The Half Rope Puzzle

[Greg_W]

Sounds common-sensical: place more pro if you're worried about a fall; which is why you place pro anyway. I place pro like this on a single (usually); if the going is easy, might as well run it out.

[Ross]

Matt,

 

>"If you lead on double ropes, and place a piece of gear every fifteen feet, alternating clips, without regard for where the crux climbing lies, you are not properly using double rope technique in my opinion. "

 

I was using the classic example from my first post, of stemming up two cracks and clipping alternately to reduce drag. Since it's such a good time for double-rope technique, it's often used for illustration.

 

Col,

 

>"That's what people have been saying, just not in idiot terms."

 

Actually, people have been saying all kinds of things ("Here's the UIAA test info," "you save weight with thinner ropes") that didn't address the question. I really wanted to know what about double-rope technique justified a difference in the rope design, and it isn't obvious.

 

>"BTW: Why did you ask a question and than argue with every person that gave you and answer"

 

I didn't know the answer when I posted, and I argued with "answers" that said things like "double-rope technique reduces rope drag." Much of what people posted is true without getting at the question.

 

Unlike you, I didn't belittle anyone who posted -- just tried restating my question to make it clear and avoid mis-answers. While working out examples, I discovered that you CAN'T get a factor 2 fall on one half rope. Weird, huh? Unlike for singles, the UIAA test for doubles exceeds the max possible force on a rope. I never knew that, never read it, and never understood why.

 

At least now we have one theory for what makes half ropes different: the second one CANNOT face the factor 1.78 fall used in the test -- not even close.

 

Have you seen that posted anywhere before?

 

>"are just an argumentative prick."

 

And thanks for your contributions here.

 

Ross

[Cpt.Caveman]

I climb on half the rope when the route is short. What's the big chatter about.?

[texplorer]

I agree Cap'n.

 

Take this to SummitPost.com

[mattp]

Ross -

 

We're beating a dead horse here but the "classic" situation you describe occurs over at Vantage not infrequently. If you are like me, however, you won't be placing your gear only once every 15 feet. And you will be doubling it up immediately prior to some climbing that looks as if it is going to get hard. To do otherwise would, in my opinion, be a poor idea.

[Cpt.Caveman]

I climb on half rope at exit 38 where all the pitches are 15 meters.

[COL._Von_Spanker]

You mean you climb on half a rope?

[sk]

uuuuuummmmmm whats a half rope?

 

 

 

[allthumbs]

it's where you cut a rope in half with your ginsu

[iain]

quite simply, it's a small coil.

[allthumbs]

heh i saw one of those in boston basin awhile back

[iain]

yes, they show up in basins from time to time. and with that I am out.

[mattp]

"uuuuuummmmmm whats a half rope?"

 

Cavey is joking about the short pitches at exit 38. You only need 80 feet of rope, he says.

 

If I am not mistaken, in the context of the rest of this thread a half rope is a thin diameter rope that is rated to be used for double rope technque where as a twin rope is rated for use in twin rope but not double rope techniue (I think I have the terms correct). The "half" rope is intended to catch a fall in the deadly "non-redundant" scenario described herein whereas the "twin" is not. These ropes are most commonly in the 8.8 to 9mm range, but some of the twins get smaller.

[sk]

Mattp... thank you, realy... but I have been following the thred, I was just joking

[Cpt.Caveman]

I do often climb on half a rope especially in small parties on glaciers. I use a 30 m line. If enough people show up I bring a second 30m line for the second team to climb on. Totally off the subject

 

[mattp]

Ah. Joke's on me.

[Cpt.Caveman]

Some vague notes from MEC.CA

 

Half-ropes are tested with a 55kg mass. They are for double-rope climbing technique. When passed, they are certified as half-ropes. Their fall rating denotes the number of falls withstood by a single rope strand (i.e., 9 - 11 (1/2)). Twin ropes are tested with 80kg on two strands.

 

What are UIAA falls?

The International Union of Alpine Associates (UIAA) tests and certifies dynamic ropes using standardized tests. Single ropes are tested by dropping an 80kg mass attached to a measured section of rope repeatedly until it snaps. The number of falls that rope withstands is its rating (i.e., 8-10 single-rope falls) - ropes that cannot withstand at least five falls are not approved

 

What is impact force?

Impact force is the measure of a rope's elasticity or ability to absorb energy in a fall. The higher the impact force, the more energy the rope will transmit to the belay system - the belayer, anchors, and harness. Low impact forces makes for a soft catch and are a benefit with uncertain protection or falls on short lengths, but they usually mean the rope will have a greater stretch, which can be a nuisance when top roping.

 

Rope Diameter Usage

Single ropes can be used individually and are broadly classified into all-around or lightweight. All-around usually have a nominal diameter of over 10mm. They tend to be more durable (thicker over an edge, able to take more abuse from abrasion, and able to withstand more test falls) but are generally heavier. Lightweight ropes usually have a nominal diameter of 10mm or below. They are great for hard redpoints, long pitches, or going light on alpine terrain.

 

Half ropes must be used in sets of two for technical climbing. Use of two ropes increases security from edges and rockfall, provides for full-length rappels, and decreases drag on wandering routes. One of the ropes is clipped into different pieces of protection as climber progresses. For simple glacier travel some climbers use one half rope.

