What's going on in this single-line rappel diagram?


Original Post
David Kerkeslager · · Brooklyn, NY · Joined Jan 2017 · Points: 45

This discussion relates to this link: https://www.climbing.com/gear/rappelling-on-a-single-line-with-assisted-braking-belay-devices/ After posting this link on a different thread, I noticed some weirdness in the first method (second diagram).

First, it indicates that there should be 30cm minimum between the knot that joins the two ropes and the alpine butterfly that attaches the carabiner, with no explanation for why this is the case.

Second, they're placing the alpine butterfly on the grey line instead of on the blue line, with the joining knot on the loaded side instead of isolated on the retrieval side. This has 3 practical implications:

  1. The knot that joins the two ropes comes under load; a failure in the knot is catastrophic. If the alpine butterfly were on the blue line that would isolate the joining knot, removing this risk.
  2. The section of the grey line between the alpine butterfly and the joining knot comes under load; a failure of the grey line in that section is catastrophic. This means the grey line must be suitably rated. If the alpine butterfly were on the blue line, that would isolate the grey line so that it's only used for retrieval, allowing you to carry a lighter line.
  3. The weight of the climber rests on the joining knot in the quicklink rather than on the alpine butterfly in the quicklink. It's unclear to me which knot would be more likely to get stuck in the quicklink.

Given 1 and 2, it seems clear to me that tying the alpine butterfly on the blue line and isolating the grey line and joining knot to the retrieval side is better. Can anyone shed some light on why Petzl is recommending it this way?

Zachary Winters · · Mazama, Washington · Joined Aug 2014 · Points: 73

The 30cm is just indications the tail length. Otherwise, I generally agree with your take on this, especially if the grey rope is a skinny tag

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 525
David Kerkeslager wrote:

This discussion relates to this link: https://www.climbing.com/gear/rappelling-on-a-single-line-with-assisted-braking-belay-devices/ After posting this link on a different thread, I noticed some weirdness in the first method (second diagram).

First, it indicates that there should be 30cm minimum between the knot that joins the two ropes and the alpine butterfly that attaches the carabiner, with no explanation for why this is the case.


That's just a description of the tail length for the EDK, it isn't  measuring a distance to the butterfly.


Second, they're placing the alpine butterfly on the grey line instead of on the blue line, with the joining knot on the loaded side instead of isolated on the retrieval side. This has 3 practical implications:

  1. The knot that joins the two ropes comes under load; a failure in the knot is catastrophic. If the alpine butterfly were on the blue line that would isolate the joining knot, removing this risk.
  2. The section of the grey line between the alpine butterfly and the joining knot comes under load; a failure of the grey line in that section is catastrophic. This means the grey line must be suitably rated. If the alpine butterfly were on the blue line, that would isolate the grey line so that it's only used for retrieval, allowing you to carry a lighter line.
  3. The weight of the climber rests on the joining knot in the quicklink rather than on the alpine butterfly in the quicklink. It's unclear to me which knot would be more likely to get stuck in the quicklink.

Given 1 and 2, it seems clear to me that tying the alpine butterfly on the blue line and isolating the grey line and joining knot to the retrieval side is better. Can anyone shed some light on why Petzl is recommending it this way?

I don't get what you're describing here.  If the alpine butterfly is on the blue line, then the joining knot has to be on the same side of the anchor as the alpine butterfly, otherwise the rappel is irretrievable.  But then nothing holds the blue rope in place for rappelling and the butterfly and carabiner serve no purpose. 

I've set up such rappels so that you retrieve the climbing line rather than the tag line, but as far as I know you have to clip the ropes together for the first person down, and then that person has to anchor the tag line so that the second person can rappel on either both lines (problematic since the tag line has to be anchored below) or the climbing line.  The second person also has to remember to remove the connection between the two ropes before leaving the rap station, otherwise you can't pull the ropes.  This system fully loads the tag line, so it has to be up to that task.

Michael T Young · · Seattle, WA · Joined Jan 2016 · Points: 5

Agreed that the butterfly should be the stopper knot for the reasons listed. I see no problem with using a butterfly as a stopper knot--the diagram assumes you're doing a double rope rappel when using a biner block.  This misses a common use of the biner block--using a grigri to do retrievable single line rappel on a single rope. In this case you have to use the butterfly as the stopper knot. I was taught this technique on a single rope with the butterfly as the stopper knot and have done this several times before.  The description on the Climbing.com article even mentions the single-rope scenario for the biner block although it does not show the diagram.  

