Pros and cons of simul-rappelling

DR Rockso. I don't care how experienced the guy was supposed to be the friction knott was not tight enough if it didn't grab with the rappelers hand on it.  You can set them up like that and they work fine at the beginning of the rappel but won't work at all at the end of the rappel when there is less weight of the rope pulling down. the only way to set it up so that it works both at the top and the bottom of the rappel is to make it tight enough that its a PINTA to slide while starting your rappel. by the time you finish the rappel it is almost slides easy but it will still grab regardless of if you grab the knott.   set it up so it  slides easy at the top and it will not grab at the bottom of the rappel and it will also not work if the rappeler grabs it. 

Nick Goldsmith wrote: DR Rockso. I don't care how experienced the guy was supposed to be the friction knott was not tight enough if it didn't grab with the rappelers hand on it.  You can set them up like that and they work fine at the beginning of the rappel but won't work at all at the end of the rappel when there is less weight of the rope pulling down. the only way to set it up so that it works both at the top and the bottom of the rappel is to make it tight enough that its a PINTA to slide while starting your rappel. by the time you finish the rappel it is almost slides easy but it will still grab regardless of if you grab the knott.   set it up so it  slides easy at the top and it will not grab at the bottom of the rappel and it will also not work if the rappeler grabs it. 

At the risk of some beginner taking anything you have to say seriously, you have no idea what you're talking about. A tended autoblock will not catch you if it continues to be tended and if you are setting it up so tight at first that it's a pain in the ass to go down then you're doing it wrong. Either choose a different material, or modify your technique. The Sterling Hollowblok works quite nicely for many rope many rope diameters. 

that's funny I only have a couple thousand hrs using the things.. Everyone always sets em up and tests them at the top of the rappel. next time you set it up with your nice loose wrap that will hold just fine with 60m of rope hanging under it and yes it will slip if you grab it.  Rap down 40m and let go. It will not hold. Add one more wrap. now its much slower, you have to work a bit to get it through at the top of your  rappel but if something happens on the lower 3rd of your rappel it will actually grab and if you grab it accidently it will still work..  but what the hell do I know...

If in 1000's of hours of practice you haven't figured out how to set up an autoblock that catches correctly without it being a pain in the ass then I am even more concerned than I would have been if you started climbing last week. 

revans90 wrote:I’m curious to how simul rappeling is considered more dangerous then normal? Is it the fact that when there is a fuck up that two people rappelling resulting in x2’s the possibility of injury? What’s the difference if you fuck up on a normal rappel  vs simul?

It’s covered in the thread above. 

I use an autoblock on the leg loop all the time. 3 wraps of 6mm supple cord on two ropes, it’s a tad bit tight at the top, only a minor issue if it’s not a vertical and my whole weight is not on the rope. And it locks up fine at the bottom.

Actually the case I mentioned the party never let go of the brake strand. Simul-Rappelling is inherently more dangerous because a mistake by either partner likely results in both parties falling. It assumes reliance on a counterbalance and there are additional failure modes not present in traditional rappelling, such as one partner unweighting the rope or taking off their device, as well as concerns with differently weighted partners. Some of these concerns can be addressed in different ways.

Many rappelling techniques are completely safe when done perfectly, so what is being discussed here is which techniques are more fool proof, less prone to error, and have the least consequences if an error is made. Of course the answer of which system to use all the time isn't easy or feasible because different situations have a different ideal technique, and that is where judgment and experience combine with your tool box to make good decisions. 

L Kap wrote:

Like seriously, one of their big take-aways was "don't use an autoblock or you'll get reliant on it - just train yourself to never let go of the rope". Yeah no. We're not going to agree on that one.

Ha, that is pretty much my perspective.  I think autoblock knots ingrain bad habits that, combined with the added procedural complexity at each rap station, make them frequently more dangerous than avoiding the "backup" altogether.

Regarding the OP, simul-rapping seems only peripheral to the Gobright accident.  He didn't let down enough rope, then rapped off the ends.  The same thing could have happened with a single-person rap.

Simul-rapping is riskier mostly because one mistake tends to have about twice the consequences (2 climber injuries instead of 1).  In this case, the other guy was basically fine.

JaredG wrote: 

Ha, that is pretty much my perspective.  I think autoblock knots ingrain bad habits that, combined with the added procedural complexity at each rap station, make them frequently more dangerous than avoiding the "backup" altogether.

