I'm looking into buying some new ice/alpine lines, and I really want a rope that is certified for BOTH twin and half(double) techniques. I looked into the PMI Verglas, and the new Monster 7.8mm by metolius. Both look pretty good, but the PMI looks a little flimsy, and i'm looking for a nice, tight sheath. Any experience with ANY twin AND half certified ropes?

i'm not sure that i understand the question since ANY rope (single, double, twin) can be used as a twin. the simple answer to your question is just find the thinnest diameter double rope. its "rated" for double rope use (which just means that it was tested that way......not that its impossible to use it any other way) but can be used as a twin and even a single in the right situation.

i'm not sure that i understand the question since ANY rope (single, double, twin) can be used as a twin.

two singles can work as a twin...........it'll just be a real heavy twin. unless someone has some info from UIAA or the rope manufacturers themselves.........i have no reason to believe otherwise.

Single ropes are designed to absorb a given amount of force over a given period of time. When there are two such ropes used as twins (a.k.a. the scenario you describe), then neither rope is required to stretch to it's normal parameter. This would create a higher impact on the piece of pro, wouldn't it? Shorter elongation and same amount of force = higher impact on the anchor (or cam, screw, stopper, whatever.)

Yeah, I would MAYBE use a half rope as a twin, but I would never use a single. Think about it this way:
You have two springs with the same spring constant (meaning that with a given weight they both stretch the same amount). First you load a single spring and the force on the anchor point is x kilonewtons. Now put two of the springs in tandem and the load ont eh anchor is 2x kilonewtons. Basically your cutting down the length that the spring (rope) stretches to catch a fall, hence rasing the impact force very high. Unless you had a good dynamic belay...read VERY dynamic belay, your looking at loading you protection pretty high. The onyl reason i say that a half might work, is that they tend to have VERY low impact forces, hence when doubled might still be low enough (<10kn or so....but only with a 55kg weight). I dunno. I was just wodnerign if anyone had any experience with these half/twin ropes, since having the ability to change depending on the pitch in front of you would be pretty nice. 7.8mm sounds really small though, although diameters really don't mean squat anyways. But it is intriguing that the 7.8mm monster rope comes in at the same weight as a beal ice twin.... for twice the versatility, and still retains a (twin rope configuration) sharp edge fall. For full specs on the monster, the Lanex (mytendon) website has some good info, as monster ropes are exactly the same, just made for metolius.

Climbing ropes don't have to stretch a certain distance to dissipate force (i.e. there is no "normal parameter" of stretch as you describe it.), rather they stretch as needed to absorb the force applied. Low force, low stretch; high force, high stretch. One rope stretching a lot or two ropes stretching a little will transfer the same amount of force to the anchor.

Bummer. I just wrote a long physics-y response to Notch's post, and then accidentally hit back. to summarize: Using two single ropes as twin ropes is a BAD idea. A dynamic rope reduces peak force in a fall because it slows a falling climber down over a longer period of time than a rope which does not stretch. The length of time over which a rope slows a person down is (nonlinearly) proportional to the amount that the rope stretches. In other words, make a rope stiffer (by, for instance, using two ropes in parallel) and you increase peak impact force throughout the system. what Notch said here:


runs contrary to F = ma, even without looking at the specific nonlinearities of rope-stretch behavior. I won't pretend to know the precise increase in impact force that is caused by using single ropes as twins, as that question is largely empirical. I can say with certainty, however, that the impact force will be substantially larger than the force of a single rope used as, well, a single.