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bthornburn
Jul 28, 2004, 6:52 AM
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I occasionally use a prussik knot or an autoblock knot to backup my rappel. The question I ask is: how safe is the prussik cord/autoblobk sling after a rappel; doesn't the friction weaken the cord/sling? We use rap-rings to protect slings from rope friction when we pull the rope, why is it any safer with prussik cords?
Looking forward to your opinions!
Brian
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ricardol
Jul 28, 2004, 7:11 AM
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uhhh .. like yeah! -- examine the cord dude -- if it looks worn .. or damaged ..replace it
its not going to last forever.
-- ricardo
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iclimblilrocks
Jul 28, 2004, 7:18 AM
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Ok I dont know much but I do know that if you rap on a sling and a prusik knot, It will burn right through.
A friend of mine only rappels, and he has a single line tied at the anchor with a figure 8 on a bite with a backup knot, and has a person on belay which mainly sits down on the bottom and holds the rope and if the person on rappel loose's control of the rope and starts falling the person on belay will pull the rope out and tight and stops it some how... I think that, that might be the safest way. but im just a newb so you should listen more to the better more knowledgeable climbers
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iclimblilrocks
Jul 28, 2004, 7:18 AM
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Ok I dont know much but I do know that if you rap on a sling and a prusik knot, It will burn right through.
A friend of mine only rappels, and he has a single line tied at the anchor with a figure 8 on a bite with a backup knot, and has a person on belay which mainly sits down on the bottom and holds the rope and if the person on rappel loose's control of the rope and starts falling the person on belay will pull the rope out and tight and stops it some how... I think that, that might be the safest way. but im just a newb so you should listen more to the better more knowledgeable climbers
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skinnyjim
Jul 28, 2004, 8:42 AM
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what the hell are you talking about iclimblilrocks?
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slobmonster
Jul 28, 2004, 11:25 AM
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He's talking about a fireman's belay, which work fine.
But so does the prussik/autoblock in under debate. Question for you: why are you rappelling so fast as to melt fibers in your prussik cord? Yes, over time the sheath of the cord can get a little worked. But remember: this sling is not really, truly load bearing; it just acts as a permanent brake hand in case you let go with your other ones. It doesn't even need to be full strength.
That said I think you'll find that if you switch over to skinny, soft 5mm cord for your prussiks you'll start to enjoy yourself a lot more.
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mheyman
Jul 28, 2004, 12:50 PM
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In reply to: But remember: this sling is not really, truly load bearing; it just acts as a permanent brake hand in case you let go with your other ones. It doesn't even need to be full strength.
Not necessarily true. Depends whether you rig it above or below the rappel device.
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dutyje
Jul 28, 2004, 12:59 PM
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I started with the prusik above the device method. It works well enough, but the prusik can be hard to release if you've weighted it. I switched over to the autoblock with the belay device using a shoulder-length runner. I experimented with the Klemheist and found that it felt more secure to me, and released just as easy as the autoblock.
My partner uses the autoblock, I use the Klemheist. On multiple occassions, we've tested these backups (to gain confidence in them) while our partner was on a fireman's belay (we also tested the fireman's belay, which is a fun way to make your partner wonder why his rappel has suddenly stopped).
Backup knot choice is a matter of preference. Play with them all to see which one seems most comfortable for you. I'd recommend testing it so you gain confidence in it.
Back on the original question -- will the friction cause any damage? It is my understanding that, over time, the sling will degrade with use. As others have mentioned, if you're burning down the rope really fast, you'll burn through your prusik really fast. I inspect my prusik after a rappel, and I haven't noticed any damage as of yet (4 months of use). I also rappel very slowly.
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zeffe
Jul 28, 2004, 1:12 PM
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what's the standard place to attach prussik to the harness? I've read that below the rap device is good because it wont ever get out of your reach if you weight it. But wouldn't it be possible for it to jam in the the rap device?
The Reverso manual shows a quickdraw attached to the belay loop and the rap device so the rap device is high, about chest height, and the prussik is attached to the belay loop as well. Is that standard practice?
I've also read about attaching the prussik to a leg loop, but it seems like this would leave you in an awkward position if you had to weight the prussik....
Thanks in advance!
-Zeffe
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nostalgia
Jul 28, 2004, 1:32 PM
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There are a few good reasons to have the backup below the belay device. One was stated above: if the knot gets weighted, it can be very difficult to unlock. Another is, if you do lose control of the rappel, and the backup locks, that backup sling is now holding your entire bodyweight.
With the backup below the belay device, if you lose control and the knot locks, your belay device is holding your bodyweight. This means the rope is carrying your weight, instead of 6mm cord. It also means the knot will be easier to release, since you can unweight it more easily.
I was shown an excellent way to make this work. Instead of attaching your belay device to your belay loop, girth hitch a sling through the tie-in points of your harness, and clip your belay device to that. Now, tie your autoblock or prusik to the brake side of the rope and clip it to your belay loop. This has a few advantages. First, it gets the belay device at a higher level, giving you better control and less chance of flipping over if you crash into something. Second, it makes it impossible for the backup knot to get sucked into the belay device - something I've been told is quite unpleasant, and is a real possibility if you clip the belay device to your belay loop and tie the backup to your leg loop.
