Cowstails

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Cowstails

Postby hank moon » Oct 4, 2005 11:32 am

There has been much discussion over cowstails on previous incarnations of this forum. Below are links to some test data performed on behalf of the HSE (UK equivalent of OSHA). The first link goes to a pdf containing just the relevant test data/summary/etc. and the second one to a page where the full report may be downloaded. The report suggests that cowstails made from knotted dynamic rope are the best choice. Check it out and decide for yourself.

http://www.hse.gov.uk/research/crr_htm/2001/crr01364.htm
Last edited by hank moon on Feb 9, 2011 11:03 am, edited 1 time in total.

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Postby David_Campen » Oct 4, 2005 12:47 pm

What is a Petzl "Jane"? Is it anything like a "Spelegyca"?
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Postby hank moon » Oct 4, 2005 1:02 pm

David_Campen wrote:What is a Petzl "Jane"? Is it anything like a "Spelegyca"?


The JANE is a short length of dynamic rope with sewn loops on the ends. Check it out here:

http://www.petzl.com/petzl/ProProduits?&Produit=310

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Postby filox1 » Oct 4, 2005 1:09 pm

Very interesting, learned one or two things....

It is obvious that the best material is dynamic rope, How about the differences in diameter of the dynamic rope for the cows tail, it seems that they used 11mm for the test, I use 9mm dynamic rope for mine

Any taught

Thanks Hank
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Postby angus » Oct 6, 2005 10:12 am

Excellent report - thanks Hank.

Probaby should be on the other post but the Petzl Stop did not come out very well in their tests! Shame they didn't test racks.

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Postby NZcaver » Oct 6, 2005 5:20 pm

Hank - thanks for posting that information! :kewl:

It makes interesting reading. Being aimed at the industrial audience, I can see why they used 11mm rope for their tests. From a caving perspective, it would be good to see how 10, 9, and even 8mm dynamic and static ropes (and accessory cords) hold up. It would also be nice to see how the butterfly knot does, as that seems to be a popular choice in the US for a mid-cowstail knot.

Coincidentally, I have just replaced my old cowtails. I was considering using an overhand loop as my new mid knot, after reading this about cowstails in Alpine Caving Techniques (the French caving bible): "this loop can be made from a simple overhand knot"..."we do not recommend using a figure 8 knot here - it is bulkier, will wear more quickly, and takes longer to tighten down to its final size". [1st English edition from 3rd French edition, page 41.]

After reading about the impact forces experienced with an overhand loop, now I'm not so sure. It's a small margin, but every bit of stretch helps to reduce the impact of a fall on other parts of the system - like the anchors, the ascender (if used), the human body, and so forth. I laugh at people with their static cowstails, who say "with such a short length, it doesn't make any difference whether I use static or dynamic..." :roll:

Personally I now use a piece of 9.7mm PMI dynamic rope for my cowstails, with both sides cut to the same (long) length. This is because one side is normally clipped to my handled ascender (Frog system), while the other side is adjustable in length. I use a Kong Slyde as my adjustment - the cowstail is threaded through the Slyde, and I just clip in to an anchor/traverse/person and pull the slack out - all with one hand.

When "overloaded", the Slyde also has a slight slip-and-grab effect which should help to absorb some shock in the event of a fall (unless the cowstail is already adjusted to its maximum length). Incidentally, the Slyde is specifically designed for use with 9mm rope - but I found that my old "soft" 9mm dynamic cowstail (not PMI rope) would bind up and lock solid in the Slyde if I hung on it for a while. It was a pain to unthread, and so I traded up to 9.7mm rope. So far it seems to work OK.

I already use a barrel knot on the fixed end of my cowstail, so now do I tie an overhand, a figure 8, or a butterfly in the middle...? :?
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Postby chh » Oct 7, 2005 10:45 am

Good info in the report. I too am wondering about different diameters of dynamic rope as I use thinner cord as well. However, I don't find the figure 8 knot in the middle cumbersome in the smaller diameters. I imagine it would be with 11mm.

NZ caver, I'd never seen a Kong Slyde before. Right now my cowstails are fixed (knotted) for my height. I was looking for a way to make one of them adjustable with the least amount of hardware possible. Thus far I've experimented with a smaller prussik cord cloved into the center knot. But I worry about the implications of that smaller (and static) line, should the worst case scenario be realized and I take a factored fall on my gear. From what I gather the Slyde is a small plate which acts with a simple friction lock. Can you rig it so that it holds in both directions, while maintaining its adjustability?

