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Tech Tip: Question Petzl Shunt (Back-up rope clamp)

Discussion in 'Tech Tips and Gear' started by Jimmy Olsson, Feb 12, 2014.

  1. Jimmy Olsson

    Jimmy Olsson

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    Have anyone tried this device from Petzl?
    http://www.petzl.com/en/outdoor/multi-purpose-ascenders/shunt

    It's not that new, It came some year ago but I havn't seen any canyoneers been using it and can't find anything about it in here. So, what do you think? Have you tried it? Would it be a good tool during rappells instead of Prusik-knots?



    It might be a good and safe tool for rappelling down as the "last man" on double rope?
  2. Bootboy

    Bootboy Atwood Gear

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    Don't waste your money.

    The most effective back up for LMAR is a bottom belay.

    Dont overthink this sport. People want to make this way more complicated than is necessary.
    Kuenn likes this.
  3. Brian in SLC

    Brian in SLC Brian in SLC

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    I have one and have used it for rappelling in a canyon, especially when you want to "eject" off the end of a rope over a really deep pool. Just fun to pull and plunge.

    I recall there's a couple of things to remember about the device that makes them subtly unsafe. One is unequal rope diameters. There's another (Hank? Help!).

    No one should probably be using a Prusik especially above their device as a back up for a rappel. I think the standard now is a autoblock below the device at best, making sure to extend your rappel device well away from the back up.

    My shunt is collecting dust filed away somewhere in devices that are interesting to play with, but, never get used in the field.
    ratagonia likes this.
  4. hank moon

    hank moon kinetically bulbous

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    Shunt: it works great for its intended purpose (rappel backup for climbers) but for canyoneering there are many other options that are lighter, cheaper and more versatile. Like Brian's, mine is somewhere collecting dust, possibly mouse poo.
  5. Chris Erwin

    Chris Erwin

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    Pros: Works on both single and double ropes, great for resetting friction points with a large group, makes for smooth ascending on both single and double ropes, no teeth, releases easily

    Cons: Heavy, only effective on large diameter ropes when using SRT, have seen newbies practice ascending with it and want to grab the housing rather than the carabiner (scary), self belays are rare in canyoneering

    In short, not very useful for our purposes.
    hank moon likes this.
  6. skeeter

    skeeter A holed piston is just an ashtray

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    I've seen it more in cave applications
  7. Kuenn

    Kuenn

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    More or less I agree with what has been said, but I have big-time bias here. Not a believer in rappel backups or auto-blocks; I've just seen way too many people fidget and fuss with them, and hold up the show. Yes, it's a personal choice (belay, baby, belay). If you're the first one down - know your stuff... or get outta the line!
  8. ratagonia

    ratagonia

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    We use rappel-self-belay at Zion Adventure Company for canyoneering clients. It works for us, but we have control over all aspects - rope or ropes size, harness setup and location of rappel device, setup of the autobloc, TRAINING of the autobloc, supervision of the autobloc attachment. What I see in the field outside ZAC is people set up some kinda thing that they have confidence in, and that absolutely will not work. And they INSIST that it absolutely will work.

    Even in the ZAC environment, it is not 100% effective (and we tell the clients this). We also add a bottom belay most of the time. In my 200 guiding days, I had one failure (that I know of) where I ok'd the client to go down with the autobloc not installed correctly. Thankfully, the client did not need to use it.

    Autoblocs are tricky to set up so they work effectively. Canyoneers in general do not use them. Even though I know how to use them and appreciate their capability, the only time I have used one outside of guiding is for picture taking.

    Better, I think, to put the time and energy into giving bottom-belays more often. Bottom belays have saved my butt on at least 4 occasions; and I have saved others from getting hurt a similar number of times - YET, we do not tend to give them (to experienced canyoneers) as a matter of course - and I think we should.

    Tom
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  9. Kuenn

    Kuenn

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    Those are valid points, Tom. Since I've never been involved in pay-to-play services, I often neglect to consider the paying client side. Although, again, most if not all can be better served with a belay. On the other hand, I guess there is the benefit of proper auto-blocking instruction... Meh, it’s like teaching someone a vice (sorry, I’m just not good at being duplicitous).
    :twothumbs: Bingo!
    Hear! Hear! Somehow, some way, we've adopted the misguided notion that requesting or offering a belay is a sign of weakness, apprentice or an insult - a trend that needs correcting. Yes, guilty as charged, but more recently, if offered I purposely force myself not to decline.
  10. ratagonia

    ratagonia

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    There are a lot of ways to do things, and some are appropriate for situation A, not so much for situation B.


