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#28480 - 04/23/07 02:45 AM Re: cordelette-attention RG [Re: rg@ofmc]
paulraphael Offline
enthusiast

Registered: 01/22/02
Posts: 321
Loc: New York, NY
 Originally Posted By: rg@ofmc
[color:blue]Think about the anchor failure that caused a fatality on the DNB a few years ago. Four pieces, none of them capable of holding 4 kN either separately or in combination. Thinking about anchoring with a 4 kN max as a guiding principle is not a good idea, in my opinion.


This is close to the point I'm trying to make. If you have a few pieces, none of which is capable of holding the maximum possible fall, then you have a serious problem ... even if you concoct some rigging that can distribute the load well enough to get acceptable overall strength. Because in this situation you have zero redundancy, and all varieties of cascading failure are possible.

On the other hand, if your individual pieces are strong enough to hold a factor 2 fall (whether you judge that to be 4 or 8 kn, or whatever), then rigging together multiples give you true redundancy. Equal or quasi-equal distribution is icing on the cake, but I think it's debateable if it's as important as some other practical considerations. Like simplicity, versatility, ease of use, ease of evaluation, etc.

All systems seem imperfect, but in this last regard the cordelette has some things going for it. Understanding its limitations (fixed direction, innability to make safe use of bad pieces) will help you decide when not to use it.

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#28481 - 04/23/07 03:34 AM Re: cordelette-attention RG [Re: rg@ofmc]
dalguard Offline
veteran

Registered: 03/22/00
Posts: 1515
Loc: CT
 Quote:
Think about the anchor failure that caused a fatality on the DNB a few years ago. Four pieces, none of them capable of holding 4 kN either separately or in combination.
Weren't those pieces clove-hitched? And aren't the people decrying the cordelette now for being non-equalizing the same people who have decried the cordelette forever for being . . . whatever? The same people who clove-hitched because it didn't require a separate piece of gear and was just more "trad"?

RG, are you now using one of those more complicated rigs that requires more gear or are you still clove-hitching? And if you're clove-hitching, do you believe you're getting better equalization that way?

I was just at R&S trying to buy one of those cordelette-on-a-spools they used to sell. As far as I can tell, they don't even sell that material anymore and told me cordelettes had been debunked. They also tried to convince me I wanted this stuff that was "stronger" but that maintained a bend when I bent it. Now the last time the cordelette was debunked, IIRC, it was the material that was in question and we were told not to use the stuff that bent like that because it weakened every time you tied a knot. R&S seemed to know nothing about that subject. I assure you I'll be checking with our mutual friend before I buy anything. I don't know everything, but I know my sources.

I'm believing nothing short of real life drop tests on real life gear that are comparative. I almost am getting the feeling at this point that people are being told option A is not good when there isn't a better option B. And FWIW, a long spool of strong, thin cord is useful for more than equalizing anchors. I use my cordelette on almost every pitch but maybe only use it to equalize an anchor on one in three and if I want another long piece of thin, strong cord I should be able to buy one without being told they're somehow dangerous.

RG, this isn't aimed at you directly. I'm getting fed-up with how people repeat things they know little about and decide that I'm unsafe when I've made a conscious decision based on more evidence and thought than they're capable of. Those who have made other decisions based on evidence and thought are totally welcome to their opinions and I'm actually interested to hear them but if all you're doing is repeating something third-hand you heard off of rockclimbing.com, please STFU.

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#28484 - 04/23/07 12:19 PM Re: cordelette-attention RG [Re: dalguard]
Mike Rawdon Offline

Carpal Tunnel

Registered: 11/29/99
Posts: 4275
Loc: Poughkeepsie
Disclaimer - I haven't read any of the cordelette testing reports.

But it seems to me that anyone who ever thought a cordelette yields 33/33/33 load distribution is woefully unaware of the basics of physics. I'm not talking PhD stuff, just things about angles that all leaders should appreciate. If the reality is more like 25/50/25, well guess what - I ain't losing any sleep over that. (And yes I realize the sum of the loads will be greater than the applied impact loading. More basic vector stuff that.)

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#28486 - 04/23/07 01:10 PM Re: cordelette-attention RG [Re: Mike Rawdon]
strat Offline
Carpal Tunnel

Registered: 04/30/01
Posts: 4242
Can I still use my cordalette to tie around sappy pine trees so that my rope doesn't get all sticky?

