/ Abseiling on single rope with pull cord

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Sean_J - on 05 Dec 2012
Say i've got a 60m single rope, 10mm diameter so not exactly super-skinny. I want to make a series of full-length abseils on the rope, and i'm planning on using a pull cord to get the rope back.

Question 1) What's a sensible diameter of cord to use? I was thinking 5mm, but i'm tempted by 4mm which is almost half the weight (11g/m instead of 20g/m). Breaking strains are 580kg/330kg for each cord diameter. As for length, something like 65m would probably be a good idea I assume (it might be that an ab station is reached on rope stretch, and the 60m single will stretch a bit under its own weight anyway).

Question 2) Where the 10mm rope is threaded through the top anchor, it is normally then tied with a fig-8 bight and a locking krab used to clip the bight back onto the downward strand, thus securing the single rope (and the pull cord is then tied to the fig-8 bight for retrieval). I'm thinking about the screwgate getting cross-loaded on the anchor(or rather, loaded in a direction perpendicular to the plane of the krab - think getting bent in half), maybe using a rap ring (30mm diameter solid aluminium round bar toroid, looks like a lower-off ring) would be safer - but more faff to rethread the next ab station as it can't be unclipped. I'm considering a maillon as a good method as well, but possibly also prone to cross loading. Any more thoughts on rap ring vs. screwgate vs. maillon? Just trying to figure out a safe and efficient system. And don't mention any fifi hook/skyhook method, not interested.

Cheers all!
Jonny2vests - on 05 Dec 2012
In reply to Sean_J:

Q1. I think snapping / cutting the pull cord is probably unlikely unless you have a lot of friction present. But I guess you definitely wouldn't want that, plus 4mm might be hard to pull on, so my vote would be 5mm. 60m sounds fine, very few abs out there > 60m.

Q2. I understand the concern, but no matter how you load it, its hard to imagine a screwgate failing under abseiling loads. I would use a screwgate rather than a maillon, just for ease of use.
Murko Fuzz - on 05 Dec 2012
In reply to Sean_J:

Hi Sean, I had a look at using 6mm cord in just the manner you describe but found that 60m of it was pretty bulky. I did use the system on rope access jobs for great conveniance. I aquired 60m of 3mm cord which packed down nice and small. Testing it for a really strong pull was fine but I never used it in the end. Quite easy to break over an edge. Maybe a good supple 4 or 5 mm will work for u.
Maybe belay master krab? Or one of those BD thingmys that can't cross load?
jimtitt - on 05 Dec 2012
In reply to Sean_J:
The idea is that the knot doesn´t go through the abseil point, the karabiner is just a backup. If the knot does go through the ab point then you´ll probably need something more than 4mm cord to pull it back through!
The thinner the cord the more it tangles and gets blown around in the wind.
willworkforfoodjnr - on 05 Dec 2012
In reply to Sean_J: I tried this with some 5mm and found it to tangle incredibly easily - it was a constant fight the entire time - it catches the wind, wraps easily around random branches etc etc. Next time I'm just climbing on doubles!
GridNorth - on 05 Dec 2012
In reply to Sean_J: Doubles or twins are far more convenient. As others have said thin cord is hard to manage. The thinner the cord the more prone it is to get tangled. I suppose you could keep it in a small haul bag though which might help.
James Thacker - on 05 Dec 2012
In reply to Sean_J: Bit of a specialist technique this, and it's an expensive set up so half ropes or twins will be better for most folk. I have only used it a couple of times (North Face of Eiger and big faces in Chamonix) when I wanted to use a single rope but have an insurance policy of full length abseils. It worked fine because I didn't need to go down...

Q1: The cord actually gets a fair bit of punishment as its pulled down, stronger is probably better. 5.5mm Spectra/Dyneema is the best for longevity - I use 6mm Aramid, 60m BUT it is expensive http://www.edelrid.de/en/sports/products/ropes/rap-line.html

Q2: Yes, sounds right. Screwgate crossloading on the anchor isn't really a big factor as the knot butts up against the ab tat/tape. It is worth having a couple of maillons though to leave, makes the process much easier.

