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looseanchor
Mar 28, 2012, 12:17 AM
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Bottom line: Is there a device that rides above the descent device that can safety stop a rappeller during an uncontrolled descent? What are your experiences with these safety devices? This involves SRT rappel. I already use a Figure 8, so am looking for something separate from the descender itself.
[Yes, learning proper rappel technique is critical, but it’s hard to guard against a falling rope protector cracking your Petzl or getting sick from eating a bad bit of roasted Guinea pig.]
The Prusik and the Auto-Block: A lot of people criticize the Prusik and Auto-Block because it takes fiddling to keep the hitch open on rappel. They also state that the natural inclination on a fall is to grab the rope (and the Prusik itself), which just opens the hitch and prevents it from engaging. Lastly, if you’re going too fast, the Prusik will just cause nylon-on-nylon glazing. They claim the Prusik and Auto-Block install a false sense of security.
Cam type devices: Cam devices require negative action – meaning the user must let go of the device to stop. There’s been a lot of criticism by very experienced folks because no one wants to let go of the rope with your guide hand at the same time you are trying to grip with your brake hand. Some people say that cam type devices also may abrade the rope and when engaged in extreme cases may sever the rope.
Again, what safety devices are out there that are separate from the descender itself (because I use a Figure 8)? What are your experiences with these devices, the Prusik or Auto-Block or any other type of hitch/device?
Thanks.
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acorneau
Mar 28, 2012, 12:58 AM
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looseanchor wrote: Bottom line: Is there a device that rides above the descent device that can safety stop a rappeller during an uncontrolled descent? What are your experiences with these safety devices? This involves SRT rappel. I already use a Figure 8, so am looking for something separate from the descender itself. [Yes, learning proper rappel technique is critical, but it’s hard to guard against a falling rope protector cracking your Petzl or getting sick from eating a bad bit of roasted Guinea pig.] The Prusik and the Auto-Block: A lot of people criticize the Prusik and Auto-Block because it takes fiddling to keep the hitch open on rappel. They also state that the natural inclination on a fall is to grab the rope (and the Prusik itself), which just opens the hitch and prevents it from engaging. Lastly, if you’re going too fast, the Prusik will just cause nylon-on-nylon glazing. They claim the Prusik and Auto-Block install a false sense of security. Cam type devices: Cam devices require negative action – meaning the user must let go of the device to stop. There’s been a lot of criticism by very experienced folks because no one wants to let go of the rope with your guide hand at the same time you are trying to grip with your brake hand. Some people say that cam type devices also may abrade the rope and when engaged in extreme cases may sever the rope. Again, what safety devices are out there that are separate from the descender itself (because I use a Figure 8)? What are your experiences with these devices, the Prusik or Auto-Block or any other type of hitch/device? Thanks.
You could always look at the Petzl ASAP on a leash above the rappel device.
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ArizonaBen
Mar 28, 2012, 1:05 AM
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Looseanchor, I was about to start a new thread with my own rappel backup question, but saw your thread and decided not to clutter the board...so I hope you don't mind if I contribute to your topic with a related question for the experienced members.
Q. When rappeling with one rope, but with both rope strands through your rappel device (ATC in my case), is it still possible to use a Prusik for a backup? If yes, must the prusik knot only be around one of the two strands or both?
I've read through most of the responses in both of these topics:
http://www.rockclimbing.com/...d;page=unread#unread
http://www.rockclimbing.com/...d;page=unread#unread
and I don't believe I found an answer to my question in them.
All instructional sources I've come across on the web for using a prusik as a backup (below the device) show the climber rappeling on a single strand of rope. (I expect that this is for good reason...)
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healyje
Mar 28, 2012, 1:14 AM
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Why are you rappelling on a single rope?
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sherpa79
Mar 28, 2012, 1:31 AM
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ArizonaBen wrote: Q. When rappeling with one rope, but with both rope strands through your rappel device (ATC in my case), is it still possible to use a Prusik for a backup? If yes, must the prusik knot only be around one of the two strands or both?
You can still do it that way, and it won't matter whether the backup is around one or both strands in most situations. If I were using a releasable hitch on the anchor instead of a biner block or something, I would use the back up around just the load strand. But in that scenario I wouldn't have both strands threaded in the ATC anyway, so it wouldn't matter. And if you have to ask what I'm talking about you should be attempting it. I assume you are approaching this more from a canyoneering point of view than a climbing one? Maybe ask the question to an audience that uses single ropes in that way more often than climbers do. Or, you know, find someone to show you this stuff instead of asking on the internet.
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dagibbs
Mar 28, 2012, 1:47 AM
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ArizonaBen wrote: Looseanchor, I was about to start a new thread with my own rappel backup question, but saw your thread and decided not to clutter the board...so I hope you don't mind if I contribute to your topic with a related question for the experienced members. Q. When rappeling with one rope, but with both rope strands through your rappel device (ATC in my case), is it still possible to use a Prusik for a backup? If yes, must the prusik knot only be around one of the two strands or both? I've read through most of the responses in both of these topics: http://www.rockclimbing.com/...d;page=unread#unread http://www.rockclimbing.com/...d;page=unread#unread and I don't believe I found an answer to my question in them. All instructional sources I've come across on the web for using a prusik as a backup (below the device) show the climber rappeling on a single strand of rope. (I expect that this is for good reason...)
