Unsafe to climb on one double rope?

[jesselillis]

I occasionally climb alpine climbs with one (not two) double (aka: half) rope. 60m, 8.1-8.5mm (depending on who owns them). Is this unsafe?

 

I gather that a second rope (of any diameter) offers a margin of safety in the event of catastrophic rope failure- either when rock fall cuts a rope, or a rope is cut over a sharp edge during a lead fall (I don't think either happens often).

 

I also gather that folks like to have two ropes for double length rappels. I tend to avoid these as I have a knack for getting ropes (especialy skinny ones!) stuck.

 

So in the absense of catastropic failure (would those failures really be so much less likely on a rope rated as a 'single'?) and acknowledging the inability for long rappels, are there other reasons (I'm primarily looking for reasons related to safety, not convenience or economy of rope life) to avoid climbing with just one double rope?

 

[Ed_Hobbick]

If you have to bivouac, a thicker rope makes for a warmer blanket and for that reason would be safer for cold weather climbs as you would have more material with which to use as insulation to stave of hypothermia.

[wetslide]

Well, one double/half rope isn't designed to be used alone. Not that many people don't do it. I like the beal jokers because they are designed to be used as twins/half or singles. Very durable as well. Great for routes where many raps are needed, the route is meandering and longer routes where you want to have options.

[denalidave]

Have you ever taken a long fall on a thin rope? I have and the rope stretch is a LOT more than a single rope (obviously). Still a great option for alpine terrain, though.

[Off_White]

You haven't said why you choose to climb on a single half rope?

 

Yes, catastrophic failure is more likely when using a rope in a capacity for which it is not rated. Climbing on a single half rope is fundamentally unsafe.

 

I've done this a few times when weight and volume are a concern, and only when I'm very confident I won't be falling and the rope is primarily intended for the safety of the follower. If you wind up on harder terrain than you expected you have the option of doubling it up and climbing half pitches.

 

One of my partners still tells the tale of the time I broke out a "ball of yarn" to lead the technical bit on the West Ridge of Stuart.

 

 

[eric8]

I used to occasionally climb on a 8.9mm double rope (but never an 8.5) as a single for alpine climbs. Even took a nice fall on it once, which I would not want to repeat.

 

These days with the ultra skinny single ropes I just don't think it makes any sense.

 

http://promountainsports.com/index.php/climbing/ropes/serenity-8-9mm.html

[Ed_Hobbick]

The question here is what specifications does the uiaa use to design a half rope as compared to a single rope.

[Dave7]

This may not answer the question directly, but here is some good data from Will Gadd's blog with regards to single rope vs half rope testing. Will Gadd Blog Half rope impact force data

[CaleHoopes]

BTW, the ROPE GUIDE in the Climbing Gear Guide 2012 is pretty awesome:

http://www.climbing.com/print/current/april_2012_304_gear_guide/ - You should be able to find the issue somewheres.

[jmace]

Yes, catastrophic failure is more likely when using a rope in a capacity for which it is not rated. Climbing on a single half rope is fundamentally unsafe.

 

half ropes are rated for single strand falls.

[Off_White]

Half ropes are tested with a 55 kg weight for 5 drops, single ropes with an 80 kg weight for 5 drops. As a single strand, half ropes are expected to sustain roughly 2 falls with a 80 kg weight, which they calculate is the equivalent of 5 falls with the lesser weight. For those of us who aren't Canadian, 55 kg is 121 lbs.

 

So, they're tested as single strands, but its not the same as being rated for a single strand. If it was rated as a single strand, they'd call it a single rope. Used as a single strand, a half rope is significantly weaker than a single rope.

[jmace]

Mammut gives you 15-16 falls on a single strand at 55kg before they suggest you retire.

 

I think the point here is that if you do go light and you do fall then the rope will not break unless you cut it.

 

But your right its not rated as a single...but then if you use doubles for wandering routes your often climbing on a single...basically dont fall

[Off_White]

Wow, good on Mammut. I think I pulled my info from Beal, though come to think of it they were generally talking about UIAA requirements rather than actual test results. I don't think I've been 55kg since I was 11 though.