Hope this helps, ta James
mark catcher - on 05 Dec 2012
In reply to Sean_J: This is a common technique in the States, but be super careful. My partner and I witnessed a death in Yosemite when, after multiple abs, one of a team of two simply forgot to put the krab in the knot and the ropes just pulled straight through. Tiredness I guess but be careful.
Enty - on 05 Dec 2012
In reply to mark catcher:
> (In reply to Sean_J) This is a common technique in the States, but be super careful. My partner and I witnessed a death in Yosemite when, after multiple abs, one of a team of two simply forgot to put the krab in the knot and the ropes just pulled straight through. Tiredness I guess but be careful.

Was that the Serenity Cracks accident?
Horrible thing for you to see. I read the report in the American journal. Two very experienced climbers who had been buddies all their lives - one died the other was left standing at the belay.

E
Sean_J - on 05 Dec 2012
In reply to Sean_J: All good answers, thanks everyone. I'm not 100% on what the ab points are (slings, bolts, chains etc) so I think i'll take along a few maillons to ab off and leave behind, that way I can ensure that the knot in the single rope will be jamming in the maillon properly. And a screwgate sounds like it will be fine as the backup, I can see how it won't be cross-loaded now thanks.

Re. cord, I was thinking of clipping a draw from me to the cord, so that as I ab down it will be kept to hand. I'll have a look at the cord in a store before I buy anything.

I would normally use doubles/halves, but weight is an issue and moving about on one rope is less faff than with two (we'll be at altitude so it'd be nice to keep light and make things simple for getting up the route itself).
martinph78 on 05 Dec 2012
In reply to James Thacker:

> Q1: The cord actually gets a fair bit of punishment as its pulled down, stronger is probably better.

If the cord is tied to the knot/locking carabiner then it's just a straight pull down isn't it? It's the rope pulling through the anchor.

Unless I'm missing something?



neuromancer - on 05 Dec 2012
In reply to Sean_J:

Could someone here explain the method of single rope abbing as described in the OP - locking carabiner and all, or link to a page that describes it? I can't visualise it for some reason.
jkarran - on 05 Dec 2012
In reply to neuromancer:

Thread the end of your ab rope through the ring/sling. Tie a fig8 on the bight in that end, just the knot forming a loop, it's tied to nothing. Clip a krab through the fig8 loop and around the long descending strand of rope. Shuffle the base of the fi8 snug against the ring/sling. Tie your thin tag line to the fig8 loop. Ab on the rope (not the cord) making sure you stay in touch with the tag line.

Half ropes are a better choice in most situations.
jk
Jonny2vests - on 05 Dec 2012
In reply to Martin1978:
> (In reply to James Thacker)
>
> [...]
>
> If the cord is tied to the knot/locking carabiner then it's just a straight pull down isn't it? It's the rope pulling through the anchor.
>
> Unless I'm missing something?

The rope and tag line usually end up touching rock somewhere on the ab, this extra friction is more punishing on thinner lines and they wear out quicker.
Enty - on 05 Dec 2012
James Thacker - on 05 Dec 2012
In reply to Martin1978: You are quite right but you are pulling on a thin diameter cord which gets a fair bit of punishment from abrasion i.e. particularly where the cord is knotted to clip into the karabiner or tied to the single rope.
James Thacker - on 05 Dec 2012
In reply to James Thacker: Exactly as jonny2vests says...
James Thacker - on 05 Dec 2012
In reply to Sean_J: "Re. cord, I was thinking of clipping a draw from me to the cord, so that as I ab down it will be kept to hand. I'll have a look at the cord in a store before I buy anything." - just put the cord through the other slot in your plate. I use a small stuff sac clipped to my harness for the first rap. There after just lob the cord as you would rope.
Exile - on 05 Dec 2012
martinph78 on 05 Dec 2012
In reply to James Thacker: Fair point. Cheers.


john arran - on 05 Dec 2012
In reply to Enty:


NO!

That's one way you can ab off double ropes with a gri gri or other single-rope belay device - and not a very good way even of doing that. It's DEFINITELY WRONG for single rope and pull-cord combinations. The problem is you're relying on the knot getting wedged in the anchor krab; if the knot makes it through the anchor krab youl'll be hanging on a short length of pull-cord only. And that's apart from the fact that it could then be virtually impossible to pull (which is why it's crap for double ropes too).


