Self-locking descender for rappelling

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Re: Self-locking descender for rappelling

Postby cavedoc » Jul 2, 2008 5:08 pm

hunter wrote:
you don't hear about people working the Stop wrong and falling often either.


Well, not to shoot a hole in my own argument but I have actually heard of this happening a few times (it is mentioned in one of the old threads about the stop).


I have seen it. Someone used the carabiner to block the stop function, forgot about it, then sat in his harness at the top of a pit without his hand on the rope. He caught himself after about 10 meters, climbed out and went home :yikes: . Granted it was not a bright thing to do but it is an example of the Stop teaching bad habits. And this was an experienced user.
He reports he did not grab for the device--he went for the free rope that he should have been holding to start with.
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Re: Self-locking descender for rappelling

Postby Stridergdm » Jul 2, 2008 9:13 pm

On comment I want to add going back to the part about grabbing or tightening one's grip when panicking. I don't have URLs handy but basically it's extremely hard to overcome the instinct to grab/tighten.

Just a point of thought.

And glad you found a solution.

And definitely some of the advice about using a rope twice the length, etc. is good stuff. Quite honestly, it's probably the easiest and safest way to get a person off rope.

Another thing I'd gain skills in is how to rig a haul system in an emergency. That gives you another option.
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 2, 2008 10:54 pm

Yeah, I think I read that. There does seem to be quite a bit ambiguity about the real statistics.

It's something that concerns me but I still believe proper practice, mindset and training can break the gut reaction.

I'm still thinking though... just found a killer deal on a Petzl I'D but from what I've read I don't think it's the best bet. The SRTE double stop descender looks great but they're expensive and hard to get in the States.

Searching the forums there is a lot of chatter about this method too (good and bad) but I'm surprised no one mentioned it.
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 3, 2008 2:25 am

Just thought of something else concerning the Shunt... what do you use for the tether? The guys are REI suggested a sling but that doesn't seem suitable. I was thinking I'd use the Petzl Spelegyca cow tail from my Frog system but I don't think it's designed for a shock load either.

It seems to me that you can generate quote a bit of momentum in a short period of time before the Shunt grips. I don't know how much it'll slip first which would be a factor but still.

Does anyone have recommendations with regard to the tether?
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Re: Self-locking descender for rappelling

Postby hank moon » Jul 3, 2008 11:44 am

There is only one bobbin I know that works well on PMI 11 mm pit rope: the SRT Stop descender. The Petzl Stop (and others) can be extremely fast or slow on such rope depending on conditions. The Anthron is particularly difficult to use on stiff rope.

The only other self-braking descender I can think of that might work well is the TROLL Pro Allp Tech.

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Re: Self-locking descender for rappelling

Postby NZcaver » Jul 3, 2008 3:54 pm

OpenTrackRacer wrote:Chatting with the guys at REI, one with a lot of climbing experience said he uses a Petzl Shunt (which is basically a mechanical Prusik) with a figure 8 or ATC. I messed with it and then did some more research and it now I'm really glad I went to REI. This device is perfect. It can be used with our current descending gear, it's simple to operate, keeps the hands where they should be and offers a second point of attachment to the rope. As an added bonus, it address the free hand issue since you can move it down the rope and then descend a bit on the ATC (with your other hand on the down rope of course) and use have a hand free for pushing off, etc.

Sometimes you end up with a solution that's completely different from where you started.

Be cautious here - the 8/ATC and Shunt combination may not provide the ideal solution you think it does. By all means try it out under controlled conditions if you can borrow one, and if you really like it then go with it. Some cavers in the past have used a Gibbs or similar mechanical shunt to do basically the same thing, either installed above the descender or below. This is known as the "spelean shunt." Few seem to use this technique any more as it has a major drawback. Once the device locks with your body weight on it, it can often be difficult to transfer your weight so you can release the shunt again.

With no offense to the employees of REI or to climbers in general, the operative term in your post was that a guy with a lot of climbing experience recommended the Shunt. Although many devices and techniques do overlap between the climbing and caving communities, there are subtle considerations which are not always obvious to climbers. Broad examples include using static vs dynamic ropes of various diameters, muddy/gritty ropes, free hanging ropes, confined spaces, ascent/descent changeovers, rebelays, etc. I personally own a Petzl Shunt, which I've seldom used. It was not purchased for use as a rappel safety for caving.

