Clipping both half ropes to a piece, then going back to normal half rope technique

TL; DR: Can clipping both half ropes to a single piece cause one rope to slice the other?

I was climbing a few months back and coming around a roof, I found it useful to clip both of my half ropes into one piece to keep them out of a crack. My partner at the time insisted that if I did this, I would have to continue the rest of the route clipping both ropes to every piece because if I didn't, differing travel distance between the ropes could cause one rope to slice the other.

At the time, I just added another draw to the piece and continued using half rope technique. My intuition says this is bunk, but I don't know for sure, and I was wondering if there's any information out there on this situation. I get what he's saying, that the ropes travel different distances through the carabiner, which does cause the two ropes to rub together, but I can't imagine this causing one rope to slice the other without concerted effort. The worst I can imagine is some extra wear on the rope sheath, but with the quartz crystals my rope runs over on a regular basis, damage from the other rope is the least of my worries.

Here is a worthwhile explanation: https://rockandice.com/climbing-gear-tips/difference-between-double-and-twin-ropes/

And if you read all the way to the end: "Some ropes, such as the Edelweiss Calanques 8.5mm and the PMI Verglas, are certified as both twin and double ropes. These you can clip any which way you like..."

D-Storm wrote: Here is a worthwhile explanation: https://rockandice.com/climbing-gear-tips/difference-between-double-and-twin-ropes/

And if you read all the way to the end: "Some ropes, such as the Edelweiss Calanques 8.5mm and the PMI Verglas, are certified as both twin and double ropes. These you can clip any which way you like..."

That doesn't really address the question, it just explains the difference between halfs and twins.

I think it's unlikely (though conceivable) that varying between half and twin techniques on a pitch will result in rope damage or cutting; however, it is likely to result in rope drag, especially if you vary between techniques frequently on a pitch.

I've heard this, but am skeptical.  Mammut and Petzl say that their ropes that are rated as twins and halfs can alternate between alternate clipping and tandem clipping. (But the Petzl page then seems to walk back some of its permissiveness, and is in any case suspect, as it provides an incorrect explanation for the use of 55kg weight in testing half ropes.) Rock climbing, Mastering Basic Skills, by Topher Donahoe and ‎Craig Luebben, on the other hand, has dire warnings (with however no explanations or references) about "significant friction and dangerous abrasion between the strands."

it seems as if the only place this even has a chance of happening is if carabiner where both ropes are clipped is the one that catches the fall.  If one of the rope paths below is significantly longer than the other, the difference in elongation could make one rope run against the other while pinched together in the biner.  Maybe this would fuzz up a sheath a bit, but "slicing" a rope or creating a core shot seems to me like an extremely remote possibility.  Once past that carabiner and clipping alternately, you could have one rope running through the jointly-clipped carabiner and another not, but the ropes are running more or less straight through at that point, so it is hard to see how you'd get the kind of pressure needed for one rope to damage the other.

Personally, I wouldn't worry about it, but then I almost never clip both half ropes to the same carabiner; if i want them clipped to the same piece for any reason, I use two draws with lengths different enough to avoid rope-end carabiner collisions.  I do this not so much to avoid one rope "slicing" the other as to keep rope friction through the system low; there isn't much room in the mini-biners I use.

Something to watch out for if you clip both strands to a single piece is the potential to lift the piece.  This happens if the two strand paths are far apart before clipping to a single piece but close together after.  If a fall higher up ends up loading both strands in this configuration, the loads might lift the jointly-clipped biner.

The problem with alternating like this is the ropes run at different rates and rub against each other which will wear through the ropes.

I was taught that the recommended way to clip 2 half-ropes to the same piece is to clip one rope to the carabiner on the end of a quick draw as usual, then add a free carabiner to the carabiner on the end of the draw, and clip the second rope though it. This keeps the two ropes running and loading relatively separately on a single piece. It is no problem to return to alternating clipping after (or before) that. Being able to double-clip in situations where gear is scarce or prior to a run out is an advantage of the technique. The key issue is the feasibility in a particular circumstance. For example, one reason to use the technique on a roof route would be to mostly clip one rope before the roof, and the other after it to alleviate rope drag. In that situation, clipping both ropes directly under the roof might not make sense.

The point of contact between ropes keeps changing for both ropes.

If you were to somehow cycle up and down climbing with the belayer taking in and giving out slack then you might be able to cause a problem, but otherwise this theory bogus.

You guys arent answering the question.

