UKC

Started to climb on Dachstein limestone in Austria here recently, where the norm can be to clip both ropes to each qd on a sparsely bolted routes. It made me wonder:

Q: Are all half ropes also rated as twin ropes these days?

I can find lots online about how specific twin ropes may not be suitable for use as halves/doubles. But can’t find information about the inverse.

I can’t see why they wouldn’t be?

Thanks,

George

In reply to 67hours:

There is no reason why not, since falls on half ropes clipped separately into gear at exactly the same height are normal.

In reply to 67hours:

As I understand it it’s whether twin ropes are rated as halves, not the other way round

In reply to 67hours:

There are three norms, single, double or twin. Different specs for different uses. You can make a thicker rope stretchier to make them suit more norms. But plenty options out there which are just half or just twin. A twin is supposed to catch your fall on both ropes at the same time, a half one on one. So impact forces on a half used as a twin can be high, as you now have two ropes stretching instead on one.

In reply to 67hours:
Twins are only rated to catch you on both strands together. Half ropes are strong enough to catch you on one line.
You can use any 2 ropes together in twin style, it just isn’t necessary.

Most important is if you choose to clip twin style (both ropes in one QuickDraw) you have to do it with them all, you can’t alternate. If you have a mix of together and single clipping into the gear the ropes can rub against each other in a fall and melt...

In reply to mal_meech:


If you're not bothered about considerably greater impact forces on the gear. Probably doesn't matter on bolts, might on small trad gear. Test results I've seen were around 1.4x the impact force of the same rope used as a single.


There was an article by mammut somewhere a while back saying that this fear - while perfectly logical and reasonable - is in reality not much of an issue.

In reply to 67hours:

Thanks all. Hadn't considered the difference in impact forces but that makes sense.

@AlanLitte - I tried to google for that Mammut article but couldn't find it. I'm familiar with the sheath-rubbing concern so I wonder why they said not to worry about it. Perhaps in reality the ropes rarely cut across to melt at a single point.

In reply to AlanLittle:


Either you or Mammut are mistaken. I've seen this happen. What the chances are, I don't know, but having witnessed it once it convinced me.

Al

In reply to GridNorth:

I suspect the reality is that if you do clip separately and then together, you would be quite unlucky to burn a rope badly because the weighted rope will tend to make its way to the bottom of the krab, where it will have much less rubbing effect of the loose rope above. However, if you were to be unlucky and you did get a stationary rope caught under a loaded, moving one, it very likely would be bye bye rope.

In reply to AlanLittle:


Which is why god invented half ropes for trad.


As Al and John have said, I think you may be mistaken. The risk here is real, it’s very easy to end up with a stationary rope under a running one if they’re following different routes.

In reply to mal_meech:

Alan wasn´ t mistaken though it wasn´ t an article, it was an answer from Mammut to the question whether it was allowed to change between twin and half-rope technique and back during a route. They stated it was fine. The actual mail is quoted somewhere on UKC.

In reply to jimtitt:

Fair enough, still not something I’ll be doing.

In reply to GridNorth:

Out of curiosity, do you recall the circumstances? Apologies if it's a horrible memory to ask about, I'm hoping that it was a terrifying experience where nobody actually got hurt. If it's something you're uncomfortable talking about, please just ignore the question.

I've also seen Andy Kirkpatrick recommend clipping both half ropes into the first piece when there's potential for a ground fall otherwise. I suspect that specific practice is probably fine because any difference in motion between the ropes that early in the route should be pretty minimal.

In reply to Luke90:


Not really true. If you twin clip the first then single clip the second, the rope on rope friction in the first could be considerable, especially if the bolts aren't directly in line.

My view is that Mammut's letter response was ill-considered, and that any twin-clipping, when mixed in the same pitch with separate clipping, should definitely use separate krabs for each rope.

In reply to john arran:


My logic was that any relative motion between the two ropes could only be due to rope stretch and slippage through the belay device. If the ropes are clipped together at a significant distance from the belay device and then one rope is loaded more heavily than the other, I can see how the stretch in that rope could make it move a significant distance over the other. So I can certainly see how there could be a problem with the practice in general. However, if the ropes are only twin-clipped within a metre or two of the belay, there can't be much rope stretch up to that point?

(Making the argument for the sake of discussion, I'm not convinced that I'm right. Just setting out my logic.)

In reply to 67hours:
Cut rope with a rope

youtube.com/watch?v=hGwdgPTAT9g&

In reply to Luke90:


Yes double clipping the same piece of gear, but through separate extenders if you follow my drift. So a fall factor 1 but equally on both ropes? Not that I actually do this unless there is a really dodgy move. But then again on a fairly serious or crux move I might use a screw-gate extender, so no chance of gate opening.

In reply to Luke90:

Falling from the second bolt, it's likely you would see at least a metre of rope pass through the top draw before you came to a stop. If the other rope isn't weighted at all, and therefore immobile, then a metre's worth of rope burn could cause a whole lot of damage.

In reply to john arran:

I'm quite prepared to accept your argument but where's that metre of rope coming from? Any slack in the system would be pulled out before any real load is applied so from the point of actually loading the rope, I can only think of slippage through the belay device and the stretch in the rope that leads to the first draw. In my head, both of those seem pretty minimal and certainly well under a metre. Do you think I'm missing another source of rope movement or underestimating the size of the factors I've already suggested?

In reply to Luke90:

I think you're underestimating. The rope will start stretching upon being weighted, expanding maybe half a metre or more. Then there will be maybe 30cm of slippage through the plate, and a fall from so low will probably also pull the belayer up half a metre or so. One metre of rope is quite a small amount in anything other than a "take me here" situation.

In reply to john arran:
On reflection, you've convinced me. I do still think that it's a safER option near the belay than further into the route, but not necessarily safe. Not something I'm planning on doing, in any case.
Thanks for responding to my nitpicking so patiently.

In reply to 67hours:

From the Petzl Technical Institute: https://petzlsolutions.com/technicalsolutions/half-rope-vs-twin-rope

"Half ropes are designed to be used in pairs. The strands can be clipped together or separately into alternating protection points throughout the route. A half rope system reduces rope drag on wandering routes, facilitates longer rappels, and provides redundancy on risky terrain."

Mammut response to the question at http://www.summitpost.org/phpBB3/school-me-on-twin-vs-double-ropes-t60874-1... :

"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,

<named removed<

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