UKH

Can some clever technical soul out there advise me....

With sport ropes getting ever thinner these days, can I use a single 9mm half rope on its own on a sport route?

If not, why not??

No, because half ropes aren't rated to take falls in the same way. If I remember correctly half ropes are tested with a certain number of falls (as stated in the spec) with a 50kg load, whereas single ropes are tested with an 80kg load.

In a half rope the sheath percentage is likely to be higher, which means that for a given thickness of rope the core is thinner. This means lower breaking strain and more static and dynamic elongation than you'd want in a single rope but more hard-wearing.

You can buy very thin triple rated ropes if you want though. I think Beal have an 8.5mm rope which has been tested as a single, a twin and a half.

If you climb sport on half ropes either:

a) clip both half ropes into every quickdraw (use as doubles)

or

b) clip alternate ropes into alternate clips - better as you don't fall as far if you fall when clipping.

Or buy a triple rated single rope.

That'd be the Beal Opera. Cracking rope! Other options are the Edelrid Canary 8.6 and Mammut Serenity 8.7. 

I've got a canary and it's the business for alpine sport. 

It is possible, I used my Mammut Genesis 8.5mm superdry before I bought a Galaxy 10mm

Pros

softer catch due to increased stretch

Lighter

Cons

More rope stretch 7.3% at 80kg vs 6%, makes resting/dogging/working on the rope a pain, the percentage difference doesn't tell the whole story, it is like a rubber band.

Genesis when tested held 12-13  factor 1.77 falls with a 55kg weight vs 10-11 factor 1.77 falls with an 80kg  for the Galaxy.

In reply to Jon Greengrass:

Do you have any evidence to support this? It's long been common practice and I'm sure I've taken falls on double-clipped half ropes without noticing any unreasonably hard catch. Remember also that clipping two half-ropes into separate gear at the same height is also common, which must be equivalent in terms of fall impact on the body.

I stand corrected, I checked Petzl's usually draconian instructions and they show that either twin or half ropes can be doubled clipped. 

Eh? surely you fall to the last clip you clipped, no matter if you're clipping one or two ropes.

Yes, but you're not pulling up slack on the rope you're about to clip if you alternate, so you won't fall so far.

This occurred to me the other day as I was climbing a straight route on half ropes, I'm glad to see it said by someone else to validate it. Seems like a pretty logical argument for alternating, as I've had big falls when clipping before (on sport routes mind)

Yes but you may have less slack out at the time on the rope going to the last clip, if you aren't pulling it up to make the next clip. It's one reason really why many people clip the ropes alternately when climbing a trad route where rope drag isn't an issue.

Though it's academic since the OP was asking about using one half rope.

It's much more useful on trad of course when there's a chance the gear placed above you may rip, giving quite a lot of slack until you get to the next piece. 

Not aware of any actual testing, but it will increase (though not double) the impact force.  Elongation of the entire system is proportional to the force in a single strand, but the force felt by the climber is the sum of that in the individual strands.  The compensation mechanism is that as the total impact force felt by the climber increases (due to reduced stretch), the force in each strand also increases and the rope will stretch by more than 1/2 of the stretch that would occur if the fall was on a single strand.

I remember working the numbers out a while ago, and the impact force of using doubles as twins did increase by a bit, but probably not enough to really make a huge difference, especially if you had stretchy doubles to start with.  Also, in the real world, one of the strands is going to take more of the impact than the other anyway, further reducing the force.

For sport climbing, falling a shorter distance (even with a slightly harder catch) is probably desirable.  At the other end of the spectrum I would probably avoid doing it on ice or weak rock gear.  A rope that is marketed only as a half may not have been certified as a twin, but I suspect that many (most?) modern half ropes would still not exceed the impact force limit if tested as a twin.

EDIT:

Actually, there are some real word tests from certification of triple rated ropes (I believe the UIAA test for twins is the same as singles).  The table in this articlehttps://www.ukclimbing.com/gear/climbing/ropes/the_ultimate_in_versatility_... shows the impact forces for single vs twin testing.  You can see that the impact force goes up a bit, but closer to 15% than 50%.

... and even those figures are based on comparing one and two strands of the same rope, rather than (in the current discussion) comparing two strands of a dedicated half-rope to one strand of a dedicated single rope. With half-ropes typically showing greater stretch under the same load I find it hard to believe there's likely to be a significant impact force gain that's even noticeable in practice let alone dangerous.

