Using half ropes with twin technique?
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I know this has been discussed in other forums. Can you use half ropes with twin technique (clipping both ropes into one peice of gear)? There seems to be conflicting answers out there. It does not appear that the impact forced will be doubled, but rather multiplied by 1.2-1.6. ( according to Beal and Mammut) This would mean the impact force could be within acceptable levels (similar to beefy single lines impact force) But I could be wrong. Please educate me. |
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I would think it depends on whether the specific ropes are also rated as twins. If not, don't use them as twins or accept added risk (sorry I don't have a scientific explanation - I just rely on the manufacturer's recommendations). |
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Michael Tilden wrote: This would mean the impact force could be within acceptable levels (similar to beefy single lines impact force) But I could be wrong. Please educate me. "Beefy" != higher impact force. Completely unrelated. Skinny ropes *can* have the highest impact forces. See willgadd.com/single-and-hal… |
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Unequivocally yes you can run them as twins. |
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Michael S. Catlett wrote: Unequivocally yes you can run them as twins. That’s what I think also, but why is this and why so much conflicting information? |
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Michael Tilden wrote: DONT USE HALVES AS TWINS!!!!, half ropes have a higher impact force than twins, there is a reason there is two different certifications for these ropes. |
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Kevin Mcbride wrote: So if I understand what you're saying: if you run half ropes (certified ONLY as halves) as twins, then you're unsafe because they together have less elasticity than would be desired - since both are catching you in a fall. Like taking a lead fall on static rope. Is that correct? |
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Kevin Mcbride wrote: This is a bit alarmist. The numbers you have found are correct, approximately 1.4 times the force, not double. So, you just have to be aware of when this might be an issue, such as high fall factor falls. High ff’s are most like early in the pitch or when really run out. Placing solid gear early and often helps to mitigate this. This was discussed a few years back. It turns out many people in Europe will alternate between half and twin technique even in a single pitch, even some well know pros. YMMV |
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Only use your rope for what it is rated to. If you buy ropes rated as half and twins go for it. The only thing I would be cautious with is you probably shouldn't project with a triple rated rope. |
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Keep in mind, there are plenty of half rated ropes that could pass the twin test. There are fewer twin rated ropes that would pass the half rope test. . But, additional certifications are costly. |
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The ropes I’m particularly concerned about are the beal cobra 2s. |
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(procrastinating house work) |
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PAGING JIM TITT |
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https://petzlsolutions.com/technicalsolutions/half-rope-vs-twin-rope
If you had a single line of protection to use it like a twin, why not just clip every other piece with alternating ropes so you are using your double as a double? |
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Bunch of good ropes rated both twin and half----the Edelrid Apus 7.9mm and Skimmer 7.1 being two awesome examples. Functions perfectly as twin or half.....made in Germany, too! |
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Greg D wrote: Keep in mind, there are plenty of half rated ropes that could pass the twin test. There are fewer twin rated ropes that would pass the half rope test. . But, additional certifications are costly. You will find it hard to buy a rope only twin rated nowadays, cant think of one at the moment. |
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Michael Tilden wrote: The ropes I’m particularly concerned about are the beal cobra 2s. The impact rating on ropes is pretty irrelevant most of the time, considering the braking foce most belay devices generate with thin half/twin ropes obe is only happy to experience any sort of force at all if one falls off |
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Jim Titt wrote: I would love to hear your view Jim. Do you think half ropes are ok for twin technique? |
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Michael Tilden wrote: Sure. |
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Michael Tilden wrote: The ropes I’m particularly concerned about are the beal cobra 2s. Just a warning that half ropes are tested with a 55 kg weight and so you can't use their impact data to divine a corresponding figure for when they are used together. There has been some informal drop-testing of half ropes used as a single rope with an 80kg weight that suggests their impact force for that use is comparable to other single ropes---the main difference is in number of falls held. So what you get if two use two half ropes together is equivalent to a relatively stiff single rope---but not a static rope---that may well still meet UIAA single-rope requirements for impact force (which are quite a bit higher than the actual impact forces for most contemporary ropes).Folks have been getting away with clipping half ropes together for years, so it is far from clear what practical implications are. Common sense suggests that if sketchy gear is involved, maybe one shouldn't exacerbate the stiffness by using an assisted braking device. Go with something with the most braking power, which according to Jim's tests seems to be an ATC-XP. I've always been a bit puzzled by these discussions, because in thirty or so years of using half ropes, I've basically never encountered the need to clip both to the same piece, the one exception being when climbing in a party of three with two climbers following simultaneously and the piece an essential directional point. But in that case, holding a high-impact leader fall is not the primary issue... |