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hosh
Feb 2, 2007, 7:25 PM
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What's the thinnest diameter of cord that one could responsibly use for a prussik without having to worry about it being unsafe? If it matters, the rope I'll be using this on is a 10.2. Any informed opinions? thanks!
hosh.
(This post was edited by hosh on Feb 2, 2007, 7:26 PM)
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moose_droppings
Feb 2, 2007, 7:34 PM
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I think 5.5mm tech cord would be strong enough at that size, but I don't prefer it for prusicks since it is slick. 2mm smaller than the rope your going to use it on is sufficient friction for a prusick. I don't think that any regular cord smaller than 6mm would be safe for all manners you might use a prusick on.
YMMV
edited for old man spelling
(This post was edited by moose_droppings on Feb 2, 2007, 7:37 PM)
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devils_advocate
Feb 2, 2007, 8:25 PM
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http://www.rockclimbing.com/...ope%20ratio;#1001255
What do you mean by unsafe? The skinnier the prussik, the more it's going to bite. So it comes down to how thin a cord you'll use, based on the rating for that cord. All the same, you'll have a helluva time trying to manage an ultra thin line. Go from experience and grab a 5-7 mm perlon. Stuff is cheap, grab a couple feet of something thinner too and see how you like it. I bet you go back to 5-7
(This post was edited by devils_advocate on Feb 2, 2007, 8:27 PM)
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hosh
Feb 2, 2007, 9:18 PM
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Thanks. I'm thinkging I'll try some 5mm. I climb with the mentality that nothing gets a free ride, and I use rxtra prussik cord to fasten my chalk bag. I'd like to get the thinnest cord possible, since it's a "just in case" kind of thing. In a pinch, I'd like to know that the cord that I've got will do the job. I've got 7mm right now, and that just feels a little bulky, I don't like it. I've tried biners but with my harness, I don't like how far the chalk hangs down with a biner. I have to reach further than I'd like to.
again, thanks!
hosh.
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chh
Feb 2, 2007, 9:30 PM
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I use 6 mil cord. I would use 5 mil if I had to but I feel better on 6. I also use a 6 mil cord for my chalk bag. Not to bulky for me. I had 7 on there before and it was a pain.
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moose_droppings
Feb 2, 2007, 9:46 PM
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For more bite, you can also put more raps on the friction hitch (which ever one you use).
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chh
Feb 2, 2007, 9:54 PM
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clayman wrote: chh wrote: I use 6 mil cord . . christ that's small! 6mils=.006 inches 
yeah, but it's really strong! It's that brand new überspectodyneematatnium. Only problem is you gotta have a magnifying glass and some tweezers to tie the 300 fisherman's knots you need to make it safe and it also slips a little......
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shorty
Feb 2, 2007, 11:27 PM
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hosh wrote: What's the thinnest diameter of cord that one could responsibly use for a prussik without having to worry about it being unsafe?
Strengths will vary by manufacturer and end retailer, but here's a ballpark for perlon:
- 7mm - 2500 to 2700 lbf
- 6mm - 1500 to 1700 lbf
- 5mm - 1200 to 1300 lbf
- 4mm - 700 to 900 lbf
- 3mm - 300 to 400 lbf
It's generally considered best to use perlon over tech fibers. Material discussions could consume much of a post -- in summary perlon will slip less, be less prone to loss of strength from flexing, and is more elastic.
I primarily use prussiks for rappel backup, for reducing lead rope management issues when rope soloing, to hold me in position while cleaning new routes (essentially a rappel backup), and occasionally for ascending fixed ropes. "Back in the day" I was taught to use 6mm cord, which I often found didn't hold well on newer and skinnier ropes, unless a large number of wraps were used. I thought about going to smaller cord, but just couldn't mentally trust it.
This all changed when I spent some time with some AMGA teaching guides. Many of these guides use 5mm, and one even advocates the use of 4mm cord. It took me awhile to be comfortable, but I now also use 4mm cord. The downsides to small cord are:
- You must inspect and replace your prussiks religiously, as small cord wears more easily. That means every year, if not more often.
- Since small cord has limited strength, it cannot be expected to hold any great falls. Personnally, I wouldn't want to take any kind of whipper which relied on a prussik to hold me, but small cords have less margin for error.
- Small cords can snag on and get caught in more climbing hardware.
The advantages of small cord are:
- It holds really well on virtually any size climbing rope.
- It does not need that many wraps to be effective.
- It's cheap, so it's no big deal replacing prussiks on a regular basis -- even multiple times per year.
- With 4mm cord it's really easy to keep a 4' long rappel backup permanently attached to one of my leg loops and still not be in the way of climbing or gear on my rack. Should I decide to use the prussik, I can rig it in just a few seconds and be on my way.
Bottom line, I now prefer 4mm but am quite happy with 5mm, too. But no way would I drop to 3mm. Go with what works for you -- I understand people's preferences for 6mm and 7mm.
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scrapedape
Feb 3, 2007, 8:27 PM
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I use 5mm.
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majid_sabet
Feb 3, 2007, 9:47 PM
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The correct recommendation size is at least 50% to no more than 75% of the diameter of the rope that it is going to be used on.
On 10.2 it would be 6 -7 mm .recommended size would be 7 mm
11 mm rope = 7 or 8 mm
(This post was edited by majid_sabet on Feb 4, 2007, 8:34 AM)
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tattooed_climber
Feb 4, 2007, 7:04 AM
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5-8 is the standard
i climb with 7 or 8 prussiks ( always carry 2...always)
i've had to use em for slings afew times and bailed off them...so i go with the stronger sizes
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brent_e
Feb 4, 2007, 7:11 AM
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if you tie yourself into the rope as you ascend you shouldn't have to worry about safety, in the respect of the prussiks failing on you falling, anyway.
unless you mean "safe" as bail gear/extra slings or something like that.
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mattyp
Feb 4, 2007, 11:46 AM
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I use 6mm perlon. I may try out 5mm just to see how much difference 1mm makes.
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greenketch
Feb 4, 2007, 9:05 PM
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I use mostly 5mm. I have expereimented with 4 but find is hard on the feet. When I am not on trad routes I am often in the alpine. The change for me was forced by my shift to Ice floss for glacier travel. on a 7mm rope the larger prussicks were too fiddly.
Just go with the 2-3mm smaller that n the rope you are cuseing and it should be fine.
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kevinheiss
Feb 12, 2007, 2:00 AM
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I use 6mm for my prussik and it has held me up on my 10.5mm and my friends 10.3mm. 7mm is a little bulky.
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coastal_climber
Feb 12, 2007, 3:28 AM
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I use 7mm, and I have had no problems. As said, get some different diameters, and try them out and see which you like best.
>Cam
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deadhorse
Feb 12, 2007, 8:19 PM
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do you guys use prussiks or one of the others? Alot of people use the term prussik for several friction knots, but personally I think the prussik is among the least advantageous of them. (unless in a situation where loading could come from up or down I suppose) I almost exclusively use Klemheists. They're fast, grab great, and easy to tend.
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paulraphael
Feb 13, 2007, 7:44 PM
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I've used 5mm and 6mm quite a bit. I much prefer 5mm. Feels more secure, especially on skinny/wet/icy ropes, and works with fewer wraps.
My initial fears were that it would wear through too quickly when backing up rapells, but after a season of use it shows virtually no wear. It's more than strong enough for anything you should be usingg a friction knot for.
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