Why Two Ropes?

Hi everyone, I’ve been getting into trad climbing as of late, and I’ve noticed (particularly on multi pitches) that many groups will use two ropes to climb with. I’m just curious as to why, and if I should be doing the same? Thanks!

Finn McGeehan wrote:

Hi everyone, I’ve been getting into trad climbing as of late, and I’ve noticed (particularly on multi pitches) that many groups will use two ropes to climb with. I’m just curious as to why, and if I should be doing the same? Thanks!

Do you mean half-ropes (double ropes) per climber? vdiffclimbing.com/half-ropes/

You can tie two half ropes together for a 60 m rappel whereas a single 60m allows only a 30 m rap.  They are thinner than singles, but used together they are strong enough for leading; tied together they are lighter than two singles for rappelling.  They also reduce rope drag on a wandering route as you can clip them alternately so each strand is relatively straight.

a bit more fiddle in terms of rope management, so as a beginner it is probably best to stick with a single rope for now. 

All the things Marco mentions, plus when used as doubles/half’s it spreads out load during a fall so that the two top pieces have reduced force going to them. Makes a difference on routes where pro is more marginal. Also why ice climbers often will use this method. 

You can also get the benefits of two ropes for approach and descent without as much faff for leader or belayer by using them as twins, if they’re rated that way. Both ropes get clipped to each piece in tandem.  

The most obvious answer is if you have two followers (yes you can also have somebody tie in short), but assuming you meant a team of two... often necessary for routes you rap that aren't set up for a single-rope rap, or can give you the option to rap the route if you need to bail on a route where the rap route is separate. If your rope management isn't careful, a second rope can easily cause a cluster so if you're still developing that skill, I'd avoid having a second rope if you can get away with it. Or a more lightweight option is a tagline, but since that also has a higher potential for misuse, read up on how to use one correctly if you go that route.

I have never gotten into double ropes, as I find using an 8.9mm single rope and a tagline is ridiculously light and although not as fast as rappelling with true double ropes, it is convenient to climb with a single and have my tiny Petzl Pur tucked away in a pack.

I'll probably get into doubles some day, but I haven't really found any significant need for it as yet in my trad climbing career. I would say start climbing with single ropes and then if you find that doubles might make your life easier then give it a try.

I've used half ropes a couple times in the Alpine. I can't say I'm proficient with them yet, but I have found that the benefits they bring are not worth the extra weight and hassle. They do offer reduced rope drag and extra fall protection on meandering face routes. However, if the route goes around corners and up chimneys, they can increase drag. Like Ricky, a skinny alpine rope plus tag line is my goto for alpine rock.

Molly Ohm wrote:

All the things Marco mentions, plus when used as doubles/half’s it spreads out load during a fall so that the two top pieces have reduced force going to them. Makes a difference on routes where pro is more marginal. Also why ice climbers often will use this method. 

For this to benefit ice gear, you would have to place two screws side by side. I don’t think that happens. 

Greg R wrote:

For this to benefit ice gear, you would have to place two screws side by side. I don’t think that happens. 

I thought about it and realized I had heard that info from someone else, so after doing some research from curiosity, the forces to the top pieces seem to be about the same as with a single rope if only caught on one piece. Forces are less however to climber and belayer because the ropes are stretchier. This stretchiness also means that, depending on your placement of pro, a falling person will begin to be caught on one piece, then the rope will stretch till the other rope catches also. Load will be (unequally) distributed. Seems it’s hard to pinpoint real life data on forces to the pro in such a scenario, I’d welcome more firm research into this. A more concrete reason why half ropes help with routes with marginal pro is because they reduce the zipper effect. If your top piece blows on one half rope, the next top piece on your other rope won’t have been loaded and pulled at a poor angle.
That all being said, each time I’ve caught a fall with halves, both ropes were loaded and caught across two pieces, so I’d assume forces were partially shared across pieces?

Maybe someone will chime in with more correct data! That pesky word of mouth info isn’t always the most accurate. 

One of the reasons half rope technique may reduce the load on gear is that half ropes tend to be stretchy compared to single ropes and thus have lower impact forces. Skinnier single ropes are reducing this difference and you also have to weigh the negative effects of a longer fall with more stretch.
Another benefit to half ropes that I’m not sure has been noted is redundancy for a cut or damaged rope. Half rope technique has been widely used in areas like the Dolomites where sharp limestone is common. A second rope is a second chance on sharp edges. 

Greg R wrote:

One of the reasons half rope technique may reduce the load on gear is that half ropes tend to be stretchy compared to single ropes and thus have lower impact forces. 

Is that really true? https://willgadd.com/single-and-half-rope-impact-forces-data/

I know we have discussed this before.

It’s worth noting that Colin Haley reports that double ropes cause more rope drag.

There are specific scenarios where double ropes can result in the least rope drag (pitches that are extremely wandering AND very difficult for the climber), but 90% of the time I find that using a single rope results in the least rope drag.

https://colinhaley.com/nugget-1-the-petzl-purline/?amp=1

I use two ropes because they allow me to extract myself from lots of pickles. As noted, I can always rappel a pitch I've just climbed, and I get some control/peace of mind over forces on anchors, rope drag, cut ropes, and protecting traverses on wandering routes. With a clever belayer, I can lower off of a single piece of gear and still be backed up by the gear on the other strand as I come down (the belayer needs to feed out rope on one strand and pull rope in on the other). And best of all, I don't have to rochambeau my partner for who gets the rope as a pillow when I bivy... 

[Insert wry comment about how I should just focus on climbing routes instead of retreating from them...]

About ice climbing: the problem is when the ice goes away, goes to crap, or starts morphing into water. Then it's nice to have both the blueberry bush and the tied-off stubby clipped to separate, skinny ropes. And it doesn't hurt my feelings to have each strand connected to its own ice screw at an anchor either, especially on a "warm," sunny day.

If you're in the mood for a journal article, I recommend Bjoern Ernst's Determination of the redistribution shock load in climbing double rope systems:

https://www.sciencedirect.com/science/article/abs/pii/S1350630708001246 

It's probably behind a pay wall; if so, talk to your local librarian.

wivanoff wrote:

Is that really true? https://willgadd.com/single-and-half-rope-impact-forces-data/

I know we have discussed this before.

Interesting data. These tests were all done with a fall factor of 1.77   It would be interesting to see what the results would be for more typical falls. 

Tom England wrote:

It’s worth noting that Colin Haley reports that double ropes cause more rope drag.

https://colinhaley.com/nugget-1-the-petzl-purline/?amp=1

This depends entirely on the nature of each specific pitch. Every pitch is unique. And some leaders can do a better job of maximizing the protection opportunities in each pitch, while minimizing rope drag. If I had to use a single rope on a zigzagging pitch, while attempting to take advantage of widely separated protection opportunities, I would most definitely have more drag while using a single rope. Using a single rope on such a pitch would require long extensions on protection pieces and thus lengthen potential falls onto those pieces.  

Btw Haley may be pushing the Petzl Pur line because he’s sponsored. Most people wouldn’t want to lead on such a “rope.” He probably uses it primarily in “Don’t fall!” situations.