Jeremy B. · · Unknown Hometown · Joined May 2013 · Points: 0
rgold wrote:

I don't get what you're describing here.  If the alpine butterfly is on the blue line, then the joining knot has to be on the same side of the anchor as the alpine butterfly, otherwise the rappel is irretrievable.  But then nothing holds the blue rope in place for rappelling and the butterfly and carabiner serve no purpose. 

Ah yes, I remember bearbreeder commenting on the diagram as well.  What I'm pretty sure the OP means is to reverse the order of the EDK and the butterfly, but keeping them on the same (original) side of the anchor.  This is to mitigate the chance of the EDK pulling through and getting the rope stuck (EDK ending up on the other side of the anchor carabiners and the butterfly still on the other.)

David Kerkeslager · · Brooklyn, NY · Joined Jan 2017 · Points: 45
Jeremy B. wrote:

Ah yes, I remember bearbreeder commenting on the diagram as well.  What I'm pretty sure the OP means is to reverse the order of the EDK and the butterfly, but keeping them on the same (original) side of the anchor.  This is to mitigate the chance of the EDK pulling through and getting the rope stuck (EDK ending up on the other side of the anchor carabiners and the butterfly still on the other.)

Yeah, I think you got what I meant. It's hard to describe this. Here's an amazing diagram:

Hopefully that makes what I mean clearer, rgold?

David Kerkeslager · · Brooklyn, NY · Joined Jan 2017 · Points: 45
Zachary Winters wrote:

The 30cm is just indications the tail length.

Facepalm I'm amazed I didn't realize this.

Michael Schneider · · Unknown Hometown · Joined Apr 2014 · Points: 735

A, 'keep it simple' moment, (&, no, I do not use a 'twist 'd cord' figure 8, (nttawwt) it is just a clear example)

Brian L. · · Unknown Hometown · Joined Feb 2016 · Points: 90

I don't have any practical expirience with this, but if you block with the alpine butterfly it seems like it would have a higher probability of being passed/jammed into the anchor ring - resulting in a stuck rope.

My  thinking is based on the profile of an alpine butterfly vs the profile of an EDK.

Isn't it pretty standard procedure to load an EDK in a two rope rappel? Is this an observed failure mode for single line raps?

John Wilder · · Las Vegas, NV · Joined Feb 2004 · Points: 1,530

#1. Not a concern. The joining knot is fine, for this. 

#2. I climb with a half rope for a retrieval line anyway. I suppose this kind might be a concern, but not really, as you wouldn't use this trick if the edk would pull through the ring in the first place. 

#3. I'd prefer the joining knot, personally. 

David Kerkeslager · · Brooklyn, NY · Joined Jan 2017 · Points: 45
John Wilder wrote:

#1. Not a concern. The joining knot is fine, for this. 

#2. I climb with a half rope for a retrieval line anyway. I suppose this kind might be a concern, but not really, as you wouldn't use this trick if the edk would pull through the ring in the first place. 

#3. I'd prefer the joining knot, personally. 

#2 I typically climb with a single rope, and frequently my partners and I use belay devices that can only handle single ropes. As such it makes sense to carry a lighter cord as my retrieval cord if I can do it. I may switch to a half rope system eventually, but that's not in my budget for the immediate future.

Why is it important that the knot not pull through? Isn't the entire point of the alpine butterfly and carabiner to avoid relying on the knot not pulling through the anchor ring?

#3 Could you say more about why this is your preference?

David Kerkeslager · · Brooklyn, NY · Joined Jan 2017 · Points: 45
Michael Schneider wrote:

A, 'keep it simple' moment, (&, no, I do not use a 'twist 'd cord' figure 8, (nttawwt) it is just a clear example)

This idea definitely simplifies things.

Michael Schneider · · Unknown Hometown · Joined Apr 2014 · Points: 735

David, 

A few things, I have not climbed in the 'regular' gunks much since the addition of the bolts. You do yourself a dis-service by not using a twin system. Getting it dailed-in, and knowing what is and what's is not ' normal' or Standard Operating Procedure.

There is no more proven crucible for learning how to Rock Climb than the Gunks. It is sad to hear that this, may no longer be the case. 

Practice building your own belay stations, ignore the 'shortened' version of the routs; climb past the bolts and belay. If you look you will see remnants or pin scars of the old stations on many routes.