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#28488 - 04/23/07 01:40 PM Re: cordelette-attention RG [Re: strat]
dalguard Offline
veteran

Registered: 03/22/00
Posts: 1515
Loc: CT
I was being grumpy last night, sorry. Anyway, the material you should use for a cordalette is Bluewater Titan. This is based on testing http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf which I'm not going to pretend I understand. R&S didn't seem to have this but I wasn't able to ask for it by name and expecting them to read my mind is unfair. It might even have been Titan that I was being shown. I just didn't like the way it bent.

As for why a cordalette might equalize a little better above the ledge than at the power point, my guess is that it's the biner being able to shift that makes the difference. From the power point, there's no play whatsoever but when you're clipped in above it, the biner can rotate as you move from side to side, thus keeping tension on all three legs somewhat better. Also, there's none of the error that was introduced by the knot not being tied with perfect tension on all three legs.

The obvious downside to ledging is that you're only using one strand of each leg which is considerably less strong. I'm usually also clipped into the power point as a backup when I ledge. One interesting possiblity which I'd never considered before is to clip into the power point and redirect through the ledge. I'm usually redirected through a single piece and if that piece blows there's obviously trouble. Redirecting through the power point would give maximum strength at the redirection point, possibly with maximum equalization (given minimum extension). The failure point might actually be the cord in that case.

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#28490 - 04/23/07 02:42 PM Re: cordelette-attention RG [Re: Mike Rawdon]
paulraphael Offline
enthusiast

Registered: 01/22/02
Posts: 321
Loc: New York, NY
 Originally Posted By: Mike Rawdon
I'm not talking PhD stuff, just things about angles that all leaders should appreciate. If the reality is more like 25/50/25, well guess what - I ain't losing any sleep over that.


Agreed. It's just important to be aware of this. The only people who are going to get in trouble are those who assume they'll get perfect distribution with a cordelette (or anything else), and based on this think it's ok to use marginal placements. But I don't think this kind of Russian Roulette says as much about the cordelette as it does about people's basic grasp of odds and redundancy. Not to mention physics.

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#28491 - 04/23/07 02:45 PM Re: cordelette-attention RG [Re: dalguard]
paulraphael Offline
enthusiast

Registered: 01/22/02
Posts: 321
Loc: New York, NY
 Originally Posted By: dalguard
I was being grumpy last night, sorry. Anyway, the material you should use for a cordalette is Bluewater Titan. This is based on testing http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf which I'm not going to pretend I understand.


What I took away from that (and other tests, including the ones J. Long did with Sterling Ropes) is that 7mm nylon is the best material.

It loses much less strength when knotted than any of the high tech cords, and is also essentially immune to fatigue--the constant weakening of the fibers from being flexed under load. All the high tech cords are depressingly vulnerable to fatigue.

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#28494 - 04/23/07 03:05 PM Re: cordelette-attention RG [Re: dalguard]
mworking Offline
old hand

Registered: 05/26/04
Posts: 764
 Quote:
As for why a cordalette might equalize a little better above the ledge than at the power point, ...

The obvious downside to ledging is that you're only using one strand of each leg which is considerably less strong. I'm usually also clipped into the power point as a backup when I ledge. ...


Guess I don't know what ledged is cause I'm lost. It sounds as if you have built an anchor and have moved away from it to belay but have the anchor rope running though a piece closer to you.

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#28495 - 04/23/07 03:32 PM Re: cordelette-attention RG [Re: mworking]
dalguard Offline
veteran

Registered: 03/22/00
Posts: 1515
Loc: CT
The "ledge" is above the knot. You have to be careful to clip one strand of each of the legs or you could end up in a situation where you're not clipped in at all if one leg blows. It actually gets you closer to your anchor, not farther away, since you're clipped higher up on the cordelette. Wish I could find a picture somewhere to show you but if you use a cordelette you could look at it the next time and imagine clipping one strand from each piece above where you tied the knot and I think you'll see what I'm talking about. If you don't use a cordelette then it's a moot point.

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#28497 - 04/23/07 04:12 PM Re: cordelette-attention RG [Re: dalguard]
mworking Offline
old hand

Registered: 05/26/04
Posts: 764
I don't often use a cordelette, but I think I understand now. You clip one strand from each piece to the knot rather than the knot itself. The purpose being to shorten the effective lenght. I would guess you tie the knot high the as well. The exra piece you mentioned before was to help ensure you stayed on the ledge.

I am not anti-cordelette, but I don't often use a cordelette becuase I have never been very happy with the results of my equlization. But early rejection resulted in little practice.

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