7mm cordelette for making cows tail?

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Re: 7mm cordelette for making cows tail?

Postby PeterFJohnson » May 11, 2013 7:32 pm

One more for those who want all the qualitative info they can get. Feel free to skip it if long documents are not your thing - it doesn't add much to the discussion that hasn't already been said:

https://docs.google.com/file/d/0B1p0Gvw ... sp=sharing

I won't beat the horse anymore than I have to but I did think it was worth pointing out one thing and the damn ungulate had it coming. That thing is that fall factors with cowstails can be much higher than you would initially suspect. The reason for this is that the connectors make up such a large % of the total length of your cowstail. If you were using the aforementioned 18 inch cowstail you might have 5 inches of carabiners/maillons in your system. In such a case over 20% of your system is completely static. This may not seem like much, but if you were to climb as high above an anchor as you could and take a fall it would probably exceed FF2. This is a large reason why knots provide so much of the energy absorbtion in the system - the rope is a far smaller % of the entire system.

Hopefully this paragraph was so painful to read you won't even think about caving ever again Andy. I am with Stan and Derek - more cave for us.

(And don't get me started on SPRAT and lanyards...)
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Re: 7mm cordelette for making cows tail?

Postby ian mckenzie » May 11, 2013 8:01 pm

I should think the opposite - because there is so much rope used up in knots, plus the harness, connectors and other slack, it'd be impossible to even achieve FF2. I understand your point, though, that chains can generate higher than FF2, but most cowstails don't have more than one biner in a row so there is no chain effect.
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Re: 7mm cordelette for making cows tail?

Postby Anonymous_Coward » May 11, 2013 11:37 pm

PeterFJohnson wrote:Hopefully this paragraph was so painful to read you won't even think about caving ever again Andy. I am with Stan and Derek - more cave for us.


Actually, I've decided to do one more cave trip. It's kind of a large one, so I am starting to shop for the trip now. Tomorrow I am making a run down to Spectra Depot. Need me to pick anything up for you?
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Re: 7mm cordelette for making cows tail?

Postby PeterFJohnson » May 12, 2013 8:56 am

ian mckenzie wrote:I should think the opposite - because there is so much rope used up in knots, plus the harness, connectors and other slack, it'd be impossible to even achieve FF2. I understand your point, though, that chains can generate higher than FF2, but most cowstails don't have more than one biner in a row so there is no chain effect.


I am not talking about chaining together two biners. In this case the issue is that a greater % of the total length of the system is made up by static connectors.

If you have a 19" lanyard with a maillon on one end and a biner on the other you now have 24" of total length. If you were to then climb 24" above your last point of protection and fall, you would fall 48" onto 19" of rope. I agree that the knots etc. would absorb more than a corresponding length of dynamic rope - this seems to be what testing shows. But using the common definition of Fall Factor, 19/48 is greater than 2.

Again, whether or not this corresponds to impact force can be debated. As Derek mentioned the reports linked to so far don't seem to isolate the shock absorbtion of knots other than to show in a general sense that knots are better than sewn connections. But the reports allude to the fact that Fall Factors are not the best way to judge impact force when dealing with short lengths of rope. I also agree that with the harness and dynamic nature of the human body you will probably encounter lower impact forces than what is shown in testing where steel plates or some other static load is used - other testing has provided evidence for this. But people don't normally account for harness/body when calculating fall factors.

The point is, fall factor aside, impact forces can be suprisingly high with cowstails. I certainly would not want to subject myself to the 7-10 kN that some of those tests show for commonly used cowstails(steel plate testing issue duly noted). So whether or not you use static or dynamic rope it would seem that the best bet is to keep your point of attachment as high as possible.

Anonymous_Coward wrote:Actually, I've decided to do one more cave trip. It's kind of a large one, so I am starting to shop for the trip now. Tomorrow I am making a run down to Spectra Depot. Need me to pick anything up for you?