I frequently rappel on both sides of a rope (two strands, but one rope), and I often use an auto-block know wrapped around both strands while doing so. A Prusik could be used similarly. (I just find an auto-block quicker and easier to tie -- it doesn't require as much dressing as a Prusik.)
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looseanchor
Mar 28, 2012, 2:17 AM
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Hi. This is commonly done in emergency rappels, because a second rope is not available or would be dangerous because two ropes may get tangled. It's also common in caving.
healyje wrote: Why are you rappelling on a single rope?
(This post was edited by looseanchor on Mar 28, 2012, 2:20 AM)
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ArizonaBen
Mar 28, 2012, 2:20 AM
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Thank you, dagibbs. You phrased that better than I did; rappeling down both sides of a single rope (after cleaning a sport top rope anchor, for example), but using a prusik as backup.
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looseanchor
Mar 28, 2012, 2:38 AM
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More info:
http://www.forums.caves.org/viewtopic.php?f=5&t=9686
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ablanchard17
Mar 29, 2012, 12:38 AM
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In reality when your using a prussik properly as a backup it will work just fine. and will stop you before you get going fast enough to melt the thing.
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healyje
Mar 29, 2012, 5:04 AM
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looseanchor wrote: healyje wrote: Why are you rappelling on a single rope? Hi. This is commonly done in emergency rappels, because a second rope is not available or would be dangerous because two ropes may get tangled. It's also common in caving.
I understand the contexts in climbing under which one could end up rapping a single rope - I was asking why you would be rappelling a single rope if that's what's going on here.
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looseanchor
Mar 29, 2012, 2:14 PM
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healyje wrote: looseanchor wrote: healyje wrote: Why are you rappelling on a single rope? Hi. This is commonly done in emergency rappels, because a second rope is not available or would be dangerous because two ropes may get tangled. It's also common in caving. I understand the contexts in climbing under which one could end up rapping a single rope - I was asking why you would be rappelling a single rope if that's what's going on here.
Oh. :) Exiting a building during an emergency. The building can be a 4 story wood structure or a 10 story high rise.
I'm in San Francisco and do light search and rescue. I want to make sure I always have an egress.
(This post was edited by looseanchor on Mar 29, 2012, 2:17 PM)
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looseanchor
Mar 30, 2012, 1:26 AM
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Thanks. I was beginning to think that the Petzl Stop might be a possible solution.
I'm kinda bummed, because over the past several days I've been sketching a device that stops upon squeeze or release (thus eliminating the problem with "negative action") . . .
I'll have to give the Anthron a try, although I don't relish losing control over the rate of descent that the Figure 8 gives me.
(This post was edited by looseanchor on Mar 30, 2012, 3:21 AM)
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squierbypetzl
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Apr 9, 2012, 4:25 AM
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ArizonaBen wrote: Q. When rappeling with one rope, but with both rope strands through your rappel device (ATC in my case), is it still possible to use a Prusik for a backup? If yes, must the prusik knot only be around one of the two strands or both?
Ok, if you're rappelling down a single rope that's bent in half at the anchors (doubled) then you absolutely have to wrap your prussik around both strands of the rope going through your ATC. An atc is not an autolocking device and your prussik will only lock down on one strand of the rope rope while pulling the rest through the atc.
I'm a big fan of kleimheists for rappelling backups since they're unidirectional while prussiks are bidirectional (pulled up hard, they lock; pulled down hard, they lock). I feel it makes them easier to get loose after I put my weight back on my belay device. If you want a back up below your device, you're better off sticking with a prussik.
In reply to: All instructional sources I've come across on the web for using a prusik as a backup (below the device) show the climber rappeling on a single strand of rope. (I expect that this is for good reason...)
If your resources are mostly canyoneering vids, then that's the reason. Otherwise, I can't imagine why they would do this, since beginners won't mostly be rapping down single strands.
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meanandugly
Apr 9, 2012, 10:20 AM
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Then what you are looking for is a bail-out kit. There are many on the market. If you are looking at just doing the occational SRT use the prussik attached to the leg-loop below the 8 on the break rope...if you glaze the prussik cord replace it. Cheap, easy, effective.
(This post was edited by meanandugly on Apr 26, 2012, 1:45 PM)
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wmgr1950
Apr 26, 2012, 7:01 AM
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 used an autoblock below my ATC, hooked into my leg loop for first time with a guide at Joshua Tree a couple of weeks ago. I am very happy with it's ease of use and especially the simplicity. The Prussik has it's advantages, too and I always place it above my device because I like the feel of having one hand on the rope(s) above the device.
My bottom line fallback is always the KISS theory and whatever forces me to slow down and be more methodical. Having a compact, simple backup that will work simply by letting go if I' knocked silly, and which is in a position that does not easily allow me to hotdog it on a rap, fits all the criteria.
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