavers are less experienced.
why the extra krab and not both into the same krab?

Online mikem

  • forum hero
  • *****
  • Posts: 2345
  • Mendip Caving Group
Re: Which knots for Y hangs?
« Reply #19 on: January 13, 2019, 06:35:01 am »
Because someone hanging on the traverse line can create a 3 way loading if you share the krab

Mike

Online PaulW

  • stalker
  • ***
  • Posts: 297
  • WSCC, WCC
Re: Which knots for Y hangs?
« Reply #20 on: January 13, 2019, 09:34:35 am »
i appreciate that reasoning. but was also after the amswer from Jason. but also what was the reason that made it best practice to rig in that way.

only because i have been told it makes no difference.

i do use that method on occasions.

Offline Jon

  • menacing presence
  • **
  • Posts: 197
    • My blog
Re: Which knots for Y hangs?
« Reply #21 on: January 13, 2019, 10:25:36 am »
Just to add to the debate...
Not that long ago, I attended a SRT/rigging course where it was suggested that best practice was to tie alpine butterflies all along the traverse, including the 'last' anchor which was also one of the Y-hang anchors, and then do a BotB (or bunny-ears) so that one of the Y-hang anchors had two krabs hanging off it, one for the alpine butterfly and one for the double knot.

The argument is that this gives you a good solid Y-hang, and makes getting on/off the pitch easier.

Of course, it also uses more rope, more time and an extra krab, but may be worth doing if the pitch is awkward and/or the cavers are less experienced.
The other reason for terminating the traverse at the y hang bolt is that you can stack your clients or mates on the traverse closer to the y hang without it affecting the y hang. If your traverse goes straight into the y hang knot then someone leaning on the traverse line will move the y hang rope. More of a comfort / confidence thing than safety.

Sent from my SM-G930T using Tapatalk


Online mikem

  • forum hero
  • *****
  • Posts: 2345
  • Mendip Caving Group
Re: Which knots for Y hangs?
« Reply #22 on: January 13, 2019, 02:59:12 pm »
The only situation I can see it being useful is where they can treat it as a rebelay to get back up to the traverse line.

Mike

Offline JasonC

  • forum hero
  • *****
  • Posts: 1033
  • KCC
Re: Which knots for Y hangs?
« Reply #23 on: January 13, 2019, 03:35:54 pm »
The only situation I can see it being useful is where they can treat it as a rebelay to get back up to the traverse line.


Yes, I think that was the main point.

As to why separate krabs were recommended - I don't know.  I can't recall pros and cons being discussed, though perfectly good reasons have been offered here.

I'm not saying everyone should use this approach, or even that I do, just that it was on the course.  Courses are led by instructors who spend lots of time discussing different techniques and who regularly lead novice trips, so are keen to use 'best practice' at all times.
For me, I'm happy with 'good-enough practice' :)

Offline Mike Hopley

  • obsessive maniac
  • ***
  • Posts: 396
Re: Which knots for Y hangs?
« Reply #24 on: January 24, 2019, 03:54:36 pm »
One more reason for possibly taking the traverse up to one of the Y-hang anchors: it simply changes the position of the traverse line, which can change the effective footholds, and also whether the traverse line itself is getting in the way of cavers as they approach the pitch head.

Depending on the pitch, it could make things easier or harder. Mostly I just use a double-loop knot (fusion), but sometimes I like this "instructor style" rigging.

Personally I wouldn't see the extra krab as routinely necessary here, but it's certainly good to consider how krabs might get loaded. :thumbsup: