Prusiks

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Re: Prusiks

Postby GroundquestMSA » Dec 19, 2014 11:22 pm

Scott McCrea wrote:Did you get any pics? This would make a nice Safety and Techniques Committee article.


No, but now that I know it'll work I'm thinking about doing a little video demo and taking some photos.
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Re: Prusiks -Extreme minimalism

Postby Marlatt » Dec 20, 2014 3:25 pm

GroundquestMSA wrote:If I ever find myself at the bottom of a pit with no gear at all...


I actually found myself in exactly that situation many years ago, in a little cave in eastern Oklahoma. We were attempting to do a loop trip, which had at one point a short rappel, for which we'd brought a similarly short bit of rope (Goldline, if I recall correctly). We get to the drop, anchor the rope, and I body-rap in (dulfersitz). Of course, turns out this wasn't on route, and it was a blind pit. We discussed options (since the drop was only 30-40 feet or so, we could communicate ok), and I decided I really didn't want to be hauled out by three guys basically just pulling me up hand over hand.

Fortunately, I had about 10 extra feet of rope on the bottom, and - equally fortunate - Goldline is fairly supple. So - I rapped out. Really. I tied an ascender knot (helical, probably) in the the tail of the rope, with a footloop tied in 4-5 ft below. Then, I wrapped myself back into the standing line in my dulfersitz. Getting back up was pretty easy: sit in the dulfersitz, move the knot up the rope, stand up on the footloop, take the slack out of the dulfersitz, sit back, repeat.

If I'd had a bit more rope, I could have tied a waist loop in the tail below the helical and provided a bit more security. There's always something of a risk of falling out of a body rappel, and the step where I took the slack out of the rope, whilst holding myself up on one foot, could have been a bit sketchy. Also, while this worked great in Goldline, I once tried it in some stiff PMI pit rope, and couldn't get the knot to hold at all. So, in those situations, you might have to resort to shoelaces.


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Re: Prusiks

Postby hank moon » Dec 22, 2014 1:34 am

GroundquestMSA wrote:I know it's not efficient.


It could be very efficient for a physically demanding cave with little vertical work. However, I am leery of diaper seats outside of last-resort emergencies due to questionable performance in case of inversion (among other things).

As in "your head a-splode" maybe :)

Go Swiss if you're going with a tied seat. Diaper risks are easily avoided, with minimal increase in weight/bulk, if any.

Note that there are ultra-light commercial harnesses out there, like the Black Diamond Couloir at only 230 g. Wear it only when needed, and durability shouldn't be an issue.

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Re: Prusiks

Postby hank moon » Dec 22, 2014 12:47 pm

GroundquestMSA wrote:Gary Storrick notes that the tail of the Blake's needs a stopper. The climber who showed me the knot says otherwise, and climbed with only a short tail (2-3") and no stopper. Since he has climbed with it for years, I'll take his word. I have been unable to get the tail to pull through while playing with the knot myself, unless I completely neglect to dress it.

The Blake's hitch would be a way to further reduce the bulk of a tiny climbing system, and it seems like a good emergency knot for cavers to know, especially since it works with a single strand and a wide variety of rope diameters. It works great with my 10.5 dynamic on Pit rope and while it gets extremely tight with tiny strands (I used some cotton clothesline), it is easier to break than a prusik.


I also do some recreational tree climbing, where the Blake's is a standard knot. It is best to get into the habit of tying a backup knot. I cannot think of a good reason knot to, unless taking needless risk for minor intellectual satisfaction is the sine qua non of your existence.

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GroundquestMSA wrote:On a related note, I would love to know of a friction hitch that will work with 11mm Pit on 11mm Pit.


Blake's hitch should work with enough wraps, as should Kleimheist (single strand). Prolly no fun, though.
Last edited by hank moon on Dec 22, 2014 1:05 pm, edited 3 times in total.

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Re: Prusiks

Postby hank moon » Dec 22, 2014 12:59 pm

NZcaver wrote:
GroundquestMSA wrote:
NZcaver wrote:Tiblocs are much more efficient, but also much more expensive and a little bulkier than simple hitches.


Have you used a Tibloc enough to gauge its effect on rope after several uses? Rope is a major expense for me and I don't want to tear it up if I can help it.

Short answer - it's also been a while since I last used Tiblocs. They are not quite as plug-and-play as a regular ascender, but I managed to use them without tearing up any rope. I keep hearing people bemoan them, but a caver I know who actually likes Tiblocs and uses them often seems to have no trouble and no adverse wear and tear on caving rope. Check the Petzl website as there's a particular handling technique, which if ignored due to lack of knowledge or if a person is tired may result in some adverse sheath wear.

Know anybody who has some you can try?


I have used them a lot, mainly on 8-9 mm rope, where it's easier to get them into "shred position" than with 11mm rope. It's really no problem to avoid shredding, just takes a little practice and awareness. Muscle memory eventually drops the risk even further. That said, I've had them slip a little due to inattention (carrying on a conversation during demo or practice) but w/o any appreciable damage to the rope.

I think the shred issue is mostly a persistent memory from the Tibloc's early days when folks were inexperienced with them, and trying lots of inappropriate uses.

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Re: Prusiks

Postby GroundquestMSA » Dec 22, 2014 6:04 pm

hank moon wrote: It is best to get into the habit of tying a backup knot. I cannot think of a good reason knot... to

I guess this is a pun. Talk about minor intellectual satisfaction... :tonguecheek:
hank moon wrote:...unless taking needless risk for minor intellectual satisfaction is the sine qua non of your existence.

I don't know what kind of Latin stuff might be in my existence, but we all take needless risks for lots of reasons, many of them of even less value than principled realism. But that wasn't my purpose in mentioning the stopper. Dr. Storrick's explicit note that the Blake's needs a stopper is, I assume, there for a reason. He doesn't claim that a stopper is needed for every single line friction hitch. So I found this difference in understanding of the knot interesting, and worthy of mentioning.
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Re: Prusiks

Postby hank moon » Dec 22, 2014 6:46 pm

hee hee. more of a non-pun.

We do take needless risk. Like caving, for example. But caving provides pleasure. What's the pleasure in not finishing your knot?

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Re: Prusiks

Postby GroundquestMSA » Dec 22, 2014 7:39 pm

hank moon wrote:What's the pleasure in not finishing your knot?


Dunno. Except the pious fulfillment that comes with avoiding the terrible waste of resources...
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Re: Prusiks

Postby hank moon » Dec 23, 2014 2:02 am

GroundquestMSA wrote:
hank moon wrote:What's the pleasure in not finishing your knot?


Dunno. Except the pious fulfillment that comes with avoiding the terrible waste of resources...



Ahhhh...pious fulfillment - is there anything more satisfying? :)

Good answer.

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Re: Prusiks

Postby GroundquestMSA » Mar 15, 2015 11:22 pm

This is what inconsistent employment does to people... society should be more choosy about who is allowed to have cameras.

True to my unfortunate word, I have filmed a brief clip of myself struggling up a bit of rope with the guts and shell of a bit of another rope. This feat is bracketed with several dim minutes of my mumbling about it. See with caution.
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