 

You're right that rope breakage is almost never the failure point, but cutting is a much higher probability. Climbing on a single strand of a half rope is a viable approach to going light, and certainly you've got the experience to make that judgment call, I just didn't want our OP, who seems less experienced, to assume it's of no consequence.

 

"Basically don't fall" is an excellent and recommended approach to alpine climbing in general.

[montypiton]

While climbing on a single twin or half rope may appeal to the weight-paranoid, please take into account one very real safety issue - even if the rope doesn't BREAK under load, it will likely stretch enough that you'll hit something you'd rather not. I often climb alpine routes with a team of three - leader leads on double strands, following climbers come on single strand. The idea is to have the safety/strength of a team of three, climbing as fast as a team of two (followers climb simultaneously).

 

Three years ago, I rigged a TOPROPE on an ice route with a single skinny rope. I popped off about forty feet up, loaded my top-rope belay, and hit the ground on rope-stretch -- hard enough to break both ankles!! There was no slack in the belay - the entire forty foot fall was ROPE STRETCH - felt like falling in slow motion, and I kept thinking I'd stop, but I didn't...(I had the full 60M of rope in play - less rope in play would mean less stretch, but you get the picture...)

 

so - yeah - climbing single strand on ropes not designed for that use can get you hurt!!! you don't have to repeat my error to learn from it...

 

for alpine routes - your stated use - the answer is simple, and I do it all the time -- just fold the rope double and climb shorter pitches or simulclimb.

[Buckaroo]

Three years ago, I rigged a TOPROPE on an ice route with a single skinny rope. I popped off about forty feet up, loaded my top-rope belay, and hit the ground on rope-stretch

 

Please be more specific, define "single skinny rope"

 

thanks

[genepires]

Dane mentioned a while ago about witnessing a very long fall on the n face of snoqualmie of a guy simu with a skinny single and large amount of rope stretch.

 

40+stretch on 60m rope is >20% rope stretch. With breaking ankles, assume it was 50 feet of stretch for 25% rope stretch. That just doesn't seem right.

 

with a little google search, mammut ropes have a max 10% elongation for static (tr) loads and about 30% for lead falling elongations.

[montypiton]

Buckaroo - rig was a 60m Mammut twin-rope, maybe 8.1mm? I do not recall the exact model name (I don't fixate on the exact model names of my ropes) but I can assure you that it was a 60m Mammut twin rope, and it felt like it stretched FOREVER. This was an embarrassing episode, and frankly, pretty disconcerting, because I had been toproping on single-strand twins for years before this, and had never had a problem. Climbs had either been shorter - so less rope in service; or not so steep - so load was reduced. On this particular instance, the climb was past vertical, so no reduction in loading. There was no slack in the belay, but neither was the belay pre-tensioned. I weigh about 180, call it about 200 with boots, crampons, ice-tools, winter clothing.

 

The key takeaway from this incident, for me, is that TWIN ropes are designed to be loaded with two strands sharing the load. HALF ropes are engineered to be loaded as a single strand. I've favored twins over the years for the weight saving, but I have been dangerously careless in my deployment of them. I am pleased to see that technology may be evolving to cover for me, as I see more and more "double" ropes certified for use as both half and twin (impact force meets criteria for certification as twin-rope, while single-strand load capacity meets criteria for certification as half-rope). Hell, Beal and Mammut even have ropes that meet the criteria for all three certifications as twin - half - single (I believe the Beal Joker was the first rope to achieve this distinction) so I really have no excuse for what I was doing.

 

Genepires - I had done the same homework, even before this episode under discussion. I would have to conclude, based on this experience, that if the rope will elongate 30% under the load of a lead fall, it could elongate that far under static load, given sufficient load. I just didn't expect that me by myself would be that sufficient load... but it makes sense to me to figure that if they are engineering twin ropes to always be loaded as paired strands, then a "climber-load" that would produce 10% elongation of a pair of strands, might conceivably produce double that elongation of an unpaired strand ...? Whatever the case, after this experience, I would never suggest anyone climb on a single strand twin-rope, even just toproping.