It seems as though in your set up you have one fixed length cowstail (to your top ascender) and one variable length equipped with the Slyde. My question is how you've rigged the slide. Does it have a free end that adjusts the length of the cowstail through the Slyde when it isn't weighted, or does the Slyde produce a loop in the cowstail that merely shortens or lengthens it depending on the size of the loop? If you have a "end" coming out of the Slyde, do you find that it gets in the way? Could you attach a locker to this free end and essentially end up with one fixed lenth cowstail (to ascender), and two lockers on a piece of cord that would be adjustable in relation to each other through the Slyde?

Sorry if I'm being thick. Maybe I'd be able to figure it out if I had one in front of me.....and had had a cup of coffee this morning :)

cave softly,

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Your words of caution are no match for my disaster style!
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Postby filox1 » Oct 7, 2005 2:54 pm

I already use a barrel knot on the fixed end of my cowstail, so now do I tie an overhand, a figure 8, or a butterfly in the middle...?


I use a butterfly in the middle of mine and never had any issues, seems to work very well.

Haven't test it on a factor 2 fall tough.... :wink:
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Postby NZcaver » Oct 7, 2005 3:46 pm

Hi chh - here's Kong's info about the Slyde (scroll to the bottom of the page) - http://www.kong.it/doc408.htm

I'm familiar with the Prusik hitch cowstail you mentioned. That should also have a slight slip-and-grab effect when overloaded, but this depends greatly on the ratio of rope-to-cord diameter, and the type of cord used. Remember - the thinner cord you're using for your Prusik is a loop, so the strength of that cord is theoretically doubled (approximately). It *should* be fine in the event of a fall, assuming it's 6mm or larger.

Back to the Slyde. When you rig it normally (the official way) it only holds in one direction - like a pull-tight buckle on a pack strap. You pull on the free end when the cowstail is unweighted, and it shortens the length. I've used my Slyde for a couple of years now, and the free end (with stopper knot) has never got in the way. I wouldn't suggest rigging a carabiner on the free end, because when you clip in and apply weight the rope will just slide through the Slyde (no pun intended!) :wink:

I was going to upload a couple of pictures of my cowstail for you, but I guess I can't unless they're already posted on a website. :x (I sent you a PM instead - check your inbox on this forum.)

And I saved the best news for last... I was talking to Alex at IMO recently, and he informed me that no-one in the US stocks the Slyde any more. Kong apparently still makes it, so you might be able to track one down from overseas. It's less weight to ship than most carabiners, and mine cost me less than $10 (US) back when IMO did stock them.

Good luck... :D
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Postby Bobatnathrop » Oct 24, 2005 2:11 pm

Sorry to up a dead thread but I had a quick question.I use 7.5mm accessory cord.Would this be static or dynamic? Is that too small?
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Postby ian mckenzie » Oct 24, 2005 2:29 pm

1. Static.

2. Depends on who you talk to. My rule-of-thumb is that cowstails should be no smaller than what you'd comfortably prussik on. But some won't go less than 11mm, while others will go as small as possible. I use 9mm dynamic.
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Postby ljthawk » Oct 24, 2005 4:59 pm

I still haven't seen any tests that take into account the dynamics of the harness movement & human body movement (arms & body flexing / swinging) with short falls. Solid mass may be a safe assumption for long falls such as when rock climbing or aid climbing, but I'm not 100% convinced the rigid mass is appropriate for testing short distance falls where other factors add compliance and dynamics to the system. Unlike when analyzing long falls, dynamics in the short lanyard may approach negligible when compared to the dynamics of the human body / harness. I don't know, but think it is an interesting thing to consider.

Regardless, still some good information in the above report.

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Postby Scott McCrea » Oct 24, 2005 8:32 pm

Here is another article that relates to cowstails and lanyards. This is an article that originally appeared in Rock & Ice magazine in Oct 2004. It's written for rock climbers, but there is a lot that can relate to cavers. It is posted with permission from the author. LINK
:kewl:
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Postby Dwight Livingston » Oct 25, 2005 8:57 am

Scott McCrea wrote:Here is another article that relates to cowstails and lanyards. This is an article that originally appeared in Rock & Ice magazine in Oct 2004. It's written for rock climbers, but there is a lot that can relate to cavers. It is posted with permission from the author. LINK
:kewl:


Scott

That's a very good article.

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Postby Bobatnathrop » Oct 25, 2005 2:02 pm

Meh, I guess since I have prusiks out of 7mm I will stick with 7mm for now.
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