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Figure 8 Leveraging The Biner on Rappel
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pelliott


Mar 26, 2002, 9:01 PM
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Figure 8 Leveraging The Biner on Rappel
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I found a great article that someone posted a link to in rec.climbing that I would like to pass on to the group. Here is the link.
http://www.uiaa.ch/journal/20003.pdf. If you go to page 5, you will see a detailed description of how a figure 8 can pry open a screw gate biner. I think back to the times I rapped off without a prusik to back me up and I shudder that something like this could have happened.


jmlangford


Mar 26, 2002, 9:50 PM
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I couldn't get the link to work(my problem-not the links)but I can picture how it might happen. I tie an 18" runner from the biner on my harness up to the 8. I then attach a Petzl Shunt(basically a mechanical prussik) right in front of me and control the rope with that. It eliminates the 8 possibly unscrewing the biner. Even without a prussik back-up a short runner up to the 8 should eliminate the problem.--My two cents--


jt512


Mar 26, 2002, 10:04 PM
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Really scary. I was going to post a message about this. Note that the biner can break under body weight alone.

-Jay


jmlangford


Mar 26, 2002, 11:26 PM
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Sounds lik a metalurgical engineer needs to get to work and design a biner that is resistent to torque.


apollodorus


Mar 26, 2002, 11:55 PM
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I've got two words for you: locker and ATC. A locking carabiner, or at least two regular biners with the gates reversed, is SOP for figure-8 rappels. ATCs, especially the ones with the tapered slots, or teeth, have pretty much made the figure-8 obsolete. And the back up of a prusik is also a good idea, no matter what you use.


jmlangford


Mar 27, 2002, 12:10 AM
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I've always used lockers and an 8 but I think I am going to use the ATC now...Still, the 8 is much better than the old carabiner 'brake-bar' I used years ago!


miagi


Mar 27, 2002, 8:42 PM
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I was testing this all out on my f8 and locking biner. Although the weight conditions werent the same (i just used my hands) It was pretty difficult to get the f8 off but i do see the potential danger. After about 12 tries i got it off with the simulated direction weight of what happened to that one climber. Scary thought, i never thought about it before.


apollodorus


Mar 27, 2002, 9:02 PM
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Hey, Miagi: one of the most treacherous aspects of climbing is dealing with the Second Law of Thermodynamics, which applies to almost any situation, climbing or not. Some people like to call it Murphey's Law: anything that can go wrong, will go wrong, and at the worst possible moment.

Basically, the Second Law means that things will go from favorable to unfavorable on their own. It's important to realize that testing and checking in a controlled environment will NOT guarantee safety when the rain/dark/fatigue/etc. conspire to make the Second Law a bitter reality.

Rapping is inherently dangerous, and every effort should be made to ensure that you get to come back, here, and post another great post. 8-)


miagi


Mar 28, 2002, 9:11 AM
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I said: Quote:It was pretty difficult to get the f8 off but i do see the potential danger. After about 12 tries i got it off with the simulated direction weight of what happened to that one climber.
I do understand what you mean but I do understand that It can happen.

Cheers! , Mike


camhead


Mar 28, 2002, 10:04 AM
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damn.
I'm just going to stick with an ATC for rapping from now on. Either that or use two opposed locking biners. Would this be overkill?


gilthanass


Mar 28, 2002, 10:26 AM
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   dude, where are you getting your information from? the second law of thermodynamics is NOT "going from favorable to unfavorable" it is "going from ordered to chaotic" basically. Meaning that if a chemical system is more ordered one was (example water) it would rather be more randow (example water vapour) which is why even on days where the tempurature is below boiling (every day) water will still evaporate. I don't know where you are comming from with your favorable to unfavorable thing.


passthepitonspete


Mar 28, 2002, 10:31 AM
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The second law, eh, Tom?

Well, when you see what my aid rack looks like with all your big honkin' cams hangin' off of it, you will understand

"the spontaneous tendency towards disorder"

Were it not for the second law, we could apply heat to our descendeur and float up the rope!

