7mm cordelette for making cows tail?

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7mm cordelette for making cows tail?

Postby abner » May 5, 2013 9:41 am

I've only used thicker rope in the past for cows tails and have been reading about others using dynamic rope... What are the potential drawbacks (if any) of using 7mm cordelette? I have some extra (new) line lying around and wonder whether to use it.
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Re: 7mm cordelette for making cows tail?

Postby Scott McCrea » May 5, 2013 10:42 am

Generally, cordelettes are not dynamic. Also, the thinner the diameter, the thinner (less durable) the sheath is. And, the thinner the cord, the easier it is too cut.

So, keeping all this in mind, taking into account your caving style and how hard you are on gear, it could be used. But, I'd keep and close eye on it and replace it quickly if there any signs of wear.

Of couse, the important thing is that you feel comfortable and have trust in your gear.
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Re: 7mm cordelette for making cows tail?

Postby Extremeophile » May 6, 2013 9:49 am

The main drawback is that it may not survive a short fall ... and you might not survive failure of your cowstail. Use 9-11 mm dynamic rope, as is standard practice. 10 feet of 10 mm dynamic rope is only ~$10.
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Re: 7mm cordelette for making cows tail?

Postby Wormster » May 7, 2013 5:50 am

7 mil for cowstails, YEAH only if you have a deathwish!!

Stick to a nice length of 10 mil DYNAMIC rope, it'll save you in a fall factor situation.

Anything else is just ASKING for the rapid presentation of a DARWIN AWARD!!
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Re: 7mm cordelette for making cows tail?

Postby LukeM » May 7, 2013 7:30 am

Anything else? What about 9 or 11 mm dynamic rope? All valid options depending on your preferences. Pretty much anything reasonably abrasion resistant and able to withstand a body-weight factor 2 fall without causing your spleen to rupture. (dynamic)
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Re: 7mm cordelette for making cows tail?

Postby Scott McCrea » May 7, 2013 7:43 am

So, just curious. Does anyone know of a report or even a rumor of a cowstail failing as a result of a fall? I can't recall any.
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Re: 7mm cordelette for making cows tail?

Postby SDcaver » May 7, 2013 9:14 am

I would agree that 7mm is probably a bit small and I personally use 9mm cord (non-dynamic). I do find it interesting that folks commonly use 9mm or even 8mm as their main line, but are saying 7mm is too small for a cowstail. And for those who blindly believe that their dynamic cowstail is going to save them during a "fall", I hate to tell you that 1 or 1.5 ft of dynamic rope is not doing a damn thing. Please show me the bodies that prove me wrong. And what situations are you putting yourself in during normal caving SRT that you are taking a fall of 1 to 2 FF?
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Re: 7mm cordelette for making cows tail?

Postby Extremeophile » May 7, 2013 9:58 am

SDcaver wrote:I would agree that 7mm is probably a bit small and I personally use 9mm cord (non-dynamic). I do find it interesting that folks commonly use 9mm or even 8mm as their main line, but are saying 7mm is too small for a cowstail. And for those who blindly believe that their dynamic cowstail is going to save them during a "fall", I hate to tell you that 1 or 1.5 ft of dynamic rope is not doing a damn thing. Please show me the bodies that prove me wrong.

I'm confused by what sounds to me like contradictory arguments. Perhaps you're saying that cowstails should only ever be expected to work as a static bodyweight support device, and not as fall protection? If you're wrong that dynamic cowstails don't work, then of course there would be no bodies ... correct?

And what situations are you putting yourself in during normal caving SRT that you are taking a fall of 1 to 2 FF?

For "normal" vertical SRT there is generally no or extremely limited fall potential. The biggest risk of shock loading a cowstail for me personally has been on traverses (e.g. the Rift in Lechuguilla). If I were to lose my footing during a traverse then there is some potential for a significant fall factor. I did in fact have a short, ~2 foot, fall while rigging a short traverse recently when my foot slipped off while stemming. The dynamic cowstail held just fine. In this particular fall there was a bit of a swing so I'm sure a static cowstail would have also held, though there may have been a slightly greater impact force.
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Re: 7mm cordelette for making cows tail?

Postby Scott McCrea » May 7, 2013 10:24 am

Cowstails, QAS's and most caving techniques are for fall prevention. If fall protection is needed, like for dome climbing, most use climbing gear.

The only way to get close to a FF2 fall on a cowstail is to climb above an over hung bolt. In a traverse, there would be too much other rope, knots, anchors, etc to add up to much of a FF.
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Re: 7mm cordelette for making cows tail?

Postby SDcaver » May 7, 2013 10:40 am

I am not saying that dynamic cowstails won't work. I am simply saying that they do not need to be dynamic. As Scott said- cowstails are fall prevention, not fall protection. On a traverse, the movement and slack within the traverse rope is going to absorb much more of the fall force than your cowstail.
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Re: 7mm cordelette for making cows tail?

Postby Extremeophile » May 7, 2013 11:13 am

SDcaver wrote: cowstails are fall prevention, not fall protection.

I guess I would interpret the difference in the following way: a cowstail as fall prevention means it's only ever holding body weight in a static capacity, whereas fall protection means it's clipped into something with some slack as a backup in case of a failure (climbing fall, bolt failure, mis-threaded descender, etc.). I use my cowstails for both purposes, and since fall protection is one of those purposes I use dynamic rope.

