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scrambled_legs

Half Ropes...

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I need some beta on half rope use. I always thought that half ropes were never supposed to be clipped into the same piece of pro like twin ropes because the impact force is like using a static rope. So I just bought my first pair and read that you can use them with the twin system according to Mammut. I guess my big question is what sort of impact forces would you have and when should you be clipping twin and when half?

 

The factory impact forces shown for the ropes can't be compared either. When they test twins they drop 80 kg on both ropes but half ropes only have 55kg dropped on one half. If you dropped 80kg on both halves the force may be through the roof.

 

So if I clip both halves I'll probably end up with some pretty high impact forces that can pop gear. If I clip left and right, you can end up with some pretty big distances between gear and are practically climbing with an 8mm single. Should I only clip twin style if I have a screamer?

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If you want to clip both half ropes into one piece of gear, use two different draws/slings, preferably of different lengths.

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I have the same concerns that you have. It seems that the impact force of half ropes keeps decreasing to the point that 2X the impact force is not a lot greater than that of a single rope.

 

I prefer to clip separately unless I have a good reason to do otherwise. I know climbers who almost always clip double, unless the route wanders.

 

The factors that go into the decision whether to clip double or not would include the amount of rope out, and the distance to the nearest ledge that you could hit, and/or run out to the next placement.

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If you want to clip both half ropes into one piece of gear, use two different draws/slings, preferably of different lengths.

thumbs_up.gif

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You are right that clipping both strands will generate bigger forces than clipping one strand to each piece and alternating strands. What Mammut is saying is that their rope has passed the tests for both half and twin ropes. This is more and more common as rope manufacturers get better at controling elongation. The Beal Joker passed the test for twin, half and single useage. I think that you will have to be the judge of when to use half and when to you twin configuration. It will depend on the quality of the pro and the straightness of the route. If the route is ice Alex suggest in this thread that using a screamer on every screw is a good idea.

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While I dont make a habbit of double clipping, intuitively it seems fairly unlikely that both ropes would be played out so evenly that the fall force would ever reach the theoetical 2X single rope limit. I would imagine that typically one rope still handles much of the initial deceleration.

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So this might answer a question I've had for about three years: Are the impact forces why half ropes are more popular than twin ropes?

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Twins are generally lighter, probably cheaper, and it is easier to belay someone with twin technique than double. However, I often use an Edelweiss rope rated for double (isn't that what they now call "half"?) as a single line on lower angled terrain.

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So this might answer a question I've had for about three years: Are the impact forces why half ropes are more popular than twin ropes?
No, the reason is that they are more versatile than twins.

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I think Catbird is right. For mountaineering or sometimes on a slab, I've used a "half" rope as a single line whereas I'd be much more hesitant to do so with a "twin" (I use and Edelweiss Stratos or Sharp with a filament that makes it less prone to cuttingg over an edge). I often use my "half" ropes as if they were twins, not worrying much about the possibility of extra shock on a piece of gear even though I think Fox's recommendation above is in fact correct, because I think Trog is correct that the problem of producing extra shock load by doing so is probably rare and because the complexity of clipping two different draws is often something I don't want to deal with. On the other hand, I would be less comefortable using a "twin" rope for double rope technique.

 

Note: there is lots of confusion in the language of twin vs, half ropes and twin vs double rope technique. You can find discussion of these concepts at Petzl and at MEC websites, among other places.

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What Mammut is saying is that their rope has passed the tests for both half and twin ropes. This is more and more common as rope manufacturers get better at controling elongation. The Beal Joker passed the test for twin, half and single useage.

 

This is what I don't get. Mammut says to use either twin or double rope technique but they don't mention anything about the ropes being rated for both. The only rope that I've heard of passing more than one category test is the Beal Joker. If Mammut has been testing their half ropes as twins and they are passing, why don't we hear the results?

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I don't believe they were designed to alternate clips but to clip the right rope to protection right of the climb and left rope to protection left of the climb. If you have a route that runs 4 pieces to the left before wandering to the right, you are climbing on a single 8mm rope for the first four pieces. If you just alternate back and forth you end up with a bunch of ugly "Z"s and a real mess. Maybe I'm misunderstanding this but that's how I understood the system was designed.

