UKC

Ok - don't worry I'm not going to run out and do this!!

But in some of the instructional videos I've been watching on here, they say that 6mm accessory cord is good up to 750 kg's or 7.5Kn. I understand it's not dynamic so falling on it would be bad (shock loading etc.) - but if it's that strong - Why can't people abseil on accessory cord? Why do they use thicker 10mm static rope or climbing rope? Why can't they make dynamic 6mm accessory cord that's good to 750kg's then we can climb on it?

I'm sure there are obvious answers, but I don't know what they are yet.

Many thanks!

In reply to elliot.baker:

Whilst not recommended it is technically possible. A small diameter cord would be difficult to control the rate of descent with and probably wouldnt provide much friction through a standard figure 8 or ATC? so whilst strength wise it could survive i dont think it would be practical to control.

In reply to elliot.baker:

Take a piece of 6mm cord and 10mm rope and scrape it around on a nice sharp rock edge for a while. See which one goes first.

In reply to Andrew William:

Thats a good reply on a "starting out " forum.

To Elliot, a good starting point is understanding the difference of static and dynamics forces.

Buy or read " multi pitch climbing by David Coley of this parish or research rope manufacturers websites.

In reply to elliot.baker:

You can (and people do) abseil on paracord (3mm thick?) if you're careful enough. But as MichaHY points out - if the cord scrapes the rock too much (and bear in mind it will probably stretch more since it is thinner), it's curtains for you.

A related thing is to use thin cord as a tag line to do a full-length abseil on a single rope. E.g. if you have a 60m single rope, and want to do full 60m abseils without hauling an extra rope, you can bring 60m of accessory cord to pull down the 60m rope (requires some extra knotting at the top). I've tried it once and it worked but because of the stretch in the tag line (I used paracord) it was very hard work, and you'd be all but unable to pull the main rope through even the smallest of jams (i.e. if it got stuck in a plant) because all your pulling strength goes into stretching the tag line.

In reply to elliot.baker:

But you CAN ab on 6mm ....

http://www.v12outdoor.com/product.php/6290/edelrid-rap-line-6mm-x-60m-oasis

In reply to elliot.baker:


Once you've made a dynamic core, and made it strong enough to take a leader fall (which can exceed 7.5 kN), and made a sheath strong enough that you're not replacing it every week or risking death as soon as it touches a sharp edge.... I think you're describing a really skinny half rope.

In reply to Andrew William:

Wow quick answers! Thanks all. In summary - technically possible but neither sustainable, wise or particularly safe! I'll stick with my cheapo 10mm rope for now!

In reply to elliot.baker:

Apart from handling issues, 6mm is simply a lot less rope than 10mm (only about a third of the mass); it's far more prone to abrasion, and if there's an issue with the rope heating up it will melt through much sooner. Comparing diameters can be deceptive - it's more relevant in many ways to compare the squares of the diameters.

In reply to elliot.baker:

It does get done quite regularly by those going fast-and-light (think Alpine or winter climbing). What is often done is to carry one thin 'proper' rope for climbing on (something like a Beal Iceline), and one length of cord used only for the second rope in abseils. You have to be very careful of choice of knot when joining two ropes of different diameters, and be aware of the different amounts of friction on the two ropes through the belay device to not, as above, end up doing a very fast rope-free descent.

In reply to Dell:


Not accessory cord though, since it isn't just a skinny nylon static (which is what accessory cord basically is) but is a dyneema-type core (not actually dyneema).

Cavers (mostly the French) will sometimes use 8mm rope (not officially 'rope' by CE standards, but the French have an 'L' standard for lightweight 8mm rope) for both abseiling and ascending (which is a LOT worse than abseiling for rope rub). But when using standard European caving rigging, the rope will never rub - if you go over an edge (which you avoid at all costs) you then rebelay just below the edge, for example. "The rope must never rub, and lightweight rope even more so!" - Alpine Caving Techniques, 3rd edition

In reply to elliot.baker:

Mammut make a specific rapelling kit, with 6mm cord;

https://www.mammut.ch/GB/en_GB/B2C-Category/Equipment/Climbing-Equipment/Be...

Just thought I'd throw that in there for discussion,

In reply to James Jackson:


As I understand it the tag line is not put through the abseil device at all, and hangs free. The last paragraph of this article describes the usual way to set up a tag line: http://www.ukclimbing.com/articles/page.php?id=167

In reply to SenzuBean:

more info
http://alpineteam.co.nz/2013/abseiling-single-rope-plus-tag-line

In reply to elliot.baker:

My wisdom is, don't take any risks abseiling. (General advice, I know, and not directly answering your question).

Signed:
Abseil - abseiling accident survivor (PS you often only get one chance. I survived and thus got two chances).

In reply to elliot.baker:

If you are thinking of abseiling on thinner rope, then you might find these photos on how to add more friction useful: http://people.bath.ac.uk/dac33/high/10GettingBackDown.htm#addingfriction

In reply to elliot.baker:
As I always tell my students-- the only stupid question is the one you need to ask and don't...

Myself, I bloody hate abseiling. It's the only time in the day when I am completely at the mercy of my anchors. I'm not mucking around with my safety margins unless I'm in a Touching-The-Void-type disaster-movie scenario and have no choice. Like everyone else is saying, thin rope is going to zip through your belay-device/ abseil-device like nobody's business, and the faster it goes the likelier it is to melt.

Bottom line: You can. But don't.

In reply to SenzuBean:

That's one way, the other is you use it as a thin double when abseiling. Pros and cons of both. Either way, this is the kind of technique you learn on the job from other experienced climbers, not after taking advice on a forum!

In reply to elliot.baker:

Would a back-up prusik be able to grab a really thin rope?

In reply to elliot.baker:

Just to hijack the thread a little (seems relevant) and ask peoples opinions; would this be an accepted method for rigging an abseil up using 6mm cord?

youtube.com/watch?v=SH1G5wUZg7o&

In reply to James Jackson:


Brilliantly true

In reply to DaveL1234:

That's an excellent demo. Was there anything you were worried about?

In reply to elliot.baker:
Lots of discussion here on UKC


/ you can abseil on 5 mill rope....... ( link not working but you should find it )

Cannot be bothered to read it again but probably varying advice from total bollocks to very useful as usual.

In reply to elliot.baker:
This is still the one true way to make full length abseils on a single rope... :P

youtube.com/watch?v=b8Ute5c2BVk&

edit: the above is a lie. Don't do this.

In reply to chris687:

Thanks. My concern was the friction between the cord and rope and if this could wear or overheat. I wasn't sure if you should have a carabiner (or alternative) between the two, to avoid the friction.

In reply to DaveL1234:

Very sensible concern - if you tried lowering off through the sling/cord rather than abseiling, you would probably cut through it before you finished your lower. Leaving a carabiner or maillon is a bit safer, but abseiling is also OK since the rope should not be moving over the cord. You would use a carabiner unless you aren't going back to the anchor (e.g. escaping off an Alpine face or something).

In reply to DaveL1234:

I've left bail anchors like this. The rope doesn't move during an abseil... as Andrew says, don't lower off like this. Also, the anchor could well be compromised after you pull the rope, so if you find in situ tat like this, have a really good check that it hasn't been cut through.

In reply to David Coley:


Thanks for this link it's a really good little page with loads of useful info.