UKC

What size and length of cord do people recommend for prusik loops?

I've seen one recommendation of 6mm cord tied with a double fishermans in to a 30mm loop. Another recommendation I've seen is for 1.5m of 5mm cord. One climbing school I attended provided two loops of 8mm cord, one about 60mm long and the other something over 120mm.

I've seen suggestions that the thinner the cord in relation to the main rope, the better it grips. I can also see that this might not necessarily be a good thing in all circumstances.

Given that a prusik loop should be a pretty general-purpose item, so I don't want to carry different ones for different uses, I'd be grateful to know what people's experiences have been with different kinds.

In reply to Martin W:

8mm cord? Is that a piss-take? I think even 6mm is a bit OTT. I have a couple of loops made of some stuff thats about 4mm thick, and I don't think they are likely to snap. It's not as though you are going to be falling on them.

Length wise, I suggest you buy about 4 metres of whatever thickness and take it down to a climbing wall when it's quiet and experiment. You should end up with the shorter loop (for the harness) about 2/3 the length of the longer loop (for your feet)

When using them tie a figure-8 into the slack bit of the rope every now and then and clip it into your belay loop, so that the thickness of the loops makes no difference anyway. Thinner cord DOES grip much better, and makes the whole thing easier.

For general scrambling/mountaineering I carry a single short loop for protecting an abseil or emergency whatever type use. For more serious multi-pitch / alpine climbing I carry a pair of loops made from the same type of cord, but slighty longer (As I said, one 2/3 the length of the other).

In reply to Vdiff Dave:

I do think 8mm is a poor choice. Although the long loop, when coiled up, makes quite a good "humane" seagull basher! I now 6mm and 5mm to experiment with.

I'm interested that you have a long loop for the foot. I'm leaning towards having two loops the same length and clipping a sling to the lower one. One reason for this is that it makes it easier to switch from abseil to ascent eg in a rescue situation: you can put the harness prusik above the belay device, and clip the foot stirrup sling in to the abseil backup prusik. If you've used the short sling below the belay device to backup the abseil, things can get tricky to arrange if you want to go back up again while dangling. Putting the backup prusik above the belay device would get round this problem, but doesn't seem to be favoured as a general practice.

In reply to Martin W:
I started out using 5mm, as suggested by one person, but moved up to 6mm because I found the 5mm too grippy and kept getting stuck. I hate abseiling at the best of times and the smoother the ride the better. It still locks off when needed. I also think that if you are stopping and starting and bouncing around on the rope because your prussics get stuck you are straining your anchors a bit more. Shouldn't be a problem if they are any good I guess, but I am, as I said, deeply paranoid about abseiling...

Apparently on the continent they are into these longer prussics, but I have always been most comfortable with the 30cm loop which can be extended if need be.

In reply to Martin W:

5mm for thin ropes (under 9.5), 6mm for thick. Too much grip is generally more of a problem than too much slip for my purposes (mostly abbing) - prefer a ropeman/tibloc for ascending. A thinner cord definitely grips more, and on an older (roughed-up) rope, it's often too much for my delicate ladylike grasp.

I find 1.5m (pre-knots) the ideal length for 3-4 wraps plus enough end to clip into, but I also carry a 2.5m.

They're so light I carry more than I think I'm going to need (winter/alpine) so I needn't worry about using them for ab tat, spare shoelace etc if needs be.

In reply to Anonymous:

sorry that's me.

In reply to Martin W:
A couple of pointers that may come in handy!
1) 5mm cord is ideal, strong enough and grips well on most rope diameters you'll be using
2) 1.5 m lengths are OK. Best to have a prussik a bit too long rather than too short, if its too short its useless, if its too long you can shorten it with an overhand knot. A longer prussik can come in handy as ab tat etc.
3) Use an open french prussik knot as they are releasable under load if you push down firmly at the top of the knot.

In reply to dan:

>Best to have a prussik a bit too long rather than too
>short, if its too short its useless

I grant you that a prusik which won't wind round the rope enough times to grip is no use. However, assuming it's long enough for that, what benefit does the extra length confer? Once the prusik is on the rope, you can clip it and then attach whatever else you need to the krab.

>A longer prussik can come in handy as ab tat etc

A reasonable point. On the other hand, I think I might prefer to ab off something more substantial than 5mm cord as a general rule.

In reply to Martin W:
Martin, - better to have prussic loops longer rather than shorter because it is easier to shorten a long loop than extend a short loop. It's also neater.

I've had to use prussiks in anger, and there is no guarentee that you will have all the bits and bobs to extend the prussik to the correct length when you need to use it. Far easier to have the right length to start with.

5mm - your choice - I've no problem with it - properly set up of course.
SteveP

In reply to Martin W:

For the general sea cliff cragging that I mainly do, I carry two 5mm cords, each about 1.2m before knots, and tie them off with a double fishermans. I take a tibloc and ropeman for escapes if necessary, but have never had to use these in anger.