-Joe
edited for clarity
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michhiker
Jul 28, 2004, 2:25 PM
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In reply to: Ok I dont know much but I do know that if you rap on a sling and a prusik knot, It will burn right through. A friend of mine only rappels, and he has a single line tied at the anchor with a figure 8 on a bite with a backup knot, and has a person on belay which mainly sits down on the bottom and holds the rope and if the person on rappel loose's control of the rope and starts falling the person on belay will pull the rope out and tight and stops it some how... I think that, that might be the safest way. but im just a newb so you should listen more to the better more knowledgeable climbers
Does he rappel on that home depot line of yours? Sorry...just coulnd't resist!
---MH
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iclimblilrocks
Jul 28, 2004, 8:20 PM
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In reply to: In reply to: Ok I dont know much but I do know that if you rap on a sling and a prusik knot, It will burn right through. A friend of mine only rappels, and he has a single line tied at the anchor with a figure 8 on a bite with a backup knot, and has a person on belay which mainly sits down on the bottom and holds the rope and if the person on rappel loose's control of the rope and starts falling the person on belay will pull the rope out and tight and stops it some how... I think that, that might be the safest way. but im just a newb so you should listen more to the better more knowledgeable climbers Does he rappel on that home depot line of yours? Sorry...just coulnd't resist! ---MH
nope, bluewater 7/16 static line
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afiveonbelay
Jul 28, 2004, 8:39 PM
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In reply to: I was shown an excellent way to make this work. Instead of attaching your belay device to your belay loop, girth hitch a sling through the tie-in points of your harness, and clip your belay device to that. Now, tie your autoblock or prusik to the brake side of the rope and clip it to your belay loop. This has a few advantages. First, it gets the belay device at a higher level, giving you better control and less chance of flipping over if you crash into something. Second, it makes it impossible for the backup knot to get sucked into the belay device - something I've been told is quite unpleasant, and is a real possibility if you clip the belay device to your belay loop and tie the backup to your leg loop. -Joe edited for clarity
way to go joe, extend the device, klemheist on the brake hand side. I use a 12" spectra runner girthed into my belay loop. It never leaves the harnes and is never in the way. Additionally, it provides a nice clip in point for directionals at a belay stance. You can also half-lap a standard length runner thru the belay loop to the device if you don't want a dedicated danglie. TOO long a runner will put the device way up and make it difficult to read correct rigging before beginning the rappel.
bthornburn. the rappel back-up friction knot shouldn't be getting that much friction. its only a back-up knot, not your main way of controling the rapppel.
I always rig a rappel back-up knot. Always. If for some reason, storm, dark, charlie foxtrot... you mis-rig your rappel device and rush into the rappel...oops. A friction backup knot is your redundancy for rappel.
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megableem
Jul 28, 2004, 8:41 PM
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taino
Jul 28, 2004, 8:56 PM
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In reply to: Someone else mentioned that you can extend your belay device to keep the autoblock from reaching it. But it's a lot simpler to hook a short cord to your leg loop. Sometimes simpler is better. You'd think that if the cord was too long it would jam in the rap device but still stop you. In the September issue of Rock and Ice there's an article about rappel backups. They did some drop tests with a cord that was too long and in every case the autoblock did not stop the rappel.
You can do that - if you extend the rappel device. The thing is, it's possible to be flipped upside down - in an extreme case - by putting the back-up off your leg loop. I'm not saying that it happens as a matter of course, I'm saying that it's possible. If one extends the rappel device to about 12"-18", and attaches the back-up directly to their belay loop, you won't flip over - and, the twain shall ne'er meet.
How long a back-up cord do you use? I use a 4' piece of 6mm cord, tied into a loop with a grapevine knot - the knots take up about a foot, leaving a manageable loop with which to back up the rappel. I can see how the R&S tests would find that, though - the back-up can't fully bite onto the rope unless it is allowed to "extend" - and grab enough of the rope. With the rappel device constantly pushing against the top of the back-up, it can't extend.
T
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yazey
Jul 28, 2004, 9:33 PM
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Prusik knot, everytime.
As a practice learned from much more seasoned climbers I now carry with me 2 prusik loops, small, around my neck, and tucked into my shirt while climbing. Always ready, for when needed, and you never know when you will need them.
On repel a prusik is attached above the belay device (reverso) with a shoulder lenght girth hitched to it for extension to either the belay loop, or the leg loop. IMO, it makes very little difference, as long as you have enough room to lock off.
The knot is held very loosely around the rope, and the repel is controlled and deliberate. Bad mistakes happen on repel, take your time.
