Self-locking descender for rappelling

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Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 1, 2008 1:12 am

Hi! A group of friends and I are into exploring old mines. We've been going down on ropes using ATC and figure eights for a while. We've started to be concerned about the possibility of being hit by falling debris or missing a foothold and getting stunned while descending.

I've started doing research into self-locking descender devices like the Petzl Stop or GriGri but I wanted to get feedback from experienced users.

The idea would be to stop an uncontrolled descent if one lost the free end of the rope or was even knocked out.

We use PMI 11mm pit rope which is fairly stiff. I know that can be an issue with some devices. The rope also tends to get dirty rather fast with fine dry dust.

I really appreciate any and all feedback.

Thanks!
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Re: Self-locking descender for rappelling

Postby Stridergdm » Jul 1, 2008 6:02 am

I have not used such devices but I would also suggest reviewing this board for the discussion on the "French Wrap".
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Re: Self-locking descender for rappelling

Postby Carl Amundson » Jul 1, 2008 10:29 am

Below is a link to a BATS newsletter that details the use of the French Wrap when rappelling with a rack:
http://bats.varegion.org/downloads/newsletter/august2003.pdf
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 1, 2008 12:06 pm

Thanks for the links... that was some interesting reading.

I think at this point we're inclined to stick with an off-the-shelf descender. We don't use racks and really are fine with ATC or figure 8 descenders... it's the "fear" of an uncontrolled descent while disabled that's the driving factor.

I have done a bunch of research and we do understand the issues with the possibility of releasing the brake rather than letting go and applying it. I believe we can train properly to account for that (and our stunned or knocked out failure mode would result in being hands off anyway).

What I'm really curious about is what people are using and experiences with these devices and the stiff PMI 11mm Pit Rope.

Thanks again!
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Re: Self-locking descender for rappelling

Postby Scott McCrea » Jul 1, 2008 12:19 pm

A fig 8 descender, 11mm PMI Pit Rope and a French Wrap is a great combination and should work well for what you are describing.

But... do you have a plan for rescuing/helping a rappeller that has been stunned or knocked out? Now that you prevented a crater with the self-locking device, how are you going to prevent the bad things that happen when unconscious on rope? An unconscious person hanging in a harness is a serious emergency.
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Re: Self-locking descender for rappelling

Postby Chads93GT » Jul 1, 2008 1:02 pm

I use a prussic backup while rappelling, however you really need a prussic for a legloop as well.

IT's wise to back up your rappel in case anything goes wrong, and so you can easily stop to untangle the rappel ropes. The quickest way is to rig an autoblock on the rappel rope just below the rappel device and clip it to your leg loop. To rappel, hold the autoblock with your brake hand and keep it loose. If you let go of the autoblock, intentionally or not, the autoblock locks and haults your rappel. To resume rappelling, simply loosen the autoblock. The autoblock also adds friction to your rappel, so you don't burn your hands on steep rappels.

6mm cord works well for tying the autoblock. Spectra works, but nylon creates better friction and has a higher melting temp.

ITs done by clipping a sling to your leg loop on the brake hand side. Wrap the sling four or more times around the rappel rope until most of the sling is used up. Keep the knot or stitching of the sling outside the autoblock and keep the autoblock free of twists. Clip the final loop of the sling back to your leg loop. Practice with the autoblock to determine the optimal number of wraps given your rappel rope and sling combo. If you have too many wraps, you'll get so much frictions that you can barely move. Too few, and the autoblock won't engage when you need it.
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 1, 2008 1:28 pm

Okay, looking into the French Wrap and autoblocks some more. It seems like there is an aversion to something like the Stop and I'm curious about that. Is there something wrong with it or is everyone trying to avoid spending the $90?

I have been making calls and have gathered some information that way too. Out of three, I got one opinion that the Stop would be very slow with the Pit Rope. Two others felt it would be fine and work as advertised. I have to say again, I'm still inclined to go with an off-the-shelf product designed for this application rather than modify my harness and make up something from scratch.

