What is the strongest rappel knot?

[Iceaxe]

What is the strongest rappel knot?
by Kolin Powick

I was climbing in Yosemite last summer and, while at a belay, was talking to a party from Bozeman, Montana. They noticed all the proto gear on my rack and deduced that I was from Black Diamond. My partner and I bailed (typical) and they were watching me like a hawk. I asked what they were looking at, and they said, "We want to see how the QA guy from BD raps.

[Bo_Beck]

The knot on two ropes tied together (and descending on both ropes) sees half the load. If rappeling on two ropes tied together, and passing a knot on descent, the knot then sees the full load. Seems that most people are using a "biner, or knot" block these days? In which case the knot used to tie the "pull cord-rope" becomes somewhat of a mute point? Seems that the weak point becomes the clove hitch or type of knot used for the block and not the type of knot connecting the 2 ropes? I believe (from 1st hand experience) that an overhand or even "parrallel" figure 8 knot can and do roll at some degree of force applied. Thats why when I use EDK I will normally tie 2-3 knots (against each other) to prevent the knot from rolling. I also leave at least a foot long tail.

[Brian in SLC]

I believe (from 1st hand experience) that an overhand or even "parrallel" figure 8 knot can and do roll at some degree of force applied. Thats why when I use EDK I will normally tie 2-3 knots (against each other) to prevent the knot from rolling. I also leave at least a foot long tail.

I think the figure eight version of the EDK can roll, but, I seem to recall some testing somewhere that showed the EDK with a simple overhand doesn't roll or slip until the force is pretty high (which is what KP's testing showed).

A few years back, I did some of my own testing with the EDK, just to convince myself that it was good to go. Tested dry ropes, wet ropes, and frozen ropes. All 8.1 beal doubles (same rope). Tied the knot loose, and, shock loaded it dry, wet, and frozen. Didn't see any slipping or rolling. It just cinched down and was fine.

I've heard it said that a knot you need to back up maybe isn't good enough to use. But, I'm like you, Bo, I usually stack another overhand up against the first one in my EDK's. Rarely I'll go off just one. Also seen folks snug one overhand knot on one rope (instead of two ropes into a second EDK) against the EDK, just in case.

I know KP got his use of the EDK from taking a guides course in Canada, where its taught by the UIAGM guides up there. I think the AMGA has adopted it as THE rappel knot too.

What bugs folks about it, I think, is it's just too simple.

Cheers,

-Brian in SLC

[ratagonia]

Thats why when I use EDK I will normally tie 2-3 knots (against each other) to prevent the knot from rolling. I also leave at least a foot long tail.

Here here. Surprised to see Kolin show the 'single' EDK, the true Death Knot. ALWAYS used with a backup knot in my book.

Tom

[Iceaxe]

Seems that most people are using a "biner, or knot" block these days?

I might be wrong.... but the biner block is kind of a 'canyoneering thing' and is not real popular in the climbing world. Which means in the grand scheme of things biner blocks are not real popular.

[Iceaxe]

I think the figure eight version of the EDK can roll, but, I seem to recall some testing somewhere that showed the EDK with a simple overhand doesn't roll or slip until the force is pretty high (which is what KP's testing showed).

Here is some interesting test data on the three knots that addresses roll.

http://www.xmission.com/~tmoyer/testing/EDK.html

The big item I take away from that data is make sure your knot is well dressed and that you leave enough tail for the knot to capsize at least one time. The knot gets stronger every time it rolls, sometimes doubling in strength.

[Bo_Beck]

I think the figure eight version of the EDK can roll, but, I seem to recall some testing somewhere that showed the EDK with a simple overhand doesn't roll or slip until the force is pretty high (which is what KP's testing showed).

Here is some interesting test data on the three knots that addresses roll.

http://www.xmission.com/~tmoyer/testing/EDK.html

The big item I take away from that data is make sure your knot is well dressed and that you leave enough tail for the knot to capsize at least one time. The knot gets stronger every time it rolls, sometimes doubling in strength.

This incident that took place on Spaceshot was one that I was directly involved with as part of the investigation. I believe that it was concluded that the "8" capsized without having enough tail to roll onto.

[hank moon]

Thats why when I use EDK I will normally tie 2-3 knots (against each other) to prevent the knot from rolling. I also leave at least a foot long tail.

Here here. Surprised to see Kolin show the 'single' EDK, the true Death Knot. ALWAYS used with a backup knot in my book.

Tom

It's "hear, hear*" and I've seen no evidence to support the notion that a properly tied EDK needs backup. That said, there's no downside - AFAIK - with backing it up...


* as in "listen up - hear what that person is saying"

[ratagonia]

I think the figure eight version of the EDK can roll, but, I seem to recall some testing somewhere that showed the EDK with a simple overhand doesn't roll or slip until the force is pretty high (which is what KP's testing showed).

Here is some interesting test data on the three knots that addresses roll.

http://www.xmission.com/~tmoyer/testing/EDK.html

The big item I take away from that data is make sure your knot is well dressed and that you leave enough tail for the knot to capsize at least one time. The knot gets stronger every time it rolls, sometimes doubling in strength.

This incident that took place on Spaceshot was one that I was directly involved with as part of the investigation. I believe that it was concluded that the "8" capsized without having enough tail to roll onto.

And the ropes were stiff as wire cable - totally unknotable!

Tom

[Scott Card]

Where is the fun in all this science. I prefer the "Good Luck" knot for really long raps. Notice the clover leaf design. It is also handy to clip a bunch of stuff to. Lucky is better than safe.

[Brian in SLC]

Here here. Surprised to see Kolin show the 'single' EDK, the true Death Knot. ALWAYS used with a backup knot in my book.

Doesn't really surprise me. Given how and by whom he was taught and his experience in the field.