I have in the past used this same set up but underneath the belay device, thinking that in the event of a fall, the knot would load, and even tangle inside the device, stopping any fall. While this may be true with the average ATC, the Petzel Reverso is another matter. Through testing on my own, it was discovered that the prusik did not lock itself off while below the device, because the runner was too long. And that the prusik cord did not tangle itself in the device either. The design of the device does not allow it.
That being said, the Reverso is still my favorite belay device.
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taino
Jul 28, 2004, 9:41 PM
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In reply to: I have in the past used this same set up but underneath the belay device, thinking that in the event of a fall, the knot would load, and even tangle inside the device, stopping any fall. While this may be true with the average ATC, the Petzel Reverso is another matter. Through testing on my own, it was discovered that the prusik did not lock itself off while below the device, because the runner was too long. And that the prusik cord did not tangle itself in the device either. The design of the device does not allow it. That being said, the Reverso is still my favorite belay device.
*ahem*
I use the Reverso exclusively when leading or swinging leads, and frequently rappel with it. I ALWAYS extend it, and put an autoblock back-up underneath it clipped to my belay loop. I've never had a problem with this. Perhaps your back-up line is too long?
T
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megableem
Jul 28, 2004, 10:03 PM
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taino
Jul 29, 2004, 2:45 AM
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In reply to: I contend that since it is an emergency backup, the risk of getting flipped over isn't enough to matter.
Foolish, IMHO.
It takes the exact same amount of time to clip your rappel device through a 2' sling girth-hitched to your leg/belt loops as it does to clip it to your belay loop. It's a matter of perhaps 20 seconds more to wrap a short cord or 9/16 webbing into an autoblock and clip it to your harness. The risk of getting flipped over, among other things, is PRECISELY why it should matter. Period.
In reply to: It's much more important to have a fast, simple system that someone will actually use.
That's exactly what I use - a fast, simple system. It just happens to avoid the very real danger of jamming the autoblock into the rappel device.
Dude, rappel however you feel comfortable. This is the way I was taught, and this is the way I teach it. Safe. Redundant. Simple.
T
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taino
Jul 29, 2004, 2:50 AM
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In reply to: I contend that since it is an emergency backup, the risk of getting flipped over isn't enough to matter.
Foolish, IMHO.
It takes the exact same amount of time to clip your rappel device through a 2' sling girth-hitched to your leg/belt loops as it does to clip it to your belay loop. It's a matter of perhaps 20 seconds more to wrap a short cord or 9/16 webbing into an autoblock and clip it to your harness. The risk of getting flipped over, among other things, is PRECISELY why it should matter. Period.
In reply to: It's much more important to have a fast, simple system that someone will actually use.
That's exactly what I use - a fast, simple system. It just happens to avoid the very real danger of jamming the autoblock into the rappel device.
Dude, rappel however you feel comfortable. This is the way I was taught by an AMGA certified guide and later corroborated through extensive field testing, and this is the way I teach it. Safe. Redundant. Simple.
T
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col
Jul 29, 2004, 3:54 AM
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If something isn't so safe/simple/comfortable/easy that you would use it as a primary method, i don't see why anyone would consider it apropriate as an emergency back up.
Besides, most likely you will stop at the bottom....
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yazey
Jul 29, 2004, 3:49 PM
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Yes, perhaps it is too long. Have you tested to see if your back up knot, below the Reverso will lock off?
Just curious?
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taino
Jul 29, 2004, 3:52 PM
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In reply to: Yes, perhaps it is too long. Have you tested to see if your back up knot, below the Reverso will lock off? Just curious?
Yes, every time, before I come off safety. I've also stopped mid-rappel and taken pictures while the autoblock holds me in place, without any trouble.
T
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dalguard
Jul 29, 2004, 5:29 PM
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What kind of lunatic are you, yazey?
In reply to: As a practice learned from much more seasoned climbers I now carry with me 2 prusik loops, small, around my neck, and tucked into my shirt while climbing. Always ready, for when needed, and you never know when you will need them.
In reply to: On repel a prusik is attached above the belay device (reverso) with a shoulder lenght girth hitched to it for extension to either the belay loop, or the leg loop. IMO, it makes very little difference, as long as you have enough room to lock off.
Well, you're wrong. If the prusik is attached above the belay device then it needs to be weight bearing, which means you shouldn't attach it to your leg loop. Below the device, the leg loop is fine.
In reply to: The knot is held very loosely around the rope
In reply to: I have in the past used this same set up but underneath the belay device, thinking that in the event of a fall, the knot would load, and even tangle inside the device, stopping any fall.
In reply to: While this may be true with the average ATC, the Petzel Reverso is another matter. Through testing on my own, it was discovered that the prusik did not lock itself off while below the device, because the runner was too long. And that the prusik cord did not tangle itself in the device either. The design of the device does not allow it.
Duh? Perhaps shortening the runner rather than re-designing the belay device is what is called for here.
In reply to: That being said, the Reverso is still my favorite belay device.
P.S. Repel is wrong - check the subject line, they got it right - but you get points for spelling prusik right.
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megableem
Jul 29, 2004, 6:40 PM
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