double ropes

[counterfeitfake]

Something I don't understand about double ropes- since you alternate clipping each rope into placements, when you fall, it's frequently (perhaps usually?) just one rope that catches you. So... what is up with that?

[G-spotter]

Ideally you should be placing and spacing pro such that both ropes catch you. Ie, you fall off 10m above pro 1 and 11m above pro 2, and come to a stop 10m below pro 1 and 9m below pro 2 with the force of the fall distributed 55%-45% on the two pieces.

 

The only way this will not work is if your pro is spaced such that you fall and end up above the pro on one rope but below it on the other. Then all the force ends up on the one rope where you are below the pro.

[counterfeitfake]

So this is something you should know about if you're going to use double ropes.

[G-spotter]

Well, ya.

[genepires]

plus if one rope is cut, then the other may save you. These ropes have less resistence to cutting than single lines. yeah you will fall farther if one cuts.

[mattp]

I'm not sure what Dru is saying, but I think he may be wrong. In normal usage, people usually do not place two pieces of pro on the two different ropes at close to the same height unless they are unusually sketched - and of course this assumes they even have the opportunity to do so. Also, frequently with double ropes one is "left" and the other "right" (not necessarily alternating) for rope drag purposes. If you clip one rope, climb another distance and clip the other, and then if you fall somewhere above that second clip, you will have less rope out on that "other" rope, and the piece it runs through will be higher than that on the first rope. You will be caught by the "other."

 

[counterfeitfake]

And in this circumstance, the half-rated rope is doing the exact same thing as a single-rated, which is what I'm confused about. I've never seen a "guide" to using double ropes that shed any light on this.

[catbirdseat]

Matt, you don't have to be sketched to want to double up on pro. A prudent climber if faced with a crux, may want to double up for certain moves, especially if there is a ledge immediately below. The same applies whether you are using singles or doubles.

[G-spotter]

I'm not sure what Dru is saying, but I think he may be wrong. In normal usage, people usually do not place two pieces of pro on the two different ropes at close to the same height unless they are unusually sketched - and of course this assumes they even have the opportunity to do so. Also, frequently with double ropes one is "left" and the other "right" (not necessarily alternating) for rope drag purposes. If you clip one rope, climb another distance and clip the other, and then if you fall somewhere above that second clip, you will have less rope out on that "other" rope, and the piece it runs through will be higher than that on the first rope. You will be caught by the "other."

 

 

This is BS. Take a look at some photos of British trad climbs and you will see they often or almost always place L+R pro close together. Just causde Americans don't do it properly doesn't mean it shouldn't be done

 

And in the diagram you show, you wouldn't end up with slasck as shown unless you were on static ropes. Dynamic ropes would stretch so they were both under tension and both partially loaded.

[mattp]

Dru and Catbird are both correct, but from what I've seen in 20 years of climbing on double ropes, both here and in Europe, the reality is that much of the time the fall comes on one rope or primarily so. I believe that the difference between ropes rated for "twin" and "double" is largely due to this factor.

 

Where I expect a fall, I will try to place pro so both ropes will be involved in the "catch," because it just plain makes me feel safer, but this is by no means something that is always possible. To suggest that you are using double ropes "wrong" if you do not always place your pro on both ropes at or near the same length is again incorrect.

 

Here is an illustration from Gunks.com

 

 

There is a good article there, outlining a lot of advantages of double rope technique, but it doesn't answer your question which (I guess) is how can they get away selling thinner ropes for double and not suggesting you use two "normal" ropes. http://www.gunks.com/index.php?pageid=67&pagenum=1&smGroup=2&smID=4

Edited June 30, 2006 by mattp

[Mark_Husbands]

the half rope isn't going to break.

[catbirdseat]

The argument goes like this. Each half rope is tested by itself to prove that it can take at least one severe fall. This means that while it can take one severe fall, it might break if a second severe fall were to occur on that section of rope. However, since you have two such ropes, this increases your safety margin against rope breakage (or being cut over an edge) so that the chance of both ropes breaking is less than the chance of a larger single rope breaking.

 

Back to the discussion of protection, both Dru's and Matt's comments explain why I like the double rope system. It is very flexible and allows many options. Obviously, if every placement were a double one you'd end up using twice as much gear on the route, assuming each set of placements were spaced as you would normally. In practice, you'd only double up certain placements where it make the most sense to do so.

[underworld]

half ropes are rated to catch a fall as a single strand or together as a system. however, they are rated for a fewer (but not 1) number of falls if single strands catch the fall.

