UKC

So as an old fart who has been getting back into climbing I spent last year getting comfey leading again, nothing over VS and on Grit, all on a single. Back in the day I mainly used a pair of 9mms and since this year I want to step things up abit I'm going back to halves, thanks to a ruddy good deal at V12 Outdoor I now have a loverly pair of Mammut Genesis 8.5s (yikes they look thin!).

Anyway they are twin rated as well as half so I was wondering if there are situations where it would make sense to use them as twins, say a very straight route where otherwise all the load is likely to go on just one rope in a fall, if using them as halves. Am I right in thinking this (twin) is best on bomber gear as the impact force is higher?

What esle should I consider?

Mostly people use twins on bolted multipitch (and less often on mellow ice or straight forward trad).

What is the difference between a pair, half and twin ropes? 

Genuine question. I thought they all meant the same thing...

Not to forget alpine rock routes (redundancy, double abseil length) 

You wouldn't like my 7.9s then..!

I wouldn't bother - I can't see a situation in which it's advantageous in trad.  If it's a small fall then I guess it'd share the load between the ropes, but Genesis are hard wearing anyway.  If it's a big fall then bugger the ropes' lifetimes - I want to minimise the impact on the top runner, which means double rope technique.  The impact force on the Genesis goes from 5.6kN as doubles to 8.3kN as twins.

If I was using them on bolted sport then yes, I might well use them as twins.

Double rope (as opposed to single rope) is a technique, splitting the gear between the ropes.

Single, half and twin are ratings that ropes get awarded.  A single is rated to be used as, well, a single rope.  Half ropes are for double rope technique.  Twin ropes are for single rope technique only - clipping both to everything.

Where it's all got mixed up is that these days most half ropes are also rated as twins, so you can choose how to use them.  And some are even triple rated.

Correct me if im wrong anyone!  I was informed a few years ago that not to use half ropes as twins (i.e. clipping both ropes) in trad as if you fall one rope may become tight first and the second one could then shock load the gear placement causing potential failure.     

If you're using two ropes as twins you'll have the same amount of rope out so I don't see how this could happen? The only situation I could see is the belayer messing up in quite a serious way. And if this did happen how would the second rope shock load the gear placement, since it's dynamic?

One thing that I have been told is that you should never switch between using them as half ropes and twins on the same pitch, because if you start leading with each rope clipped into separate pieces and then put them both through the same crab in the event of a fall one rope could run over the other and potentially cut it.

To avoid the burning risk you'd simply use a second crab or draw in series on that piece of gear ( the one you'd twin at). Common in winter.

Be careful when comparing impact forces in standard uiaa tests.

Iirc half/double ropes are tested with a 55 kg weight and single, twins with an 80 kg .

So not directly comparable.

TY, didn't buy them for the twin rating, just a bonus so made me wonder.

many halfs these days appear to be dual rated i.e halfs and twins.

Re: The 55kg vs 80kg. Having read up I see the logic of the different testing, just need to remember that the different testing conditions mean that the half results are only meaningful when compared to other halfs but twin (when used as such) and single results are comparable to each other.

The main occasion you might use half ropes as twins is when protecting two seconds on a traverse, or otherwise when there's a crucial bit of protection which you want to have both seconds' ropes clipped through. Though of course there's the option of having the first second unclip themselves and clip the other second's rope in as they pass the gear.

Yeah i know that, but its the method of using them that are different. 

You could still have each rope becoming tight a fraction of a second apart which could shock load the gear.

Completely agree also shock loading the gear.

This is a really poor understanding of the physics involved. Neither scenario will "shock load the gear", even if they are both undesirable. They would both involve ropes absorbing forces they are designed to.

This is true. Nothing to do with shock loading (which as Wil says is not something that dynamic ropes will do). The issue is that if your two ropes take different paths from belayer but then pass through a single krab, it's possible for one to run over the other, and a moving rope running over another which is in tension is a good way to cut a rope.  If you've started out a pitch using double rope technique you need to complete it in that fashion. If you need to clip both ropes to one runner to protect a reverse for two seconds, then (as Basemetal says) best practice is to use two quickdraws, or a second krab on the quickdraw.