Tim White wrote:The GriGri does not work well on Pit rope, it's to stiff IMO.

Keep your rope clean and prepare to spend some big $$ for the I'd. This is the most common descending device used by professional rope access technicians. A SOLID piece of equipment, but it would never hold up in a cave environment due to the working mechanisms vs mud.

:exactly:

hank moon wrote:There is only one bobbin I know that works well on PMI 11 mm pit rope: the SRT Stop descender. The Petzl Stop (and others) can be extremely fast or slow on such rope depending on conditions. The Anthron is particularly difficult to use on stiff rope.

The only other self-braking descender I can think of that might work well is the TROLL Pro Allp Tech.

:agree: Although I have to say my Petzl Stop usually seems to work OK on PMI 11mm *for me* - your experience may differ. I also have an SRTE Stop which works nicely, but my one is all stainless steel so it's VERY heavy and not my first choice for carrying. The Allp descenders are nice, but like the SRTE they are quite expensive if you can even find them in the US.

If you haven't totally ruled out the Petzl Stop, I found a few old topics you might like to read.

Bobbins and Stops

Anyone use a Petzl Stop Descender?

Spinoff post about the stop
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 3, 2008 4:35 pm

I agree about REI and climbers versus cavers. I don't know for sure he was a climber and not a caver but statistics say he probably was. I haven't tried the Shunt in an actual descent but I got a basic feel for it at the store. If rigged correctly it seemed pretty straightforward to use.

Unloading the Shunt once it's locked is something I'd already been thinking about. With an ATC also in use I think it would be pretty easy to inch up the rope just enough to release it. If not, we always have a handled ascender handy. I think the real idea is not to let it lock up unless things are going very wrong.

What do you think about the shock loading issue with the Shunt? That was something that started to concern me more than anything else once I thought more about it.

Do you think the I'D would work with 11mm PMI or would it be as bad as the GriGri? I have access to a great deal on an I'D if I want. It's not really designed for sport use however. We don't usually encounter mud in the mines but it's very dusty.

I have not ruled out anything. I e-mailed SRT about getting their products in the States but I haven't heard back. I'm guessing however that my companions will not want to spend that kind of money. I moved away from the Stop after reading all the comments about how poorly it works on the Pit Rope. It seemed pretty nice and easy to use when I messed around with it at the store. I still feel comfortable with the single safety aspect but it's poor descending or not stopping when released that has me concerned.

I really appreciate the feedback and any more comments you have to offer!
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Re: Self-locking descender for rappelling

Postby hank moon » Jul 3, 2008 5:14 pm

NZcaver wrote::agree: Although I have to say my Petzl Stop usually seems to work OK on PMI 11mm *for me* - your experience may differ.


Personal factors (such as weight) can affect performance - just didn't work so well for me on the old and stiff stuff. Works purty good when the rope new and clean, though...

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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 3, 2008 5:30 pm

I just read all the Stop threads again and I have to say I'm leaning back that way. My biggest hangup is thinking about how it will work on 100-300' of dusty Pit Rope. I have to say we had no problems with an ATC on our Pit Rope. We don't usually do any single long rappels. The next mine we're going to will have a few 150 foot or so rappels down ladderways. You need to go slow in these to maneuver around platforms placed every fifty feet or so. As long as the rope feeds, I think the Stop would be fine and work about the same as an ATC or figure 8 with the added safety of the "Parking brake".

Still researching (and open to any and all comments)!
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Re: Self-locking descender for rappelling

Postby NZcaver » Jul 3, 2008 5:39 pm

OpenTrackRacer wrote:Unloading the Shunt once it's locked is something I'd already been thinking about. With an ATC also in use I think it would be pretty easy to inch up the rope just enough to release it. If not, we always have a handled ascender handy. I think the real idea is not to let it lock up unless things are going very wrong.

It's not quite as simple and convenient as it sounds. I suggest trying it out for yourself.

What do you think about the shock loading issue with the Shunt? That was something that started to concern me more than anything else once I thought more about it.

