/ Abseiling on two uneven diameter ropes

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Pete_Frost on 29 Aug 2013
It is common alpine practice to climb on a single rope and to carry an equal length of 6mm static cord to use for pulling down the rope when abseiling (see Trad Climbing + and other books for details). Given that the 6mm cord doesn't take any body weight, and is just used to drag the single rope down, why use 6mm? Why not go for the smallest diameter that is comfortable to grip?
A Crook on 29 Aug 2013
In reply to Pete_Frost:

its does take body weight. as its tied to the end of the climbing rope.

I think any smaller and you may get slippage through the stitch plate. I have never tried it mind as I always seem to have double ropes on these routes due to:

Either being part of a three or the routes a harder and double makes it less draggy
lithos on 29 Aug 2013
In reply to Pete_Frost:

i'd guess a few reasons ....

* so you can use the 6mm just in case to ab on (scary as .... though)
* its strong and used as tat, 3mm may not be
* 5/6 maybe the smallest that is comfy to haul on.
jkarran - on 29 Aug 2013
In reply to A Crook:

> its does take body weight. as its tied to the end of the climbing rope.

It doesn't have to bear weight or run through the plate, it can just be used as a tag line to pull down the ab rope.

OP: Is it actually common practice?

Why 6mm? You're unlikely to snap it pulling a stuck rope. You can ab on it in extremis. It handles ok. It has a reasonable balance of cost/weight/strength.

The downside is it's less useful than a second dynamic rope should your lead rope get cut, stuck or lost.

jk
A Crook on 29 Aug 2013
In reply to jkarran:
> (In reply to A Crook)
>
> [...]
>
> It doesn't have to bear weight or run through the plate, it can just be used as a tag line to pull down the ab rope.

so you are actually abseiling on the knot (whihc connects the rope to the tag line) jammed up again the maillon / tat?
ice.solo - on 29 Aug 2013
In reply to Pete_Frost:

pretty much what lithos says.

thinner than 6mm will work, but having done it ive felt the extra few mms to have some margin and peace of mind to be worth it. in a nasty world id ascend a 6mm if i had to, a 5mm....? im already whincing.

also, 60m of 5mm seems to have double the rats nest factor of 6mm. not sure if this would double again for every mm down, but its an expensive and somewhat sketchy exercise to find out.

basically i stick with 6mm because im a sissy.
lithos on 29 Aug 2013
In reply to A Crook:
> (In reply to jkarran)
> [...]
>
> so you are actually abseiling on the knot (whihc connects the rope to the tag line) jammed up again the maillon / tat?

no

thread your 9.1 mm through the anchor, tie a loop knot (fo8,oh etc) clip to krab and clip
krab to your 9.1. tie a loop knot in your haul line (6mm) and clip to krab,
ab on 9.1 and pull on 6. The krab gets jammed against anchor/bolt/maillon
A Crook on 29 Aug 2013
In reply to lithos:
> (In reply to A Crook)

>
> thread your 9.1 mm through the anchor, tie a loop knot (fo8,oh etc) clip to krab and clip
> krab to your 9.1. tie a loop knot in your haul line (6mm) and clip to krab,
> ab on 9.1 and pull on 6. The krab gets jammed against anchor/bolt/maillon

after posting i did think of this option.

But having had numerous rope jams on just using an overhand knot there is no way i would do this.

1.It increases friction when pulling down, which is hard work when you have 10 abs to do as you all know.

2.Its just increasing the getting jammed factor and the ball ache that ensues.

Think I will stick to putting the 6mm it through the plate, and using 2 overhands.
Marcus Brewer - on 29 Aug 2013
In reply to A Crook:
This is quite informative. I thought so anyway :)
http://www.caves.org/section/vertical/nh/52/BinerBlocks.pdf
Pete_Frost on 29 Aug 2013
In reply to jkarran:
> (In reply to A Crook)
>
> [...]
>
> It doesn't have to bear weight or run through the plate, it can just be used as a tag line to pull down the ab rope.
>
> OP: Is it actually common practice?

