UKC

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If I have 4m of 5mm accessory cord, what lengths should I make my prussik loops?

1.5 and a 2.5? 1 and 3? Even stevens?

In reply to neuromancer:

Fwiw, they're to be used just like any other prussik, for ab backup and for rope ascending/crevasse rescue.

In reply to neuromancer:

1 metre is a good length for the ab back up.

Kirill

In reply to neuromancer: mine are 1.5m. if I need a shorter one I just put an overhand in it.

In reply to neuromancer:

It doesn't matter so long as they're not too short. Mine were the same sort of length as a 60cm sling (~1.5m of cord) and they worked fine. Personally I'd keep the cord as ab tat since I generally just use a sling when I need a Prussik these days.

jk

In reply to jkarran:

All my slings are dyneema, which doesn't take well to friction as I'm sure you know.

In reply to neuromancer:

Steve Long recommends thumb to elbow when tied - ie loop it over your thumnb
and it should reach your elbow (ish) !

why not tie one, adjust it to roughly that length (12..15inch ish)
and see if you like it, wraps well enough (you can get enough turns
around your main rope) when its good for cut it and now you can make
another.

some people like having 1 long and 1 shoty, i cant be bothered!
Mine are sort about that size ish ! see how precise I am

In reply to lithos:

Yeah, what you said Rob :0)

In reply to neuromancer:


So are mine, they work just fine.
jk

In reply to jkarran:

Ok, well I do wish you all the best, and i hope your friction knot doesn't generate too much heat in your very-low-melting-point sling.

To others, thats a good idea, I'll knot it and see how it runs.

In reply to neuromancer:

my pruisk loops are 130cm of 6mm chord looped and tied with a double fishermans. all you need.

In reply to neuromancer:


Fair enough, I'm comfortable with what I do but if you wouldn't be that's fine. It has to be slipping *under load* to generate any heat and under the same conditions nylon won't actually fare much better.

jk

In reply to neuromancer:

Personally I hate to have long loops as they just get caught up in stuff. My finished loop lengths are about 60cm (circumference) made from 1m of cord. That is long enough to form the knot but not so long that you are getting cord stuck in abseil devices - speaking from bitter experience of having to try to cut one free. ( the short loops also stow away easily and are a good length to act as back up extenders when everything else is used up)

In reply to neuromancer:
You can always make a longer prussik smaller with an overhand, also they pack small once you learn this knot

http://www.chockstone.org/TechTips/Prusik.htm (bottom of the page)

In reply to neuromancer: I use one short and one long - long ones snag up all the time and are no good for abseil backup unless you shorten them which is a faff.

In reply to neuromancer: cut 1.25m and double fishermans, i find 1m too short

In reply to neuromancer:

it can be handy to be able to put a prussik over your head and one shoulder if you want it out of the way but need to use it again in a short while. i find 1m a touch too short for this.

its all down to personal preferance

In reply to neuromancer:

After numerous failed attempts to buy a suitable length of prusik I ended up just copying the options on needlesports:

5mm x 1.25m (Short)
5mm x 1.5m (Standard)
5mm x 2.5m (Footloop)
6mm x 1.5m (Short)
6mm x 1.75m (Standard)

5mm x 1.5 is what I'm finally happy with. Better to go too long than too short as you can always shorten, but you can't lengthen.

In reply to neuromancer:

Is that 1.5m then tied, or 1.5m total circumference?

In reply to neuromancer: Keep them as short as possible so they can stay out the way on the back of your harness and you've always got them as a "get out of jail free card". You will be carrying slings anyway, so just clip on a sling if you need extra length for a footloop or whatever.

In reply to neuromancer:

From the replies so far, you probably realise that there is no right answer. Whatever works for you.

In reply to neuromancer:

thats 1,5m of rope, then tied.

In reply to neuromancer: I find the Needlesports recommendations for short prussik loops work perfectly (1.25/1.5metres for 5/6mm respectively) and have used them in pretty much every conceivable scenario from abseil back-ups, to crevasse rescue and improvised rescues.