The Shunt is designed to be reasonably gentle on the rope in cases of shock loading - certainly no less gentle than a Stop.

Do you think the I'D would work with 11mm PMI or would it be as bad as the GriGri? I have access to a great deal on an I'D if I want. It's not really designed for sport use however. We don't usually encounter mud in the mines but it's very dusty.

My I'D works fine on PMI 11mm (above ground). Prolonged/severe exposure to dust and grit may cause problems for the I'D mechanism as well. The I'D is a nice toy, but not really designed primarily for what you want to do. It's designed for the industrial rope access market.

I moved away from the Stop after reading all the comments about how poorly it works on the Pit Rope. It seemed pretty nice and easy to use when I messed around with it at the store. I still feel comfortable with the single safety aspect but it's poor descending or not stopping when released that has me concerned.

Again, find someone who has one and try it out if you can. Also, there are other rope choices out there besides 11mm Pit Rope. Regarding the "not stopping" - yes, this descender is sometimes known as the Petzl Slow. If you stop and the descender does creep a little, simply push outward on the handle and you should stop completely. Alternatively, lock off the descender like you should do anyway before taking your hand off the rope. I don't recommend trying to descend fast and suddenly release the handle, as this could damage the rope. But if you release the handle while descending at a sensible pace (as if you became incapacitated) a short distance of slow creep should not be a huge cause for alarm. Your companions will have bigger things to worry about.
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Re: Self-locking descender for rappelling

Postby hank moon » Jul 3, 2008 6:25 pm

OpenTrackRacer wrote:I guess everything is a trade off. I'm going to get some cord and mess with the French Wrap and autoblock as well (without modifying my harness). It's virtually free so why not experiment.


Hi MIke

Good luck with your experimentation - I think you will like the ATC/friction hitch combo (perhaps better after the fiddling stage is over). You may have seen recommendations to attach the friction hitch to the leg loops of the harness. This is not the best way. It is better to extend the ATC using a sling and attach the friction hitch to the belay loop and/or ventral attachment point of your harness. Doing this (correctly) can eliminate the common problem of defeating the locking action of the hitch by butting it against the ATC. Also, harness leg loops are not designed as suspension points!

The leg loop attachment makes more sense with a rack due to its extreme length but there is no good reason to do this with an ATC or figure 8.

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Re: Self-locking descender for rappelling

Postby hank moon » Jul 3, 2008 6:38 pm

cavedoc wrote:it is an example of the Stop teaching bad habits.


Do cars teach speeding? Guns teach killing? How about pizzas? What do they teach? :tonguecheek:

No rappel device teaches anything. Howver, some devices enable actions that could have deadly consequences with another, simpler device. It is up to the USER to avoid getting complacent with equipment. This requires constant awareness and good discipline...qualities anyone messing around on rope should cultivate!

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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 3, 2008 7:08 pm

Yeah, I expect your right about the shunt being harder to deal with than one might think.

I'm really leaning back towards the Stop now. It's good from a heat dissipation standpoint compared to an ATC and we really don't lose anything compared to an ATC or figure 8 if used correctly (and we gain the auto brake which is the goal).

I'm starting to feel more comfortable that it will work with the Pit Rope.

I'm still thinking about trying an I'D. I can get one for $100 which makes it very tempting.

Hmmmmm...
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Re: Self-locking descender for rappelling

Postby hank moon » Jul 3, 2008 7:11 pm

OpenTrackRacer wrote:Yeah, I expect your right about the shunt being harder to deal with than one might think.


The Shunt is actually very easy to work when used correctly (below the device). It's just kinda heavy to carry around compared to a bit of cord for a friction hitch. The stopping action of a Shunt is more reliable than that of a STOP, too (less dependent on rope condition/diameter).

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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 3, 2008 7:23 pm

I was actually planning on using it above my ATC but within easy reach and just short of engaging it by putting tension on the tether. Having it below would work too but I like the have the ATC close in and my hand further up on the rope (or Shunt). I guess if I used the Stop my hand would have to be low however unless I used a sling.

I think having the Shunt below the ATC would also make it harder to unload the Shunt if it's activated since you'd have less leverage with the ATC further away.
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