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barefooter
Jan 3, 2004, 6:50 AM
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Is 6mm Accessory cord strong enough to be used as a cordelette or is 7mm the minimum? I hope I didn't just buy 25' feet of cord I can't yet use.
I did a search and couldn't find if 6mm was adequate.
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coldclimb
Jan 3, 2004, 7:08 AM
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I use 6mm, because for the normal cordelette usage, you're just TRing or tying yourself to the anchor. Works fine for that, and honestly I figure it would be fine for a lot of other uses too. I'm no expert, but I believe I've seen hexes slung with 6mm before.
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oldrkr
Jan 3, 2004, 12:43 PM
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I have both 6 and 7mm cordelettes, never had a problem with the 6mm. I do tend to use the 7mm more often, must be a visual security thing.
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j_ung
Jan 3, 2004, 3:15 PM
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Yah, barefooter, 6mm is fine as long you tie your anchors in such a way that you aren't relying on only a single strand of it to do too much - you know, pre-equalized tie off or some such. But then, the same advice goes for 7mm, too! And actually, if you ever use your cordalettes for friction hitches, the 6mm will work way better than the 7.
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barefooter
Jan 3, 2004, 3:30 PM
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Thanks for the help, those were just the answers i was looking for.
I was practicing the pre-equalized anchors last night by turning a wicker chair over on its side then I used hexes to get 3 anchors, then tide my cordelette.
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dino
Jan 3, 2004, 5:23 PM
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barefooter, I used a 6mm cordalette until I used a web-o-lette once. I have never used the 6mm cord since. I have a Yates 18' web-o-lette. Try both and decide for yourself.
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csoles
Jan 3, 2004, 5:24 PM
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Just remember that when you decide to be a tightwad cheapskate, you are also risking the life of your climbing partner who may not even be aware of your poor choice. The time that 6mm nylon proves to "be a problem" is when you are both plunging to the deck...until then it's fine. Heck, use 5mm nylon--it'll work well *most* of the time too.
OTOH, if you have a life wish, then 7mm nylon or 5mm high-tenacity cord is all that you'd use for anchors on multi-pitch. Chop up the 6mm nylon for prusiks.
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vegastradguy
Jan 3, 2004, 5:44 PM
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actually, 7mm is the minimum recommended diameter for perlon cordlette. 6mm is just a little too thin.
hexes should be slung with 5 or 5.5mm tech cord (NOT perlon), which is rated much stronger than 7mm perlon.
Sterling makes a 6mm cordlette which is rated much stronger than standard 6mm perlon.
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moeman
Jan 3, 2004, 6:10 PM
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In reply to: Chop up the 6mm nylon for prusiks.
I'd say go with this option. You would be better off with 7mm cordelettes, and 6mm is a good size for prussiks, so chop em up.
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barefooter
Jan 4, 2004, 1:34 AM
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i retract my previous statement.
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cracklover
Jan 4, 2004, 3:34 AM
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Csoles, I'm curious about what your beef is with 6mm nylon cord. I'm sure you know what you're talking about, but still, I wonder. So let me wonder aloud for a moment...
Your typical cordelette anchor connects three pieces of gear with an 8 on 3 bights, right? Well, I just checked out the spec for mammut 6mm, it's 8kN. So each piece of gear is connected to the power-point of the anchor with a loop of cord. Doubled strand, no knots, that's 16kN. That's half again more than the rated strength of large nuts, and as much as the destruction point for the largest cams. Do you have a beef with that? So maybe the other side of the knot is where the problem is? Well, you've got three independent loops, just like the one described above. So the power-point should be good for 48kN(!) That seems like plenty.
So... where's the beef?
GO
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andypro
Jan 4, 2004, 5:24 AM
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as I recall, the knot is the weakpoint in any rope system. I believe that a rope will break at a knot before it breaks form exceeding it's working strength limit. So whether theres 3 or 20 loops down there, it may not make a difference. Of course, I may be wrong, in which case this is a moot point, but I'm pretty sure Ir ead it somewhere reliable.
