As Ed Viesturs famously said, “Getting to the top is optional. Getting down is mandatory.” And sometimes getting down safely means doing it quickly. Simultaneously rappelling, or simul-rapping, is an advanced skill where two climbers descend one rope at the same time (or two ropes tied together: climbing.com/skill/rappel-knots), and one climber’s weight counterbalances the other.
The margin for error is small, but it’s a good trick to know. It’s useful for bailing during a sudden, dangerous storm, or for rapping off opposite sides of a fin or spire where there are no anchor points, which is common in places like the Needles of South Dakota’s Black Hills. The setup is the same as a standard rappel (clip your device onto the rope and descend by letting the rope slide through in a controlled manner), but instead of putting both strands of rope through the device, you take just one. Your partner will take the other, and you will each descend a separate, single line at the same time. We talked to four AMGA guides who have used this technique, and they gave us the lowdown on how to do it safely and properly.
Note: This is an advanced technique only to be employed by experienced climbers who are proficient with rappel systems.
Weight (and unweight) the rope simultaneously. If one person weights the rope without the counterbalance of his partner's weight, he will fall and pull the rope through with him. Stay clipped in to the anchor until you’re absolutely sure that your partner is weighting the rope. Do this by pulling slack through your rappel device and locking it off until it’s clear the rope is taut and holding you both. There should be some slack in your personal tether. It helps to communicate something like “1, 2, 3, weight.” This also goes for unweighting the rope at the next anchor: Make sure you are both secured to the next anchor or safely on the ground before unclipping from the rope.
Communicate. You need to rappel at approximately the same speed and be very aware of what your partner is doing.
Tie knots in the ends of the rope. If one person rappels off the end of the rope, the second person will fall because his weight is no longer being off set. This should be a normal practice when rappelling—unless your rope is touching the ground.
Consider weight differences. If one person is heavier by about 45 pounds or more, he may descend at a quicker pace and potentially pull the rope through the anchor with him. The heavier person should rap on the side that pulls the knot into the anchor, and slightly below the lighter person, with a double-length sling connecting the climbers. Another solution would be a Reepschnur rappel; learn the setup at climbing.com/skill/reepschnur. This allows the heavier climber essentially to “tow” the lighter climber down the wall.
Use an assisted-braking device (e.g., Petzl Grigri or Trango Cinch) or a friction-hitch rappel backup, aka “third hand” (e.g., Klemheist hitch or auto-block). If one person loses control for any reason (gets hit by a rock, has a seizure, etc.), the second person loses his counterbalance, and the consequences will be devastating.
Don’t use only webbing as a rappel anchor. Always rappel off a metal point, like a quick link or rappel rings. The rope slides back and forth through the anchor with any rappel, but there is more movement with simul-rapping. That additional movement, plus the added weight (two people on the rope and anchor), creates more heat and friction; webbing can be easily sliced in two, and the whole system will fail.
Don’t get too far apart. Stay less than 15 vertical feet apart so you can maintain good communication, and you don’t risk knocking rocks down onto your partner. Never rappel off a questionable anchor. This is true any time you descend, but simul-rapping will put more force on the anchor, so it’s crucial that it’s a bomber anchor.
Avoid simul-rapping on difficult terrain. If the terrain is loose, you increase the likelihood of kicking debris onto your partner. Ropes running over sharp edges can be severed more easily with the added weight. You also want to know exactly where you’re rapping to and that your rope reaches.