This tip was written with the help of Bryan Hall, who is certified by the Society of Professional Rope Access Technicians (SPRAT) at their highest level. Connect with Bryan at www.rosecityropes.com
Note - This post discusses techniques and methods used in vertical rope work. If you do them wrong, you could die. Always practice vertical rope techniques under the supervision of an experienced climber, and ideally in a progression: from flat ground, to staircase, to vertical close to the ground before you ever try them in a real climbing situation.
You’re rapping on two ropes tied together in a single strand, and you need to pass the knot connecting the ropes to make it all the way down.
Solution: Tie a butterfly knot just below the knot connecting your ropes. Use the butterfly loop as a ready-made clip in point when you’re passing the knot.
Some more detail on the image below. A Flemish bend connects the green rope and the blue rope. The green rope is fixed at the anchor on top.
You rap down the green rope, and stop when you get just above the knot.
You clip a short leash into the butterfly loop.
Now, you can safely take off your rappel device from the green rope, reattach it to the blue rope below the butterfly, and continue with your rappel.
So, you may be wondering, in what situation might you find yourself rapping on two ropes tied together in a single strand? This could happen for several reasons:
You’re between one and two rope lengths up on a climb, and you have some sort of emergency situation: injured person, incoming lightning storm, impending darkness, whatever, and you just want to get to the ground ASAP and leave your ropes to get later.
You have two or more rope lengths below you on 4th class terrain or steeper snow that at least one person on your team is comfortable down climbing without a rope. You send your whole team down on the two ropes tied together. The last person unties the rope, tosses it, and solo downclimbs. (or “downleads” by cleaning gear left by the next to last person. (That’s another tip you can read here.)
You’ve fixed two or more rope lengths up to the high point on a big wall, and you are rapping back down to the bottom. In a day or two, you’ll come back, ascend your ropes, and continue with the route.
Anyway, those are some not-so-normal-but-entirely-plausible scenarios where you might need to pass the knot on a single rope. (Can you think of any others? )
Typically, this is set up with just a knot connecting the two ropes, such as a rewoven figure 8 bend, also known as the Flemish bend, or simply a flat overhand bend, previously known as the “European Death Knot”, or EDK.
Sure, this is safe enough, but it sure doesn’t give you any assistance when you need to get past the knot. This is the beauty of the butterfly loop - you have a ready made clip in point to attach a short, repeat, short, leash to add an instant safety when you’re unclipping your belay device from the top rope and reattaching it on the bottom rope.
This process is MUCH easier if you can find a small stance for your feet so you can momentarily take your weight off your belay device. This of course should be easy on steep snow, 4th class terrain, or low fifth class rock. If you’re trying to pass a knot on a completely free hanging free rappel, things get more complicated. (We’re not going to cover that in this tip, because it’s a fairly unlikely scenario unless you’re an advanced climber, and if you’re that good, you’ll probably figure it out on your own. :-)
Typically, when tying two ropes together for a rappel, you tie the knot with long tails, at least one foot. Some folks do it closer to two feet (the extra length doesn’t make them not any safer or stronger, but it might add a little psychological boost.) The tail length really doesn't matter, because it's up at the anchor point.
However, in this case, you want to avoid using very long tails. Reason: the person rappelling could make the fatal mistake of reattaching their belay device onto the tail, instead of the actual rope. Yes, it has happened. It probably sounds like a mistake you would never make if you’re reading this indoors on a nice sunny day, but if it’s at night, raining, in a cave, you’re mentally tired, whatever, simple mistakes like this can happen all too easily.
So in this case, the better practice would be this:
tidy up and snug down (aka “dress it and stress it”) your knot really well
try to keep the tails about 12 inches inches or less
Any longer than that, tie an overhand stopper knot in the end to hopefully prevent anyone from rapping up the end of the tail. A stopper knot is also as a good visual reminder that that’s the wrong strand to clip to.