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Chockstone Forum - Gear Lust / Lost & Found

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Author
A question on doubles
prb
13/08/2010
12:47:23 PM
Four of us were in the Alps last year with a variety of ropes. We climbed mountains as 2 pairs. For the Hornli Ridge of the Matterhorn, we agreed to split 60m double ropes and use one rope per team. For the normal route up the Dent du Geant, however, there was disagreement. Two people (one from each "team") thought splitting doubles again would be fine while the other two thought (presumably because there's some genuine pitching on the Dent) that a 60m single rope for each team was best. We went with the single ropes and, as luck would have it, I got hit by a boulder, went spinning down the mountain and was saved by the rope!

So, should double ropes be split at whim or only when there is good reason to?

Ps. We also climbed the north ridge of Piz Badile (on 60m singles with the teams joining forces for the 30+ raps on descent). That's a superb climb.
hargs
13/08/2010
12:50:37 PM
Were these doubles rated as single/double, or just double?
widewetandslippery
13/08/2010
12:59:00 PM
Younger, lighter and braver I always climbed on a single 9mm double rope. Never broke but did wear out quick. I see no problem climbing on a single double rope unless you are really pushing impact forces which most mountaineers don't. Chop resistance is an issue again but sheath wise there are many stury doubles and some very lightweight singles out the. That comes down to brand.
bradc
13/08/2010
1:18:53 PM
Beal Jokers would be a good option for that scenario. Rated as singles but only 9mm and quite light. If it didn't involve real pitching I'd be comfortable with a double to catch any slips.
prb
13/08/2010
3:08:14 PM
>Were these doubles rated as single/double, or just double?

Are not, by definition, all doubles rated as single/double unless they are twin ropes which should always be used together (including clipping both through each runner)?

>Beal Jokers would be a good option for that scenario.

That was my single rope on the Dent and Piz Badile!

ajfclark
13/08/2010
3:14:20 PM
On 13/08/2010 prb wrote:
>Are not, by definition, all doubles rated as single/double unless they are twin ropes which should always be used together (including clipping both through each runner)?

That's not my reading of this http://www.mammut.ch/en/ropes_dynamic_ropetypes.html

Particularly "Half ropes [doubles], with regard to strength and weight, lie between single and twin ropes. They only offer standard safety when they are used as a pair."
hargs
13/08/2010
4:25:52 PM
I own a couple of Mammut half-ropes, so that link is pretty much what I've been going by. A couple of things bother me though. First, they test half ropes with 55kg (instead of the 80kg used for singles) -- and I'm well north of 55 -- and second, what happens when you're climbing on the "right side" rope and you're yet to clip the "left side" rope, or you clipped it way below your last few pieces on the right side? Should you abandon the one-rope-per-side idea and clip alternate ropes so you'll catch on both ropes rather than just the one?

Apologies for the hijack, but I might get this back on route: If the one rope per side idea is good and it's OK to fall on one half rope, then you should be able to split them up. I'm not convinced though.
citationx
13/08/2010
4:32:40 PM
On 13/08/2010 ajfclark wrote:
>On 13/08/2010 prb wrote:
>>Are not, by definition, all doubles rated as single/double unless they
>are twin ropes which should always be used together (including clipping
>both through each runner)?
>
>That's not my reading of this http://www.mammut.ch/en/ropes_dynamic_ropetypes.html
>
>Particularly "Half ropes [doubles], with regard to strength and weight,
>lie between single and twin ropes. They only offer standard safety when
>they are used as a pair."

I have often thought about this, and like the next line which is "But here you have the choice between twin rope technique, where both ropes run parallel through the protection and half rope technique, where the «left» and «right» ropes run separately through different protection points. "
So what they're essentially saying, is that you can fall on one, but if it does fail, you have another independent chance for the second rope to not fail too...
Meh. I think the chances of the first rope failing are small enough to not worry too much about using the two together...
davepalethorpe
13/08/2010
4:45:29 PM
On 13/08/2010 ajfclark wrote:
They only offer standard safety when
>they are used as a pair.
"

I guess that as they don't meet the testing standards of a single rope, it would be a little irresponsible of the rope manufacturer to avocate using a double rope as a single...but that doesn't mean that it isn't ok to do it.
prb
13/08/2010
4:46:04 PM
On 13/08/2010 ajfclark wrote:
>On 13/08/2010 prb wrote:
>Are not, by definition, all doubles rated as single/double unless they
>are twin ropes which should always be used together (including clipping
>both through each runner)?
>
>That's not my reading of this http://www.mammut.ch/en/ropes_dynamic_ropetypes.html

My understanding was that half ropes could be used singly if necessary, but mammut (quite rightly) are taking a conservative position. It sounds like they wouldn't approve of our Matterhorn decision.
citationx
13/08/2010
5:25:21 PM
On 13/08/2010 davidn wrote:
>A standard single holds what 16kn?
>
>What would a double hold? I like having a few hundred kg 'play' in my
>system!

Er, typical single is "rated" to 22kN. I'm sure it actually holds much more.
davepalethorpe
13/08/2010
6:04:17 PM
On 13/08/2010 citationx wrote:

>
>Er, typical single is "rated" to 22kN. I'm sure it actually holds much
>more.
>

Had a quick google, but couldn't find a definitive answer. Did see testing from BD on rap knot strength, and the highest one pull tested to 6630 lbf on a 10.2mm rope (which google translated to about 30kN)....and knots reduce the strength of the rope somewhat also. A lot stronger that I thought it would be!
One Day Hero
13/08/2010
7:46:12 PM
Use the thicker rope if you even think you're gonna fall on lead. For an easy ridge scramble where you don't really bother with belays, the skinny rope won't be the most dangerous bit of your day.

I get shitted climbing with people who take stupid risks to save trivial amounts of weight. Has 250g + or - ever made fark all difference to anyones success or enjoyment on a climb?........going light on rack and then having to pull 20m runouts on steepish loose stuff, however, makes me cranky.

ajfclark
13/08/2010
10:20:30 PM
On 13/08/2010 hargs wrote:
>First, they test half ropes with 55kg (instead of the 80kg used for singles) -- and I'm well north of 55

I assume the difference in weight because they assume that part of the load will be taken by the other strand.

Twins are tested in a pair with 80kg, singles with 80kg, doubles with 55kg on one strand.

voodoo
13/08/2010
10:42:52 PM
On 13/08/2010 ajfclark wrote:
>On 13/08/2010 hargs wrote:
>>First, they test half ropes with 55kg (instead of the 80kg used for singles)
>-- and I'm well north of 55
>
>I assume the difference in weight because they assume that part of the
>load will be taken by the other strand.

This exact question came up in Rock & Ice Issue 181. Jim Ewing (product manager of Sterling Rope) provided the explaination. The weight discrepancy has absolutely nothing to do with what weight the rope will take and everything to do with testing procedure. Originally they tested half-ropes with the standard UIAA 80kg test mass (as per standard ropes) - if it withstood that drop, it passed. But one single drop doesn't produce enough test data for it to be accurate. So they lowered the mass to 55kg and raised the standard to 5 drops.

Why is this? Because a labcoat-wearing, calculator massager worked out that 5 drops at 55kg has the same mass value as a single drop at 80kg.

So essentially if your rope is rated to 5 drops at 55kg you know, with a much better degree of accuracy and reliability, that it is capable of withstanding a single UIAA 80kg fall.

ajfclark
14/08/2010
8:35:13 AM
Thanks Voodoo. I've always wondered the reasoning for that testing.

There are 16 messages in this topic.

 

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