I should mention that we don't do any really long rappels. The longest vertical rappel we've done so far was fifty feet or so. We've encountered some shafts that were 200 feet or so but haven't gone down yet. That's about the longest I'd expect to encounter. We do go down longer inclined shafts but I'm not worried about those.

Rescue is a very good point Scott. What we do would depend on the situation of course. If we still had people above we would descend and asses the injured persons condition. From there we could lower them down to the bottom of the shaft or leave them in place while we get help. We could also ascend from below and do the same thing if the rest of us were already down. It would really boil down to the extent of the injuries. If someone was hurt bad we would not attempt to extract them ourselves but would seek help.

Compared to other guys we encounter exploring mines, we're being super cautious and trying to anticipate the worst that can happen. We're not opposed to spend some money to get the right gear to be as safe as possible. It also allows us to access places in the mine that not many people have visited due to what's required to get there.
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Re: Self-locking descender for rappelling

Postby Tim White » Jul 1, 2008 2:15 pm

The Stop was designed for the softer more supple European rope. When used with the stiffer PMI Pit rope the Stop can become a “Slow”. It will often creep down the rope without coming to a true STOP. Still much better than the fast ride on a Figure 8 or ATC if you become incapacitated.

IMHO the Stop works very well with 10mm PMI, etc.
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Re: Self-locking descender for rappelling

Postby Stridergdm » Jul 1, 2008 11:14 pm

OpenTrackRacer wrote:<snipped>

I should mention that we don't do any really long rappels. The longest vertical rappel we've done so far was fifty feet or so. We've encountered some shafts that were 200 feet or so but haven't gone down yet. That's about the longest I'd expect to encounter. We do go down longer inclined shafts but I'm not worried about those.

Rescue is a very good point Scott. What we do would depend on the situation of course. If we still had people above we would descend and asses the injured persons condition. From there we could lower them down to the bottom of the shaft or leave them in place while we get help. We could also ascend from below and do the same thing if the rest of us were already down. It would really boil down to the extent of the injuries. If someone was hurt bad we would not attempt to extract them ourselves but would seek help.

Compared to other guys we encounter exploring mines, we're being super cautious and trying to anticipate the worst that can happen. We're not opposed to spend some money to get the right gear to be as safe as possible. It also allows us to access places in the mine that not many people have visited due to what's required to get there.


If I can add a few comments here:
For 50 feet or 20 feet, the dangers are fairly similar. If you're off the floor and can't stand up, to a point it doesn't matter if you're 10' off the floor or 100'.

If you have someone above the person, how do you plan on descending? Separate rope I hope. If ascending, again, a separate rope or on the existing one? These can lead to very different approaches in getting someone untangled. And keep in mind, it may not be an injury, it could be a piece of clothing, hair, etc. that has jammed up the descender.

As for seeking help, if you're not familiar with with Harness Hang Syndrome. In the time it takes to get help, your stuck person may go from a slightly injured person to one who is severely medically compromised. If nothing else, get someone to teach you how to do a 2 rope pick-off and make sure you've got a 2nd rope ready to go.

Also, I don't see what you're doing for ascending.

Good equipment is good, but training can overcome some equipment limitations, but the best of equipment can't really overcome decent training.
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 1, 2008 11:35 pm

I agree about the height... I mentioned it only because several people told me the Stop isn't good for long rappels on stiff rope. Twenty feet is more than enough to kill you.

Rescue from above would be on a separate rope. If it had to be from below (because the injured person was the last one down) it would have to be the same rope. Leaving someone hanging free would be very bad. If they were in good condition but upright it leaves more options. We always have ascenders with us (frog system) as well as a backup descender (ATC or figure 8).
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Re: Self-locking descender for rappelling

Postby fuzzy-hair-man » Jul 1, 2008 11:58 pm

OpenTrackRacer wrote:If they were in good condition but upright it leaves more options.