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rocknmedic
Jan 4, 2004, 6:11 AM
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as I recall, the knot is the weak point in any rope system. I believe that a rope will break at a knot before it breaks form exceeding it's working strength limit. So whether theres 3 or 20 loops down there, it may not make a difference. Of course, I may be wrong, in which case this is a moot point, but I'm pretty sure Ir ead it somewhere reliable.
You are right on both counts... the knot is the weakest point in the system and where a failure will more than likely occur (barring a sharp edge catastrophe). You can also distribute the weight on multiple strands by looping it several times. If you were to take a piece of thread and make a small tied loop and pulled on it, it would break rather easily. But if you were to take the thread and wrap 10 - 15 loops and tie it off and try to break it, it would take much more. The advantage of load distribution.
Just my opionion of course....
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robmcc
Jan 4, 2004, 6:26 AM
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In reply to: hexes should be slung with 5 or 5.5mm tech cord (NOT perlon), which is rated much stronger than 7mm perlon.
Right. NOT perlon. Spectra. 5.5mm Bluewater Titan is rated at 20kN.
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tedc
Jan 5, 2004, 4:54 PM
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cracklover,
Factor "almost"2 fall with rope redirected through the power point can be as much as 20KN; so I'd say 16KN is a little weak. Thus 6mm cordalette is MARGINAL at best.
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cracklover
Jan 6, 2004, 8:57 PM
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In reply to: cracklover, Factor "almost"2 fall with rope redirected through the power point can be as much as 20KN; so I'd say 16KN is a little weak. Thus 6mm cordalette is MARGINAL at best.
But the power-point is good for over 40kN!!! The only place where there's 16 kN is in *each* of the loops going to pro. Well equalized, they should be worth well over 20kN together.
As for the issue with knots being the weak-point - that's true. But if you do some research you'll find out that the higher the ratio of the diameter of the cord to the diameter of the bend the cord must take entering the knot, the more the cord is weakened. Point is, a figure-8 on three bights of rope creates a knot that's about as good as it gets in conserving the strength of the cord. To get from 48kN (no strength reduction) down to 20kN (your factor-2 redirected fall) you'd have to have a strength reduction of nearly 60%. I've never seen anything like that in any tests.
I'm not saying 6mm is definitely okay to tie your cordalette with, I'm just asking csoles (or anyone else) to explain why it's not?
GO
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tedc
Jan 7, 2004, 7:53 PM
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In reply to: But the power-point is good for over 40kN!!! The only place where there's 16 kN is in *each* of the loops going to pro. Well equalized, they should be worth well over 20kN together. As for the issue with knots being the weak-point - that's true. But if you do some research you'll find out that the higher the ratio of the diameter of the cord to the diameter of the bend the cord must take entering the knot, the more the cord is weakened. Point is, a figure-8 on three bights of rope creates a knot that's about as good as it gets in conserving the strength of the cord. To get from 48kN (no strength reduction) down to 20kN (your factor-2 redirected fall) you'd have to have a strength reduction of nearly 60%. I've never seen anything like that in any tests. I'm not saying 6mm is definitely okay to tie your cordalette with, I'm just asking csoles (or anyone else) to explain why it's not? GO
All legs of your anchor should be good to your max expected load otherwise it is not REDUNDANT. If you are 100% sure that each of your anchor pieces won't fail; why place more than one. Just place the 100% sure piece, fig-8 on lead line and climb on. :shock:
A "well equalized" cordalette is an oxymoron.
60% strength reductions are possible with poorly (quickly) tied knots.
Cordalettes often fail at the power point knot when tested to failure.
Once again using 6mm is not a "death trap" but I still say it's MARGINAL. You just really need to consider what you expect your anchor to experience.
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j_ung
Jan 7, 2004, 8:16 PM
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In reply to: All legs of your anchor should be good to your max expected load otherwise it is not REDUNDANT. If you are 100% sure that each of your anchor pieces won't fail; why place more than one. Just place the 100% sure piece, fig-8 on lead line and climb on. :shock: A "well equalized" cordalette is an oxymoron. 60% strength reductions are possible with poorly (quickly) tied knots. Cordalettes often fail at the power point knot when tested to failure. Once again using 6mm is not a "death trap" but I still say it's MARGINAL. You just really need to consider what you expect your anchor to experience.