I too was taught this, although I am skeptical about it. The theory is this: If you clip the two ropes together, but continue clipping separately afterwards, in case of a fall, the rope that has been clipped last (top piece) will accelerate quickly while the other could stay (relatively) stationary in the biner where they are both clipped together. This could -in theory- lead to the rope catching the fall (the one accelerating) to burn/cut through the other one.
How realistic this scenario is? I have no idea. No clue if there is any data to back it up either. But I keep clipping as I was taught: one you clip them together, keep doing so. 

the dude wrote: You guys arent answering the question.

I too was taught this, although I am skeptical about it. The theory is this: If you clip the two ropes together, but continue clipping separately afterwards, in case of a fall, the rope that has been clipped last (top piece) will accelerate quickly while the other could stay (relatively) stationary in the biner where they are both clipped together. This could -in theory- lead to the rope catching the fall (the one accelerating) to burn/cut through the other one.
How realistic this scenario is? I have no idea. No clue if there is any data to back it up either. But I keep clipping as I was taught: one you clip them together, keep doing so. 

The question has been answered very well above by Rgold.  In summary, in order for the rope that is moving very quickly to damage or cut the stationary rope in the biner there must be a force pulling the moving rope against the stationary rope.  In reality, there is nothing to hold the ropes in direct contact with each other, so little to no damage can occur.

rgold wrote: it seems as if the only place this even has a chance of happening is if carabiner where both ropes are clipped is the one that catches the fall.  If one of the rope paths below is significantly longer than the other, the difference in elongation could make one rope run against the other while pinched together in the biner.  Maybe this would fuzz up a sheath a bit, but "slicing" a rope or creating a core shot seems to me like an extremely remote possibility.  Once past that carabiner and clipping alternately, you could have one rope running through the jointly-clipped carabiner and another not, but the ropes are running more or less straight through at that point, so it is hard to see how you'd get the kind of pressure needed for one rope to damage the other.

I don't know about that...  I don't use half ropes, but I did stay at a Holiday Inn express last night, and I am an engineer...   The ropes are not always going to slide through the biner side by side, it is very possible that they end up in a configuration where one is against the biner and the other is running through the middle.  If that rope is the one you fall on and it is caught on a higher piece, the unweighted rope isni't going to slide, but the weighted rope will pull tight, then rapidly slide as it stretches to adsorb the shock.  If the unweighted rope is pinched between the weighted rope and biner, it could cause enough friction to damage the rope.  Is it going to damage the rope to the point where it is no longer structurally sound... I don't know.  By gut is that it probably won't, but you are adding an extra element of uncontrolled risk to your system, and that isn't something I like to do.

As others have noted, using a spare biner to separate the ropes is neither a huge effort nor cost in weight, so that is what I would do.

Matt Himmelstein wrote:

I don't know about that...  I don't use half ropes, but I did stay at a Holiday Inn express last night, and I am an engineer...   The ropes are not always going to slide through the biner side by side, it is very possible that they end up in a configuration where one is against the biner and the other is running through the middle.  If that rope is the one you fall on and it is caught on a higher piece, the unweighted rope isni't going to slide, but the weighted rope will pull tight, then rapidly slide as it stretches to adsorb the shock.  If the unweighted rope is pinched between the weighted rope and biner, it could cause enough friction to damage the rope.  Is it going to damage the rope to the point where it is no longer structurally sound... I don't know.  By gut is that it probably won't, but you are adding an extra element of uncontrolled risk to your system, and that isn't something I like to do.

As others have noted, using a spare biner to separate the ropes is neither a huge effort nor cost in weight, so that is what I would do.

I´ve used half-ropes for (ahem) 50 years and I´m an engineer and I might even have stayed in a Holiday Inn Express once.....

I´ve also done  lot of testing on ropes and the unweighted rope is always squeezed out of the way by the weighted rope, it is inconcievable that the rope could become trapped and cut through. It is also the case that generations of climbers have had two unequally loaded ropes pressing against each other in a  karabiner and nothing interesting has ever happened, before aluminium HMS karabiners came on the market standard practice was to use a D shaped karabiner for belaying which always forced the two strands together if they were loaded, I still belay with one sometimes as they can have slight advantages.
I have never hesitated to mix-and-match clipping techniques and see no reason whatsoever to change.

