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scrambled_legs

Half Ropes...

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Dru wouldn't know majesty if it bit him in the face.

 

I think I can improve on your methods using some chiaroscuro shading. laugh.gif

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I dunno if this has been said yet, but you're never going to subject a single strand of a double rope to factor 2 forces. If you climb above the belay and fall with no pro, both strands catch you. If you place pro on one strand and then fall, the fall force is reduced (because you have placed intermediate pro), but yes, it is absorbed by a single strand. Is this the answer you were looking for?

 

Max fall factor with double ropes (on a single strand) < max fall factor with single rope.

 

Yes, that's the "smaller than" sign.

 

Thanks greek geek, that is exactly what I was looking for. I guess this is the reason why they use the different weights. When a guy considers this and the rope stretch returning in real world, not falling on the same point etc. it adds up to them being pretty safe.

 

I haven't used 8.0mm half ropes until this season and it even made my willy pucker. I was just looking for some reasons why they are safe to climb on other than, "You shouldn't fall on ice or alpine anyways." I wanted to know why some of the old school guys refused to use half rope technique and why some rope manufacturerers say to only use half rope technique when their ropes aren't rated the same as singles.

 

I think I'll use the different length draws if I have the ropes over a sharp edge still but after actually looking at it, I guess the half rope techniqe is bomber. Twin technique seems kind of pointless if the ropes are safe and it only increases the chances of your screw/gear failing.

 

CatBird, thanks for the tips. Ya, I realise that the tests are the extreme. When I said I retire a rope rated for 12 falls after 8 good ones, I meant that it's probably had a couple of dozen falls on it in total but if there were 8 good falls, over factor 1, then I would probably retire it. I've never had big enough balls to get anywhere near that before the rope is retired for age or sheath wear but I would never want to push it to the testing limits. Thats why I was worried about using half ropes with what looked like some pretty slack testing. After everyones comments, I've realised that it isn't that slack and I'm willing to trust the rope. I just needed to know in the back of my mind that it will gaurantee a catch on a big whipper before I could put myself out there and push it. It felt like I was climbing on floss with an 8.0 after having climbed on 10.5s or 11.0s all my life.

 

Dru... I'm done now, you can breathe easy.

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I haven't used 8.0mm half ropes until this season and it even made my willy pucker.

 

Well, we sure wouldn't want that...

 

Glad we cleared that one up. Now why am I not in bed? Good night, world.

wave.gif

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I've never had a fall with a fall factor greater than 1, although one fall came close to that. I doubt more than a handful of people ever have.

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Cat, I've fallen clipping the second piece... over factor 1, ended up below the belayer. Not a big deal on a single but I doubt only a handfull of people have done this. I had a friend witness someone placing their second screw whip and they went well below the belayer... over factor 1. Screw and half rope both held crazy.gif I imagine we wouldn't be 2 of 5 people worldwide that have done this.

 

I e-mailed a few rope manufacturers about my questions. The one manufacture said that they had tried the single test but couldn't get it to consistently pass a 5 fall rating. They said that 3 is probably a realistic number. They also agreed that it is strange that they don't pass the single rating even though being subject to the same forces. I think Geek hit the money in that they cannot be subject to a factor 2 fall like a single can.

 

They also said that internal tests produce low enough impact forces when used in twin technique to be able to pass the UIAA standards. The problem is that it costs a lot of money to have this certification done and from their standpoint, its not worth the costs to have it officially classed as both a twin and a half from a cost benefit marketing standpoint.

 

They also said the practice of mixing methods, Twin/Half in the same pitch is not recomended (where you are clipping the ropes to seperate gear and then clipping both through the same biner).

 

I think this clears up everything now.

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Thanks-- very useful discussion. Just to add a Canadian perspective (whatever that is)- essentially in ice and alpine climbing the use of half-ropes provides redundancy, as the pro is often suspect, and here in the Rockies chops from falling rock are a real concern. Standard practice is to alternate clipping in ropes to closely spaced pro above the belayer, running it out more as you proceed. W/ regard to cruxes, I again place multiple closely spaced pieces and alternately clip in. I don't see any particular advantage to using twin ropes (perhaps a slight weight savings?), and have never encountered a situation where it is necessary or desirable to clip both half-rope strands into the same piece.

 

Additionally, a recent 20' leader fall on ice on a standard draw (3rd piece above belay-- screw held) scared me-- went out and bought a bunch more screamers. Basically, whatever you can do to reduce force on suspect pro is desirable. Unfortunately screamers weigh more, but they do add peace of mind.

 

The only time I use a single half-rope is in situations where 1) I'm assured there won't be any rock or ice climbing of significance (e.g. some classic mountaineering glacier routes), and/or 2) there won't be any full-rope rappels. These situations are rare in the Rockies, so usually we carry two. When we first moved here we were in multiple situations where we tried to save weight by carrying one rope and regretted it. Sometimes if only (2) is relevant we'll use a half-rope plus carry a 7mm zip line to save weight, but this is rare at least for routes we do.

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