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Cordalette Diameter
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Donated my cordalette to the tat gods yesterday. I've always used 7mm cord with no real reason other than years ago the homie at my climbing shop suggested it for a cordalette. For a non TR-gangbang anchor, is there a reason to not go 6mm? Should be strong enough (8.8kn) but a little less durable? Dave |
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No reason really, especially for cordalette. I use sterling's 5.4mm vtx cord, which is rated for 15kn (insane). I know some folks use it with a single for full length rappels too, it packs down insanely small. |
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7mm is the traditional recommendation. It's much stronger. Remember knots weaken cord significantly. https://stephdavis.co/blog/cordelettes-for-climbing/ If you want less weight/bulk I say go for broke with the 240cm dyneema sling. |
jdejacewrote: Assuming 50% strength reduction from knots, wouldn't 6mm be almost as strong as a dyneema sling? (2kN less) 6mm ~ 8.8kN vs. Sling ~ 11kN |
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How Not to Highline did a test breaking a quad on a dyneema sling with figure 8 knots and it broke at 40kn. It's super strong for how light and easy to pack it is. |
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You're multiplying 8.8x2 because you're looping your cordalette? Probably doesn't actually double the strength. https://stephdavis.co/blog/cordelette-for-climbing-what-are-the-issues/ |
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I was taught that you want 7mm if you will be slinging horns, wrapping boulders, threading holes or otherwise using the cordalette on the rock. If you're only clipping it to gear, 6mm is fine. I don't have any data or analysis to support that, but I've stuck with 7 mil. And 240 cm runners. Isn't it time for someone to say a "use the rope" platitude? |
jdejacewrote: Super interesting! Yes that was my reasoning. Thanks for sharing. |
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They break an old loop of 6mm here at 14kn FWIW. https://youtu.be/Hfn21EzAHgU?t=1045 Check out that YouTube channel, they break a lot of stuff. I don't know that they've broken just a classic cordalette with overhand master point though. |
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Keep in mind that nylon cord will be pretty much just as strong as it started after 10 years of use. Dyneema, not so much. |
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Interesting article. What circumstance is going to create enough force to break the cord of a pre-equalized belay anchor made from 6mm that 7mm would hold? I used 6mm for belays until I got freaked by the considerable difference in strength and how everyone seems to use 7 or 8mm (this was early on). Now I typically just use the rope, or slings if I'm leading blocks, but carry 6mm for threads, slinging boulders and for rap anchors because it's a lot more compact and weighs less. We usually run the rope through the top or strongest piece off the belay, which is generally a well-placed nut or cam rated to 12+kn, so does the strength of the cord really matter? |
jdejacewrote: I'm not sure if they actually used 6mm. When you compare it to the biner it looks like 7mm cord. |
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Split the difference. Blue water makes a 6.5 mm cord. |
Scurvy Davewrote: 8.8 is not nearly strong enough. Think a .3 is 8 kn I believe, Wanna do a one point anchor off of one .3? Starling power cord, 5.9 mm 18kn or vtx cord is also good by sterling 15 kn and 5.4 mm,
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I highly recommend edelrid 12mm tech webbing less bulk and weight than 6mm but stronger than 7mm and thanks to the load bearing dyneema core you have a similar uv and abrasian resistance to traditional cords. You could also check out the edelrid hardline 6mm cord but from previous pull tests done on dyneema core cords i wouldn't be confident in its strength when knotted. |
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Powercord is the best of both worlds. 5.9mm but like 20kn. I need to buy another one as I can't find my old one. https://sterlingrope.com/store/work/cordage/high-tenacity-cords/5-9mm-powercord |
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Cord of diameter that can be rigged to at least 22 kN, factoring in strength-reducing knots. Why go less than the common sewn sling ordinarily placed on lead? |
Bill Lawrywrote: LOL your rope is weaker than that. |
that guy named sebwrote: Ah but a dynamic rope has a relative ton of stretch - not to be taken for granted. Ever taken an FF2 directly onto a sling? I pity the fool. |
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What happens if you tie an overhand knot in the loop of runner? Strength of Dyneema runner with overhand knot on a bight 22 X .5 = 11KN Strength of 6 mm Nylon cord runner with overhand knot on a bight 7.5 x 2 x .7 = 10.5 KN Strength of 7 mm Nylon cord runner with overhand knot on a bight 10.5 x 2 x .7 = 14.7 KN Strength of 5/8" Nylon Tubular web runner with overhand knot on a bight 9 X 2 X.7 =12.6 KN Strength of 1" Nylon Tubular web runner with overhand knot on a bight 18 X 2 X.7 =25.2 KN (Strength of Black Diamond Stoppers 6-10 KN) In that Steph Davis article they said 7mm nylon cord was 13 KN single strand, but the rated strength I see advertised is 10-11 KN, so the loop strength with a fishermen's knot should be more like 1.7% not 1.35%. In either case the tied loop of 7mm is 17.5 KN, excess of what most pro is rated for. I would worry more about cutting over an edge than outright breaking strength of any of these runners. |
Bill Lawrywrote: I have read people on the forum who have, it's not nice but they're not ripping anchors out of the wall, the reality is we absorb a lot of force since were big bags of water. I assume you only use quads or sliding x's? edit: 6mm is enough it would seem, |
