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aprice00
Jun 1, 2011, 5:22 PM
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Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is...
Is an autoblock prussic only used on a single strand rappel?
What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you?
Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up.
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csproul
Jun 1, 2011, 5:30 PM
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A Klermheist or a Prusik both work fine around a doubled-up rope as long as you use an appropriate diameter and # of wraps.
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rtwilli4
Jun 2, 2011, 12:12 AM
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csproul wrote: A Klermheist or a Prusik both work fine around a doubled-up rope as long as you use an appropriate diameter and # of wraps.
Correct. I usually use somewhere between a 9 and 10 mil rope and I think one of my prussic cords is 3 or 4 mil and the other is 5 or 6. Either will work on a single line and either will work on a doubled rope. You just have to practice and see how many wraps you need.
There are a lot of different friction hitches and they are all best suited for different things. The one I use to back up rappels doesn't even have a name (or at least I don't know it), but it works to back up rappels. It would also work for ascending a rope or hauling someone, but it wouldn't be the best hitch for the job.
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clc
Jun 2, 2011, 6:00 AM
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aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up.
Dude, 
You would have spent less time actualy testing your theory with the diiferent prussics than writing in this forum.
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j_ung
Jun 2, 2011, 12:42 PM
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aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up.
You're mistaken. If the cord thickness is appropriate, then an autoblock will work just fine. I use 6mm cord for it, with an additional wrap on single-rope rappels.
(This post was edited by j_ung on Jun 2, 2011, 12:42 PM)
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philbox
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Jun 3, 2011, 11:16 PM
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What people need to get their heads around is a basic fundamental understanding of the physics involved in abseiling/rapping.
You need to overcome gravity by way of friction. If your autoblock works on a single rope rappel then it will work even better on a double rope rappel.
6mm nylon prussik cord on a 10mm rope with 4 wraps will always hold.
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aprice00
Jun 7, 2011, 7:00 PM
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j_ung wrote: aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up. You're mistaken. If the cord thickness is appropriate, then an autoblock will work just fine. I use 6mm cord for it, with an additional wrap on single-rope rappels.
Ok so I didnt even think about wrapping both strands. I was thinking the prussic is wrapped around one strand and the second is free which I would never trust. But yeah wrapping both strands totally makes sense.
Thanks for the school'n
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drector
Jun 7, 2011, 8:27 PM
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aprice00 wrote: j_ung wrote: aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up. You're mistaken. If the cord thickness is appropriate, then an autoblock will work just fine. I use 6mm cord for it, with an additional wrap on single-rope rappels.
Thanks for the school'n
It's scary to think that some other climber might also think that they should wrap just one strand but are then not smart enough to mistrust it.
A more detailed analysis of every procedure is in order if wrapping both strands wasn't an obvious alternative to the crazy idea of wrapping just one strand.
Dave
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maldaly
Jun 7, 2011, 8:28 PM
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Thanks for the humility.
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aprice00
Jun 7, 2011, 10:01 PM
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drector wrote: aprice00 wrote: j_ung wrote: aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up. You're mistaken. If the cord thickness is appropriate, then an autoblock will work just fine. I use 6mm cord for it, with an additional wrap on single-rope rappels.
Thanks for the school'nIt's scary to think that some other climber might also think that they should wrap just one strand but are then not smart enough to mistrust it. A more detailed analysis of every procedure is in order if wrapping both strands wasn't an obvious alternative to the crazy idea of wrapping just one strand. Dave
Ha thanks for the tact while calling me an idiot. If its any conciliation I don’t get on anything that I need a back up for I am just thinking ahead.
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chris
Jun 12, 2011, 12:46 AM
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aprice00 wrote: drector wrote: aprice00 wrote: j_ung wrote: aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up. You're mistaken. If the cord thickness is appropriate, then an autoblock will work just fine. I use 6mm cord for it, with an additional wrap on single-rope rappels.
Thanks for the school'nIt's scary to think that some other climber might also think that they should wrap just one strand but are then not smart enough to mistrust it. A more detailed analysis of every procedure is in order if wrapping both strands wasn't an obvious alternative to the crazy idea of wrapping just one strand. Dave Ha thanks for the tact while calling me an idiot. If its any conciliation I don’t get on anything that I need a back up for I am just thinking ahead.
Your signature talks about getting kicked in the vagina, and you're going to criticize someone else for tact? Priceless. 
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cjon3s
Jun 12, 2011, 6:42 AM
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You never need a backup until well, you actually need it. Anytime you rap, there's no reason not to use one. What if a rock hits you in the head and knocks you out? A backup takes all of 10 seconds and can save your life.
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patto
Jun 12, 2011, 3:11 PM
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cjon3s wrote: You never need a backup until well, you actually need it. Anytime you rap, there's no reason not to use one. What if a rock hits you in the head and knocks you out? A backup takes all of 10 seconds and can save your life.
There are plenty of reasons not to use a prussik style backup. And plenty of ways still have an out of control rap accident while using one.
Also there no need at all to use an added backup from your harness if your partner can give you a firemans belay.
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cjon3s
Jun 12, 2011, 3:17 PM
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Give me a good reason not to use one when it is used properly. With a slightly extended belay device or a short autoblock, the device is prevented from jamming. What else do you have going wrong?