Not quite, if they are immobile they are in danger of harness hang syndrome (HHS), in trials conducted by a french group (I think) as little as 6 minutes hanging immobile was required for an otherwise healthy person to loose consiousness in some of these cases the person complained of not feeling well and before they could be lowered they had lost consiousness. The trials weren't completed despite having medical staff nearby such was their concern for the subjects.

Hanging back so that you are horizontal is one of the ways to combat HHS but really they need to get off rope as soon as possible.

Here's a previous topic about HHS:
http://forums.caves.org/viewtopic.php?f=7&t=2816&st=0&sk=t&sd=a
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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 2, 2008 12:04 am

I wanted to make another post in an attempt to gain some feedback on bobbin style descenders (which I'm still interested in). I've found info on the Petzl Stop, Kong Indy and the Anthron Double Stop.

I'd really like to hear from people who use these. I'm very interested in feedback on possible troubles with these when using PMI's 11mm Pit Rope (which is quite stiff).

I like the abrasion resistance of the Pit Rope but if descending is going to be problematic then I might look at 11mm EZ-Bend.

Thanks again!

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Re: Self-locking descender for rappelling

Postby OpenTrackRacer » Jul 2, 2008 12:12 am

That's quite an interesting read. I didn't realize that my handy harness could be so deadly.

Does this apply if you're able to move your legs or is someone in danger from just sitting in a harness for too long?


fuzzy-hair-man wrote:
OpenTrackRacer wrote:If they were in good condition but upright it leaves more options.


Not quite, if they are immobile they are in danger of harness hang syndrome (HHS), in trials conducted by a french group (I think) as little as 6 minutes hanging immobile was required for an otherwise healthy person to loose consiousness in some of these cases the person complained of not feeling well and before they could be lowered they had lost consiousness. The trials weren't completed despite having medical staff nearby such was their concern for the subjects.

Hanging back so that you are horizontal is one of the ways to combat HHS but really they need to get off rope as soon as possible.

Here's a previous topic about HHS:
http://forums.caves.org/viewtopic.php?f=7&t=2816&st=0&sk=t&sd=a
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Re: Self-locking descender for rappelling

Postby fuzzy-hair-man » Jul 2, 2008 12:54 am

If you are able to move your legs and get the muscles pumping blood back out of your legs this can delay the onset of symptoms but if I remember correctly it can also cause the condition to become worse if they are subsequently unable to keep this up. It's not enough to just move your legs you need to relieve the pressure at the back of your thighs. I'd consider anyone stuck on rope in danger of HHS, usually by the time they become stuck they have struggled for a while and are tired and exhausted which raises their risk further.

It is a pretty frightening thing!

Regarding your other question, bobbin style descenders are like Stops a European style descender, I use one and find they work well on 10 and 11mm rope, both stiff and new, longer drops (greater than say 60m, which is ~180' right?) have had me have to feed my bobbin but it's not really been a problem. I prefer the bobbin because I thought the Stop taught me and others bad habits (but this isn't likely to be true for everyone), I also find the bobbin simpler and allows me to negotiate difficult edges etc more easily as I don't have to squeeze a handle (yes you can disable the handle).

Double brake stops have been reported to have a relatively small sweet spot between the two brakes being activated which can make them tricky to use and fussy about rope diameter and rope condition. They do stop if the user grabs the handle in panic (an instinct that I could believe would be very hard to overcome) whether it's worth it is up to you to decide.

Descender choices seem to be a pretty personal decision and everyone has their own preferences, depending on what makes them nervous or on the style of rigging where they go caving or the depths of pitches they want to go down.

<EDIT> I'm not using PMI ropes (of any kind as they are uncommon in Aust.) so I can't say how a bobbin or stop would work on those ropes but I suspect they'd be OK.
Last edited by fuzzy-hair-man on Jul 2, 2008 1:12 am, edited 2 times in total.
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Re: Self-locking descender for rappelling

Postby cavedoc » Jul 2, 2008 1:07 am

fuzzy-hair-man wrote: I prefer the bobbin because I thought the Stop taught me and others bad habits


Thank you! :thanks: :exactly: :agree:
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