However, in addition to carrying two 5mm prussiks and a Petzl tibloc, these days I generally also carry 3metres of neatly coiled 5mm on the back of my harness which then gives me more than enough options.

In reply to The Ex-Engineer:

A follow on question, perhaps: where does one use 5mm/6mm/7mm accessory cord? (in prussiks and maybe in other rigging). Clearly each has a different strenght (listed on spec sheet), but what does it mean for application? Can you rig your anchors for a top-rope belay station using accessory cord? (I bought 10.5mm static rope for such rigging, but curious)

(wall-climber, 2 day course outdoors done in Sept, going to head outdoors ASAP in spring so getting bits of gear already...)

In reply to neuromancer: My top tip would be not to make it so long that you can't reach it. Yes, happened to me after I recently made new prussik loops up. Hanging on belay device to clean gear, the device slipped/creeped and I found the prussik was just an inch too long for me to reach and release.

Lucky I had my pack on with a knife in it.

Lesson learned!

Might sack-off my longer prussick though and use a 120cm sling as a foot loop instead.

In reply to michaelc:

Absail tat etc.

In reply to Martin1978:

How could it be too long for you to reach? I'm not sure I understand, could you explain?

In reply to neuromancer: Black and White Answer:

Cut two lengths of 1.5m and one length of 2m. This allows you enough length to add a turn when you feel you need it (such as pulling someone out of a crevasse etc) but is not so long that it is a pain.

If you do find it too long when abseiling, just put an overhand knot in one end to shorten it.

I know that many climbers only carry one, maybe two prussiks, but you mention that you intend to ascend ropes and use them for crevasse rescue, presumab Having three can make this a lot easier. Especially if you intend on learning some self rescur techniques etc.

Ryan

In reply to neuromancer:

I guess he was using the prussic above his belay device (possibly extended on a sling) on the live rope and when it took his weight it was too far up the rope to reach to release.

OP's question has been answered; shall we all have an argument about prussik above/below the belay now?

In reply to michaelc:

Strength isn't usually the issue with different accessory cord diameters - abrasion resistance is. Thicker cords spread their contact over a wider area and are therefore less susceptible to cutting. How anyone would quantify this is anyones guess.

If in doubt, why not try a few scenarios out for yourself ?

In reply to andic:


Below! When abing with the loop above my belay device, I rested on the prussik to clear some gear, then couldn't release it. Had to use my knife. With the prussik below, there's no problem.

In reply to Mark Kemball:

Couple of factors to debate here - I've played around with various prussiks as part of SPA training and whilst a conventional or klemheist will jam up, a french prussik will not.

Also when abbing with prussik below, I find it very slow and have to actively feed the rope through...

What are other peoples experiences here?

In reply to andic:


Yeah, that's what happened First time it's happened. It was a new cord I'd made a bit longer so I could get an extra turn round the rope then forgot to make the extra turn when I came to use it. Silly mistake.

Not going to get into the whole above/below argument as it has been done to death. I'll stick with above and just keep it a bit shorter :p

In reply to neuromancer:

1.5 meter, 5mm cord, used as french prusik under belay device every time for me.

In reply to Landy_Dom:

If it is just at the start of an abseil on easy angled ground, then that is often to be expected. But if it is near the bottom of an abseil and on steep terrain, then you just need more practice or need to experiment with your prussiks.

It is actually a surprisingly tricky technique to get right. Well over 60% of the people I have ever taught how to use a prussik back-up have struggled to get the hang of it initially.

In reply to Landy_Dom: I only use a French prussik for abseiling as it will release if squeezed even under load and I keep the kleimheist for the second prussik when ascending a rope during a crevasse self rescue ( which I've only done in practise so far, luckily). I don't ever use the original knot or the Bachman.

In answer to the first question I generally use 1 1.5m and 1 1.25m of 5mm cord but I also have some of the same lengths in 6mm cord as I find these work better depending on the thickness of the rope I'm using.

In reply to neuromancer: has anyone asked Num Num how long his is?