As for rappelling, y'all oughta know that's the way too many good guys get the chop! [Ask]

BACK UP! BACK UP! BACK UP!

Build some redundancy into EVERY system, especially your rappelling system!

And, uh, buddy is right, eh? You probably meant to say "ordered to disordered"(?)

Gads, me lecturing on thermo. My prof would roll over in his grave, even if he is not yet dead. That guy passed me just to get rid of me!


camhead


Mar 28, 2002, 11:01 AM
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uhhh...
I think I know about MURPHY'S LAW of thermodynamics.


jt512


Mar 28, 2002, 1:15 PM
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Miagi, et al, you did not recreate the problem with the fig. 8 and locker. The problem is that under the right circumstances, the fig 8 can put leverage on the sleeve of the locking biner that breaks the sleeve, allowing the biner to open.

When using any equipment with a locking (or non-locking) biner, it is imperative that the biner be loaded only along its major axis. It is worth noting that in at least two of the accidents reported, the victim was using a BD harness with the locker threaded through the two tie-in points. This puts a triaxial load on the biner and aligns the biner poorly for either rappelling or belaying. Belay loops are put on harnesses to help prevent these kinds of problems. If you do not have a harness with a belay loop, get one, and use the belay loop for both rappelling and belaying.

-Jay


miagi


Mar 28, 2002, 4:11 PM
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Well the situation I created worked none the less. If the small eye of the f8 goes around the autolocking sleeve, then is pulled in an upward direction it will lock on the sleeve and turn since your weight is turning it. The situation I did, did indeed open the gate.


mtngypsy


Mar 29, 2002, 10:15 AM
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This is a great article that originates from studies done by the UIAA, and first appeared in their yearly publication. A good reason to support the UIAA.

Long before this article came out I experienced this problem first hand and almost decked from two pitches up. Everyone that insists on using a figure 8 for rappelling should review the article. I personally will not use a figure a for rappelling anymore.

The problem arises from going over an edge while rappelling with a figure 8. When the person repelling moves from the horizontal plane to the vertical it can cause the figure 8 to lever the gate of the locking biner. The leverage can be strong enough to brake or deform (in the case of plastic) the locking collar and allow the gate to open and release the figure 8 from the carabiner. A back up prusic would definitely be life saving in this situation, but could still leave you in a very funky situation.

Two points raised earlier are of little help. The harness I was wearing was a standard Arc teryx model with a proper belay loop, although I can see how the alpine bod, or diaper style harness could contribute to the problem, I strongly feel this is a accident that could happen with any current harness design. The other point about redesigning locking carabiners is also of little help. I donít think climbers or manufactures want equipment that is overly expensive and overly heavy to guard against every single possibility of failure. This is a very rare occurrence that can easily be solved by either redesigning the figure eight for those who insist on using one, or melting them all down to covert them to pooper scoopers , the best solution. The figure 8 has a host of other problems and drawbacks that had already tuned them into a antique novelty items in most climbers gear boxes.

Check out the article then either pressure the gear companies to redesign the flawed eight, or start making pooper scoopers. With all the dogs at our local climbing area a Black Diamond scooper might be just the ticket. Petzl has a new fiqure 8, I haven't played with it so I don't know if it solves this problem or any other F8 problems.



[ This Message was edited by: mtngypsy on 2002-03-29 10:29 ]


pelliott


Mar 30, 2002, 9:11 PM
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I came up with a possible solution. I have some small sewn loops of webbing in my gear bag. I threaded one of them through the figure 8 and then clipped my locking biner into both of the ends of the loop. This keeps the figure 8 away from the locking biner and prevents any torque on the the gate to pry it open. Viola! Problem solved. Now I just have to get out there and try it. What do you all think?


fo_d


Mar 30, 2002, 10:00 PM
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I dont use my belay loop but it seems that it might reduce the chances of this happening. But on the other hand maybe I should either use a back-up or a belay tube from now on.

thanks Pat

Les


paintinhaler


Mar 30, 2002, 10:44 PM
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just use your freakin belay, its alot better eather way


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