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theooze
Apr 15, 2003, 11:37 PM
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Small diameter ropes, e.g. double ropes, don't give you as much friction passing thru a typical belay/rap device. I remembered this during a long free-hanging rap on Sunday. Felt like I was really holding on for dear life, while freeing the ropes from a tree on the way down. Unpleasant at best.
I had an autoblock on, but I couldn't trust it. Remember, when the diameter of the autoblock (prusik, klemheist etc.) cord is close to the diameter of the rope, it is MUCH less effective. My prusik loop is 6 mil.
It seems to me that these two factors could create a very dangerous situation if you weren't expecting it.
When I used to climb on doubles a lot, I used the old Lowe Tuber. It was easy to turn it around so that the narrow end of the tube was facing me, which increased the friction on the doubles quite a bit. Many new fangled belay plates can't be used that way.
I've thought about using thinner high-strength cord for the prusik, but what about the friction/heat? Bad idea?
What do you double-rope afficianados suggest?
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ricardol
Apr 15, 2003, 11:54 PM
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i've got the same concerns .. i just bought a new set of double ropes ..
8.6mm bluewater ..
.. pretty skinny ..
for safety sake i've decided that the first time i rapp these puppies i'm going to use 2 carabiners to create more friction
-- ricardo
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davidji
Apr 16, 2003, 12:01 AM
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In reply to: i've got the same concerns .. i just bought a new set of double ropes .. 8.6mm bluewater .. .. pretty skinny .. for safety sake i've decided that the first time i rapp these puppies i'm going to use 2 carabiners to create more friction
Those are the ropes I'm using. They work great for rappel with my ATC-XP, even in the low friction mode. May be slicker on first use and be better in the high friction direction. I just use one biner.
David
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crotch
Apr 16, 2003, 12:02 AM
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texplorer
Apr 16, 2003, 12:48 AM
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Autoblocks are for gumbies. I do use the double carabiner setup though for single or small diameter ropes and it works well.
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dirtineye
Apr 16, 2003, 4:12 AM
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THe auto block holding power is directly related to the number of wraps you put on it, as crotch has already sug4ested. I always use a sling, and I vary the number of wraps depending on the ropw diam, and the dual or single line rap.
In this way you can fine tune your autoblock to perfection for whatever rope you are on.
One fine point, an autoblock is not reliable until it is set. One more point, if it is slipping, use more wraps.
As for autoblocks being for gumbies, see my tag line.
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alpnclmbr1
Apr 16, 2003, 4:41 AM
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I use 8.2 doubles and a trango jaws, works better then a regular rope with an atc. An atc is not rated for skinny ropes.
when I use the 8.2 as a trail rope, I use the jaws to.(most of the time)
otherwise I use an atc
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flying_dutchman
Apr 16, 2003, 5:13 AM
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how do you place the second biner to create more friction? I've never seen a double biner setup for rapping before. Do you simply add a second one to the atc and run the rope around both biners?
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drkodos
Apr 16, 2003, 6:06 AM
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You can also give yourself a "Self Fireman's Belay" by wrapping the rope around your leg, freeing your hands to work whatever.
Usually two to three wraps will do for a 9mm rope.
No extra gear needed..... 8)
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ricardol
Apr 16, 2003, 6:17 AM
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i use a reverso for belaying and rappeling -- i bet the ATC is the same way though..
if you use more than one carabiner to thread the rope through (as in having 2 biners on your harness belay loop) .... the rope will have more friction during a rappel (or belay)
-- ricardo
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crotch
Apr 16, 2003, 6:13 PM
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jhump
Apr 16, 2003, 6:42 PM
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Autoblocks are for gumbies. They are the only ones who get blasted unconscious by rock or ice fall way up on alpine walls rendering them unable to hang on to their rappels. Real climbers just go unconscious and ride the rappel out at warp speed and let their knots at the ends of the ropes stop them. Wait, knots are for gumbies too. Real climbers are immune to rock fall. My bad.
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rgold
Apr 17, 2003, 7:49 PM
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Here is an important related issue: If you are struggling to control a rappel, if you have to double the biners or have to rely on additional friction from an autoblock, then how are you going to hold a hard fall on a single strand? I think quite a few belay devices are inadequate for thin half ropes. In my opinion, the best traditional style device is the Metolius BRD (I like it better than the Jaws, which used to be my choice), and the best new-fangled gadget is the TRE Sirius.
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drkodos
Apr 17, 2003, 8:01 PM
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Manufacturers (and those in the know) recommend specific belay plates/devices for using small diameter ropes.
Climbing gear and computer games seem to have in common that people rush right in to use their new "toys" without reading any of the info that comes along with the packaging.....ALL small diameter ropes come with a caveat that implores the use of devices specifically designed for thin cord, but why read and learn when you can climb and get into a world of sh*t for misusing/not understanding gear?! 8)
Plus, the internet is here to save the day with all this helpful spewing.... :shock:
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smithclimber
Apr 17, 2003, 8:45 PM
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Ooze, if you were fond of the old Lowe Tubers, check out the Trango Pyramid belay device. It's very similar to the old Lowe Tuber, it too can be inverted to alter the friction like the Lowe Tuber did.
