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merganzer

twin ropes

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Yes, I have/use them. They are distressingly thin, but if you can take the fear factor that any sharp edge will kill them, they're remarkably versatile. At 35 g/m they are about the same weight as ONE 10.5. Ya just gotta be careful with em. I would rather go for an 8 mil setup. Millet makes a cool 8.1 twin setup (though they term it a half rope I use it as a twin) as does of course the venerable Blue Water jobs.

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i think the only benefits of using twins over a single is that the system is redundant ("safer"), you can rap farther, and you can split the weight between two people for carrying purposes.

 

you can always use twin-rope technique with half/double ropes. (roca also makes nice 8.1 half ropes.)

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I'd have to look, but I believe that the impact force on twins as opposed to a single would be less as well (generally speaking). Anyone have some data handy on this?

 

Another advantage that goes along with being able to rap farther on each rap, is having alot more material for use as rap slings if you have to start cutting the ropes.

 

IMO, I actually feel safest for redundancy on halves because they aren't running in the exact same place. I figure anything that will chop a single will chop twins too. At least with halves they are separated. And as jordop noted, you can use the halves in a twin con figuration, but not vice-versa (well you could, but they aren't rated for it).

Edited by willstrickland

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While on the topic of twin ropes, I got a few thoughts and questions.

 

The impact forces are higher for using two strands than using one strand. So, for the first couple of pieces of iffy pro with high fall factors, would anyone out there clip one strand into each piece. Obviously this would be bad right off the ground were rope stretch might create a ground fall, but how about way off the deck?

 

I got a old copy of Long's "How to" book. He instructs to use two biners to connect twins to pro. Anybody carry enough biners to be able to do this? Ever heard of a rope failure from a fall onto twins and having the rope burn each other?

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Yes, I have/use them. They are distressingly thin, but if you can take the fear factor that any sharp edge will kill them,

 

They are actually rated at 2 sharp edge falls where I believe that many single ropes are rated at 0 sharp edge falls please correct me if I am wrong.

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I used twin 45m 9's for many years. I used them as tho they were a single rope. Strength, rapping out of the way of thunder showers in the Bitterroots, alpine versatility, less likely to be cut on edges or rck fall. I took many falls on this setup and didn't ever see any sign of ropes burning each other.

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Here is some random data from the Mammut website:

 

Type....Diameter....Falls....Impact Force....Sharp Edge Falls

 

Single...10.5............11-12....9kN..................0

Single....9.5...............7.........9.1...................0

Double...8.5 ............14-15....6......................0

Double...9.0.............14-15....6.2...................1

Twin.......7.5.............16-18....9.3...................2

 

So, if you want low impact force, doubles are what you want.

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Thanks for the info, CBS thumbs_up.gif

 

The 9's may be a little heavier, but one of the nice things about them is that I feel comfortable pushing myself on a hard clean (no edges) line with one of them, should the opportunity present itself.

 

I am interested why the 7.5's took two edge falls but the 9's only took 1? wazzup.gif

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I'd like to know more about the sharp edge test. Are some of these Mammut ropes specially designed to take the edges or is it a function of the rope diameter?

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Remember that these ropes are tested differently.

 

Side by side comparisons of the numbers is not realistic.

 

chris

 

(edited for typos)

Edited by chriss

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From http://www.usmga.net/guidelines/guidelinesropes.htm

 

"The UIAA tests for half ropes are done on a single strand with a 55kg load rather than with the 80kg load as in the single rope test. This test can be misleading since the 55kg drop load would obviously be less severe than the 80kg single rope drop load."

 

The author goes on to say:

 

"Typically half ropes should not both be clipped to the same piece of protection, as this has the potential to generate dangerously high impact forces in the event of a leader fall. It is suggested practice for half rope system leaders to arrange protection and ropes so that it is likely that both ropes will eventually be involved in arresting a fall. Although the primary shock in the system is being absorbed by one strand, the second rope engages soon after and diminishes the strain on the other. For this reason the 55kg test drop load is still considered appropriate."

