Joining two ropes

As pictured, one doesn't do a double rope rappel; one rappels on a single rope (in this case, the blue rope). the knot and biner close the system.

this technique is used when the second rope (i.e. the grey rope) is thin (5 or 6 mm pull rope)

The idea is to lead the pitch using a single rope; take your thin pull line out of your backpack and then do a full length rope rappel.

It is an attempt to save weight (not having to carry two full strength ropes or do a double rope lead/belay).

This works fine for rappelling with a single rope with a pull cord. I am not sure if there would be any advantage to this if you were rappelling with two singles, halfs, or twins. The main disadvantage would be that you are more likely to get two figure eights and a biner stuck pulling down the ropes than an edk. At least, that's what my brain says.

If I'm going to rappel with 2 ropes (as opposed to rappelling on one and using the other as a pull-cord as shown) I use an EDK or a double-fisherman's if the rope diameters are unequal.  Connecting them with a carabiner strikes me as more work, a bit sketchier, and probably somewhat more likely to get stuck.  It seems like a fine system for rappelling on one rope, because then in return for these downsides you get the advantage of only having to carry one rope.  Using it when you have two ropes you're going to rappel on gives you the downsides, but I'm not seeing what you get in return.

I think there are two difference scenarios being described here:

1. Rappelling on two strands (either two "standard" ropes or a single rope paired with a smaller rappel line)

2. Rappelling on one strand with a tag line that is only used for pulling the rope

In scenario 1 you typically tie the strands together using an EDK (or similar), rappel on both strands, and pull using either strand (depending on which side of the anchor the knot is on).

In scenario 2 you need something to prevent the rope from moving through the anchor as you descend on the single strand. This is the scenario depicted in that picture. The function of the carabiner (beyond attaching two ropes together) is to prevent the attachment point from moving through the anchor (notice it's clipped to the main line after it runs through the anchor).

To answer your question: there is nothing wrong with doing a two strand rappel on the system depicted in that picture but you're right it just over-complicates the system and is more likely to cause a stuck rope when pulling the ropes.

Hope that helps!

-Alex

edit: looks like others already answered. Anyway, maybe this is still useful.

It makes me wonder if there is any advantage at all to linking the rappel rope and the pull cord with a biner. Is there some advantage to having the biner slide down the whole length of the single rope when pulling the pull cord? 

If you are rappelling off two equal diameter ropes keep it simple.  Tie a tight and very well dressed "EDK" with no twists and back this up by butting up another EDK below (or above this one) and make sure you have long tails (1foot or more).  The weighted EDK trys to "flip" but the unweighted EDK prevents it from flipping.  Dress those knots well.

If you are rappelling with different diameter ropes such as when you are using a thin pull line there are systems similar to the picture you show that are better.  Make sure if you try this method you understand it fully.  It's very easy to make a fatal mistake with this setup.  Simple is usually safer.  

I can think of a few instances where I would use the pull cord, but the risk of it getting stuck, tangled, on something seems pretty high. That said, knowing how to set this up is really helpful in the event of a damaged rope and only being able to rap on one side. I've been there, glad my partner knew how to do this because I didn't, until then. 

A more streamlined way would be to use a stopper knot on the rap line with a 16" tail, then use an arborist throwball line to tie a pile hitch to the tail of the rap line. This eliminates large knots, loops and that damn biner. Probably safer to. I use something similar every day to get into the tree.

jeremy long wrote:

A more streamlined way would be to use a stopper knot on the rap line with a 16" tail, then use an arborist throwball line to tie a pile hitch to the tail of the rap line. This eliminates large knots, loops and that damn biner. Probably safer to. I use something similar every day to get into the tree.

That works to join the ropes, but the main point of the setup being asked about is the ability to rappel on one rope and to do that you need something like the carabiner to block the knot from slipping through. Obviously at some point you can make a knot big enough that it won't, but that's a crappy way to risk your life when there is a safe way to do it with a carabiner. 

You would not be risking your life at all. A stopper knot could never pull through a quicklink that size. My main tie in on my tree harness operates off the same principle. It's ANSI and OSHA certified. At least for suspension, and that's all you are doing when rappelling. Check out some arborist videos on YouTube, similar systems are well developed. You could even use your own retrievable rings.

I would store my throw line in an old chalk bucket, stacked NOT COILED! It will feed nice on rappel.

Give my method a try and you will believe!

