Why don’t we tie the ropes together as a stopper when rappelling?

So fyi I’ve been climbing for like 15 years or something. I’ve always tied two stopper knots in the end. Why don’t we just square knot them together and then toss the rope bomb? Semi serious question, just really a thought I had. 

I have heard form Andy K that you don’t want to do it because as the ropes spin the will get bound up and furthermore the loop is more likely to get stuck!

I’m in with Finn:  more likely to get stuck on something and/or twist up.

Some will instead tie the ends of the ropes to their harness for the rap.  Have seen significant twist-age issues this way as well.

https://people.bath.ac.uk/dac33/high/10GettingBackDown.htm ( with plenty of neat diagrams to help explain things). 

Control + F  ----- "B. Putting Knots in the End of the Rope"  

Control + F ------"F. Making Sure you Don’t Let Go of the Rope "

It's an option, I imagine the ropes would twist a bit because the ends aren't free to spin separately. I haven't tested this yet. I definitely wouldn't use a square knot in climbing rope though. That thing comes undone like the dickens in my experience.

Finn Lanvers wrote:

I have heard form Andy K that you don’t want to do it because as the ropes spin the will get bound up and furthermore the loop is more likely to get stuck!

I wonder if the site I posted here has information he no longer agrees with then/has since changed his mind? 

Not too hard to try out and find out.  That's how Kirkpatrick acquired the knowledge he shares.  

I’ve tried it and can confirm that it becomes a twisted nightmare.

aside from the twisting problem, getting both ends stuck is infinitely worse than having a free end to work with. 

A couple of folks mentioned the rope twisting up, but I'd also be concerned to whether the knot would hold if a climber lost control of their rappel, slid fast, and hit the knot with a lot of force.

Is a square knot a good enough stopper to keep from reefing or rolling if you push up hard into it? The way your rappel device pushes on the knot might matter a lot to how the knot fails.

Have you tried rigging it on the ground, and pulling it with body weight? I don't have any data to start thinking about this -- maybe somebody else has some experience, or can point to some pull/drop test results.

In a tagged rappel context, I've been told that a flat overhand / EDK will start rolling ~4kN in climbing rope. But as a rappel stopper, it seems like a different kind of loading, and I wouldn't want to guess.

Maybe you could tie a barrel knot on both strands, together? Not a double fishermans bend... More like a "flat barrel", I guess, but I've never heard that term. If i was forced to set this up at gunpoint, I'd probably do it this way -- but without some testing or real world observation, I'd still have concerns.

Very cool question, though. Fun to ponder.

Tying the ends together is one of many options that exist when rappelling. 

There is no universal option for knotting your rope when rappelling - you need to assess the situation and decide. There are even situations where NO knots is appropriate.

Ryan Lynch wrote:

A couple of folks mentioned the rope twisting up, but I'd also be concerned to whether the knot would hold if a climber lost control of their rappel, slid fast, and hit the knot with a lot of force.

Ryan, 

Really good point!  I see a lot of newer climbers incorrectly tying the stopper knot and/or, not leaving enough tail behind the knot.  I've seen this in both rappels and when "closing the system" in other scenarios.