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Serious simul-climbing accident

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Serious simul-climbing accident

Postby mvs » Fri Jul 02, 2010 10:05 am

These guys were trying to climb 100 pitches in a day in Eldorado Canyon. But there was an accident, basically a long (factor ~2) leader fall. One of the climbers wrote a detailed accident report, check it out here.

One of the dangers of simul-climbing is expressed here in a particularly scary way:

In simul-climbing it is much, much worse if the second climber falls than if the first climber falls. If the first climber falls and the gear is solid, it can be very similar to a regular belayed fall, though much scarier and potentially much more serious. But if the second climber falls and the leader is any distance above his last piece, it will likely kill the lead climber. This is because he will be pulled the last piece of protection and then abruptly stop - not getting the advantage of the dynamic rope which stretches to cushion the impact of a fall.


The placement of a Ropeman device here and there can theoretically prevent that worst case scenario.

Best wishes to the victim for a full recovery.
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Postby The Chief » Fri Jul 02, 2010 2:13 pm

Another way to remedy this is to climb untied when simul climbing when on this type terrain. Never have I nor will I ever climb tied to my partner if we decide to march on in this fashion. Unless of course Guiding over Glacier/Crevassed Terrain on a Short Rope. Different ball game though.

You will move faster as a team as well if untied.

PS: Hey Michael!!! How's life rolling on ya? When are you coming back out to get on some Sierra BC Secret Stuff????
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Postby brenta » Fri Jul 02, 2010 4:41 pm

This story has obviously been big news here in Boulder. Even those like me who are not personally acquainted with these guys had heard of them. Here's to Tom K's continued recovery at the very fast pace he's kept so far.

A couple of remarks:

1. If they had been untied, and Tom had fallen, he would be dead.

2. Bill's analysis of a follower's fall, which is also in the book Speed Climbing! he co-authored with Hans Florine, is pessimistic. In particular, if there is no slack in the rope, and the two climbers have the same mass, then the effect of the falling second is to double the effective fall factor for the first. (Or, if you prefer, to double the first's effective mass.) This is obviously serious, but nowhere near the infinite fall factor that Bill assumes.

Simul-climbing is obviously more risky than regular roped climbing, but in the situation in which Tom and Bill were, I believe it was a lot safer than soloing.

Finally, kudos to Rocky Mountain Rescue!
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Postby mvs » Fri Jul 02, 2010 9:18 pm

The Chief wrote:...

PS: Hey Michael!!! How's life rolling on ya? When are you coming back out to get on some Sierra BC Secret Stuff????


Real good! Well I changed jobs and the opportunity for travel out there hasn't come up. Man, I would love to join you though for a few days. The only thing that intimidates me is the seemingly ungodly weight you can carry in a pack :lol:

But I'm making do. Heading to the Dolomites in a few weeks, not the same as splitter backcountry granite, but it has it's charms :).

--Michael
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Postby nartreb » Sat Jul 03, 2010 4:40 am

Bill, you're predicting that the leader will actually hit the biner on the last pro, with his harness. That would indeed be a static landing, like hitting a ledge. (edit: given the context that started this thread, removed speculation as to injuries that might result from such a sudden arrest.)

But it's likely that the leader will in fact fall past the pro. Imagine that the leader and follower fall simultaneously - in that case there's zero tension on the rope, because the leader and follower accelerate downward at equal rates. The leader's fall is mostly the same as it would otherwise be, except that he gets caught at about the height of the last pro (instead of a distance below it equal to his original height above it) - the follower's fall acts like taking in slack, though without actually removing any length from the rope. Of course, the rope has to absorb BOTH the leader's fall and the follower's fall. But the odds that the leader actually hits the biner with his harness are too small to worry about - he'll fall past it faster than the rope can pull him towards it, even though the rope will start to come under tension as he approaches the height of the piece.

In a real follower fall, the follower gets a head start downward, putting tension on the rope that will pull the leader toward the last pro. But gravity still acts on the leader, and he won't fall in a straight line to the last pro unless he starts EXACTLY above it. He may have only a small amount of rope between his harness and his pro, but we know from everyday climbing experience that it's not that length that matters, it's the length of the rope in the system relative to the fall. Granted, higher forces (still have to absorb both fallers) means higher friction so the rope won't stretch over the 'biner as easily as in a one-man fall, so the rope won't act quite as dynamically as in an ordinary leader fall. Also the pendulum into the rock face would still be nasty and short. But it wouldn't be a static landing.
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Postby brenta » Sat Jul 03, 2010 5:46 am

Bill,

Thanks for chiming in.

nartreb gave a good qualitative analysis. In sum, the connection between the biner at the highest piece of pro and the falling leader is through the rope. As the tension on the leader's side exceeds the tension on the second's side (plus friction), the rope starts flowing through the biner towards the leader.