Could you pick any Hitler Spectra up for me Andy? I need to use it to attach my six extra QAS that I use in my unorthodox high attachment vertical system I wear while caving without a helmet. Also, I think three sources of light is ridiculous and manilla rope suits me just fine. Backsights are for ninnies who can't read instruments(Did I miss any hot topics?).

Wait, you have a Spectra depot in Utah?
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Re: 7mm cordelette for making cows tail?

Postby Stan Allison » May 12, 2013 9:18 am

Actually, I've decided to do one more cave trip. It's kind of a large one, so I am starting to shop for the trip now. Tomorrow I am making a run down to Spectra Depot. Need me to pick anything up for you?

Hey Andy - I think that you are preparing for the same trip that I am. Thanks for the offer of picking up some stuff for me at Spectra Depot, but after carefully reading all of the above posts, I've decided to stop using my 9mm dynamic cowstails with barrel knots on the carabiners and an overhand knot on the half-moon maillon. I'm switching to a chain of carabiners which will give me a lot of flexibility at each rebelay in the length of my cowstail. I will just clip whichever carabiner in the chain is the most appropriate length into the anchor. I'm certain that these will be much safer since aluminum is obviously stronger than nylon! :tonguecheek:

Pete - I agree that it is important to not put oneself into a situation where a high FF could be placed on a cowstail regardless of whether you are using a chain of carabiners or a dynamic cowstail. The report that you posted was pretty interesting. It's conclusion was that knotted dynamic rope cowstails worked best, knotted static was second best, sewn dynamic was third best and 26mm tape was the worst choice and broke in their testing. Back to the original post, I suspect that 7mm spectra cord cowstails would also probably break under the above testing. I intend to use Andy as a "crash-test dummy" on our upcoming trip and see if I can put him through some FF8 testing on his shiny new spectra cowstails! :banana_yay:
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Re: 7mm cordelette for making cows tail?

Postby Stridergdm » May 12, 2013 2:53 pm

Stan Allison wrote: I intend to use Andy as a "crash-test dummy" on our upcoming trip and see if I can put him through some FF8 testing on his shiny new spectra cowstails! :banana_yay:


Just remember to pack out what you bring in. No matter how many trips it takes. :woohoo:
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Re: 7mm cordelette for making cows tail?

Postby Wormster » May 12, 2013 5:23 pm

NSFW ALERT!!!

[spoiler]http://www.youtube.com/watch?v=kBvCPTK1MmY[/spolier]
Madam in the morning I will be sober, but you will still be ugly.
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Re: 7mm cordelette for making cows tail?

Postby Stan Allison » May 12, 2013 5:39 pm

Excellent Solution Wormster! Rather than carrying our crash test dummy's body out, we'll chop it into six pieces and bring some pigs into the cave. We could have a little bit of trouble clearing the pigs with the cave specialist that manages the cave - he's a bit uptight about pigs in caves and he and I don't get along so well. :tonguecheek: But perhaps we could put lipstick on the pigs so that the cave specialist thinks that they are Sarah Palin and not pigs!!! :big grin:
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Re: 7mm cordelette for making cows tail?

Postby Wormster » May 12, 2013 6:10 pm

Nah mate half a dozen dripping tackle bags, and off down the hill to the waiting pigfarm!

simples!
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Re: 7mm cordelette for making cows tail?

Postby ian mckenzie » May 13, 2013 6:12 pm

PeterFJohnson wrote:The point is, fall factor aside, impact forces can be suprisingly high with cowstails. I certainly would not want to subject myself to the 7-10 kN that some of those tests show for commonly used cowstails(steel plate testing issue duly noted).

Thanks for that clarification, good points duly noted.

It has been pointed out previously (somewhere, here) that the only way to approach a theoretical FF2 with cowstails is to use them improperly (i.e. to protect a short leader fall, rather than for rebelay changeovers and other mundane usages).
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