Enty - on 05 Dec 2012
In reply to john arran:

Yeah you're right. That's only going to be any good on thick ropes with a small rap ring.
I rushed into finding a diagram.

E
mark catcher - on 05 Dec 2012
In reply to Enty: Yeah, it was Enty - pretty bad scene, though I thought they were father and son, could be wrong. Were you in the Valley then too?
The Ex-Engineer - on 05 Dec 2012
In reply to Sean_J: I've got a drum of standard Mammut 5mm sitting here that isn't getting used, so if you want to use 5mm I'd be happy to sell you 60metres for £27 posted (i.e. £0.45/metre).
Enty - on 05 Dec 2012
In reply to john arran:

Hows this pal?

http://www.flickr.com/photos/elcap2011/8246865699/

Just like JK explained higher up the thread.

E
Pete O'Donovan - on 05 Dec 2012
In reply to Sean_J:

Dave Hesleden and I used a single rope + 6mm drag-line on some multi-pitch bolted free routes in Madagascar last year.

The rationale for this was that neither of us likes climbing with a sack (filled with water, food, etc) and that we would use the drag-line for hauling, as well as for the multiple rappels required to get back down.

As it turned out, on all but the very hardest pitches the second ended up carrying the sack — it was just too much of a faff hauling it every pitch, as well as time-consuming (it gets pitch dark there at 6pm in August).

After the first few rappels of the very first route, using the system described by various people in this thread, we were desperately wishing we'd opted for twin 8.5's, but as these were back home in the UK there was nothing we could do but persevere.

Here are a few points arising from our experience, which may be of use to you (and maybe others).

1) Take some spare maillons. If the rap anchors are joined by a leave-behind krab (and most people tend to leave really manky ones) this can get horribly cross-loaded by the knot and screwgate of the rappel rope pressing against it. At the very least take a roll of 25mm finger-tape so you can tape shut non-screwgates on the belays.

2) Even with a 6mm (static!) it was a big effort pulling the ropes down after long raps, particularly if there was any drag. God knows what it would be like with a 4 or 5mm!

3) Because you are always pulling down the rope which will NOT be threaded through belay, it slows down the process of setting up the next rap.

4) While retrieving the ropes at each stance, if by any chance they should get jammed somewhere above (on a flake, say) after the end of the lead rope has passed beyond your reach, you will be left contemplating a prusik on your drag-line!

Hope this helps.

Pete.
henwardian - on 05 Dec 2012
In reply to Enty:

NO! DO NOT DO THIS!

the overhand knot in this picture is completely unsuitable for a situation where one rope is a very different diameter to the other rope. Furthermore, in this setup, you are relying on your thin pull cord to take load during the abseil, which you certainly do not want to be doing.
Jonny2vests - on 05 Dec 2012
In reply to Pete O'Donovan:

Some useful insights there Pete. Sounds like 8mm halfs would be less bother and not much heavier.
Captain Gear - on 05 Dec 2012
In reply to Sean_J:

What route are you planning on using this technique on?
Enty - on 05 Dec 2012
In reply to henwardian:

Read the whole thread mate.

e
valjean - on 06 Dec 2012
what would be considered too thin to use as a pull cord?

a mate of mine got a hold of some sailing cord... cant recall details, its strong (cant recall test strength) and was supposed to be heat resistant... im sure someone in this forum will know what im referring to. It was super skinny, 2mm maybe

so first potential problem is the difficulty of yarding on some thin line. the other would be the potential chop factor.


We had a 70+ metres section ready and packed for the "just in case" situation where we might want a full rope abseil. We climbed mostly on fat singles on pure ice climbs. Anyone see any problems with using a tag line this skinny?

RossG123 - on 06 Dec 2012
In reply to Sean_J: Hi Sean,

I’m climbing a lot in Squamish these days where the normal practice is to use a fairly meaty single rope, and a tag-line for multi-pitches. In the spirit of “When in Rome”, we tried this technique and quickly came to the same conclusion as Pete in an earlier post, it’s just not as good. First of all, a single rope is great for straight up splitter cracks and most bolted pitches but a bit of weaving around is reality on most multi-pitch trad routes so doubles are better there. Secondly, abseiling with double ropes is just easier and less prone to stuff ups than a tag line, this is not to be underestimated when you’re tired and the situation is already turning into an epic!

