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bearbreeder
Apr 12, 2011, 4:02 AM
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anyone know or have any issue of using twin ropes of different brands and sizes ... ie something like a 8,5 and a 8 twin?
thanks
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coastal_climber
Apr 12, 2011, 4:32 AM
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Impact forces.
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uni_jim
Apr 12, 2011, 5:08 AM
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yeah, impact force is going to be the difference, but since BOTH are rated as twin ropes, they both have enough stretch that you'd be fine.
I mean, If you have one that is a little stiff and one that is soft, you are still getting a softer catch than with a pair of the stiffer twin ropes, but not as soft as if you had a pair of the soft ropes.
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healyje
Apr 12, 2011, 7:14 AM
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Using slightly mismatched ropes as doubles is one thing - using mismatched twins is an inherently bad idea.
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iknowfear
Apr 12, 2011, 10:52 AM
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bearbreeder wrote: anyone know or have any issue of using twin ropes of different brands and sizes ... ie something like a 8,5 and a 8 twin? thanks
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Guran
Apr 12, 2011, 11:24 AM
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healyje wrote: Using slightly mismatched ropes as doubles is one thing - using mismatched twins is an inherently bad idea.
True, I would not climb on unmatched twins.
Probably OK, though. The main issue is of course the risk of the two ropes rubbing against each other, but since they act in parallell, the softer ropes elongation is always limited by the stiffer one, so as long as the ropes stretch equally along their lenght you should be fine.
Better safe than sorry, though. I could imagine different sheath distributing stretch unevenly etc etc...
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uni_jim
Apr 18, 2011, 5:17 AM
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ok, so it looks as if I'm the only one who wouldn't have a problem with mismatched twins. Can someone educate me as to why this is bad so I don't kill one of my friends? (mind you, I'll likely never use twins anyway, I like my halfs)
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cantbuymefriends
Apr 18, 2011, 9:34 AM
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uni_jim wrote: yeah, impact force is going to be the difference, but since BOTH are rated as twin ropes, they both have enough stretch that you'd be fine. I mean, If you have one that is a little stiff and one that is soft, you are still getting a softer catch than with a pair of the stiffer twin ropes, but not as soft as if you had a pair of the soft ropes.
One end of both ropes is tied to the climber, the other is connected to the belay device. If used as twins, they both run in parallell through the same biners.
Please explain how and where they would stretch differently.
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brokesomeribs
Apr 18, 2011, 12:10 PM
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cantbuymefriends wrote: Please explain how and where they would stretch differently.
Is this a real question? Think about it for a second.
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sungam
Apr 18, 2011, 12:16 PM
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cantbuymefriends wrote: uni_jim wrote: yeah, impact force is going to be the difference, but since BOTH are rated as twin ropes, they both have enough stretch that you'd be fine. I mean, If you have one that is a little stiff and one that is soft, you are still getting a softer catch than with a pair of the stiffer twin ropes, but not as soft as if you had a pair of the soft ropes. What he said. One end of both ropes is tied to the climber, the other is connected to the belay device. If used as twins, they both run in parallell through the same biners. Please explain how and where they would stretch differently.
The only real problem I could think of is that the lower-stretch rope would be taking more of the load each fall, and I guess twins don't really like to catch a fall with out their birthday-buddy there. If there was a large enough difference in the stretch it could be an issue.
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Guran
Apr 18, 2011, 1:05 PM
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cantbuymefriends wrote: Please explain how and where they would stretch differently.
OK, imagine two mismatched twins A and B.
A is "softer" than B while B's sheath has less friction against the biners.
In a fall both ropes will of course stretch the same amount, but the stretch in B will be better distributed along its length. (the stretch in A will primarily be between the climber and the last draw)
Therefor B will rub against A in that biner.
Granted, this will probably not be much in any real world scenario but it is definitly possible.
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sungam
Apr 18, 2011, 1:11 PM
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Guran wrote: cantbuymefriends wrote: Please explain how and where they would stretch differently. OK, imagine two mismatched twins A and B. A is "softer" than B while B's sheath has less friction against the biners. In a fall both ropes will of course stretch the same amount, but the stretch in B will be better distributed along its length. (the stretch in A will primarily be between the climber and the last draw) Therefor B will rub against A in that biner. Granted, this will probably not be much in any real world scenario but it is definitly possible.
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Guran
Apr 18, 2011, 2:29 PM
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Nah probably nothing to worry about.
But if I ever realized I was at the sharp end of a pair of mismatched twins, I would be too preoccupied figuring out exactly why that would kill me to enjoy my climb.
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Gmburns2000
Apr 18, 2011, 3:06 PM
Post #14 of 14
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Guran wrote: cantbuymefriends wrote: Please explain how and where they would stretch differently. OK, imagine two mismatched twins A and B. A is "softer" than B while B's sheath has less friction against the biners. In a fall both ropes will of course stretch the same amount, but the stretch in B will be better distributed along its length. (the stretch in A will primarily be between the climber and the last draw) Therefor B will rub against A in that biner. Granted, this will probably not be much in any real world scenario but it is definitly possible.
Just out of curiosity (really dumb question here), but wouldn't it almost always be the case that one rope is going to rub against the other regardless if they are the same or not? It seems that one rope will always catch before the other, and thus start stretching first, because: a) one will sit lower in the biner and; b) it has to be impossible to have the exact amount of slack out on both ropes at the same time (we being humans and all).
Am I just missing something here?
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