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Making a Purcell Prusik: Dynamic vs. Static Cord
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By redlude97
Sep 1, 2010
So i want to try out the PP as a personal anchor, and I've read all the threads on them from various forums. The suggestion is usually for 6-7mm cord ~14' in length. There have even been some suggestions for using the bluewater/yates dynamic prusik cord, but I haven't been able to find anyone that has actually done it and commented on it. For one thing it is difficult to source even online which may contribute to the limited use.

So for those that use a purcell prusik as a personal anchor, is yours static or dynamic cord and if you were to make one today which material would you prefer.

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By Rich Farnham
Sep 2, 2010
I see two ways to look it.

As you said, dynamic cord in that diameter is really difficult to find and the static will work fine for this application. In theory, if you load it heavily (i.e. fall onto it) the prussik will slip to absorb energy, making dynamic cord unnecessary.

Another way to look at it would be to add safety where it can be easily achieved. The prussiks slip at a fairly high value. It's a force you wouldn't really want to feel. It's safe and survivable, but not something I'd be looking forward to. Why not add the energy absorbing properties of dynamic rope to help out if you can find a good source for it?

The bottom line is either would work, and unless you like to climb above your connection point and take high fall factor drops (>1) onto your anchor, you'll probably never notice the difference.

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By Jon H
From Boulder
Sep 2, 2010
At the matching crux
Rich Farnham wrote:
I see two ways to look it. As you said, dynamic cord in that diameter is really difficult to find and the static will work fine for this application. In theory, if you load it heavily (i.e. fall onto it) the prussik will slip to absorb energy, making dynamic cord unnecessary. Another way to look at it would be to add safety where it can be easily achieved. The prussiks slip at a fairly high value. It's a force you wouldn't really want to feel. It's safe and survivable, but not something I'd be looking forward to. Why not add the energy absorbing properties of dynamic rope to help out if you can find a good source for it? The bottom line is either would work, and unless you like to climb above your connection point and take high fall factor drops (>1) onto your anchor, you'll probably never notice the difference.


Rich nailed it.

Or better yet - just use the rope and a clove hitch. No need to carry anything extra, dynamic, and failsafe. If you're really anal, use an extra 48" runner to back it up. Lighter, less bulky, win on all counts.

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By dannl
Sep 2, 2010
You can buy dynamic rope by the foot here:

innermountainoutfitters.net/ca...

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By Monty
From Golden, CO
Sep 3, 2010
Just a teaser
I've used a Purcell prusik for a long time and have always used 6mm static cord. Anytime when on a multi pitch, I will clove hitch to one part of the anchor, and personal to the other. Bomber. The thing I love most about the purcell prusik is just how easy it is to get comfortable at a belay. If you need a little extra room you just push up and bam, no unclipping and your nice and cosy.

I think I normally buy 14ft of cord to make mine, and then chop off any extra if needed. Think of it this way, when your prusik is cinched in all the way, it should be about the length of a 24" sling. That will give you plenty of extra length and adjustability.
cheers

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By Derek W
Sep 3, 2010
First summit of First Flatiron
Mine is out of 6mm nylon accessory cord which has some stretch built into it, as well as the slip in the prusik mentioned above. The other thing that I did was I tied the two ends together just above the prusik to make a small loop I can clip into if I need to clip in really short for some reason. I have really liked that addition to what you normally see in the books.

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By Joby Spencer
From Boulder, CO
Sep 3, 2010
Almost to the belay for Celestial Omnibus.  I'm fe...
+1 for Rich's post. I am also considering switching to a PP. Two partners use standard 6mm cord, but I would also like to get a piece of the new dynamic cord.

More general questions for anyone who might know....
1) Does the load absorption performance of the Purcell degrade considerably if you don't leave enough "slipping room" for the prusik? The tests from Mike Gibbs (Rigging for Rescue) showed that the slipping of the prusik is a key component of the PP's success at absorbing the fall. If you have it fully extended (or almost fully extended), what happens? Does the PP lose most of its "strength" when you don't have any slipping room for the prusik? I realize that two strands of 6mm cord is still pretty strong, but will it still hold a FF1 or FF2 fall of the belayer? Or is it a matter that the PP does great with some slipping room, but will break when fully extended with these bigger factor falls? I can take a guess, but I'm wondering if anyone has checked this out.

2) Does anyone replace the normal 3-strand figure-8 knot and girth hitching to harness, and instead just re-tie in with a follow through F8 using the 2 strands of the cord? Pain to tie in every time, but you get 2 strands through your harness, and no cinching around your tie-in loops from the girth-hitch.

3) Anyone replace the normal Figure-8 with a Fisherman's Loop knot (aka: ONE & A HALF GRAPEVINE LOOP -> rescuedynamics.ca/articles/kno... that uses two strands instead of one. Ie: Exact same Fisherman's Loop knot, but do it with two strands side by side instead of just one. Again, you get 2 strands girth-hitching through your harness instead of one. Might get bulky with the 2 strand girth-hitch???

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By fivefun
Sep 1, 2011
A fun hand crack
Joby Spencer wrote:
2) Does anyone replace the normal 3-strand figure-8 knot and girth hitching to harness, and instead just re-tie in with a follow through F8 using the 2 strands of the cord? Pain to tie in every time, but you get 2 strands through your harness, and no cinching around your tie-in loops from the girth-hitch.


I too am interested in this answer.

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