Its time I finally got a 2-rope system. Mostly I'll be using it for ice climbing, although it will see use as a multi-pitch trad option to limit the weight of carrying two full-size ropes.

Anybody have experience on both? I don't like meandering routes, but that really has no bearing on how often i end up climbing them, especially in the alpine realm.

Its time I finally got a 2-rope system. Mostly I'll be using it for ice climbing, although it will see use as a multi-pitch trad option to limit the weight of carrying two full-size ropes.

Anybody have experience on both? I don't like meandering routes, but that really has no bearing on how often i end up climbing them, especially in the alpine realm.

Doubles for all the reasons given. You can choose to use doubles as twins (I suppose there might be exceptions to that) but generally you can't go the other way.

I haven't used doubles since the nineties some time, so take this for what it is: the musing of, for all intents and purposes, a doubles gumby. That said, I was under the impression that it didn't necessarily go either way, and that it was actually a pretty bad idea to do so, unless the rope maker specifically states go for it.

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From everything I've been taught halfs don't really work as twins because of the increased impact force clipping both pieces creates (a problem twins have anyways). You CAN do it, but your putting much more force on your system/protection. IMO this would contradict one of the best bonuses of halfs, which is the decreased impact force on your protection. It's also kinda annoying to have to clip twice at each piece. As well you can use halfs for a party of three. Which is something not recommended with twins.

Twins seem to me to be a bastardization of the weaknesses of both halfs and singles. You get some of the benefits of each, but gain all the weaknesses. For example you gain full rappels, but twins are heavier than singles. Twins are lighter than halfs, but not as dynamic or durable.
My 2¢, I have a single and a set of mammut Genesis and love them.

Half ropes, with regard to strength and weight, lie between single and twin ropes. They only offer standard safety when they are used as a pair. But here you have the choice between twin rope technique, where both ropes run parallel through the protection and half rope technique, where the «left» and «right» ropes run separately through different protection points.

And if you climb on bomb-proof runners? (Bolts, screws…) is it still necessary to separate the strands ?
Most often it is unnecessary, runners are in general in line (Preferable, if necessary, to lengthen with extenders to bring them in line with the rope).
As these points are not unpredictable, and they don’t risk failing because of a too-high impact force, it will be preferable to clip the strands of rope together in order to help to resist the repeated falls which characterise routes safeguarded by bomb-proof anchor points.

Well, you folks have sent me looking.

Sterling's site does not mention using twins as halves or halves as twins. (At least in my 60 seconds of searching).
Mammut's site saysSo, they seem to endorse it.
So it is possible, and endorsed by some.

Edelrid's site didn't seem to present much information (again, very cursory search).
Same for BlueWater

Beal saysAlthough they also state that on less than perfect pro you don't want to clip both strands (20-25% increase in impact force!).
My point exactly. You could use halfs as twins, but with an impact force penalty

My thoughts. If you are at an intermediate belay, and the leader heads out on doubles (2 half ropes) and falls, you are looking at a high fall factor. But, at least in my experience, rarely are both strands totally equal - usually one strand will catch first, then the other. So, while in theory you're being caught by two strands, which would result in a high force; in practice you are caught by one strand, decelerated, then caught by the other. Not as bad. Realistically, most falls are at low FF, so the impact force is less severe.

Overall: I'm comfortable using halves as twins (although I won't bring them back together after separating), but could possibly be persuaded otherwise.
Your comfortable, I wouldn't outright recommend it; but also wouldn't go so far as to say "yer gonna die" either

And your point is????

Also I would like to use the Beal Joker as a case study. The impact forces for the UIAA test are Single 8.2 Half 6 and Twin 9.5. Lets ignore the Half test as it uses a lesser weight (55 not 80kg). The single test records about 14% less impact force then the twin test. If we use this as our baseline then a 5.5kn fall force on a top piece w/ one half would turn into a 6.3kn fall with both halfs (hypothetically). This could make the difference between a small cam or a less than perfect screw holding or not. However because of your above argument that both strands will not have the same amount of slack out I agree you would fall on one first, then the other (if at all???? slack dependant) which would probably make the 14% even smaller in a real world situation.

Thanks, you gave me some other info to think about Bill. I'll restate my position, in some circumstances you could use halfs as twins. So the only argument for twins then would purely be a weight perspective then. (unless I'm missing something????)

I am uncomfortable with all the calculations and scenarios the guys write about. I'd rather use a simple, robust system, and stick to consistent methods. When I'm on the rocks, I don't want to start thinking about a "better" way to use the gear I climbed with. I'd rather clip-and-go.

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From everything I've been taught halfs don't really work as twins because of the increased impact force clipping both pieces creates (a problem twins have anyways). You CAN do it, but your putting much more force on your system/protection. IMO this would contradict one of the best bonuses of halfs, which is the decreased impact force on your protection. It's also kinda annoying to have to clip twice at each piece. As well you can use halfs for a party of three. Which is something not recommended with twins.

Twins seem to me to be a bastardization of the weaknesses of both halfs and singles. You get some of the benefits of each, but gain all the weaknesses. For example you gain full rappels, but twins are heavier than singles. Twins are lighter than halfs, but not as dynamic or durable.
My 2¢, I have a single and a set of mammut Genesis and love them.

What do you mean you are "uncomfortable with the calculations and scenarios"? Do you mean that you don't understand the math associated with it, or does the thought of a climber doing these things actually bother you? Shouldn't you know the extent of your gear and how it should be used prior to getting on the rock?

Twins that aren't rated as a half rope should theoretically have a lower peak impact force than a rope rated as a half-rope and not a twin (when the half rope is used in twin configuration). So, if you need the redundancy of two ropes on each piece, AND want a lower peak impact force, that's a reason to go with twins. That sure sounds like a very specific scenario though, and not a compelling reason for twins.

No.

I am careful to select gear that I think will work, and I practice knots and routines. But that's at home.

On the rocks, is not the time to second-guess the scenario, or work the calculations. On the rocks, I've got the gear, and the rest is mostly clip-and-go.