Matt Himmelstein wrote:

I don't know about that...  I don't use half ropes, but I did stay at a Holiday Inn express last night, and I am an engineer...   The ropes are not always going to slide through the biner side by side, it is very possible that they end up in a configuration where one is against the biner and the other is running through the middle.  If that rope is the one you fall on and it is caught on a higher piece, the unweighted rope isni't going to slide, but the weighted rope will pull tight, then rapidly slide as it stretches to adsorb the shock.  If the unweighted rope is pinched between the weighted rope and biner, it could cause enough friction to damage the rope.  Is it going to damage the rope to the point where it is no longer structurally sound... I don't know.  By gut is that it probably won't, but you are adding an extra element of uncontrolled risk to your system, and that isn't something I like to do.

As others have noted, using a spare biner to separate the ropes is neither a huge effort nor cost in weight, so that is what I would do.

What force is there in the system that is going to pinch the unweighted rope between the weighted rope and the biner?  There is nothing confining the two ropes to ocupy the same space inside the biner.  Because one rope is unweighted it is free to move around anywhere within the biner and it will be forced out of the way of the weighted rope sustaining little if any damage.

TL; DR: Can clipping both half ropes to a single piece cause one rope to slice the other?

Not in my experience. 

Another consideration is posed by Chauvin and Coppollilo:  If you end up mixing the systems you can get away with going from alternate clips to clipping both. But twin’ing to then separating them invites serious problems. If you have introduced any twists, they will catch on the first piece after beginning to alternate clips, causing severe rope drag and/ or displacement of the piece ( p. 85). 

David Kerkeslager wrote: TL; DR: Can clipping both half ropes to a single piece cause one rope to slice the other?

I was climbing a few months back and coming around a roof, I found it useful to clip both of my half ropes into one piece to keep them out of a crack. My partner at the time insisted that if I did this, I would have to continue the rest of the route clipping both ropes to every piece because if I didn't, differing travel distance between the ropes could cause one rope to slice the other.

At the time, I just added another draw to the piece and continued using half rope technique. My intuition says this is bunk, but I don't know for sure, and I was wondering if there's any information out there on this situation. I get what he's saying, that the ropes travel different distances through the carabiner, which does cause the two ropes to rub together, but I can't imagine this causing one rope to slice the other without concerted effort. The worst I can imagine is some extra wear on the rope sheath, but with the quartz crystals my rope runs over on a regular basis, damage from the other rope is the least of my worries.

There's alot of things that could theoretically happen in climbing but just never do. As usual there's more important issues to divert your attention to than fear xyz of the week. 

Ropes are pretty strong and durable, blowing the sheath happens but it's not insta death. 

As usual, rgold and Jim provide good evidence both based in personal experience and testing. Marco Velo, in his limitless wisdom provides the BEST ADVICE EVER, well...because he used my name. Dude. Woh. I'm a g'damn internet sensation. Well, maybe more accurately, I broke up some paragraphs, added some punctuation, and polished Chauvin's Jedi-genius content....nevertheless. What Marco's talking about *usually* pertains to a single leader trailing two ropes to two followers. That has a higher likelihood of twisting one's trailing ropes. If followers twist around each other on a belay ledge, for example when prepping to follow a pitch, it could introduce a twist into the ropes....if the leader elects to go from clipping both strands through his gear (parallel system) to alternating clips (traditionally called "half-rope technique") then a twist could exit the last carabiner through which both ropes are clipped (the parallel section of climbing) and then pull up and against the first carabiner where the leader has gone to alternating (half-rope system). Bit less likely, I think, with a single follower, but it could happen.

Anyway, manage your ropes carefully and always, always quote The Mountain Guide Manual in all your posts. Ha! RC

Here’s link to an article in the Austrian Alpine Club’s journal from Chris Simmel that address some of the issues raised with tests carried out at Edelrid’s testing facility in 2017. The article is in German, but the tables and graphics are easily understood. Here my reading of the findings, which say:

• it is okay to switch between half and twin rope configurations and back again (provided your rope is rated for both)
• on a multipitch route, it is advisable to clip the first protection in a twin configuration whether or not the remainder of the route will be climbed using a twin or half rope configuration
• this is due to the Tubular devices limitations regarding holding falls on just one strand and the friction of one quickdraw on the first bolt is borderline
• on a banshee belay Fixed Point Belay (belay direct off the anchor) on a mutipitch route, a Tube with an brake-stand-redirect-carabiner between the brake hand and Tube stopped a fall in half the falling distance compared to a hms/munter/italian hitch

https://www.alpenverein.at/bergundsteigen_wAssets/abo/archiv/2021/1/34-41(halbe%20sache%20oder%20optimal).pdf?v=1

Scenario and background. (see image)
A fall on a single half rope 2m above a single bolt, which is 1m above the belay. Total 3.5m of rope in system. Test were carried out using Munter, ATC guide, ATC guide alpine and Reverso 4. Almost not falls for heavier climbers (120kg) were held and only some falls for lighter climbers (90kg) were held.

