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Pros and cons of simul-rappelling

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526

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 · · Unknown Hometown · Joined Oct 2013 · Points: 50

It seems to be more of an argument of human error rather than normal rappel vs simul rappel. Of which both are deadly when an error is made. 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.

Also why use an auto block when you can use a prusik?

revans90 · · Unknown Hometown · Joined Oct 2013 · Points: 50
rgold wrote: 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?

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

Edit : body rappel?
rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
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.

revans90 · · Unknown Hometown · Joined Oct 2013 · Points: 50

Yes
Avoid complacency with a safety check? By verbalizing the safety check to yourself or your partner. seems stupid but works. 
Iv fell victim to this literally and was lucky to walk away with just a scar in my arm. I just find the argument one is more dangerous then the other isn’t true. Both are dangerous but are completely safe when all measures are taken. We the user make the system dangerous or safe.  

pooch · · Unknown Hometown · Joined Jan 2011 · Points: 185

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. 

Drederek · · Olympia, WA · Joined Mar 2004 · Points: 315
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.


revans90 · · Unknown Hometown · Joined Oct 2013 · Points: 50
Drederek wrote:


You read my mind 

JNE · · Unknown Hometown · Joined Apr 2006 · Points: 2,035
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?
revans90 · · Unknown Hometown · Joined Oct 2013 · Points: 50

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?

What?

Serge Smirnov · · Seattle, WA · Joined Oct 2015 · Points: 380

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.

revans90 · · Unknown Hometown · Joined Oct 2013 · Points: 50

Page 11 here we come

Nick Goldsmith · · Pomfret VT · Joined Aug 2009 · Points: 440

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.

Tim Stich · · Colorado Springs, Colorado · Joined Jan 2001 · Points: 1,482
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.

pooch · · Unknown Hometown · Joined Jan 2011 · Points: 185

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...

Bill Lawry · · Albuquerque, NM · Joined Apr 2006 · Points: 1,696
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.

Bill Schick · · Unknown Hometown · Joined Oct 2019 · Points: 0
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.

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
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.  

L Kap · · Boulder, CO · Joined Apr 2014 · Points: 95
rgold wrote:

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.  

I agree with you that simul-rapping is more than twice as dangerous and will propose a fourth reason.

1. It has all the same failure mechanisms as regular rapping.

2. If one partner messes up, both can suffer the consequences.

3. It has some unique failure mechanisms that are non-intuitive and go against "normal" rappel habits, like the fact that you absolutely cannot stand on a feature on your way down.

4. It is not as easy to execute as a normal rap because it has more variables to manage and pay attention to....and attention suffers when climbers are distracted, hungry, cold, tired, in a hurry, etc. I doubt it's a straight line function between number of variables that you have to execute perfectly and increasing risk. I'd bet it's more exponentially curved. 
FosterK · · Edmonton, AB · Joined Nov 2012 · Points: 60
rgold wrote: [...]  But a new and I think genuine issue arises: how do we stay properly afraid of consequences now rendered somewhat remote?

This is a divergent thread unto itself, but:

I think climbers can learn much from progress that has been made in recreational avalanche management, and backcountry skiing regarding how to manage the risks. I think Steve House adequately summarized this new approach for climbing with his Alpine Principles. While these are aimed at alpine climbing, they are just as applicable to any climbing discipline or mountain sport. In particular, the debrief is a useful discussion to be had, whether with the systematic approach advocated by House, or a more casual approach.

Guideline #1: Don't be a jerk.

General Climbing
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