UKC

Just been thinking about this and was wondering if how I would do it is deemed "correct". Ive not been taught this or spent any considerable time pondering the safest way to do it so this may well be wrong.

1. Get to just above the knot and allow the prussik (above knot, on leg loop) to take the weight.

2. Prussik (or two if you have them) on above the belay device and extended down to the belay loop.

3. Make the prussik/s tight.

4. Remove abseil device and leg loop prussik and put them back on below the knot.

5. Take tight on the belay device again and remove the prussik/s from above the knot(easier said than done in practice?).

6. Continue.

Thoughts? Please dont let this turn into a shouting match if theres some disagreement.

In reply to Will Hunt:

It's much easier if you have the prussik above the belay plate, but only for this situation

In reply to Will Hunt: Hardest bit will be unweighting the top prussik...a second prussik below the descender with a long loop would allow you to stand up to unweight that first (top) prussik, then gently lower yourself back onto the descender...remove lower prussik and continue...

In reply to Will Hunt:

It's recommended to clip in to a fig-8 or overhand tied on a bight, below the knot, as a back up - before you unclip from the rope in stage 4.


Other than that, sounds about right, as mentioned might be easier to start out with backup prusik above the device until you reach the knot.

IME point 5. is, as you say, easier said than done especially if you are free hanging. Sometimes it might be necessary to put another prusik on the rope as a stirrup to stand up into, to get your weight off the top prusik - a lot depends on exactly how long your prusiks are, the distance you are above the knot, whether you extend the belay device, etc.

Probably worth doing it before you need to use it in anger.

In reply to Will Hunt:

Pretty much it, I think.

If you tie the ropes together using a double fishermans then tie that off with an alpine butterfly (so the original knot is part of the loop - does that make sense?) you can clip a cow's tail into that to provide a second bomber attachment, removing the need to use a second prussik in step 2.

Once you've got your belay device attached below the knot, TIE IT OFF, then use your second prussik with a leg loop to unweight the original prussik. This can be well tricky if you've not got your steps 1-4 quite right - practice above ground if you can maybe?

Out of interest, where are you heading that requires you to do this?

In reply to Andy Hobson:
Nowhere that I know of but it came up very briefly in another thread and it set me off thinking about it.

All that makes sense so thanks peeps. Ill probably have a wee practice at a local crag before I have to do it properly somewhere. Im the kind of person who learns this stuff best by doing so always have a go at doing something before I need to use it.

In reply to Andy Nisbet:

Ditto that.

In reply to Ghastly Rubberfeet:

and the prusik above should be attached to waist loop not leg loop.

I usually use it this way and am not sure why all the nay sayers denigrate it.

Know your gear and how it works.

Its only not recommended for 2 reasons that I can think of - not releasing when loaded. I find the Klemheist okay here but guess the French would maybe solve this.

Getting grabbed by someone panicking and not grabbing. This is experience. Never done it myself.
Prusik above is also easier to use on less steep (not free hanging), diagonal or with wet ropes.

In reply to Will Hunt:

Only done it once (I think) on Mercury. Used a fat Figure of Eight and a knot with longish tails. Managed to feed the knot through the Fo8 - saved a lot of chuffing about!


Chris

In reply to Will Hunt:

The main point is have a loop pre-tied at the knot. This can be a overhand in one of the free ends or use a figure eight joining knot ( see caving section in Petzl catalog or web site ) . then clip to this loop via a cows tail while you do the swop over. How you swop over is up to you, however make sure you are safe on the cows tail.

In reply to Will Hunt:

Point 0) Under no circumstances jam anything against the knot.

Basically you're right just tie yourself off more and use a french prussik (best tied in a Nylon Sling) above the knot and your ATC as it can slide when weighted if you grab the top of it. Now that I'm more experienced than I was (and I have one) I'd use a shunt as the top prussik if possible, and tie a loop into the bottom prussik and stand in that once the ATC's below the knot) to weight the bottom rope and allow me to move the top prussik/ device.