Source: “Halbe Sache Oder Optimal?”  Bergundsteigen, no. 114, 2012, Austrian Alpine Club.

Tube with an brake-stand-redirect-carabiner
Source: “Halbe Sache Oder Optimal?” Bergundsteigen, no. 114, 2012, Austrian Alpine Club.

Test for mixing half/twin configurations. Both rope were clipped as twins at the first bolt and only one strand clipped at the next bolt at an angle of 130° from it to simulate a change to half rope technique. At the firs bolt, both ropes were intentionally placed into the carabiner so that they were on top of each other. A weight of 90kg was dropped several times. No damage was observed to the second rope, not even slight burn marks were observed.

Conclusion. It is perfectly legitimate to switch from half rope to twin rope configuration, and, theoretically, it would also be possible to switch back. The only question here is whether it makes sense to do so due to consideration regarding rope friction and the hardness of the fall, as a belayer may wish belay more dynamically higher up the route.

^^^ Thanks for posting that.

I have never hesitated to mix-and-match clipping techniques and see no reason whatsoever to change.

Nor have I.

Noel Z wrote:

Here’s link to an article in the Austrian Alpine Club’s journal from Chris Simmel that address some of the issues raised with tests carried out at Edelrid’s testing facility in 2017. The article is in German, but the tables and graphics are easily understood. Here my reading of the findings, which say:

• it is okay to switch between half and twin rope configurations and back again (provided your rope is rated for both)
• on a multipitch route, it is advisable to clip the first protection in a twin configuration whether or not the remainder of the route will be climbed using a twin or half rope configuration
• this is due to the Tubular devices limitations regarding holding falls on just one strand and the friction of one quickdraw on the first bolt is borderline
• on a banshee belay (belay direct off the anchor) on a mutipitch route, a Tube with an brake-stand-redirect-carabiner between the brake hand and Tube stopped a fall in half the falling distance compared to a hms/munter/italian hitch

https://www.alpenverein.at/bergundsteigen_wAssets/abo/archiv/2021/1/34-41(halbe%20sache%20oder%20optimal).pdf?v=1

Scenario and background. (see image)
A fall on a single half rope 2m above a single bolt, which is 1m above the belay. Total 3.5m of rope in system. Test were carried out using Munter, ATC guide, ATC guide alpine and Reverso 4. Almost not falls for heavier climbers (120kg) were held and only some falls for lighter climbers (90kg) were held.

Source: “Halbe Sache Oder Optimal?”  Bergundsteigen, no. 114, 2012, Austrian Alpine Club.

Tube with an brake-stand-redirect-carabiner
Source: “Halbe Sache Oder Optimal?” Bergundsteigen, no. 114, 2012, Austrian Alpine Club.

Test for mixing half/twin configurations. Both rope were clipped as twins at the first bolt and only one strand clipped at the next bolt at an angle of 130° from it to simulate a change to half rope technique. At the firs bolt, both ropes were intentionally placed into the carabiner so that they were on top of each other. A weight of 90kg was dropped several times. No damage was observed to the second rope, not even slight burn marks were observed.

Conclusion. It is perfectly legitimate to switch from half rope to twin rope configuration, and, theoretically, it would also be possible to switch back. The only question here is whether it makes sense to do so due to consideration regarding rope friction and the hardness of the fall, as a belayer may wish belay more dynamically higher up the route.

Just to say that's possibly a slightly incorrect use of the term Banshee Belay. A banshee belay is just one where the bolts are linked in series not parallel. This is what is shown in the graphics, but the hanging the belay plate off the belay is not necessary for it to be a banshee. 

All the best, 

D

David Coley wrote:

Just to say that's possibly a slightly incorrect use of the term Banshee Belay. A banshee belay is just one where the bolts are linked in series not parallel. This is what is shown in the graphics, but the hanging the belay plate off the belay is not necessary for it to be a banshee. 

I have changed "banshee belay" to Fixed Point Belay. Thanks for letting me know.