I usually back it up too. But, I guess its for my piece of mind, not because it makes much sense.

Here's some spray on the topic, which, has been beat to death ad nauseam:

Petzl catalog/website: multi-pitch climbing tech tips, section:

[bruce from bryce]

Took a YOSAR ranger into Egypt 2 about 3 years ago and upon seeing my biner block he said, "what the f..k is that". The 3rd member of our party, who climbs more than does canyons states: "Oh, that's what they use in this sport. But let's back it up."

[oval]

Seems that most people are using a "biner, or knot" block these days?

I might be wrong.... but the biner block is kind of a 'canyoneering thing' and is not real popular in the climbing world. Which means in the grand scheme of things biner blocks are not real popular.

I was thinking about this today at work. Is a clove-hitched biner more or less likely to get hung up than something like the Alpine Butterfly (which can take pull from 3 directions without capsizing)? I'd love to know the answer to that, but my guess is that... I'll never know :D

[sarahlizzy]

Took a YOSAR ranger into Egypt 2 about 3 years ago and upon seeing my biner block he said, "what the f..k is that". The 3rd member of our party, who climbs more than does canyons states: "Oh, that's what they use in this sport. But let's back it up."

Trying to picture this - I've backed up a biner block with a figure eight attached to the anchor for the first members of the team, in case the clove hitch slips (do they ever actually do that under typical rappelling loads?), but it has to be removed for the last person (and attached to the pull cord with a backed up EDK, if the rope isn't long enough to serve as its own pull cord), otherwise one can't get the rope back. How might one "back up" a biner block and still have the rope retrievable?

[oldno7]

There is no reason to back up a biner block.
Having said that, each time the block is cycled, it should be checked by the next person to rap. Never presume anything was done right or hasn't changed from person to person. Always inspect for yourself.

Also the clove hitch should be set on the backbone of the biner, and pulled tightly(dressed)before rappelling.

[sarahlizzy]

There is no reason to back up a biner block.

That's what I figured. I'm thinking the guy in question, apparently having never seen one before, got a bit paranoid, so I was wondering what he might have had in mind.

The best I could think of at short notice is something like this:



Biner block with an alpine butterfly tied on the pull cord side and the rappelling side passed through it, so if the biner suddenly flashed out of existence in some freak quantum physics event, the whole thing would pull tight around the rapide.

(Just to be clear, I'd never use something like this - I'm just curious about what someone unfamiliar with a biner block might be tempted to do to try and add some redundancy)

[oldno7]

It would be a lot of work and time consuming to thread the rope through the alpine butterfly, especially if it was a longer rappel. If they need the warm fuzzies, just tie a figure 8 on a bight and clip it to the anchor with a biner.
I wouldn't allow much slack if attaching this way to avoid a shock load, that will never happen.(biner block won't fail if done correctly) But if you do this, why use a block in the first place? There needs to be a reason to use, or not use a block.
You might want to look into dynamic blocks rather than static for your beginner friend.

[sarahlizzy]

I wouldn't allow much slack if attaching this way to avoid a shock load, that will never happen.(biner block won't fail if done correctly) But if you do this, why use a block in the first place? There needs to be a reason to use, or not use a block.

My canyoneering experience is rather limited, having only done class 3 canyons in Zion, but I've been using them for 3 reasons:

1) So that I can set the length and rappel off the end of the rope in the event of a rap into water.

2) When the rope isn't long enough to be doubled (separate pull cord needed).

3) Because I've come to prefer rappelling single strand.

[Brian in SLC]

If they need the warm fuzzies, just tie a figure 8 on a bight and clip it to the anchor with a biner.

Could also just clip the bight back into the loaded rappel rope, too, methinks. Would be retrievable that way, also, would be a way for the pull cord to direct the rap line if need be too.

Biner blocks, at first blush, don't inspire confidence, to be sure. Climbers almost never ever use them, which is why it's no surprise that they'd raise an eyebrow from a climber. Especially if you could just rig for a double rope rappel.

There's folks who post here who've had a biner block fail...because the attached rope wasn't clove hitched, but, rather munter hitched and it slipped.

I think some canyoneers kinda like the biner block, as, it sets them apart from climbers. And, really, for that reason more than using one where they make sense is the underlying feeling I get.

Any rappel is unforgiving to certain errors, and, the biner block is no exception. Rappelling wrong side of the block (accident in Zion), having the block release (accident in Zion), having the block slide through the anchor (fatality in Zion), and on and on. Its a technique that seems prone to accidents.

Its kinda sobering to reflect on a bit. The only climbing fatalities in the park have been rappelling accidents. The ones I can think of had to do with mismatched rope diameters where the ropes slid creating mismatched lengths and the rappeler coming off the rappel line. And one where the knot for connecting two ropes capsized, rolled, and/or otherwise failed and the guy fell from the anchor after launching into the rappel.

But, the canyoneering accidents involving the use of biner blocks seem to be getting pretty common. Whether its blowing the block, having the block pull through, rappelling the wrong side of the block, or, losing control on a skinny single strand (epidemic!), there seems to be an inherant risk or at least much more vigilence needed.

Take care out there, and, double and triple check yourselves...

Cheers,

-Brian in SLC

[sarahlizzy]

But, the canyoneering accidents involving the use of biner blocks seem to be getting pretty common. Whether its blowing the block, having the block pull through, rappelling the wrong side of the block, or, losing control on a skinny single strand (epidemic!), there seems to be an inherant risk or at least much more vigilence needed.

On the latter, I've taken to always putting a carabiner on my leg loop and passing the dead rope through that (I use an ATC-XP). This allows me to massively increase friction by pulling the rope up, and if I need more I have a couple of wiregates on my equipment loop which can be used to convert to a Z-rig mid-rap if need be.