Is "EDK" european death knot? I have extensive background in high angle rescue, arbor work and rock climbing. Overhands are trash unless they are a water knot and that is only bomber if tied with flat webbing. I have seen overhands roll through multiple feet of rope. Just sayin.

EDK is euro death knot, yes. It's also the recommended and probably(?) the most commonly used knot in this situation. 

That setup allows you to rap with a GriGri. It makes the pull more difficult.  It is not necessary when rapping with a skinny tag if your knot is substantial and you put both ropes in your device.  

jeremy long wrote:

Is "EDK" european death knot? I have extensive background in high angle rescue, arbor work and rock climbing. Overhands are trash unless they are a water knot and that is only bomber if tied with flat webbing. I have seen overhands roll through multiple feet of rope. Just sayin.

There is nothing wrong with using a flat overhand bend (aka euro death knot) to join 2 ropes for rappelling. It doesn't even need to be backed up. It will not roll off the ends. It is safe. It is almost certainly the best option for joining two rappel ropes. Thousands of people have been using it for decades. I too have over 10 years of tree work and decades of rock and ice climbing. I have rappelled hundreds of times with the "EDK". It is safe. I am 100% positive you have never seen an "EDK" roll off rappel ropes during normal climbing usage.

I have used a rope with a tagline a lot. 

When using tighter rap links where I have high confidence the knot can not slip through, I join the fat to the skinny with an EDK.  In failure, the EDK rolls towards the tails.  So I tie it so the skinny cord has to roll over the fatter cord during the first roll.  I usually tie a backup knot by tying the skinny tail around the fat tail - like a half of a double fishermans.

But I instead rig what's shown in the Ryan's (OP's) picture when the rap rings are big enough that a joining knot might slip through.  Except I prefer the fat cord to run through two rings/links instead of just one ring/link. The hardware in the picture does not seem to allow that.

Raps that use a skinny tag line require a fair amount of awareness on the parts of all involved due the possible issues:  knot pulling through rings/links, skinnier cords tangle more, skinnier cords are harder to pull all else equal, skinny cord may not be strong enough by itself for body weight, etc..  So I tend to not use a tag line if I'm with someone pretty new to multi-pitch.

And I do prefer to lead on a single fat rope.  But I also have double ropes when called for.  So - these days - the tag line gets brought with a single rope when doing a long route where the skinny cord will not be used unless we have to bail (e.g., weather).  Otherwise, the doubles come if double-rope raps are required for descent or climbing as a threesome.

JBernard wrote: I am 100% positive you have never seen an "EDK" roll off rappel ropes during normal climbing usage.

I too have confidence in the EDK for rap use.

But it has happened although likely due to improper knot or simply not dressed and/or tightened well.

Bill Lawry wrote:

JBernard wrote: I am 100% positive you have never seen an "EDK" roll off rappel ropes during normal climbing usage.

I too have confidence in the EDK for rap use.

But it has happened although likely due to improper knot or simply not dressed and/or tightened well.

If by "improper knot" you mean a parallel Figure 8 rather than the overhand, then I agree.  Rock & Ice's very poorly written articles on the EDK - wherein they used this term to refer to the (known-to-be-deadly) Fig 8 variant - have REALLY muddied the water when we talk about the safety of the EDK.

I didn't mean that particular Figure 8, but I do recall that messy R&I article.

The fatality I recall reading about was on Guide Wall in the Tetons.  Double rope rap.  First person went - the most experienced if I recall correctly.  The next to go died during rap when the two ropes separated.  As reported by the third person, the second was uncomfortable with the knot, actually started to change it somehow but then thought better and went on rappel.  Don't know if it was improperly retied or perhaps poorly dressed.  Testing shows dressing it poorly can be a factor.

Nick Evans wrote:

It makes me wonder if there is any advantage at all to linking the rappel rope and the pull cord with a biner. Is there some advantage to having the biner slide down the whole length of the single rope when pulling the pull cord? 

My inference is using distinct knots for each rope addresses the issue of significantly different rope diameters, which compromises many types of knots used to join ropes. But maybe there is another reason....

jeremy long wrote:

Is "EDK" european death knot? I have extensive background in high angle rescue, arbor work and rock climbing. Overhands are trash unless they are a water knot and that is only bomber if tied with flat webbing. I have seen overhands roll through multiple feet of rope. Just sayin.

This is factually incorrect.  The flat overhand with plenty of tail is the standard for joining ropes for rappel. Just sayin.