    Hmmm. Are you contradicting your previous, wise statement?

    An Autobloc is a powerful tool. Not an easy tool to set up and use, and not very useful if it is not set up and used correctly. Most of us substitute other tools to perform this function. But don't dismiss the Autobloc just because YOU don't find it useful.

    It has some subtleties you might be surprised by.

    Tom
  11. Kuenn

    Kuenn

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    Me? Contradict myself? No never! ...well maybe occasionally. :eek:

    Maybe that's my problem (or at least one of them). Could it be that I've never been properly schooled in the value and use of them? Tell you what, next time I'm out there I'll be your student...who knows, could be a pizza in it for YOU. :)

    So as not to appear disingenuous and putting all jokes aside, I realize there is value in it, as well as personal preference.
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  12. gajslk

    gajslk

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    I don't know. You'll probably get a chance to practice switching to ascend mode and back to rappel ... that practice might be useful someday. ;)

    Gordon
  13. Andrew Humphreys

    Andrew Humphreys

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    I hope people picked up on this piece of advice! Such a gem!

    Andrew Humphreys
    Operations Manager
    Canyoning.co.nz
  14. Kuenn

    Kuenn

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    I typically use a prusik for this but could see where the shunt may be a tad more convenient, especially on double rope. Care to elaborate on advantages / setup / experience, Chris or Andrew?
  15. Bootboy

    Bootboy Atwood Gear

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    I wish that for rappel backups the prussik would fall out of favor. There are knots that are better suited to the task.

    Once a prussik locks up, that's it. It can't be released in the slightest once weighted. If I ever do use a backup, I carry 2 eye-eye cords of 8mm tech cord. I use a VT hitch or a MT hitch. They are way easier to tend, can move under moderate load, faster to tie, locks better when it needs to, and it works on double rope.

    What's not to love? The prussik is bad-news-bears for a personal backup knot and has no place in canyons IMHO. Except when used in a tandem belay in a rescue scenario.
  16. Deerchaser

    Deerchaser JB

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    I wasn't ever taught to use a Prussik. I use a VT also when needed.

    Do you tie the VT the same on a double rope? Seems to grab too much on a double rope setup.
  17. Kuenn

    Kuenn

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    I concur.
    I guess it depends on the interpretation of "friction points"... sounds like we're talking about two different things here (likely my misunderstanding).
    Since I don't do rappel backups the use of a prusik wouldn't even be a consideration for that app.
  18. ratagonia

    ratagonia

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    The term "Prusik" is used as a general term for any rope-grab knot. So sometimes when people say prusik, they mean a different knot.

    Tom
  19. Andrew Humphreys

    Andrew Humphreys

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    The technique is called "gestion des frottements" in french, literally meaning "abrasion management." It is used to move the point of abrasion on the rope from a sharp edge. The idea is simple, move the rope position up or down a little between each person's rappel so that all the rub isn't focused in one place on the rope.

    The shunt is particularly useful when you use a toss and go technique. Attach the shunt to both strands a short way down from the anchor. Then clip the shunt back to the anchor with a quickdraw. At this point, the shunt should be holding the rappel side of the rope, and there should be a little slack between the shunt and the anchor. After each person rappels, change the amount of slack in between the shunt and anchor, which in turn changes the point of abrasion below. The last person simply removes the shunt and quickdraw, and rappels down.

    This technique can be replicated with a prussik around both strands or clove hitches on each strand. The shunt is a tiny bit easier to adjust the strands quickly, but it runs the risk of releasing if pressed against the rock. Regardless of what you use, it is important to always use the quickdraw, as it makes a cut and lower extremely simple, but that's another technique...

    Andrew Humphreys
    Operations Manager
    Canyoning.co.nz
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  20. Kuenn

    Kuenn

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    Very nice explanation and information.
    That was my interpretation of "resetting friction points".
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