Rick is absolutely right about comparing impact forces for twins and half errors, and I should have been clearer about that! But it is still the case that you'll get a higher force from clipping both so in a trad scenario that's generally to be avoided.

Re: Impact force.

Had a look on mammut website they quote 8.3kN impact force when used as twins, I then looked at their single ropes and found impact forces ranging from 8.3-8.5kN (range of ropes from 9.2-10.5mm). Now these are like for like figures same test 1.77FF 80kg. So no difference on impact load between these as twins and using a single rope, which surprised me, therefore if you would be happy to fall on a single on trad gear you should be just as happy with the twins. Now instinct says using halves as halves will give a lower impact force, which is good, but it would be interesting to see data from tests that fairly put halves, twins, singles against each other in the same situation. However I expect coming up with a fair test is going to be the hard part as the sharing between 2 half strands is going to vary alot from equal to all on one.

Anyway my general sense is that whilst its nice to know that my 2 new ropes can work as twins its unlikely that I ever will do so.

Not really sure why you opened with this when you've clearly not listened to either of the people who did what you suggested! (Explained clearly and politely that you were wrong.)

Worth clearing up that the impact force won't necessarily be higher. It might well be the same as a single or a half.

The twin rating sets a maximum allowable impact force to be seen in the short sample in the drop test. [Think of how high the impact force from the same drop test would be for a wire cable, or a static rope]. The stretchier the rope, the lower the impact force, and all we know from the UIAA rating is that a sample of the rope produced less than the maximum allowed in its test so the batch gets its rating stamp.

Back in the real world we have dynamic belays and actual ropes that can differ in performance way above ( hopefully not below) the rating limits. We know ropes come in prices and qualities and some manufacturers publish specs better than the ratings require.

So a twin could outperform two halves or a single. Or any other way round.The ratings are performance minimums is all.

Basemetal, yeah thats what I've realised see my post a couple up. Twin impact force is in the same ballpark  as for a single and since I'm happy to trad lead on a single no harm in giving twin a try if in a suitable situation. After all I'm unlikly to take single and pair to the crag.

That said I brought the ropes as halves as I wanted halves, the twin rating is just a nice extra that didn't affect my choice. Having never thought about using twins I posted here out of curiosity.

While you were on the Mammut website you could have looked at a triple rated rope and got the answer!

Incidentally, despite what is posted earlier Mammut have said it is perfectly acceptable to mix the clipping between double/twin and vice versa, this has been discussed ad nauseum on UKC and elsewhere.

As someone up the page has said, it's about your system of usage and what the rope is rated for. Each loading used in rating the rope is different and is designed to simulate the specific intended usage. If you look at a triple rated rope like the Mammut Serenity you will get a much clearer picture what happens in each scenario of usage. The point about double rope rating is that the load is much smaller to simulate the ropes being loaded simultaneously on two seperate anchors. If the load is NOT shared equally, then the impact force on the piece is higher than that stated in the rating. So for example, if you are climbing a very straight up route and you clip alternately and you fall, thus loading only the rope clipped through the top piece, you are effectively loading it like a single rope. I.e. in the case of a serenity, you are looking at a load of 8.4kN, not 6.3 kN. If you clipped as a twin you would see 9.7Kn. So realistically, clipping as a Twin will not make a huge difference if your piece is solid compared to clipping it as a half but not placing multiple pieces of gear in close proximity to split the impact between those pieces. 

So the take home is don't expect miracles from double ropes - if you don't place parallel pieces you will not really see the benefit. If you want redundancy, for example your ropes are running over a sharp edge, twin rope usage could provide a benefit. If you happen to be ice climbing and are worried about putting a front point through your rope (maybe you're going through a narrow section and have to place your feet close to the rope) it could be useful. I guess you just need to understand that the impact force will be higher. Safety is not only about the impact force on the top piece.