At most places where you're supposed to do it, even on Mercury, the guidebook tells you to rig the ab so the changeover takes place at a ledge ideally. That or recommends you buy 100m of static rope in advance.

This is the sort of thing you cna mess about with hangin off a tree or on the stairs at home.

P.S. Don't let the tide come in and get the bottom of your rope caught round boulders - hank it up neatly or stow it run through higher than the high water mark or you'll waste a day retreiving it/ have to climb at the same crag tomorrow.

In reply to Will Hunt:

Let's keep this really simple:
1 tie the ropes together using overhand knot (nice lnog tails)
2 abseil with an Italian hitch on a large HMS (DMM Boa is great)
3 abseil past the knot with no faff

Lets face it if you are doing this for real it needs to be really easy!
enjoy
Bryn

In reply to bryn:

Does that work? For real? You tried it? A mate reckoned he tested out every configuration he could think of and given this requires zero extra gear I'm gonna need convincing.

In reply to bryn: Just tried it wihotu weighting it under body weight. If you can get the knot thorough the krab twice (passing he tails through) it still catchs under a loop of rope. But you're lowering this rope as it's the dead rope. So if you don't mind a big bounce as you flick the lengthened but taught loop of rope over the knot it could work. I think it's worth me testing when I'm not counting on it. I think I'd try to find some way to incorporate prussiks.

Nice idea anyway. Won't this be a nightmare on static rope?
 

In reply to Will Hunt:
theres actually a special prussik type knot/hitch thing called a valdertane used just for this.
you abseil to about 3m above the knot, lock off and tie the valdertane with it clipped to a daisy or tail, take the abseil device off the rope, use the valdertane to slide down the rope till its about 1m above the knot, put the abseil device back on below the knot and lock it, use the valdertane to lower more until weight is back on the abseil device, take the valdertane off, on your way again.

the valdertane itself is a length of 10mm dynamic with a clip loop in each end. ideally its had a few strands removed from the core and even better is wet to reduce friction. it tied a bit like a prussic and clipped with an HMS. the knot causes lot of friction and has a release function.
canyoning and caveing types carry them.

In reply to nz Cragrat:

Completely agree, never understood the leg loop thing?
I have done this in anger loads of times, but my advice is have a practice, in fact everybody ought to practice this, just so its not scarey when you need to do it.
Oh, and do it while hanging free, any fool can do it on the merely vertical.

In reply to Paz:

Done it for real and its what i now show folks on courses. You can include a prussic to help take the strain off the hitch, but it is far less complicated than previous methods!

bryn

In reply to bryn:

Oh right cool. Do you know if it works on static, and doesn't it twist your rope to buggery abing for ~>50m on a hitch? I'd start the ab with a prussik above the italian hitch, then once it was through the device stick one on below it and remove the top one. Cheers anyway, it's not often you learn a new neat trick on Rocktalk.

Inreply to ice.cool:

I hope you've just mistyped your instructions in the wrong order. Whatever this knot thing is, even if it's a shunt you want your abseil device to be unattached from the rope for as short a length of time as possible. So once you've removed it from above the knot, pull up the rope and attach it straight back below. I think you're just coming at this from a caving/ canyoning backround maybe where the ablines might be tied off at the bottom, but in our climber's big scary sea cliff situation you want to stick the ATC back on ASAP.

In reply to bill briggs:

http://en.petzl.com/petzl/SportConseils?Conseil=43&Activite=26

In reply to Will Hunt:

Practical Example, While exploring sea cliffs in Ireland only access to one cliff was a 450 ft free ab.

So 3 ropes tied together each with cows tail loop at joint.
Ab to joint with safety prussik above ab device,
clip cows tail to joint loop,
hang on safety prussik ,
swop over ab device ,
step down from prussik ,
transfer to ab device ,
transfer safety prussik ,
unclip cows tail.
Continue.

When hanging free with 300 ft of rope below joint ( this is the situation for second , third , etc person ) it is very difficult to pass knot through ab device due to weight of rope.

PS this is standard method in caving.