I'm reasonably confident that the vast majority of half ropes available are actually rated as both half and twin ropes. Clipping both ropes to the same gear isn't a problem as long as you're consistent and clip all of your gear with both ropes.

If you alternate between half rope and twin rope technique and fall off, the ropes can rub against each other and be damaged or worse.

This is not what some rope manufacturers say.

What do they say then?

I'd be interested to hear more; I thought it was accepted fact that climbing on half ropes and clipping both to ome bits of gear and only one to other bits of gear (through the same krab - obviously clipping with two different krabs isn't a problem) is poor practice and potentially hazardous. I've heard it said and repeated quite consistently ever since I started climbing.

Thanks, you are of course both correct and I should have known

I'm blaming the heat, but perhaps I might be an idiot too.

Believe it or not I've explained this to someone, myself when they asked about using two ropes.

I'm going for a lay down.... in the fridge. 33.5 here today, and it's cloudy!!!

"you had a question on your Mammut rope Phoenix 8mm and whether it can be used in twin and half rope technique in one single pitch. This is the case, you can always clip the two rope strands as twins, then split them as doubles, join again etc. This is exactly the advantage of half ropes compared to twin ropes where you always need to clip both ropes."

Hope this helps you,
best regards from Switzerland,

Productmanager Climbing Equipment
Mammut Sports Group AG, Birren 5, CH-5703 Seon"
 

Thanks. It would have been nice if they'd directly addressed the potential issue of wear on one rope caused by the other in a fall. 

I find that quote from Mammut very surprising given that there have been cases where one strand was damaged by the other when mixing twin and half rope techniques.

I can't find it just now, but there was a case documented by photos. The leader was climbing using twin rope technique, at one clip he managed to only fumble one rope into the clip, then fell. The strand that was clipped into the last draw held the fall, the other strand was cut (!) at the draw below. I remember seeing the pictures a long time ago, more then 10 years - maybe someone is better than me at digging them out?

Worst case scenario would be bringing up two seconds with twin technique, one falls thereby cutting the rope of the other. It's probably very rare, but it is possible.

I've taken plenty of falls onto parallel, equal tension halves, indeed quite a few onto two full ropes in side by side runners (reassuring on sharp/loose rock). Blindfolded I couldn't have told you which was which even compared to single-strand catches. Only time a rope has ever hurt me was fairly short factor 1 ish fall onto pair of parallel full ropes, not topping out at Brimham, unfortunately I toppled, flailing, back first, the ropes snapped tight just before my head, chest and legs decked on the stretch. Wasn't very nice but I walked away from it very creaky and winded, mostly due to the boggy ground.

jk

This is a topic I struggled with when I wrote my book. It seems possible that this could happen  but I found no evidence that it had. But maybe that's because few clip like this. Some do and have taken falls with no damage, but that doesn't mean it would always be fine. In the end I gave up and just said it was unwise, therefore further embedding what might well be myth. If worried, just use another longer draw. 

It makes sense that ANY passage at speed of one rope in contact with another will inevitably have a negative effect on the non-moving strand, even if it's only a marginal effect that will mean the rope starts to look furry that little bit earlier in its life. The fact that few if any cases have been reported of immediate serious damage due to a single incident alone is reassuring and should help people keep risks in perspective and not get too paranoid about such finer subtleties of rope management. But it's also clear that there is at least a theoretical potential for serious single-incident damage, however unlikely it may be in practice, so people should generally avoid creating situations where that potential may be realised.

Yep, that was much my thinking - best not as a standard technique. However, if one is about to double clip previously separated strands, you would be doing it for a reason, or I hope you would be. And it is the balancing of the odds which is the important thing I believe when writing about various techniques. For example, belaying with a grigri on trad: yes the potential for more force on the runners, but if the route is long and the belayer eating and drinking less chance of being dropped.

So, what is the reason one might double clip previously separated strands? One would be an attempt to reduce stretch because of a ledge, another to keep a rope away from a loose boulder. On an easy route I'd use 2 draws. But if I thought I'd fall if I don't clip as fast as possible?

My guess at why damage is unlikely, is that if there is friction between the two ropes, the one taking the strain pulls the other with it to some degree. Hence there is no single trapped rub point. If the pulling continues such as the previously slack rope goes tight, then they will both be moving.

As ropes are soft compared to rough rock, I'm guessing that the potential for fluffing the rope up is no more than when it gets dragged hard over rock between the runners when the leader falls.