This link is interesting:  willgadd.com/single-and-half-rope-impact-forces-data

Four half ropes were tested as singles  (80kg) and and compared to manufacturer's data  for six singles: "This range is from 7.7kN to 9.0kN" (singles); "not a lot of difference from the Half rope range of 7.35kN to 9.22kN ". 

But to my knowledge, they haven't justified this by explaining why one of their ropes isn't going to run over the other in the event of a fall, or said why this for some reason wouldn't be a problem?

I'm no expert but surely at the top krab (the only protection where this might happen) the weighted half rope would push the unweighted rope to the side and wouldn't burn through it (presumably a weighted half rope runs next to a stationary unweighted half rope at the belay plate when only one half rope stops a leader fall, and doesn't damage it).  I think I've read this in another thread.

Maybe nobody asked them?

Exactly.

Indeed.

I've a huge amount of respect for the expertise that people like you bring to UKC, Jim, but I'm struggling to accept this point.  'Don't switch between twin and half clipping' has been given as best practice for an awfully long time - it was certainly how I was first taught in the late '90s by various MIA and MIC instructors.  There works seen to be a clear (albeit unlikely) mechanism for the damage to take place.

The point that 'Mammut says it's ok' is repeated in several threads here and elsewhere, but when you track them down they all seem to come back to a single email, sent by a Mammut employee in 2011.  I've had a quick look for primary evidence that any other manufacturer ever agreed with this (or even that Mammut stand by it) and I can't find anything. At least one other manufacturer (Sterling) said that they've not done any detailed testing on this and that in the absence of better data, they recommend sticking with the traditional advice.

Unless we have any more evidence that the practice is safe beyond that single email, I'm not persuaded that we should change the advice - especially as I still don't see any particular advantage to switching between clipping methods that could outweigh the potential risk. 

Well it was after a series of interminable posts with loads of opinions and no facts that someone actually bothered to go to the horses mouth and ask Mammut. Those who don't like the answer could always ask the other rope companies!

Unsafe covers a lot of ground but the loaded rope cutting or damaging the unloaded strand (if this does actually occur) would be annoying but by definition the other strand is already holding the faller so safe.

The traditional advice (and technique) from the pioneers of twin rope use in aid climbing was that changing from twin to clipping singly was the correct method, was Cassin wrong?

My understanding is that it is okay to start using twin rope technique, and switch to half/double rope technique mid pitch. But that once you have swapped you can not revert back to twin rope technique mid pitch.

Equally if you start the pitch using double rope technique you should do so for the whole pitch.

This is because if you fall off once the ropes have been split, they will move at different speeds, and could damage each other. If the ropes have not been split they will move at the same rate.

Hope this makes sense.

We know what the concerns are, the two relevant questions are a) does the tensioned rope actually lie over the untensioned one and cut it, b) since the untensioned rope is playing no part in stopping the faller is it being cut unsafe?

Thus is maybe OK as a theory for a party of two on a single pitch crag.

Do you want damaged ropes halfway up a multi pitch route?

What about bringing up two seconds , one falls off then the other wants lowering?

Two tensioned ropes running at different speeds thro one krab both individually the single safety line for each climber. Definitely not good. Safer just not to do it or use two quickdraws for the odd piece that needs both ropes .

wuoa. my post was before the other replies!!!!

Perhaps that person could have explained climbers' concerns, and Mammut could have then explained why they didn't consider there to be a problem, rather than just a single question with a yes/no answer? I'm not going to adopt different thoughts and practices on the strength of a simple statement without reasoning.

I've found a thread that discusses this, some replies seem to point to the practice being safe based on a lot of experience and knowledge. Of course, as you say, two quickdraws would be fine anyway.

https://www.mountainproject.com/forum/topic/114552186/clipping-both-half-ro...