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directional figure 8 vs. butterfly

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
Tom Nyce wrote: Do this with a regular overhand bight, or a figure eight on a bight, and the knot tends to start "rolling inside out." Do this with a butterfly, or a directional figure 8 and the knot just cinches down nicely.
The tests that exposed rolling as a conceivable issue never used the loading patterns associated with the use of a loop. To replicate those tests, the rope would have to be loaded but there could be no load on the loop---in which case the loop would never have been tied. Although there are no tests at present, intuition would suggest that loading the loop inhibits the slack needed for rolling. Combined with the stellar performance of the EDK in the field mentioned by Patto, I'd say there isn't a shred of concern for using an overhand loop in any ordinary climbing situation. For a big complicated rescue situation with lots of weight on the loop for long periods of time and possibly cyclic loading, it would make sense to use something else.

I still think the bowline on a bight is the best alternative, given the DAV testing of it as a superior harness tie-in knot.
Tom Nyce · · Flagstaff, AZ · Joined Nov 2010 · Points: 45
patto wrote: Rolling? You better tell that to all those people using an overhand to tie two ropes together. AKA the EDK. (An overhand on a bight being loaded on either end has the same knot topology as an EDK.) Please explain further the problems associated with the overhand and why we should worry about it on a bight but not when joining rappel ropes.
In various situations, knot choice is a matter of weighing the advantages and disadvantages. When joining two ropes for a rappel, you are in a situation with very low force load (half the weight of a single climber), and where the knot is going to be dragged over a bunch of rock. The EDK is a reasonable choice in that situation. But that situation has little to do with the main topic here.
patto · · Unknown Hometown · Joined Jul 2012 · Points: 25
rgold wrote:For a big complicated rescue situation with lots of weight on the loop for long periods of time and possibly cyclic loading, it would make sense to use something else. I still think the bowline on a bight is the best alternative, given the DAV testing of it as a superior harness tie-in knot.
I have no arguments there. :-)

Tom Nyce wrote: In various situations, knot choice is a matter of weighing the advantages and disadvantages. When joining two ropes for a rappel, you are in a situation with very low force load (half the weight of a single climber), and where the knot is going to be dragged over a bunch of rock. The EDK is a reasonable choice in that situation. But that situation has little to do with the main topic here.
What do you see as the "main topic here"??

The EDK is perfectly fine for clilmbing loads. The rope breaks at the knot before a knot failure occurs. Sure it is 10%-20% weaker than some alternatives.
Jon Rhoderick · · Redmond, OR · Joined Jul 2009 · Points: 966

Can someone who 'gets it' explain the butterfly method shown in the 18 second video?
I'm hopeless.

climber pat · · Las Cruces NM · Joined Feb 2006 · Points: 286
patto wrote: I have no arguments there. :-) What do you see as the "main topic here"?? The EDK is perfectly fine for clilmbing loads. The rope breaks at the knot before a knot failure occurs. Sure it is 10%-20% weaker than some alternatives.
I think you should read user.xmission.com/~tmoyer/t… before declaring the EDK suitable for climbing loads. It can fail (roll) at suprisingly low loads if not well tied. Make sure you tie the knot cleanly, preload all 4 stands, and allow plenty of tail to accomidate a know roll. I know people who have had this knot roll. Even well tied it really is only suitable for low loads (i.e. rapeling).
Gregger Man · · Broomfield, CO · Joined Aug 2004 · Points: 1,759
Jon Rhoderick wrote:Can someone who 'gets it' explain the butterfly method shown in the 18 second video? I'm hopeless.
I like methods of knot tying that are more tactile than visual. I try to handle the knot in a very specific way so that it isn't even necessary for me to look at what my hands are doing. The key to this method is in how the right hand reaches between the two strands to grab the bight wrapped around the knuckles of the left hand. Folding the strand that was draped across the thumb creates an 'X' when it is blocked by the right wrist. Pull the loop that was around the knuckles to whatever length you would like for the loop to be, then send it through that space above the 'X'. Voila. Butterfly.

youtube.com/watch?v=PRs-8qr…
patto · · Unknown Hometown · Joined Jul 2012 · Points: 25
climber pat wrote: I think you should read user.xmission.com/~tmoyer/t… before declaring the EDK suitable for climbing loads. It can fail (roll) at suprisingly low loads if not well tied. Make sure you tie the knot cleanly, preload all 4 stands, and allow plenty of tail to accomidate a know roll. I know people who have had this knot roll. Even well tied it really is only suitable for low loads (i.e. rapeling).
I read that years ago. There is little new there.

I'm confused why you are worried about a knot rolling on the bight when there is not possibility of failure for continued rolling but not on rappel when the continued rolling does result in failure.

Better yet describe a scenario where you would expect an overhand on a bight (not on a free end) to roll and what problems it could cause. Please, go ahead.
rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
climber pat wrote: I think you should read user.xmission.com/~tmoyer/t… before declaring the EDK suitable for climbing loads.
I think most of us have read it by now. The rolling threshold on dry 11mm dynamic ropes was about 6kN, but as I explained in an earlier post, those tests aren't relevant to the loop situation. Moreover, the fact that the loop will contain a locking carabiner makes it impossible for the knot to roll off the end of the rope as is possible with the EDK.

I wouldn't hesitate to use an overhand loop in an anchor rope as a place to hang a guide plate for an upper belay. For setting up fixed lines that are going to be loaded for a while, even if with not much more than body weight, the overhand loop may be hard to untie, same for the figure-eights, and (again as mentioned above) the bowline on a bight seems to be a better choice.
climber pat · · Las Cruces NM · Joined Feb 2006 · Points: 286
rgold wrote: I think most of us have read it by now. The rolling threshold on dry 11mm dynamic ropes was about 6kN, but as I explained in an earlier post, those tests aren't relevant to the loop situation. Moreover, the fact that the loop will contain a locking carabiner makes it impossible for the knot to roll off the end of the rope as is possible with the EDK. I wouldn't hesitate to use an overhand loop in an anchor rope as a place to hang a guide plate for an upper belay. For setting up fixed lines that are going to be loaded for a while, even if with not much more than body weight, the overhand loop may be hard to untie, same for the figure-eights, and (again as mentioned above) the bowline on a bight seems to be a better choice.
I got confused by use of EDK to refer to an overhand on a bight. EDK is an overhand at the end of a rope to connect two ropes for rapelling.

I too regulary use an overhand on a bight.
Guideline #1: Don't be a jerk.

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