If the cowstail is being used for fall protection I'd rather not try and convince myself that the FF is likely to be low enough that it's okay to use static rope or webbing. Even if the FF is always less than 0.5, why wouldn't one choose dynamic for this purpose.
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Re: 7mm cordelette for making cows tail?

Postby Carl Amundson » May 7, 2013 11:17 am

As Scott stated, cowstails are for fall prevention.
With the project caving I do, I regularly negotiate a lot rebelays. I never liked the stretch and thickness of dynamic cowstails.
A couple of years ago I move to 8.5mm static rope (Petzl Vector) for my cowstails and really like them.
I use a standard tied cowstails, with a long & short tails and non-locking biners on the ends.
I use barrel knots at the biners and a figure 9 knot to attach it to my D-link.
The Petzl Vector is very abrasion resistant, using a 32 carrier sheath.
It's cheep, easy and does not add bulk to my system.

For those that have not seen this, here is a very nice document about cowstail testing.
They tested sewn and tied cowstails (with various knots). It's a good read.
http://www.caves.org/section/vertical/nh/53/lanyard_tests_v6.pdf
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Re: 7mm cordelette for making cows tail?

Postby Anonymous_Coward » May 7, 2013 12:21 pm

junkman wrote:As Scott stated, cowstails are for fall prevention.


...except for when they are used for fall protection.
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Re: 7mm cordelette for making cows tail?

Postby SDcaver » May 7, 2013 12:51 pm

Thanks for posting the link Junkman! You beat me to it. This paragraph from their conclusion sums up my thoughts- (bold is added my me)

"One of the lessons from this series of tests is that the theory behind Fall Factors inadequately
explains how shock loads are absorbed by Cow' Tails. In particular it is the knots that absorb the
greater part of the energy from a fall
and in various identical set-ups, it has been demonstrated that
the shock loads are inversely proportional to the fall factors (see p. 3213). Despite this we should
continue to teach that cavers should not position themselves above their anchor point when using
Cow's tails; fortunately this is a situation which is quite easy to identify. The tests carried out in less
favourable conditions gave shock loads well in excess of those that can be sustained by the human
body. Tests also showed that heavily used Cow's tails can break on the first fall."

If you truely want fall protection then use a dynamic rope as your main line. If you rock climb, would you climb using a static rope with only 12 inches of dynamic at the end? Dynamic rope is designed to stretch over length, and 10-14 inches is not much length (well, depends on what we are talking about :big grin: )

Also I find it interesting that Petzl makes a sewn static cowstail, which preforms the worst in all tests. Yet, where are the lawsuits involving injuries or worse due to their correct use?
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Re: 7mm cordelette for making cows tail?

Postby Extremeophile » May 7, 2013 2:29 pm

After scanning through this report it doesn't appear that static rope cowstails were tested ... all of the knotted cowstails were various types of dynamic rope. I think this supports my earlier claim that the use of dynamic rope for cowstails is "standard practice".

SDcaver wrote:"One of the lessons from this series of tests is that the theory behind Fall Factors inadequately
explains how shock loads are absorbed by Cow' Tails. In particular it is the knots that absorb the
greater part of the energy from a fall
and in various identical set-ups, it has been demonstrated that
the shock loads are inversely proportional to the fall factors (see p. 3213).

I believe the second sentence is a mistake. The data they collected clearly shows a direct, not inverse, relationship between shock load and fall factor. I'm also not sure about the validity of the first sentence. They do demonstrate that the use of knots reduces shock load over sewn terminations, but I don't see any data that shows how much of the impact force is absorbed by the rope vs. the knots. Perhaps if they measured the shock load using a steel cable then we could make a better comparison.

"Despite this we should continue to teach that cavers should not position themselves above their anchor point when using
Cow's tails; fortunately this is a situation which is quite easy to identify.

Hopefully the general idea of minimizing fall factor exposure is well understood by both cavers and climbers. Perhaps it can generally be stated that reducing your potential fall factor, using knotted rather than sewn terminations, and using dynamic rather than static rope are all strategies for reducing shock load forces in the event of a fall. In the example of the Rift in Lechuguilla it is common that the D maillon is above the rope on many parts of the traverse. Ideally you should always be below your anchor, but in practice there are sometimes exceptions.

Dynamic rope is designed to stretch over length, and 10-14 inches is not much length (well, depends on what we are talking about :big grin: )

My cowstails are a bit longer than that. Still, cowstails aren't very long, but then the potential fall distances aren't very great either. It's all relative. I trust 40' of dynamic rope to catch a 20' leader fall just the same as I trust a 2' dynamic cowstail to catch a 1' fall in a cave.

Also I find it interesting that Petzl makes a sewn static cowstail, which preforms the worst in all tests. Yet, where are the lawsuits involving injuries or worse due to their correct use?

I argue above that I use my cowstails for fall protection, and I think a great many other cavers do the same, but I suspect cowstails are very rarely called upon to catch a fall, and when they do it's probably a very low fall factor. I've been ice climbing for 16 years and never taken a leader fall. In theory I could have done all that climbing with a static lead rope, or no rope at all, and the results would have been the same. I'm not sure that's evidence that static ropes are safe for leading ice.
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