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Millet makes a cool 8.1 twin setup (though they term it a half rope I use it as a twin)

 

I'm new at this game, but was told yesterday by a rep for a rope brand to never use half ropes clipped together as twins. His explanation was that the force that would be put on a protection in a fall would be much greater (by about 30%) and the protection likely to fail. Twins are designed not to stress the protection as much and obviously need to be clipped together.

 

drC

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Although I've never used twins I've been told that on rock the rope drag is worse than a single and a lot worse than halfs clipped alternately.

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Here is some random data from the Mammut website:

 

Type....Diameter....Falls....Impact Force....Sharp Edge Falls

 

Single...10.5............11-12....9kN..................0

Single....9.5...............7.........9.1...................0

Double...8.5 ............14-15....6......................0

Double...9.0.............14-15....6.2...................1

Twin.......7.5.............16-18....9.3...................2

 

So, if you want low impact force, doubles are what you want.

 

CBS...your impact force...does it account for the different test weights between single and doubles and halves? Or is it maximum transmitted force...your answer will affect how to interpret your numbers...

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Rope drag is dictated more by the placement of gear and slings extending the clip then whether or not you have twin or single ropes. This is true on rock or ice. I suppose that in identical positions, some twin systems may weigh more than a single, making it a little more difficult to pull, but I seriously doubt that rope drag with a twin system is inherently worse. Anybody?

 

I am familiar with double/half rope systems and like them a lot for certain applications. Half/double ropes do allow you to clip alternatively and thus (when gear and slings are placed correctly) allowing one to reduce rope drag. thumbs_up.gif

 

I recommend AGAINST clipping a double/half rope as a twin (clipping both ropes to a single piece). hellno3d.gif

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"Although the primary shock in the system is being absorbed by one strand, the second rope engages soon after and diminishes the strain on the other. For this reason the 55kg test drop load is still considered appropriate."

 

 

Most of the time the these ropes are not used in a way that this will be true. Think of how close and often the protection would need to be for this to work as stated. Used correctly on a wandering route is where the advantage lies.

 

chris

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That's true. As well, it also gets me wondering how they can do an appropriate edge simulation when you are supposed to be clipping the doubles at different protection points.

 

Perhaps the reasoning is that you place two pieces of gear closely and clip seperately.

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In my experience, twins offer less rope drag than a single strand of the same length. Also, not mentioned previously, is that the skinnier the rope, the more prone to tangling. Rope management becomes very important when climbing on twins.

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In my experience, twins offer less rope drag than a single strand of the same length. Also, not mentioned previously, is that the skinnier the rope, the more prone to tangling. Rope management becomes very important when climbing on twins.
Drag should be proportional to surface area in contact with the rock which is proportional to total circumference:

 

8.1 mm twins: 2 x 4.05 x 4.05 x 3.14 = 103 mm

10.5 single: 1 x 5.25 x 5.25 x 3.14 = 86 mm

9.2 single: 1 x 4.60 x 4.60 x 3.14 = 66 mm

 

The single rope system should have less drag, assuming both strands are clipped to every piece.

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i thought "rope drag" pertained more to the resistance felt based on pro placement. (like more rope drag when you use short sport draws on a wandering route than when you use nice long alpine slings.) ???

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I think CBS is WAY over simplyfying it.

 

It has a lot to do with the angles which the rope travels between pro and around/over objects. The rope could be in such a position as to not even come into contact with the rock and yet still have a lot of rope drag. The difference in rope drag between a twin system and a single rope set up in the identical scenario is likely to be very little.

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I think CBS is WAY over simplyfying it.

 

It has a lot to do with the angles which the rope travels between pro and around/over objects. The rope could be in such a position as to not even come into contact with the rock and yet still have a lot of rope drag. The difference in rope drag between a twin system and a single rope set up in the identical scenario is likely to be very little.

 

I totally agree with Rodchester on this one; CBS is way off in his thinking. The more a rope runs in a straight line, the less drag in the system. The more bends or corners it takes, the greater the friction. That's why you sling pro, dude. Don't they teach that shit to you Mounties? hellno3d.gif Scary if they don't; it's fundamental.

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