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Braumeister

Z-rig w/ belay plate autoblock

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The only "autoblock" info. I could find on a search of the forums related to auto-locking mechanical devices such as a Grigri, so perhaps some of you more experienced climbers can lend your comments on the following.

 

While researching and practicing a Z-rig in my back yard, I noticed a suggested variation in "Glacier Travel & Crevasse Rescue" is to install a "ratcheting auto-block" on the system to better facilitate crevasse rescue. I can see how this would be particularly helpful in a two-man rope team.

 

The basic premise is to feed the rope through a Sticht-type belay plate at the initial anchor point with a prussik above it. When hauling, the prussik jams against the plate to allow rope movement, but when tension is let off the haul line, the prussik sets itself to hold the victim and give the hauler a rest.

 

My question is this: is a Sticht-type plate necessary to really make this thing work, or will another device such as an ATC suffice? Has anyone used this system and would you comment on its relevance? Or is this just neat stuff to know but not really necessary?

 

Thanks!

 

B. bigdrink.gif

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Do you mean using a sticht plate with a pulley instead of using a prusik minding pulley? If so, that is all it really is, simply a way of preventing the prusik from jamming into the pulley. Yes, it does make things easier, and yes other things besides a sticht plate can be used.

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The plate is to prevent the prussik from jamming in the pulley. A Bachman knot can be used instead of a prussik and it tends to self-manage much better if you don't happen to have a plate. Heck, you could cut yourself a prussik minding plate out of a 1/8" aluminum disk. It would be lighter than the Sticht plate.

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It sounds like people don't carry the ATC as standard gear anymore. I would imagine that any tube or plate belay device would work for this purpose. Then you aren't carrying a specialized second piece of gear.

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Have any of you actually and really used a prussik in a crevasse rescue? They really suck and they are time consuming. They really are. The way to get around the problem of the prussik and the stichtplate is to use an ascender. It's easier. It works better.

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I've used a prusik in practice. If you use your ATC like Braumeister suggested, it's pretty quick and easy. No extra gear, no extra weight. I suppose a Tibloc would be a good compromise for weight.

 

Plus prusiks can grip icy ropes of any diameter and can be used for other things (v-threads, slings, etc).

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Have any of you actually and really used a prussik in a crevasse rescue? They really suck and they are time consuming. They really are. The way to get around the problem of the prussik and the stichtplate is to use an ascender. It's easier. It works better.

 

or you can just cut the rope and let crevasse bound partner rescue themselves and then become a famous author and movie star cool.gif

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Since you mentioned a 2-man rope team, something else to look at is the Garda knot, which uses 2 carabiners to allow for one-way hoisting. You can pull rope through it one way, but the rope will not slide back , so you don't need a prusik to hold the rope when it's time to reset your Z. The cost is that it adds considerable friction over a decent pulley, although I've practiced with it and the friction didn't seem that bad. No reason to use it if there are plenty of pulleys and prusiks available, but it's worth knowing and trying out sometime in practice, especially if you do travel in 2-man parties. I first ran across it as part of a 2-man system called the Canadian Drop Loop System, described in the Falcon book called "Glaciers! The Art of Travel and the Science of Rescue".

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You can use the rope with a Garda knot instead of a foot prussik, but it is only good for one foot, and if you want to take off your pack and let it dangle from the bight of rope, this wouldn't work.

 

I'd say it is more appropriate as a rock climbing rescue technique where you don't have a pack to deal with, and you don't put prussiks on the rope in advance.

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Tiblocs are perfect for crevasse rescue. They are lightweight, fast to setup, autoblocking, quickly resettable, and work beautifully. It's good to know how to make a prusik Z-rig, but once you use tiblocs, you'll always carry them instead.

 

Check out diagram 3c on the tibloc info sheet and note that you can put a pulley on the "lower" carabiner to reduce friction (I always do this, I don't know why Petzl doesn't show one).

 

Petzl Tibloc info

 

p.s. and "Prusik" is the correct spelling rolleyes.gif You would think CBS of all folks would get that right!

Edited by Alpinfox

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I don't think there is one accepted spelling. I've seen it both ways. And besides on cc.com spelling is all relative. grin.gif

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I bet Dr. Karl Prusik would think otherwise. Though he probably doesn't care that much, as he wasn't engaging in all this geek crap and was actually out in the caves and hills.

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Swaterfall,

I use a tibloc for my foot loop (texas prusik-type setup) which I keep tucked in my jacket or harness and a regular prusik knot for my waist prusik which I keep attached to my harness. Why not a tibloc on the waist prusik you ask? Because tiblocs tend to slip down the rope while hiking on the glacier. This gets annoying and is dangerous because the tibloc can work itself far enough away from you that if you or a partner were to fall, the weight would come onto your waist-prusik-tibloc-setup rather than the rope tied to your harness. You DO NOT want to take a dynamic fall on a tibloc. It can severly damage, if not sheer the rope completely. Having the standard prusik on the waist loop (above the foot prusik) holds everything in place. I carry my second tibloc on a locking oval biner on my harness, ready to slap on an anchor in the event someone falls and I need to yard 'em out of a hole. Oval biners are prefered for tiblocs and pulleys, and I feel more comfortable with lockers on the anchor position.

 

I do recommend knowing how to do the standard prusik setup as well as using slings instead of perlon. It's good to have a big bag of tricks, but the tibloc setup is the best in my opinion.

 

Cheers,

-AF

Edited by Alpinfox

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