simul rapping with a 3rd person as the backup(what's the actual name for this technique?)

I was recently multipitching in a group of 4 and we had 12 pitches worth of raps to do. I am typically wary of simul rapping since i know the consequences of a failure are a bit higher but one of the guys we were with introduced me to a technique for simul rapping that seemed to eliminate a lot of the risk inherent in simul rapping.

basically if you're in a group of 3, one person would pre-rig themselves with their rappel device, then the two simul rappers will get set up below the first person. Essentially the pre-rigged person acts as a backup so the rope doesn't move if one simul-rapper screws up and raps off the end which in a normal simul rap would kill the other climber.

I'd like to do some reading about this technique(ie. any negatives for this that i haven't considered as well as best practices). Does anyone know the name for this technique?

I've googled a bunch with queries like "simul rapping with 3 people", "simul rapping with a 3rd person as a backup", etc... and haven't had much luck

I do something similar. Set the rope and clove one strand to the anchor with a draw. Two people can rappel simultaneously, but each strand is now isolated so none of the consequences of traditional simul rappeling. Third person pulls the draw and raps normally. 

Agreed with pat if you have a person at the anchor no reason you couldn’t just throw the strands on a clove or knot and basically rap on fixed line strands. Makes it 100% safe 

In a party of 3 this makes sense and I've used this technique frequently when I've been unfortunate enough to have to climb in a party of 3. I'd recommend rapping the single lines with a gri gri, it's faster to setup and gives more control than an atc on skinny single lines. Obviously knotting the end is the imperative thing here, as it is in simul rapping without the prerigged 3rd person, tying a bight knot and Clipping your respective end is a good technique to ensure you haven't forgot to tie the ends off and keeps you from having to pull the rope back up to untie the knot at the next rappel station. 

As another user said,  you could also fix both lines via a knot or hitch. Given that the 3rd has to get on rappel eventually anyways, you might as well fix the lines with their device initially. 

Here are some thoughts from my blog:

https://climbpotrero.com/2019/11/27/to-simul-rappel-or-not-in-el-potrero-chico-and-elsewhere/

Chase G wrote:

Agreed with pat if you have a person at the anchor no reason you couldn’t just throw the strands on a clove or knot and basically rap on fixed line strands. Makes it 100% safe 

yep, that technique certainly works as well. As I mentioned, I'm looking for info specifically on the technique I described.

DrRockso RRG wrote:

In a party of 3 this makes sense and I've used this technique frequently when I've been unfortunate enough to have to climb in a party of 3. I'd recommend rapping the single lines with a gri gri, it's faster to setup and gives more control than an atc on skinny single lines. Obviously knotting the end is the imperative thing here, as it is in simul rapping without the prerigged 3rd person, tying a bight knot and Clipping your respective end is a good technique to ensure you haven't forgot to tie the ends off and keeps you from having to pull the rope back up to untie the knot at the next rappel station. 

As another user said,  you could also fix both lines via a knot or hitch. Given that the 3rd has to get on rappel eventually anyways, you might as well fix the lines with their device initially. 

Here are some thoughts from my blog:

https://climbpotrero.com/2019/11/27/to-simul-rappel-or-not-in-el-potrero-chico-and-elsewhere/

So one of my main questions regarding this technique is... does the pre-rigged climber need to put a prusik on or is a rigged ATC enough to keep the rope from slipping?

Let's say one of the simulers rappels off their end, theoretically the other climber could put enough weight on one rope to have it slip through the anchor and the pre-rigged belay device. In practice, it seems like there would be too much friction for the rope to slip. Does that make sense? I might not be describing it properly.

dsauerbrun wrote:

So one of my main questions regarding this technique is... does the pre-rigged climber need to put a prusik on or is a rigged ATC enough to keep the rope from slipping?

Let's say one of the simulers rappels off their end, theoretically the other climber could put enough weight on one rope to have it slip through the anchor and the pre-rigged belay device. In practice, it seems like there would be too much friction for the rope to slip. Does that make sense? I might not be describing it properly.

I do all of the above frequently. In your scenario, if rappeller 1 slides off the end to their demise, it's a toss up if the rope will start sliding through from the weight of rapeller 2. Factors like friction on the rock, through the rings, rope size, fuzziness of the rope, whether or not rapeller 3 is somewhat tensioning the pre-rigged ATC (is their connection to it totally slack etc. 

In my experience, if it does start to slide, it is usually more of a creep and all rapeller 3 has to do is grab the ropes. That said, it can be a bit unnerving! putting a prussic on definitely helps and imo is a great step to do in this setup. I would certainly consider all of this an advanced technique that should only be used by care with people who understand how it could fail etc. 

Also: The Mountain Guide Manual discusses this technique for parties of 3 as mentioned and is worth taking a look if you're interested. It's also a fantastic resource for a lot of not-so-common techniques. 

https://www.amazon.com/Mountain-Guide-Manual-Comprehensive-Reference/dp/1493025147

A little off topic, but descent time for a rap once the lines are hanging nicely is about 30 seconds to 1min per person per pitch for the experienced. Therefore simul rapping can save 12min on a 12 pitch descent. However I have noticed that the greater risk and desire to go at the same pace can lead to a slower descent. So I'm guessing 6min saved? 

Might not be worth it? 

What does speed things up is getting all three plates on the rope at the same time. I have timed this. It allows the second and third tons of time to perform checks and get a prusik on whilst the first descends. Basically they just jump as the rope goes slack. It doesn't even matter if they jump too soon most of the time. They just hang there until the rope goes slack again. None of that, is she down / off the ropes worrying or shouting

David Coley wrote:

A little off topic, but descent time for a rap once the lines are hanging nicely is about 30 seconds to 1min per person per pitch for the experienced. Therefore simul rapping can save 12min on a 12 pitch descent. However I have noticed that the greater risk and desire to go at the same pace can lead to a slower descent. So I'm guessing 6min saved? 