As several above have mentioned, you can add a second biner to increase friction.
If you are finding that your current "autoblock cord" is too close, in diameter, to the rope(s) you are rapping on, then switch to a smaller diameter "autoblock cord". I.e. use 5mm instead of the 6mm you currently have.
Use PERLON cord rather than any of the high strength cords that are better suited for slinging protection (the high strength cords [spectra, kevlar, vectran, technora, etc.] tend to become weaker with repeated flexing than perlon. This [repeated] is exactly what you will be doing each time you construct/dismantle an autoblock, therefore perlon is recommended over the high strength cords). Also, some of the high strength cords have low melting points (a concern when using them for friction knots), another reason to choose the perlon.
A better alternative to decreasing the size of the cord is to increase the number of wraps you use when setting up the autoblock.
Also, as mentioned above, consider using a piece of 9/16" NYLON webbing (DO NOT USE SPECTRA OR DYNEEMA WEBBING) and practice a bit to figure out exactly how many wraps work best for the ropes you are rappelling on.
Cheers, Wes
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theooze
Apr 17, 2003, 9:02 PM
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In reply to: Use PERLON cord rather than any of the high strength cords that are better suited for slinging protection (the high strength cords [spectra, kevlar, vectran, technora, etc.] tend to become weaker with repeated flexing than perlon. This [repeated] is exactly what you will be doing each time you construct/dismantle an autoblock, therefore perlon is recommended over the high strength cords). Also, some of the high strength cords have low melting points (a concern when using them for friction knots), another reason to choose the perlon.
Right, that was sorta my thought. Thanks, Wes.
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slcliffdiver
Apr 17, 2003, 9:36 PM
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Depending on belay device for long rappels on skinny ropes, I use double biners and a biner through my leg loop. Don't just clip a biner through the leg loop and the tail through the biner and go. Get someone who knows how to do this to show you the ins and outs to keep you from screwing up and dieing. Also don't try this until you have safe rappeling down pat. I'm not comfortable writing instructions up for this. Ask around a good percentage of experience trad climbers should be able to show you how to do this. There are a couple of minor variations on this theme but I like using the leg loop redirect the best, at least for long raps. If the person showing what to do doesn't make you put on a backup knot/hitch above the belay device for the first several times at the very least fire them.
Peace
David
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pico23
Apr 18, 2003, 7:16 PM
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In reply to: I had an autoblock on, but I couldn't trust it. Remember, when the diameter of the autoblock (prusik, klemheist etc.) cord is close to the diameter of the rope, it is MUCH less effective. My prusik loop is 6 mil. It seems to me that these two factors could create a very dangerous situation if you weren't expecting it. What do you double-rope afficianados suggest?
Doubles Rock. But rapping can be a little scary. I use two biners for increased friction. Two of the same is best.
A reverso is also convenient because it has an increased friction mode for rappels but isn't necessary with two biners, although the reverso is very handy for doubles.
As far as the prussik I believe the as long as the diameter is in the 60-80% range it will hold just fine. I use the same 6mm on all my ropes including my 8mm glacier rope (although a 5mm would be better 6 works fine), my 8.5 mm doubles, my 9.6 single, and my 10.5 single.
If you have doubts test the prussik, you may need more raps but it should work just fine.
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mojorisin
Apr 20, 2003, 1:06 AM
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This reminded me of the time I rapped off Dracula with a Reverso and 7.6 ropes,, needless to say it was a fast ride down. This was before the petzl warning came out. But small ropes are fast. I like to use my shunt for backing up a rappel off the leg loop but I can use a 5 mm prusik or a nylon auto block on 8.1 mm ropes without any trouble. And I think its safe to say you should NEVER rappel without a back up. If that makes me a Gumbie,,I will live to be an old one,, 8)
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ricardol
Apr 23, 2003, 4:46 PM
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well -- this last weekend we did several raps .. (red rocks)
the longest rap was about 160' i believe .. on geronimo ..
rapping on 8.6mm ropes .. it was no problem -- used only 1 carabiner .. the rap got a bit fast at the bottom, but no problem ..
.. the only difficulty was figuring out how many wraps to use on my backup .. -- sometimes i used too many and it was a pain to move -- another time i used too little .. and it was hard for it to engage at the bottom of the rap ..
.. though since the ropes were new there were getting tangled together anyways, and there was no way for me to fall of the end! ...
.. after several raps i finally just stopped using backips since they were slowing the rap down quite a bit -- and we needed to get off from crimson crhysalis .. -- nothing bad happened , but i can see why the backup is really required on 8.6 -- if i had slipped there is no way i would have regained control of the ropes -- they build up friction on your brake hand quite fast .. (almost burned my hand several times)
-- ricardo
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tim
Apr 23, 2003, 5:22 PM
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Being in too much of a hurry to rappel strikes me as suicidal.
You really only get one chance, if you blow it, good-bye.
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