Disagree. What bad habits? Whenever I rap without an autoblock I think about how all it would take is losing control of that hand (lose footing and fall on that hand, hit by rockfall, etc. unlikely but possible) and you fall.

Simul-rapping is riskier mostly because one mistake tends to have about twice the consequences (2 climber injuries instead of 1).  In this case, the other guy was basically fine.

I’d say it’s riskier because human error is the main cause of rappel accidents and you are approximately doubling the chance that would happen since two people have to not make errors. 

All the technology developed from climbing tends to isolate us from what would otherwise have been immediate catastrophes. (eg BITD, if you let go of the brake strand you died).  In my view of human nature, this removal from consequences can't help but make them less influential in our behavior.  The absolute imperative to hold on to the brake strand or die now becomes something a person might find it useful to train themselves to do.  The perspective is totally changed.  The good news is that, overall, we're safer.  The bad news is that some of that safety margin is eaten away by a reduced attention to consequences that are no longer immediate and final.  We have improvements, but they aren't as effective as they could be, because they are undermined by human nature.  I think the reality of this undermining is not enough to condemn the technological advances themselves as some would like to do; most of us are safer with the technology than without it.  But a new and I think genuine issue arises: how do we stay properly afraid of consequences now rendered somewhat remote?

revans90 wrote:

Don’t tie knots in the end of your rope?

Edit : body rappel?

I assume you're being facetious.  In case not,  I didn't ask how to go back to the old ways, I asked how to mitigate the downsides of the new ways.

An autoblock will NOT stop you from rapping off the end of your rope, no matter what device you are using. I think there’s some misconception about it’s uses. Try it over a crash pad under a tree branch. A “shunt” is the only device I’ve ever seen/used that can prevent this.

As for it not grabbing at the end of a long rappel is due to friction loss, not weight of the rope that’s left hanging. The weight creates a bend in the rope which creates friction as it passes thru the autoblock/prussik/whatever, more wraps always  = more friction, then diameter comes into play, blah blah...

The friction loss after rappelling some distance is due to the fibers of the autoblock/prussik/whatever “burning” for a lack of a better term, as it travels over your rope. All the fibers momentarily compress, which hardens that area, makes it slicker, and loses some friction. Speed of the rope also comes into play, try to get a prussik/autoblock to grab on a rope that’s passing thru it fast, it’s almost impossible, you have to move it away from it’s attachment point and physically try to lock it. 
There’s a reason tandem prussiks have been phased out in the rescue industry, they have a 50/50 track record of working in critical scenarios when there’s been a system failure. 

revans90 wrote:  So there is no difference if you fuckup on a normal rappel vs a simul?

Remember we are talking about pros and cons not hypothetical errors.

If you fuck up a normal rap your partner probably wont die. If you fuck up a simul rap he has a good shot at it.  As long as you're the one fucking up theres no difference.

rgold wrote: how do we stay properly afraid of consequences now rendered somewhat remote?

By never forgetting that our primary means of safety is our ability to hold onto the rock, or the rope, or whatever else, and always remember that the backup is an inferior system only there 'just in case', and that due to it's inferiority it should be treated with a bit of mistrust. So, basically, see things for how they really are.

Also, consider the following (rhetorical) situation:

You are sampling members of the population to record their eye color and they all have either brown or green eyes. You know 90% of the population have green eyes, and 10% brown eyes, and the population is 100 people, and once you have recorded someones eye color you obviously don't need to record it again. Now, pretend you keep finding people who you have yet to record, with only green eyes: what is happening to the probability that the next person you talk to (considering you have yet to record their eye color) has brown eyes?

Maybe the main reason for recommending a tether is for the situation where one of the 2 people hits a section of lower-angle terrain.  The natural instinct (from individual rappelling experience) is to reduce friction until you start making progress despite the low angle.  But with simul-rappelling, if the other person is still on a high-angle section, releasing tension on your side causes them to drop instead of you.  And, since you're still stationary, your instinct is to keep reducing friction.  Eventually you hear strong language from the partner and grab the rope tighter, but by that point (a) the rope is no longer centered at the anchor, (b) the partner may have gained some speed, so stopping them may be harder, and (c) the partner may have already hit something (probably not fatally, but perhaps hard enough to cause them to let go).

A tether mitigates this in 2 ways.  First, it reduces the chances of the 2 of you being on terrain of vastly different angles.  Second, if it does happen and the partner starts dropping, the partner almost immediately pulls you down via the tether, so you start dropping too and your normal instinct to grab the rope tighter re-engages.  I suspect this direct mechanical feedback works much quicker than your response to the partner's screams or your system 2 analysis of what's happening.