[catbirdseat]

By the way, some of the smaller single ropes give test data for the half-rope test (55 kg vs. 80 kg) in addition to the standard single rope test. If the impact force is less than 8 kN in the half rope test, it means it passes and therefore can be used as a half rope. This answers Matt's question on why not two single ropes, apart from the fact that two singles are generally heavier.

[DirtyHarry]

Skinnier ropes stretch more and therefore put less impact force on the pro too. That might have been what you just said CBS, but I couldn't translate all that geek-speak into engrish.

[catbirdseat]

Indeed it is what I said. But where Matt and I disagree is on the propriety of clipping both strands into the same piece of pro.

 

My position is if it is a bolt or a really bomber piece, or if the fall factor is low, go for it, otherwise don't.

 

Matt's position is that if a piece is going to blow, it will blow regardless of whether you clip both strands to it or not.

[DirtyHarry]

I'll often clip both if its a bolt or a super bomber piece.

 

I disagree with Matt. Rope stretch could clearly equal a couple KNs and that could make the difference b/w a piece blowing or not, especially something like a micro wire, where the wire will break before the piece blows - if the rock is good.

[G-spotter]

well you are compressing three categories into two.

 

1: will not blow

2: will blow if loaded with 1 rope but not 2 (say between 12 and 25 kn)

3; will blow if loaded at all

 

[catbirdseat]

Okay, Dru. Forgive the oversight. I forgot about those crap placements.

[DirtyHarry]

According to CBS, Matt was saying categories 2 and 3 are the same. CBS and I were saying they are different.

[G-spotter]

They're only crap if you clip 2 ropes to them! Like ice screws.

[mattp]

Catbird has referred to a past conversation we have had, I suppose in order to generate more to talk about, but he has not accurately stated what I said in that past conversation: I believe that on most climbs there are relatively few (but more than zero) placements where the extra shock put on a piece due to clipping both ropes will make the difference that causes the piece to fail.

 

In a placement with questionable rock, like maybe a thin flake or a flared crack or whatever, I’ll certainly be more likely to favor only clipping one rope. When climbing on good rock, and where I am worried about falling shortly after placing pro, I am often more concerned about my belayer's having difficulty feeding one rope out while taking the other in and keeping a good grip on both ropes. It is all a matter of sizing up the situation.

 

Also, and Dru or Catbird may disapprove of this, but I frequently violate the "rule" that if you are using separate pro anywhere on a pitch, you should not clip both ropes into the same biner anywhere else on that pitch.

 

Again, each situation is different, and I do what makes sense balancing a bunch of unrelated factors such as (1) how solid do I think the pro is, (2) am I emotionally more secure about having both ropes clipped to that last piece whether it is "technically" correct or not (3) how much do I want to / can I stand there and dink with the pro, (4) what will the placement do to rope drag, (5) how will it affect my second's belay, (6) do I trust my belayer to feed one rope out while taking in the other and keep both snug as possible, (7) what did I have for breakfast.

 

Also, Dru left out category 2.5: pieces that will blow if shock loaded with a falling climber but will withstand body weight.

[chucK]

With respect to the belayers ability to bring one rope in while letting the other out, it greatly simplifies (and safetyfies) things if the belayer concentrates primarily on keeping the highest rope snug. If you end up being caught by the lower piece, then your fall's probably gonna be long enough that a bit of slack in that rope is not likely to make any difference.

 

One of the great boons of alternating clips with double ropes is the abililty to be able to pull out clipping slack while not lengthening your potential fall. Clipping both ropes to a piece nullifies this, unless you clip them one at a time.

 

Also, if the belayer and climber are both in synch with the fact that the next clip is going to be on a different rope than the current high protection piece, the belayer can put a bunch of clipping slack into the clipping rope in advance (while keeping the current pro rope snug), which avoids that ugly situation of not having enough clipping slack at a tenous stance.

[mattp]

That gunks.com article has some discussion of this "alternate clipping" method favoring a reduction in potential falls while clipping, as opposed to the more traditional double rope technique oritented more toward concerns for rope drag.

[catbirdseat]

The only data I could find on impact force of one strand versus two strands is for the Beal Joker which is rated as a single, double and twin. Impact of a single with 80 kg weight is 8.2 kN. It increases to 9.5 kN used as a twin. That's impressive. So Matt, if you were climbing on a pair of Beal Jokers, I'd grant you that 1.3 kN difference is not very significant. Maybe that's the rope you want to get to replace those ropes you are so unhappy with.