I always use one of the loops as an autoblock (French prussik) for abbing, usually on the same furry 11mm rope. I find that the grip of the loop can vary from too much and a bloody nuisance, to just fine. I dont really know where the variation stems from, but it probably is a direct function of how many times I loop the loop around the main rope, and which end is clipped above which. (I think friction on capstans goes exponentially as the number of times you loop the rope around the capstan) I have always been too gripped to be consistent about this, but a quick experiment now, at home shows that:

2 turns : no grip.
3 turns : enough grip to hold me reliably if I clip the loop end that comes out from over the rope under the loop end that comes out from under the rope, if you see what I mean. Less grip if I clip these the other way around - the loop can slide if it starts off loose, as the prussik loops unravel more.
4 turns : (just enough cord for this) enough grip either way.

So the variations I have experienced probably arise from using one or other of the 4 possibilities that 3/4 turns offer.

In reply to Martin W: Just a quick note to say thanks for all the useful responses to my question. Ta...M

In reply to Martin W: Just to change tack slightly, do people put the prusik above or below the belay device? Putting it below (and attaching it to a leg loop) would appear to make the prusik lock off the belay device, thus not taking much weight (safer?) whereas having it above appears to make ascending easier (if necessary). Any thoughts?

In reply to Rick:
I use the leg loop generally just because it is easier, though prefer to use an extended krab through the tie in loops of my alpine harness as the leg loops are a bit wide.

Changing tack back again, I have since tried these funny foreign practises of using long prussics, and have to say that for the Alps I have changed my mind about short ones, longer is a lot more convenient. Its a vital peice of kit for crevasse rescue and the longer it is, the easier to set up in gloves, you need one for carrying coils etc too and lo and behold, it becomes a piece of abseil tat that you can add to the piles already in place for peace of mind...

In reply to Rick:

If you think you will got down OK, but might have to stop mid-way (to throw the rope of a ledge etc) you can use the leg loop method, as it is easier, but beware, if you find you need to climb back up the rope, and don't have any spare prusiks, it's much, much easier if your only prusik is attached above the belay device. So, if you can't see what you are abseiling into, I'd use the latter method.

In reply to Vdiff Dave:
One more reason for putting the prusik above, if you ab off the end of rope it gives you the last chance saloon

In reply to sutty:

If you can remember to put it above in case you abb off the end, why not remember to put a knot in the end of the rope before setting off instead?

In reply to Vdiff Dave:

I feel more comfortable with it on the leg loop. (a) It doesn't take much strain when it's locked off, as somepone pointed out above and (b) I was taught to ab with both hands below the device, on the grounds that a hand above the device does sod all with respect to controlling a descent.

Since I automatically have both my hands below the device, it feels more natural to control the prusik with one of them. I always have a second prusik with me anyway, in case I need to ascend.

In reply to Rob Naylor: After Simpson's experience in dropping his prussik, I carry three, just in case.

In reply to stonemaster:

I've usually got a bit of cord stashed somewhere, as well as the 2 made-up prusiks.

In reply to Rick:

I put my abseil back-up prusik below my belay device. The belay device screwgate is on short extender, attached to my harness belay loop by another screwgate. You could also use a short QD with both the krabs at one end, with their gates opposed. The back-up prusik (french prusik/autoblock) is also attached to my harness belay loop on another screwgate. That's why the belay device is on the end of a short extender, so that there's room for the prusik.

If I let go the dead rope for any reason the back-up prusik bites and holds me on the belay device. I can stop any time I want to without worrying about the prusik slipping because it's the belay device which is braking the rope; the prusik is just holding the rope in the correct braking position. My legs are not encumbered by having dead rope wrapped round them (although I could do this as well if I wanted to, for even more security) or by having a prusik clipped in to one of my leg loops, so I can still maneouvre myself around the rock face if I need to eg to reach a stricken partner. If anything untoward should happen to the belay device then I can still hang on the prusik by my belay loop, although to be honest I'm not sure what might happen to a belay device which would lead to this eventuality, I've just heard it suggested as another reason to favour the belay loop over the leg loop.

Putting the abseil back-up prusik above the belay device means that you have to keep one hand on the rope above the belay device in order to descend. Controlled tests indicate that people who lose control of their belay device will instinctively grab at the rope above them. If you already have a hand on the rope above your belay device then you will likely as not grab with that hand, which in all probability will release the back-up prusik as well, thus removing all braking from the system and leading to a rapid and potentially painful descent.

To avoid the risk of abbing off the end of the rope, tie knots in the free ends before throwing them down. Trusting a prusik to hold you on the last foot or so of the rope if your belay/ab device has just dropped off the end is optimism of the highest order, IMHO.

If at any time you need to re-ascend, you use a second prusik, or a tibloc, or a sling or anything else suitable that you have to hand. It's just something else you should check before you commit to a "blind" abseil: am I carrying the kit I need to get myself out of trouble if this turns out to be a bad line to ab down?

But then I am paranoid about abseiling and always check everything twice before setting off, including asking myself these sorts of questions. You are so completely dependent on your equipment when abbing, and too many other people have hurt themselves by not being careful enough.

All that being said, if all I had left after an accident was a rope and one non-locking krab, and if the only alternative to going down was imminent death from exposure, then I'd probably take my chance on the rope.