The doubling of the effective fall factor is easily derived from conservation of energy. The effect of slack is also easily modeled. As one would expect, slack makes things worse. Arguments based on conservation of energy obviously lead one to disregard a lot of factors, but they shed light on the main forces at work.
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Postby The Chief » Sat Jul 03, 2010 6:59 am

When I do in fact simul with my partner and remain tied in (which is very rarely indeed and only done with a partner I climb with regularly etc), the slack factor is always a concern in both of our minds as well as consistent solid pro placement to avoid large gaps of slack from between the leader and their last piece of gear. Keeping the rope as taught as possible and maintaining consistent yet a very conservative pro spacing (no more than 10' between placements and avoiding long ass runouts as may be the case here), is another way to avoid long distance leader falls, upward pulls on the second and maintaining a good solid amount of pro between climbers reducing the potential for total failure of the system.
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Postby phlipdascrip » Sat Jul 03, 2010 11:33 am

Interesting topic. Guess you'd have to research documented cases of follower falls to get to a conclusion. My understanding is that if the follower falls, there's a very high chance the leader will be pulled towards the last piece as he approaches it. If both climbers weigh about the same, the leader should not have created a stronger force than the follower, so no slack would be pulled back towards the leader upon impact.
But I'm also thinking that in the moment the follower pulls the leader off the rock, the follower's fall is decelerated a bit as he accelerates the leader. This would give the leader a small "head start" over the follower, and falling faster than him the leader 1) might pass the last piece of pro before the rope comes tight, and/or 2) have a stronger fall force to actually pull some rope back towards him upon impact.
That's all my guess though.

Here's a thread on the topic over at supertopo:
http://www.supertopo.com/climbing/threa ... _id=144455
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Postby mvs » Sat Jul 03, 2010 10:34 pm

phlipdascrip wrote:...
Here's a thread on the topic over at supertopo:
http://www.supertopo.com/climbing/threa ... _id=144455


That is a really good thread. I recognize that the whole topic is "playing with fire" but it's nice to see some opinions there backed by experience.
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Postby brenta » Sun Jul 04, 2010 1:20 am

phlipdascrip wrote:If both climbers weigh about the same, the leader should not have created a stronger force than the follower, so no slack would be pulled back towards the leader upon impact.

This is the all-too-common confusion between force and energy. Suppose two identical climbers have the same speed. Then they have the same kinetic energy. The forces on the climbers, however, are

1. Gravity. This force is the same for both because they have the same mass and the gravitational field is effectively the same at both positions. Since gravity is the same, we can ignore it in this discussion.

2. Elastic force due to the rope. This force is governed, in first approximation, by Hooke's Law, which applied to a rope of uniform construction says that the shorter the rope the higher the force for the same elongation.

Initially, when the rope has just come taut and the tensions are low, static friction prevents the rope from moving across the biner and the climber with less rope is decelerated more violently. However, the tension in the rope on his/her side increases until the difference in tension between the two sides cannot be compensated by friction. Then the rope moves. It's Newton's second law of motion, nothing more, nothing less.

phlipdascrip wrote:But I'm also thinking that in the moment the follower pulls the leader off the rock, the follower's fall is decelerated a bit as he accelerates the leader. This would give the leader a small "head start" over the follower, and falling faster than him the leader 1) might pass the last piece of pro before the rope comes tight, and/or 2) have a stronger fall force to actually pull some rope back towards him upon impact.

What happens is that elastic waves travel along the rope.
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Postby The Chief » Sun Jul 04, 2010 1:24 am

Hey Brenta....

What is the longest leader fall you have ever taken?
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Postby brenta » Sun Jul 04, 2010 1:30 am

The Chief wrote:Hey Brenta....

What is the longest leader fall you have ever taken?

About ten meters, in 1985. Why?
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Postby The Chief » Sun Jul 04, 2010 2:48 am

brenta wrote:
The Chief wrote:Hey Brenta....

What is the longest leader fall you have ever taken?

About ten meters, in 1985. Why?

How often do you take 20 footers or more and when was the last time you simul'd a 5.8 or greater?

Just curious.
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Postby brenta » Sun Jul 04, 2010 3:56 am

Just curious. I see. I'm relieved that you are not trying to derail the conversation by making an ad hominem argument.

At any rate, you shouldn't indulge this curiosity of yours to such an extent. In a grown-up man, it may be construed as a character flaw.

Now, can we return on topic?
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