A factor two fall onto any cordalette sucks. It's prime time for a dynamic belay, bay-bee!. There are ways to minimize impact forces other than protection, and if your climber is about to factor two you, you do those things, no matter what the diameter of your cordalette. If you fall onto your belay, generate 20Kn o' force and your belayer grabs you with a totally static catch, you're in deep sh_t even if/when the anchor holds.
Why is there no emoticon for a snapping spine?
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tedc
Jan 7, 2004, 9:42 PM
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So are you indicating that the original poster should go ahead and use the 6mm cordalette or is this just a random off topic comment on belay technique?
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tradklime
Jan 7, 2004, 9:44 PM
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[quote="tedc"]
All legs of your anchor should be good to your max expected load otherwise it is not REDUNDANT. If you are 100% sure that each of your anchor pieces won't fail; why place more than one.
In reply to: This goes back to the statement that if each loop of the cordelette is good for 16kn, then that exceeds the rating for the gear placements. So each leg would be as good as the piece will hold... If 6 mm cord is that strong, then it should be fine, although less durable then 7 mm. It's not about thickness, its about strength, as demonstrated by 5.5 mm tech cord.
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cracklover
Jan 7, 2004, 9:58 PM
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In reply to: All legs of your anchor should be good to your max expected load otherwise it is not REDUNDANT. If you are 100% sure that each of your anchor pieces won't fail; why place more than one. Just place the 100% sure piece, fig-8 on lead line and climb on. :shock:
Dude, that makes no sense. All legs should be good to your max expected load? If that were true, the only acceptable gear would be a bolt. Most normal people would consider three well placed #13 BD stoppers in good rock to be an excellent anchor. Each of those is rated to "only" 10kN.
In reply to: A "well equalized" cordalette is an oxymoron.
In reply to: 60% strength reductions are possible with poorly (quickly) tied knots.
In reply to: Cordalettes often fail at the power point knot when tested to failure.
In reply to: Once again using 6mm is not a "death trap" but I still say it's MARGINAL. You just really need to consider what you expect your anchor to experience.
I would amend your statement to say: build your anchor not based on what you expect it to experience, but the worst-case scenario it could experience (close to ff2). Assuming that's what you meant, I understand your conclusion perfectly well, you just haven't backed it up with any logic that holds water. The only thing that's close to marginal is the individual "ears" of the cordalette anchor (as I said in my original post). But it seems to me that they are on the *safe* side of the margin.
GO
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tradklime
Jan 7, 2004, 11:54 PM
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Perhaps the better question is what the minimum strength should be for cord used as cordelette. Not all cord is equal. Different manufacturers report different strengths for the same diameter cord. We can all pontificate about the use of 6 mm vs. 7 mm cord, but it doesn't mean much without some data to support it.
Somewhere it was decided that 7 mm cord was the standard for cordelette. This was based on some testing I'm sure. And I assume that what cracklover is really asking for is what are the important variables. I'll contend the most important factor is strength. As materials and manufacturing processes improve, so will strength of a given diameter. To mearly state that 7 mm cord is the minimum may not be accurate. To state that cord with a minimum strength of -?-, probably is.
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csoles
Jan 8, 2004, 1:37 AM
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BD rates their 6mm at 6.8 kn. So double that for a loop but take off 10% for the knot, another 10% for going through a carabiner, and another 10% for abrasion and dirt. You are now down to 10 kN per anchor. Factor in that a cordelette is almost guaranteed to put most of the strain on one or two pieces and you are playing russian roulette.
No matter how you look at it, 6mm nylon is cutting too close for comfort. And for what? To save a few pennies or grams? Lame, lame, lame.
Whether cordelettes are safe with trad gear is another issue...the jury is still out but, in many cases, probably not. Over-hyped and under-researched.
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janr
Jan 8, 2004, 1:50 AM
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Using this same analysis (and BD specs), 7mm cord would only be good to 13.5 KN per anchor, weaker than a .75 Camalot Jr.
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