And someone has to get to the ground in the first place genius, take my scenario to be in multioitch trad for instance, a firemans belay is not always an option. An autoblock is.
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aprice00
Jun 12, 2011, 4:45 PM
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chris wrote: aprice00 wrote: drector wrote: aprice00 wrote: j_ung wrote: aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? Unless im mistaken 1 prussic on a doubled over rope may slow you down but is more likley to get you hurt when you go hands off thinking your backed up. You're mistaken. If the cord thickness is appropriate, then an autoblock will work just fine. I use 6mm cord for it, with an additional wrap on single-rope rappels.
Thanks for the school'nIt's scary to think that some other climber might also think that they should wrap just one strand but are then not smart enough to mistrust it. A more detailed analysis of every procedure is in order if wrapping both strands wasn't an obvious alternative to the crazy idea of wrapping just one strand. Dave Ha thanks for the tact while calling me an idiot. If its any conciliation I don’t get on anything that I need a back up for I am just thinking ahead. Your signature talks about getting kicked in the vagina, and you're going to criticize someone else for tact? Priceless.
The man used tact I acknowledged it. Not a criticism.
The signature was amusing to me so I kept it. It's not necessarily something I would say.
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patto
Jun 13, 2011, 12:01 AM
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cjon3s wrote: Give me a good reason not to use one when it is used properly.
Speed and efficiency is the reason why I don't use it on many of my rappels.
cjon3s wrote: With a slightly extended belay device or a short autoblock, the device is prevented from jamming. What else do you have going wrong?
cjon3s wrote: And someone has to get to the ground in the first place genius, take my scenario to be in multioitch trad for instance, a firemans belay is not always an option. An autoblock is.
Hey there is nothing wrong with using an autoblock. I certainly have used it countless times. By I object to the matra that it needs to be used on every rap.
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cjon3s
Jun 13, 2011, 12:09 AM
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Okay, I understand your points. When used priperly, it's a great thing. I've done plenty of rappels without one. I just always have cord on me and it's so simple that I use it almost all the time.
People need to learn how to do things before they need it.
As was said earlier in another thread, knowledge is the lightest, most useful thing you can bring on a climb.
Finally, you're right. Always and never are not good to use witg regards to climbing. Each situation dictates different methods and techniques be used and must be approached as such.
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perelman
Jun 14, 2011, 8:36 PM
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aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you?
Are you absolutely sure you want to trust rappelling advice you get from an online forum? Talk to some experienced climbers, or at the very least consult a reputable source like Freedom of the Hills, or John Long or Craig Leubben's books. There's a fair serving of horseshit on this forum.
Are you talking about an autoblock below the belay device? Or a backup above? It's a much debated issue, but no one has even brought it up yet. Please, consult a reference. I could tell you what works for me based on what I've learned - which I trust - but then, I don't think you should be trusting random strangers.
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aprice00
Jun 14, 2011, 9:09 PM
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perelman wrote: aprice00 wrote: Ok so I just recognized a gap my understanding of an autoblock and didnt find anything in a search. So the question is... Is an autoblock prussic only used on a single strand rappel? What about a doubled over rope that you plan on pulling from the bottom? You dont actually set up two prussics do you? In reply to: Are you absolutely sure you want to trust rappelling advice you get from an online forum? Talk to some experienced climbers, or at the very least I dont blindly trust anyone. I listen to opinions and make judgements based on all the information that I have. In reply to: Are you talking about an autoblock below the belay device? Or a backup above? Im asking about a autoblock below the ATC. I'd be interested to hear what works for you. In reply to: There's a fair serving of horseshit on this forum. Thanks for the warning but I read alot more here than I post here so I know about sifting through the bs. In reply to: consult a reputable source like Freedom of the Hills, or John Long or Craig Leubben's books. I actually have/had all three of those books. FOTH was lost in a move but I think it will show up, and the long/leubben books just came in the mail two days ago. I have to say though the new books are painfull to read. Its the 21st century I Need Colour!!
(This post was edited by aprice00 on Jun 14, 2011, 9:21 PM)
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perelman
Jun 14, 2011, 9:23 PM
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Fair enough. I use the Web similarly I suppose.
This is what I use: http://www.youtube.com/watch?v=gqBTV16dpN0
Instead of beginning with a girth-hitch on the leg loop, you can just clip both ends of the cord sling into the biner. I've verified both of these setups with two very experienced climbers.
For cord I use 6 mm. With the backup below the ATC it's important to have the right size sling. I find a 5 ft length of 6mm cord is perfect. This is on my 10.5mm rope.
(This post was edited by perelman on Jun 15, 2011, 2:43 AM)
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squierbypetzl
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Jun 15, 2011, 7:03 AM
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"Ok" (hehe), use a locking biner. you're depending on this thing to stop a potentially lethal fall, an open biner doesn't fit into that equation. Other than that, the method is solid, commonly used too.
I tend to use a klemheist tied above my rap device, especially if there's any chance I could run out of rope.
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perelman
Jun 15, 2011, 6:49 PM
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Right, thanks for clarifying that. I do use a locker.
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