Jason Halladay · · Los Alamos, NM · Joined Oct 2005 · Points: 10,337
John Wilder wrote:

#1. Not a concern. The joining knot is fine, for this. 

#2. I climb with a half rope for a retrieval line anyway. I suppose this kind might be a concern, but not really, as you wouldn't use this trick if the edk would pull through the ring in the first place. 

#3. I'd prefer the joining knot, personally. 

I concur with all of John's points. The setup in the diagram is my SOP. 

John Wilder · · Las Vegas, NV · Joined Feb 2004 · Points: 1,530
David Kerkeslager wrote:

#2 I typically climb with a single rope, and frequently my partners and I use belay devices that can only handle single ropes. As such it makes sense to carry a lighter cord as my retrieval cord if I can do it. I may switch to a half rope system eventually, but that's not in my budget for the immediate future.

Why is it important that the knot not pull through? Isn't the entire point of the alpine butterfly and carabiner to avoid relying on the knot not pulling through the anchor ring?

#3 Could you say more about why this is your preference?

#2- My *trail line* is a half rope- I don't like having a rope I can't lead on in a pinch. I lead on single lines. 

It's important that the knot doesn't pull through because you're rappelling on a single line. The butterfly is your *backup* to keep you from dying if it does. Using the clove on the spine of a carabiner would be a viable alternative- in which case, i would put that up against the rap ring and the joining knot below. 

#3- If i'm going to rappel this way, and it is HIGHLY unusual that I do- i want the system to look and function like my regular rappel system, so that no one gets confused. Usually if I do rappel this way, it's because I'm dumb and forgot my ATC, in which case, my partner is rappelling as usual. In this case, they'll undo the butterfly and set the system as normal for rappel. 

You can skin it any way you like- if everyone is rappelling on grigris, i'd probably just do the clove/carabiner trick- i recently learned this canyoneering and think its pretty slick for sure.

All of that said- since I rappel with a single rope and half rope, i usually just use an atc.

physnchips · · Boulder, CO · Joined Jan 2016 · Points: 0
Michael Schneider wrote:

A, 'keep it simple' moment, (&, no, I do not use a 'twist 'd cord' figure 8, (nttawwt) it is just a clear example)

Yeah, this works for rappel lengths of single rope.

To anyone reading the article, do not use the last method. It's okay on it's own, but it's not simple and if you end up getting confused and make a flat figure-8 the knot rolls super easily and will suck up your tails until there are no more and you die.

Michael T Young · · Seattle, WA · Joined Jan 2016 · Points: 5
physnchips wrote:

Yeah, this works for rappel lengths of single rope.

To anyone reading the article, do not use the last method. It's okay on it's own, but it's not simple and if you end up getting confused and make a flat figure-8 the knot rolls super easily and will suck up your tails until there are no more and you die.

The flat figure 8 is definitely a widow-maker, but I don't think you could accidentally tie a flat-figure 8 if you start with a figure-8 on a bite and rethread it with the other rope.

Em Cos · · Boulder, CO · Joined Apr 2010 · Points: 5
Michael T Young wrote:

The flat figure 8 is definitely a widow-maker, but I don't think you could accidentally tie a flat-figure 8 if you start with a figure-8 on a bite and rethread it with the other rope.

Well, all that would take is to start your rethread from the wrong end. 

Michael T Young · · Seattle, WA · Joined Jan 2016 · Points: 5
Em Cos wrote:

Well, all that would take is to start your rethread from the wrong end. 

ok but by this reasoning you should never tie the flemish bend either.

Em Cos · · Boulder, CO · Joined Apr 2010 · Points: 5
Michael T Young wrote:

ok but by this reasoning you should never tie the flemish bend either.

I'm not reasoning any such thing. Just explaining to you how you could start with a figure 8 and by rethreading still manage to tie a flat 8. 

Marc801 C · · Sandy, Utah · Joined Feb 2014 · Points: 65

Since there's a strong LNT ethic among a certain percentage - fortunately increasing - of canyoneers, the canyoneering community has gone far beyond the climbing community in coming up with techniques to satisfiy the principles of LNT. I'm not sure where the biner block originated, but you see it far more often in canyoneering than in climbing. Then there's the Fiddle Stick:

http://www.canyoneeringusa.com/techtips/fiddlestick/

Guideline #1: Don't be a jerk.

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