In the end, my regular partner (another British transplant) and I, regularly find ourselves the only team on the wall using double ropes, but safe in the knowledge that it’s the best way!

Ross.
Jonny2vests - on 06 Dec 2012
In reply to RossG123:

I too mainly climb on doubles in Squishy, often to the surprise of the locals. I have a single 70 though for those speed attempt days.

J2V
(Vancouver)
Jonny2vests - on 06 Dec 2012
In reply to valjean:

Lots of reasons up the thread why that is a bad idea.
valjean - on 06 Dec 2012
In reply to jonny2vests:
ok thanks
i saw one bad one the rest appear to me as non-issues
if the odd chance the rope freezes or gets caught on some ice feature, ascending a thin cord is simply not a good plan
neuromancer - on 06 Dec 2012
cbonner - on 06 Dec 2012
In reply to neuromancer: Looks right to me, alternatively you could clip the cord to the karabiner.
walts4 - on 06 Dec 2012
In reply to cbonner:
> (In reply to neuromancer) Looks right to me, alternatively you could clip the cord to the karabiner.


Always found that it pulls easier with the cord tied directly to the rope rather than the krab.

Still a faff & very rare that its worth it.
rgold - on 08 Dec 2012
In reply to Pete O'Donovan:

I'd like to second everything Pete said. Thin tag lines are an inferior solution. They slow you down, they add a number of more dangerous scenarios to your list of risks, and they make it more likely that you'll get stranded, either because you can't budge a rappel pulling on a tiny cord or because your main line hangs up on the way down, leaving you with nothing but a thin cord for your only rope. I've never been able to grasp why my fellow American climbers are fond of the technique.

Maybe, just maybe, a thin tag line makes sense for emergency use when you really don't intend to be doing multiple rappels. But if the emergency does arise, you are stuck with an inferior system with a decent capability to escalate the level of risk---the last thing you want under the circumstances.

If weight matters, use twins. Otherwise half ropes.
Bruce Hooker - on 08 Dec 2012
In reply to rgold:

Couldn't agree more, redundancy is important, but for some reason this subject comes up regularly on ukc. I didn't know it was used a lot in the USA, maybe this is why such an apparently dodgy system still has so many supporters?
nking100 - on 08 Dec 2012
In reply to Sean_J:

A couple of point that have been covered I think but are worth emphasizing:

The anchor MUST have a maillon on it, if there is not one present, you will have to add it and you will not get it back, so carry spares.

This method is prone to getting hung up, a lot more than double ropes are

I only use this on alpine routes that have only a few long raps or as a just in case back up
knudeNoggin - on 10 Dec 2012
In reply to henwardian:
> (In reply to Enty)
> [...]
>
> NO! DO NOT DO THIS!
>
> the overhand knot in this picture is completely unsuitable for a situation where one rope is a very different diameter to the other rope. Furthermore, in this setup, you are relying on your thin pull cord to take load during the abseil, which you certainly do not want to be doing.

1) I took the image to presume that the offset water knot would be jammed into the anchor sling on abseil; then, there'd be no load on the retrieval line abseiling.

2) The offset water knot can actually be **better** with different-diameter ropes if its oriented so that the thinner rope would have to be pried out around the thicker one. Best to tie off the thinner tail to the thicker tail with an overhand, to preclude such prying at all. Depends how stiff the thicker line is; between 6 & 10mm, though, I'd think the prospects are pretty favorable.

NB : : THIS (thick-2-thin joint) IS SOMETHING EASILY TESTABLE WITH YOUR PARTICULAR ROPES,
in the calm of comfortable settings --i.e., we need NO break test at X thousand pounds force!


Regarding the OP's lamenting using an abseil ring, for needing to reeve the 60m line back through it on each subsequent abseil, that's not necessarily the case : rather, the attachment to it could be un-/re-tied each time, working at just one end of the line. THIS, however, might be a poor task to put oneself to for work that might come with fatigue & fading light.

*kN*

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