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I agree with Cobra, with a few exceptions:

 

1) When climbing as a party of three (leader on doubles, each follower on a single strand) and there's a traverse involving mroe than one piece of pro, if you alternate clips, then you're setting your followers up for large pendulums. Here, I generally clip both ropes into a single piece (with two separate biners, ideally);

 

2) If the first piece of pro is bomber (i.e. a good bolt or equally good piece of gear placed for upward and downward pull) then at times, I'll clip both ropes into the first piece as a multi-directional first piece.

 

Otherwise, I tend to alternate clips if the route is straight up.

 

If the route follows two completely separate crack systems, I'll stick with one color for the one crack, and the other color for the other crack (i.e. green on the right, red on the left).

 

 

Seems like this thread comes up about every 6 months or so....

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generally i clip twin when on bolts and double when placing gear. darrington & static have plenty of routes that have pitches of each. or just long bolted routes that you need the 2 ropes to rap.

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This is what I don't get. Mammut says to use either twin or double rope technique but they don't mention anything about the ropes being rated for both. The only rope that I've heard of passing more than one category test is the Beal Joker. If Mammut has been testing their half ropes as twins and they are passing, why don't we hear the results?

I just went to the Mammut website and you are right they don't mention passing both tests. It seems very odd and no smart legally speaking to suggest a use for which they do not have UIAA approval. I am not sure what to say about that. I also checked the PMI website and they have some ropes that passed both the Twin and Half tests. The Verglas 8.1 and the Fusion . There may be others.

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Kind of interesting to see the impact force change. It goes from 5.2kn and 8 falls when tested for the half test to 8.9 and 18 falls on the twin test. My Mammut Phoenix is 6.0kn and 8 1/2-9kn in a half so you could guess that it would be around 10kn and 20 falls if it multiplies by the same figures. If you look at the Mammut 7.5mm twighlight twin it has a rating of 10kn and 19 falls. Doesn't really add up, would be interesting to see the results.

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The reason for not clipping half ropes into the same piece is primarily due to friction. You either have to clip them eachinto their own binner or clip both into the same biner/piece for the hole climb. If you climb up a ways alternating clips then decide to clip both into the same piece/biner, then climb up a ways and take a big fall the length of each rope out from the belay is different for each rope. As you fall one rope will travel faster through the binner, for which both strands were clipped through. This can result in onrope burning through the other. I don't know if this makes sense, but the bottom line is that when climbing with half ropes, each strand should be clipped to its own binner, either on seperate pieces or on one piece to combat this issue of differential rope travel speed. This is what manufactures of half ropes have printed in their literature, at least this was described in the literature that came with my sterling half ropes.

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This is straight from the Mammut website:

 

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. This technique allows friction to be reduced in the case where protection points are widely spread and reduces impact force. This is of benefit when climbing traditionally protected routes. A belay method which enables the independent control of each rope must be used.

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I climb with half ropes, I use them like twin, halfs and singles depending in the situation and what I know of the cord that I am using. Yes that is not what the manufacturer recomends, but it is mainly because they were rated as half ropes and because of liability. They have to cover their asses. The ropes that I use have quite a bit of elongation so I am not too worried of generating excessive forces on my gear. I do worry sometimes about running a half as a single over a sharp edge, weighted I have seen the sheat cut relatively easily. When I use them as halfs, I do watch for my landing and might use a little more gear in tricky situation to minimize the ride.

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I don't believe they were designed to alternate clips but to clip the right rope to protection right of the climb and left rope to protection left of the climb.

 

I assume you were refering to the quote from Mammut you posted?

Quote:

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.

 

But I think you may be reading this too literally. By left and right, I believe they are just designating the individual ropes, not describing where on the route to use them. The salient point is if you fall, it will be onto one rope. whether you have clipped that rope in an alternating fashion or consecutively along one side of the route is completely dependant on the route, and (in a vacuum) not going to determine whether the rope fails or not. hopefully someone will correct me if I'm way off.

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That's what I thought. If you them into different piecs at different points, with basic geometery that means one rope will take the fall. Or do you clip both into the same piece before the perceived crux?

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Cobra's summed it up as well as you can. There are infinitely varying scenarios, but it all boils down to the fact that one rope is designed to hold a fall, but in re: Plexus, I would just place two pieces close together and clip them alternatively at the crux. and of course there's always the fact to consider that clipping alternatively will reduce your fall slightly if you fall while pulling up rope mid-clip.

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