Pre-rigging a rappel (known by some as a “stacked” rappel) is a common technique with guides and clients. But, it has some benefits that crossover well to recreational climbers too.
What is a pre-rigged rappel? It’s when everyone on the climbing team (or, as many of them as can comfortably fit near the anchor) attaches to the rope at the same time with an extended rappel. There are various ways to rig an extended rappel; we’ll cover them in another tip. The extended sling allows the people waiting to rap to be connected to the rope, but not be pulled around by the rope tension from the person on rappel.
An extended (or stacked) rappel setup. Purple sling is rapping first, while black sling is also ready to rap the moment purple goes off rappel. (Yes, eagle eye, the yellow biner needs to be locked . . .)
Okay, got it. So . . . why would you want to do this?
A pre-rigged rappel improve safety.
We always give our partner a safety check when we’re climbing up. Why not do the same on the way down? With everyone pre-rigged at one time, teammates can give each other a proper safety check of BRAKES (Belay device, Rope, Anchor, Knot, Extension and Safety backup).
Compare this to the traditional rappel method, where the last person waiting to rap rigs up completely on their own, with no one there to give them a safety check. This risk can be increased when an inexperienced rappeler is the last person heading down, which is typical in a two person team - the most experienced person would almost always go first, to find and rig the lower anchor, or to give a fireman’s belay to the second person down. That’s a reason why guides like this method.
A pre-rigged rappel improves speed.
I’ve read a bunch of articles and web discussions on a pre-rigged rappel, and curiously no one seems to mention this benefit. You get everyone down the rappel faster. Why is this? Because it eliminates the downtime of waiting for climbers to rig the rappel one by one. After rigging up, everyone can be on the tensioned rope without being yanked around because of the extension. When Rapper 1 is on rappel, Rapper 2 is putting on their autoblock knot. The moment the Rapper 1 goes off rappel (or just feeds a couple meters of rope through their device) apper 2 can head down immediately. The movement of climbers down the rope is pretty much constant, with no waiting for someone to rig. (Of course this downtime is much less with skilled climbers, but it can be an eternity with a larger group of beginners.)
The one downside to a pre-rigged rappel is that the first person down can’t do a test pull to see that the ropes pull smoothly, because the person above is essentially locking the rope in place. If you have any doubts about pulling the ropes, you might not want to use this method, because pulling the rope without issue is more important than adding a small degree of speed and safety by pre-rigging.
Should you use a pre-rigged rappel every time you rap? No, probably not. But, if you find yourself with an inexperienced partner, or with a larger group, it can add a margin of safety and save you some time.