UKC

I usually climb on 2 x 8mm half ropes (Mammut Phoenix) on most trad multi pitch routes; rock or ice. I once did Variety Show in Bosigran. I climbed up the first pitch. My second came up to the stance and said I clipped both ropes into one of the quickdraws. I explanied cos the line of the first pitch was more or less straight up the crack so I clipped both ropes together in one quickdraw; with all the other runners clipping alternate (or at least separate) rope. I know some people do say when you climb on 2 half ropes as opposed to twin ropes (like Mammut Twilight 7.5mm), you should clip one rope/quickdraw.

Now my question is why can't you clip both half ropes in the same quickdraw as long as the line is straight? This leads to another question why twin ropes have to be clipped together (I understand they're too thin to be fallen on just one so you have to use them as a single rope but enable full length abseil and all that). If this is the principle for twins, why not for halves clipping together? People came up with explanations like the 2 half ropes will rub together when you fall on the runner, which might burn each. How come twin ropes don't do that? Is that because they're thinner. My Phoenix are 8mm already. Twilight aren't any much more thinner at 7.5mm.

In reply to Skinny Kin:

The difference being that you did a bit of both, if you always alternate, or always clip both they shouldn't rub on each other. If you clip both and then alternate, or the other way round then the ropes will each get a different loading - how much risk this is in practice I don't know, but it's a bit pointless to clip both half ropes since one will do and you're putting more load on the runner with both.

In reply to Skinny Kin:
Here's what Mammut say about each system. They seem to say it is OK to use half ropes as twin rope system. If the manufacturer says it's ok, it must be ok.
http://www.mammut.ch/en/ropes_dynamic_ropetypes.html

In reply to katonka:
I don't think there's no point on clipping both. My brain was telling me that if I had 2 ropes in one runner, 2 ropes would be stronger than just 1. Effectively, your load will be halved on the ropes as it's often only one runner will take the load as long as it stays put. The lower runners are effectively redundant.

In reply to Skinny Kin:

"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."

Yes it is, but that's not what you were doing. The point was that if you clip both through some runners and clip them individually as well on the same pitch that might cause problems.

In reply to Skinny Kin:


Your runner is far more likely to rip than your rope is to break.

In reply to katonka:

Why do you think that? Whatever the force is acting on the runner during the fall is the same regardless of how many rope you've got in the runner? If your fall is 10kn onto the runner, it'll always be 10. But with one rope in, that one rope will take 10. If you have 2 ropes in, each will take 5. Just a bit logic. Mind you, I'm talking about a route more or less straight up. So only the top runner will come to take the load first, which means if you have 2 ropes separately clipped. The rope with the next runner down will not take any load as it's slack.

In reply to Skinny Kin:

The force in a fall has as much to do with the ropes as your fall. It's not as simple as you suggest.

In reply to Skinny Kin:
katonka mntioned the reason for not using both systems (i.e. half and twin rope) together. with alternately clipping ropes (double rope system) you will have different amounts of rope out, when you clip them in s single point (twin system) and than fall the ropes will pass through that clip at different speeds leading them to rup at each other (danger of melting).

You can use half ropes as half and twin ropes, as long as you stick to one system and don't change it mid pitch.
twin ropes can only be used as twin ropes since the single strands are not strong enough to catch a fall.

In reply to katonka:
That's what I don't understand. You need to explain the complexity then.

In reply to uncontrollable:
I can understand where you're coming and appreciate the length difference. That's why I wouldn't change from system to another mid pitch. However, as I mentioned the situation the route was straight up so was the ropes. It means the runout of both ropes should be practically the same. Would that be a problem?

In reply to Skinny Kin: You will get a greater load on the gear as you are being decelerated over a shorter distance, thus your deceleration is greater and therefore the force is greater (f=ma, a is getting bigger, m is constant therefore f gets bigger.)

In reply to katonka:


Agree... as do BMC... http://www.alunrichardson.co.uk/uploads/rock%20climbing%20pdfs/ropes17.pdf

In reply to remtherockclimber:
Not sure about that. If you have less distance to fall, then you have less time to pick more acceleration in order to decelerate. The runner as where it is is what situation dictates. You find a place to put gear, you put it in. When you need to fall, you need to fall. It's not something you could control if you know what I mean. I'd say it's more correct to say if you've more runout in the system, then you've got more rope to absorb the energy. The distance you fall is out of your control. The belayer may have some more control over that in comparison.

In reply to Skinny Kin: Your going to have the same amount of speed/energy however many ropes you have clipped, the issue is how that energy is absorbed.

Ropes absorb energy by strecthing, so if you have 2 ropes clipped to one piece of gear each will absorb half the energy and stretch a certain distance. If you only have one rope clipped that rope must absorb all the energy and will stretch further, as it must absorb more energy.

Going back to forces, if your being decelerated over a shorter distance (when you have both ropes clipped) the deceleration is going to be greater than when you have one rope clipped and will therefore impart a greater force on the gear.

In reply to Skinny Kin:

He's entirely right. No question whatsoever that in otherwise similar circumstances 2 ropes loads the gear more than one.

Imagine a fall that is the same in terms of the runner andthe distance you are above it. If you fall on a piece of bungee rope it stretches miles, so the deceleration is very slow. If you fell onto steel cable you would stop instantly with a very high deceleration. Now since your f=m*a and your mass is constant you put more force on the system.

One rope is more stretchy than two, so you would end up putting moreforce through the runner. The combined ropes stretch less because there are twice as many strands to absorb energy so each one has to stretc. Less distance to absorb that energy.

In reply to AJM:

Quite so.

The one remaining piece of bunkum is the ropes rubbing against each other - people merrily clip both ropes into the belay krab and stop a fall on one rope without any adverse effect on the other.

I don't clip both ropes into one runner when using placed gear because of the impact loading. When sport climbing using double ropes (Verdon gorge, say) I sometimes do, but mostly don't because clipping one is easier most of the time and it's quite nice having reaching a high clip with the other rope still snug through the last bolt.

In reply to nniff:

I think in most belay plates the ropes are a lot more seperate, and also that the degree of movement is massively less than you could engineer through wrong clipping. I'm not sure ropes have moved much through the plate even onthe biggest falls I've held.

In reply to Skinny Kin: is it poss ible that with two ropes through the same crab(on the end of the runner)ther might be a wider load on the crab if u fall as opposed to one rope?? thats sort of an answer and a question... if thats already been disscussed above then just ignore me!!

In reply to nniff:

A belay device is likely to let no more that 30cm or so of rope slip through before the fall is fully arrested. By contrast a decent fall could easily generate a metre or two of rope stretch on one half-rope while the other half-rope sits there through the same karabiner getting abraded. I agree that in general such 'dangers' are usually overstated and the actual risk of catastrophic failure is probably close to negligible, but in this example I would expect the wear on the sheath of the rope could - if you're unlucky - be considerable. Even if it's unlikely to fail as a direct result, it's fair to ask what you're gaining from risking trashing your rope - not a lot it seems.