Core shots
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This may have changed but when I learned to climb (early 70's) we were taught that the strength of a rope was all in the core, that the sheath was merely to protect the core and did not contribute much, if any, strength. |
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That is primarily where the strength is, yes. It would be interesting to see what a core without a sheath can hold as opposed to a regular rope and also a sheath alone. |
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As I recall the arrival of the "STRATOS" sheath 1st pioneered by Edelweiss was the start of |
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It is somewhat true, but irrelevant. Tensile strength is not a concern with dynamic climbing ropes as the most harshest of falls (FF2) on the most worn ropes wont produce enough force to exceed the tensile limit of the rope. You'd have to weigh 300+ lbs and take an FF2 for that to happen. |
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Damn that's a pretty crazy video.. I guess that when you're jugging you're pretty much all on the sheath? I always figured the sheath is nothing and the core is everything. |
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I took a ride a few years ago while ascending fixed lines above Heart Ledge when the sheath separated and slid down the rope with me and my jugs on it. I slid about 7-8 feet until the sheath bunched up. Quite the wake up call. |
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MacksWhineturd wrote: So is the unicore sheath woven into the core or something?Yes. |
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The vid is interesting. Mostly they show the sheath being cut and the rope not breaking, which would jive with my old understanding of the sheath/core relationship. At one point though, the rope breaks. If the strength is all in the core, and this test is not over and edge, why does the rope break? |
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Beal the only one who makes ropes with the Unicore, or is this now the standard across all companies? |
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In the video, one or two of the tests apparently showed the rope failing entirely once the sheath was cut--which jives with what someone in an earlier comment said. I am still not clear on why this should happen. Anyone care to explain. |
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I don't think the core is failing. Rather, the sheath is failing completely and sliding off of the short section of rope being tested. The "rope clamp" only adheres to the sheath, and when the sheath fails the clamp pulls it off of the core of the non-unicore rope. If there was a knot in the end of the rope being tested then the sheath would just bunch up and the test weigth would be caught. |
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John Wilder wrote: Just Beal and Edelweiss, to my knowledge. I think another brand (i want to say Mammut) has something similar, but its not standard.I want a Beal or Edelweiss bi-pattern 70m dry treated, unicore rope. What do I buy? Looking at websites reveals a dizzying array of things I don't want, or things that I cannot tell if it is what I want. |
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And, BTW, that core shot in my photo was cause by a rounded edge, as round as your finger. |
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Mark Hudon wrote:And, BTW, that core shot in my photo was cause by a rounded edge, as round as your finger. Jess, yes, I think you are correct.The old "edge cut" test that they used to perform on ropes a few years back (I don't think it's done anymore...this is when mammut made their Supersafe rope and edelweiss was advertising the edge resistance of their fat Stratus rope) was performed on a rounded piece of metal that was about the diameter of a pencil if I recall correctly. The rope cuts because of heat (and consequent heat transfer between the individual strands of the core) not because of some sort of sawing action. Thus all you need is to have a small enough edge (sharp or not) and you can cause the rope to cut. This is why the way the made edge proof ropes was to coat each individual strand of the core with an insulating coating that cut down on the heat transfer and hence the failure of the whole core. Not sure what happened to this idea. Too expensive? Consumers didn't care? Not possible on skinny ropes? |
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J. Albers wrote: The old "edge cut" test that they used to perform on ropes a few years back (I don't think it's done anymore...this is when mammut made their Supersafe rope and edelweiss was advertising the edge resistance of their fat Stratus rope) was performed on a rounded piece of metal that was about the diameter of a pencil if I recall correctly. The rope cuts because of heat (and consequent heat transfer between the individual strands of the core) not because of some sort of sawing action. Thus all you need is to have a small enough edge (sharp or not) and you can cause the rope to cut. This is why the way the made edge proof ropes was to coat each individual strand of the core with an insulating coating that cut down on the heat transfer and hence the failure of the whole core. Not sure what happened to this idea. Too expensive? Consumers didn't care? Not possible on skinny ropes?More like radius 0.75mm if my memory hasn´t failed. The test gave erratic results and was abandoned anyway. The mechanism of failure was described by David Smith at Strathclyde University. |
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Jim Titt wrote: More like radius 0.75mm if my memory hasn´t failed.Correct. The test jig was not round by any means. It basically represented dropping the rope over the edge of the edge of your desk, except your desk is made out out of steel. It is possible for a rope to fail if loaded over an abrasive but round edge. I've seen a rope desheath when a guy fell and his rope got caught between the main rock face and a stalagmite-like formation. The distance between the ends of the stalagmite was probably 10" long, so plenty round, but the rock where the rope touched was highly abrasive which was enough to desheath the rope. |
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Chris treggE wrote: Looking at websites reveals a dizzying array of things I don't want, or things that I cannot tell if it is what I want.Edelweiss only makes some ropes with Unicore tech. They call it something else also. Best bet is to call them or look more on their website. I just wish the tech was available on ropes that dont stretch so damn much. Beal ropes like wet noodles. I want something with a bit less stretch. |