Note that this can happen a long way from the ends of the rope, so knotting the ends doesn't address it.  Nor does a friction hitch backup, since you instinctively keep that disengaged when you want to make progress rappelling.

Note also that this failure mode is unique to simul-rappelling.  Because of this (and perhaps other failure modes I'm not aware of - I've only tried simul-rappelling a couple of times), I think the chance of things going wrong with simul-rappelling is much greater than 2x normal.

Pooch bullshit.  Do some actual testing. I have.    A loose easy to use auto block will only work with long 30m tails.  the same number of wraps will not reliably work with 5m tails.  Rveans 90. the difference between simo rapping and solo rapping is simple. If I Fck up on a normal rap I just kill myself. Simu rapping you are at the mercy of the other rappeler  and their mistake may very well kill you and either one of you makes a mistake you are both hurt or dead.

rgold wrote: The absolute imperative to hold on to the brake strand or die now becomes something a person might find it useful to train themselves to do. 

This.

NG, sounds like your argument is over a tightly wrapped autoblock as opposed to a loosely wrapped one, in which I’d 100% ageee with. Length of rope behind the autoblock is insignificant and an insane argument. The weight of what’s behind it would be fair, as it increases friction while your hand is trying to hold it up. Autoblocks are categorized as a friction hitch for a reason.
Since you’re the darth vader of testing and I apparently have never done anything, try testing this: hang a 15lb weight on the end of your 5m tail and see what happens to both of your scenarios. Hell try it on your 30m tail too, bet that gets exponentially more difficult as well...

Serge Smirnov wrote: Maybe the main reason for recommending a tether is for the situation where one of the 2 people hits a section of lower-angle terrain.  ....
A tether mitigates this in 2 ways.   ....  knotting the ends doesn't address it.  Nor does a friction hitch backup,  ....  unique to simul-rappelling.  

Thank you, Serge.  That very clearly explains the potential need of a tether during a simul-rap.  I've edited one of my comments from a few pages back to reference your explanation.

rgold wrote:The perspective is totally changed. 

I don't think it has so much among the core participants.  

What I see is the clumsy, weak and careless that never would have made it off a racquetball court without a sprained ankle 25 years ago are now all into these adventure sports.  The two no-talent clutzs in this video from 2012 have since most likely quit and moved on.

Serge Smirnov wrote: Maybe the main reason for recommending a tether is for the situation where one of the 2 people hits a section of lower-angle terrain.  The natural instinct (from individual rappelling experience) is to reduce friction until you start making progress despite the low angle.  But with simul-rappelling, if the other person is still on a high-angle section, releasing tension on your side causes them to drop instead of you.  And, since you're still stationary, your instinct is to keep reducing friction.  Eventually you hear strong language from the partner and grab the rope tighter, but by that point (a) the rope is no longer centered at the anchor, (b) the partner may have gained some speed, so stopping them may be harder, and (c) the partner may have already hit something (probably not fatally, but perhaps hard enough to cause them to let go).

A tether mitigates this in 2 ways.  First, it reduces the chances of the 2 of you being on terrain of vastly different angles.  Second, if it does happen and the partner starts dropping, the partner almost immediately pulls you down via the tether, so you start dropping too and your normal instinct to grab the rope tighter re-engages.  I suspect this direct mechanical feedback works much quicker than your response to the partner's screams or your system 2 analysis of what's happening.

Note that this can happen a long way from the ends of the rope, so knotting the ends doesn't address it.  Nor does a friction hitch backup, since you instinctively keep that disengaged when you want to make progress rappelling.

Note also that this failure mode is unique to simul-rappelling.  Because of this (and perhaps other failure modes I'm not aware of - I've only tried simul-rappelling a couple of times), I think the chance of things going wrong with simul-rappelling is much greater than 2x normal.

These interesting observations lead me to up my estimate and now think that simul-rapping is more than twice as dangerous as ordinary rapping (how much more I wouldn't pretend to guess), as there are failure modes that are unique to simul-rapping I hadn't accounted for.  This also illuminates another critical aspect of the discussion: when you embrace a complex procedure, it might have failure modes you are unaware of.  I've done some simul-rapping, not a lot, and have never encountered the situation Serge describes.  So there's a lurking liability I don't know about and which is absent from my estimations of risk.