Might not be worth it? 

What does speed things up is getting all three plates on the rope at the same time. I have timed this. It allows the second and third tons of time to perform checks and get a prusik on whilst the first descends. Basically they just jump as the rope goes slack. It doesn't even matter if they jump too soon most of the time. They just hang there until the rope goes slack again. None of that, is she down / off the ropes worrying or shouting

Things can go faster if the simul rappers are experienced with it, but I agree with David that the time savings of simul-rapping aren't consequential.   Still, I think there can be times when there are advantages to having both members together rather than having one waiting and waiting at the top while the other does...who knows what.

Stacking all the rappellers has become common practice, and works well with curated rap stations where it is reasonable to assume that there will be no problems pulling the rope.  But for improvised rappels, the stacked rappellers prevent the first person down from checking how well (or whether) the ropes will pull, leaving the potential for a substantial epic.

If there are three people and one wants to have two simul rap but doesn't want to stack the other two so that the rappel pull can be tested, then I think the Stone Knot ( canyoneeringusa.com/techtip…) is an excellent alternative.

If one is going to have two people simul rap in a party of three, it seems to me to make more sense to have the single rappeller go first.  The first down can resolve the kinds of tangles and hangups that would force simul rappers to divert their full attention,  prepare the landing stance, anchor the ropes to prevent anyone from going off the end, and supply simultaneous fireman's belays to the simul rappers.  (This is best done by keeping the ropes in the fireman-belayers rap device.)

If pre-installed devices are called for to save time, the simul-rappers can each have their device pre-installed on one of the rap strands. (If they leave enough room and aren't weighting their strands, the first person down can still test the pull even though the party above is installed). Done this way, the party gets whatever time advantage is obtainable and also the efficiency of pre-installing the devices.

to the OP, we're you climbing a (presumed) 12 pitch route with 4 people on 1 rope?? i'm assuming you were climbing in 2 groups of 2 and had 2 ropes, in which case i would advocate for tying 2 ropes together and rapping 1 at a time... as previously mentioned, there is little (if any) time to be saved in simul rapping.

Its called "pre-rigging," "pre-rigged rappel," etc... sorry, you answered your own question.

When you have pre-rigged, you have isolated the individual strands of rope to allow people to rap single strand. They are no longer simul-rapping. Canyoneers do similar for large groups using the "stone knot" and sometimes some very weird releasable setups with figure 8's.

Useful for rapping multipitch in a party of 3, especially when 1+ of the people only have GriGri or other single rope devices, or allowing multiple parties to all rap quickly as a public service to help everyone get down off crowded multipitch. I have also isolated strands like this when set up with a big group somewhere like Chrysler Crack, where you scramble up some stuff that would suck to down climb, then rap off later. By pre-rigging the rap line or otherwise isolating the strands, like with a Stone knot, anyone who needs to leave early can just peace out and go rap, regardless of what device they have available without needing to reconfigure the rap rope setup.

To me, the one of the biggest benefits of pre-rig is that only one strand needs a knot. This means you don't need to pull up the rope after it falls from the previous anchor and past you. 

If you start doing isolated simul-raps on single stands, you'll need to pull that end of rope up, otherwise someone is rapping on an open system. I suppose if you're okay with that risk (I'm personally not), or if the first person down rigs on the closed system and beats the second person down (and ties a knot for them) it's okay. 

In my experience, the part of rappelling that's time consuming is the rope management, not the actually rappelling. So getting ropes off bushes, chicken heads, ledges, out of cracks, down slabs, etc and the rigging of the next rap.

rgold wrote:

If one is going to have two people simul rap in a party of three, it seems to me to make more sense to have the single rappeller go first.  The first down can resolve the kinds of tangles and hangups that would force simul rappers to divert their full attention,  prepare the landing stance, anchor the ropes to prevent anyone from going off the end, and supply simultaneous fireman's belays to the simul rappers.  (This is best done by keeping the ropes in the fireman-belayers rap device.)

This.

dsauerbrun wrote:

So one of my main questions regarding this technique is... does the pre-rigged climber need to put a prusik on or is a rigged ATC enough to keep the rope from slipping?

Let's say one of the simulers rappels off their end, theoretically the other climber could put enough weight on one rope to have it slip through the anchor and the pre-rigged belay device. In practice, it seems like there would be too much friction for the rope to slip. Does that make sense? I might not be describing it properly.

My testing seems to support that the ropes don't really move even if the 3rds hands are not on the brake strands. Of course with their hands on as they should be the strands are assured to be completely and reliably fixed.  A third hand isn't really necessary.  

Regarding people's comments about the atc rappeller going first,  I've found that in practice the simul rappellers can go much faster given they only have 1 rope each to untangle, on gri gris there is no additional that needs to be given to have the same level of safety as an atc rappellers on both stands with an autoblock. 

I rapped a 9.8mm single strand below the single, prerigged, weighted ATC of my partner and it worked fine with no slip. I believe the weighted component is important as it applies more braking force on the strands, but I would want to see that tested.

The situation was that my ropes’ halfway marker faded (Mammut ropes ofc) and I misread the halfway point while rigging the rappel at dusk. One strand was short about 10ft from the anchor and my partner was prerigged above, so I untied the stopper on the short strand and rapped on the single remaining strand to the next anchor. Sketchy but went totally fine! Would do again, hopefully don’t have to, and would recommend my partner tie an autoblock in-situ.