 

Twin ropes offer the same benefits as half ropes (except for decreased drag) and are often lighter. Both strands must be clipped into each piece of protection.

 

 

 

[iain]

I'm worried about the state of this website cavey, that post was far too helpful and objective.

[mattp]

Anybody interested in this thread may be interested in the following links, sent to my by Ross:

 

gunks.com web page 1

 

 

gunks.com web page 2

 

 

 

 

[Cpt.Caveman]

Just make sure you know you are buying a twin rope or a half rope.

 

**********************************************

 

 

The rope end indicator allows you to assess an unlabelled or used rope. If it has passed the Standards, it will feature the CE and UIAA symbols, and it will also indicate the length and type of rope using the following symbols:

 

SINGLE ROPE

Used in single form as the name suggests. Designed for rock climbing, best suited to relatively straight pitches and routes that do not require an abseil descent.

 

HALF ROPE

Half ropes, as used in double rope technique, are recommended for trad climbing, mountaineering and long rock routes where abseil descents are required. Also recommended whenever runners are of dubious quality notably on ice and snow.

 

TWIN ROPE

Now of limited use, with a requirement to clip both ropes every time. New low weight half ropes with greater safety and usefulness have virtually replaced this type.

 

MOUNTAIN WALKING or TOUR ROPE

Used to assist security on mountain walks, glacier or ski mountaineering trips. Normally 8mm dynamic, in a choice of lengths, with and without tie-in markers. Not suitable for rock or mountain climbing.

 

 

[Jim]

Great link Matt. Thanks. Having led Arch, Son of Easy O, and Frustration Sydrome (with some suffocating rope work) I could see the advantage. I'll be at the Gunks this summer for a week and may try the double rope set up. This has been an informative discussion - thanks.

[fleblebleb]

Yeah, good info Ross and Matt and Cpt. although Ross might have shared it a bit differently... Now I know why Twight's book says not to take more than factor 1 falls on half ropes

[mattp]

Fleb-

Ross and I have continued the discussion in private messages and I said one thing to him that I will repeat here: don't concentrate on the mathematics like whether you face a factor one vs factor whatever fall. When you begin a lead, one look at the situation and a modicum of common sense tells you to place gear to protect your belyer from a big shock. When you are looking at a difficult move with a potential splatter below, the same analysis will tell you to double up on the pro and, if I am leading on two ropes, I will see if I can get both ropes involved. The calculations may be interesting, but they don't really affect my practices - in the field.

 

As to your conclusion that one should not take a factor one fall on a half rope, I am not so sure that is correct. Isn't the point that the half-rope will stretch at a lower load than a full rope - so you won't generate the same forces? Again, my resonse to such a concern will be exactly the same as stated above.

[fleblebleb]

Err, well, it was actually Mark Twight's conclusion. I re-read his book over the holidays because I couldn't get out climbing, because I was in bed with the flu.

 

So I'm hip with all the funky quotes right now. Wanna know how many screamers to carry on an extreme alpine route? How about how much gu to eat every half hour and what intervals to set your heart rate monitor alarm to go off at and remind you to take a sip of water? Well, I know! I'm big on the academic stuff...

 

Seriously though, I like double ropes for reducing rope drag and doing double rappels. I only use a pair for alpine/trad climbing and only do that stuff well within my limits. When I run into a difficult move with a potential splatter below I'll start looking for a rap anchor long before I start contemplating anything close to a factor 1 fall, or any fall whatsoever onto pro that isn't bombproof. I'm not that brave...

 

The exception is right at the beginning where you're leaving the belay and there is always a possibility of a high factor fall - but those cases always involve both ropes and the concern is with the strength of the anchor.

 

However, I like to use a single 30 m half rope for easier alpine routes that are mostly 4th class but with short steps of up to mid 5th. You can simulclimb most of the way which is just a blast, and then set up a belay for the occasional step. Since the entire rack is available it's usually possible to get a very solid anchor.

 

But, this scenario has potential for a short fall directly onto the anchor, with a high fall factor - factor 2 if the belay were completely static and not through the anchor, maybe more like factor 1 given a proper belay.

 

I don't like to go more than 10' away from the belay without placing gear, and I stack the odds towards me by belaying through the anchor which I think is appropriate in this situation (maybe even through a screamer after all that reading - but that's not going to help the rope any).

 

What system do you use for climbs like this?

 

 

 

[mattp]

I'd probably carry a single 9mm stratos, but mostly that is because that is the kind of rope that I have. I'll often lead "short bits of mid fifth" on a single strand or, if need be, double it up when I think I'm facing some serious-fall potential. I know, the stats say "you can't do that" so maybe that means you should ignore everything else I've said, but on the kind of ground that you are talking about I feel pretty safe doing this because you are not talking about climbing Index town wall, but ridge lines and psuedo-scrambling where you are going to take sliding and bouncing falls. When simul-climbing, a short rope is usually easier, and in that case I just coil up part of the rope and throw it over my shoulder. I have a half-rope length of 8.5mm rope which I sometimes carry on scramble climbs when I have a partner who may request a belay somewhere. It is also pretty nice for canyoneering, though it has been a long time since I've been to points SW.