You guys seem to be ignoring the example given above. I have no reason not to believe johannes, even if he can't find the source now.

I guess an obvious reason for employing both strands on a runner is if the ropes are running over potentially sharp edges below, and a fall onto the next runner a long way below would mean hitting things. In theory it seems more problematic to me to go from twin rope technique to clipping the ropes individually, rather than the other way round (when neither rope would be stationary). So once employed, best to stick with it if practicable. 

One of the reasons, at the time, that it was advised not to clip both half ropes ropes into one karabiner was because the combined area of loading on the krab would be excessive.  Bear in mind this was when half ropes tended to be full 9mm and karabiner technology less developed than it is now. IMO the bigger issue these days is that one rope could melt the other if both ropes are clipped but then separated in different runners afterwards. In this scenario one rope has the potential to run very quickly through the system whilst the other rope remains static, increasing the risk of the static rope melting. I don't know the likely hood of this occurring but I always stick to one system or the other as I can imagine this possibility.

Al

Not ignoring it, hence my "few if any" phrase above, but it's clear that such incidents are at best extremely rare.

Another possible reason for double clipping would be to keep both ropes out of a rope-eating crack - particularly on the lip of a roof. Yes, you normally would be advised to use separate krabs for each rope, even into the same piece of gear, but you can only hang on for so long to do so and may choose to accept the extremely small risk rather than pumping out while doing so.

Can you use twin/double ropes with a gri gri?

Another good reason IMO is that if the top piece fails, the next piece has not been molested by a tensioned rope, and the rope has not been pre-stretched (as it often is when the piece almost held, slowed the climber, and then gave).

I've always taught* that with doubles you either use single rope technique (ie as twins) or double rope technique, and that you don't switch between the two mid pitch, for exactly the reason that's given.  I'm sure I remember once being told that you can cut a lead rope by sawing it with an accessory cord (but I'm damned if I can find direct proof of that right now) so rope-on-rope friction does concern me.

Interesting that Mammut don't think this is an issue; Beal, Petzl and Edelrid all have little pictograms in their paperwork that I take to mean 'don't rub a moving rope past a static one'. Mammut don't quite have the same image - it doesn't indicate either rope moving, and I'm not really sure what it's trying to say! 

In the absence of evidence that it's a safe thing to do, I think I will continue not doing it.  As David points out it's a slightly odd thing to do except in some rather specific situations.

* A long time ago the accepted wisdom was that doubles not also rated as twins shouldn't be used as twins, because of the increased impact force, but that seems no longer to be of concern - most manufacturers now say that ropes marked as doubles may be clipped as twins (interestingly Beal don't).

No, but I'm sure you know that, so I'm not sure what you question is about. The point I was making that often in climbing compromises need to be made: Place another shit runner and risk pumping out and risk dying, or go for it and risk dying....etc.

I don't think we are. We are thinking about this as a non-standard technique, which might have some risk attached to it, but might keep you from hitting a ledge, or pulling a block off onto your second and when you are pumped to the point of no return. If the un-weighted strand is no longer offering useful protection as the previous runner in it is more than half way to the ground, this addition risk seems very small.

I think we're probably all agreed that it's best avoided, but when there's a reason to double clip it's probably a good one. Additionally it's perhaps not double clipping per se, but switching back to clipping individually which has potential issues, so best to keep double clipping once you've started, unless again there are good reasons (e.g. rope drag) not to. 

I always thought that the main thing was not to use twins as halfs, but the other way round was fine. 

I'm with you on that, though since we were talking about half ropes, you wouldn't be setting off with someone using a grigri, no matter how inattentive they were. So surely, you're initial choice is to tell the shit belayer to FRO and be a bit more safe from move one.

Yes, absolutely.

Nowadays most manufacturers are happy with this (though as I said, Beal still say not).  Certainly when I started in the late '90s the prevailing advice was that doubles clipped as twins could unacceptably increase impact force, but that is no longer a concern (I suspect that mostly what's happened is that doubles are routinely certified as twins as well).

I guess we all find it hard to stay completely focused for a 16 hour shift of belaying on a big route.

Or use a Megajul or equivalent which is what I do with novice seconds

Isnt' it fairly easy to put a couple of quickdraws on one piece of protection and then clip one rope through each? Doesn't sound like it's going to add onerous amounts of extra time and effort? (and if you're clipping a cam you can just use the draw on the cam and a short quickdraw as well)

Tim