Thanks for your comments - yes, it is common practice on harder climbs and speed alpinism. See Mark Twight's "Extreme Alpinism" for an analysis of different rope combinations.
Pete_Frost on 29 Aug 2013
In reply to all who have posted on this topic:

A huge thanks to everyone for the helpful and constructive responses. Ease of handling and potential emergency use seem to me to be the most compelling reasons for using 6mm cord.

Manipulating full size ropes covered in ice, using frozen fingers when strung-out in storms and darkness is enough of a challenge for me, so I won't be going down below 6mm: I'll just train harder so I can cope with the few extra ounces of weight.
jkarran - on 29 Aug 2013
In reply to Pete_Frost:

Sorry, I guess I wasn't too clear. I know it's commonly written about, I just wondered how many people these days would actually choose such a system when super-thin dynamic ropes are becoming widely available?

jk
humptydumpty - on 29 Aug 2013
In reply to jkarran:
> (In reply to Pete_Frost)
>
> Sorry, I guess I wasn't too clear. I know it's commonly written about, I just wondered how many people these days would actually choose such a system when super-thin dynamic ropes are becoming widely available?
>
> jk

Possibly more popular in USA? An American friend was suggesting it to me last night.

Sounds to me like the karibiner might get stuck on the way down, but maybe no less likely than an overhand knot.

Does smaller cord stretch more? Or maybe cut into your hand more when trying to tug it? I'm not very keen to try, anyway.
HeMa on 29 Aug 2013
In reply to humptydumpty:
> (In reply to jkarran)
> [...]
>
> Possibly more popular in USA? An American friend was suggesting it to me last night.

Or on those lovely vertical to overhanging alpine "sport" climbs with abseil descents like say Wendenstock and numerous lines in Rätikon.
Aly - on 29 Aug 2013
In reply to Pete_Frost: Just to add to what others have said above, whilst the practice of using a single rope and a tag line is well documented I wouldn't (in my experience at least) say that is it 'common practice'. The advent of skinny 8mm half ropes, and 7.5mm twins means that it is usually easier, more efficient and safer to just take two ropes (or to just take one and abseil lots or not retreat).

It does work, but pulling the line through adds a lot of friction (it's hard work), and there's more chance of the knot jamming. Any cord thinner than 5 or 6mm is difficult to pull on hard, and also tangles badly (as well as being a bit too thin to abseil on itself if required). Using two 'proper' 7.5mm twins adds little in terms of weight, but allows easier abseils and adds redundancy which is useful if ascending/descending technical or mixed ground - I have killed three icelines on alpine routes (and been glad I had redundancy in the system), but have never felt the need to save 200g for the added hassle it would cause.

Having said that, the system would work well in some circumstances, such as a solo descent of non-technical and moderate angled ice where weight saving was at a premium and jamming of, or damage to the rope unlikely.
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David Coley - on 29 Aug 2013
In reply to Pete_Frost:
Hi,
I've just spent a week in Ailefroide using a pull line. The reason was that I was climbing solo using an Eddy as both the belay device and the rap device. Hence I had to use a pull line. It worked well. My pull line was a single strand of a twin rope (7.7mm).

I have also used 5mm (static) and 6mm (dynamic) pull lines. The 5mm looked more like 4mm and was a right pain. It cut into my hands, blew all over the place and got in a right mess. However 50m of it fitted into a very small bum bag and was just the job on routes with only one or two full length raps and meant we could climb on a single and belay with a grigri.

The 6mm was MUCH better. 50m fitted into a 1litre water bottle.

In my mind, the choice to use a pull line is more about the rope you want for the main climbing as it is about total weight. A set of twins will be a better choice 9 times out of 10 unless you want to be climbing on a single (so you can use a grigri or a minitrax (for moving together)).

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