Cowstails

[NZcaver]

Fuzzy - did you ever find a Petzl Zyper to try?

Almost got one from ebay but the other guy wanted it more than I did

Next time you're over, you're welcome to try mine.

Love the translation of the expe instructions:

The brochure avoids the loop in the lanyard, so congested link belt and wear the skirts in this presentation.

[NZcaver]

Hey NZ did you use the whole enchilada as is or did you hack it up and just use the buckle/plate? The sewn eyes wouldn't have the same shock absorbing qualities as barrell knots so I think I'd prefer the barrel knots, plus they hold your carabiner straight.

It's the whole enchilada - no hacking involved. (I just couldn't bring myself to hack it up, it's so pretty...)

The sewn eyes hold carabiners beautifully - they have clear plastic shrouds that enclose/protect each sewn joint, and also hold the carabiner in place at each end.

I use ~10.5mm rope anyway more because it was convenient and has good abrasion resistance than anything else (around here it's also hard to find someone who will sell you a short length of dynamic rope they all want to sell 50m lengths)

I have some - next time your over...

Is it the current Zyper or have they changed since?

Mine is the original Zyper - the current version is the Zyper Y. It's the same, except one end of the rope is attached to 2 lengths of webbing where you attach carabiners in the ends - "Y" style. There's also now a sewn webbing loop which attaches between you and the Zyper buckle, and a little plastic clip in the other end which reminds you not to clip it into anything important.

Once you get an idea in your head it's hard to get it out isn't it? I ended up with a Troll Allp(older version) after hank advertised them on here, they are a rather neat descender, yet to try it out though. There's something about vertical gear particularly descenders for me that's so "I gotta have one so I can give it a try" anyway I'm

Uh-huh. I have a couple of Allps (2 different older versions) myself. I keep telling myself, Gary Storrick, and anyone else who will listen that I'm really NOT a collector...

[NZcaver]

Could a rock climbing belay plate be substituted for the Zyper? It seems like theres more than enough flavors of those around to suit what anyone could want.

Not the belay plates I know because to stop a fall they need intervention by the belayer a cowstail is used as a clip in and then your able to move both hands away. There are shock absorbers which are metal plates that the rope runs through to absorb some of the energy of the fall and can be bought seperately but most of these are pretty large.

To be worthwhile the plate needs to be pretty small, for more than half the value of these things is thier potential to tidy up and be more compact on my D mailon, that and it should be easier to replace the rope in my cowstails.

Good question, Mike.

Remember FHM, just because you have a belay plate it doesn't mean you have to thread it like it says in the instructions. If you're using the plate as an adjustable and/or shock absorbing link, there may be more effective ways to use it "hands-off". In fact, some years ago I came up with a method for doing just this with an original Sticht Plate (without the wire). I never tested it, nor really even used it in anger (no falls). This is not rocket science, but of course one might want to be a little careful playing with any experimental rope techniques.

[MessedUpMike]

How about somethinmg like this?
http://www.libertymountain.com/catalog. ... t&id=18677

[NZcaver]

A little bulkier and more expensive than a simple knot in the middle of your cowstail... but I suppose it's an option if you really need that shock absorbing factor. I imagine the rope threaded through 6 holes makes it a real pain in the butt to adjust the length.

[hank moon]

A note about rope/brake-plate Via Ferrata shock absorbers:

They are designed for Via Ferrata, not for caving. Keep in mind they have not been tested with wet and/or muddy rope. When brand new, clean, etc. some of these devices do not slip at all until sustaining a load greater than around 4-6 kN, depending on the rope used, conditions, etc. Performance also varies with bodyweight. Please do not make the mistake of thinking that the test data provided with these devices is relevant to caving use.

[fuzzy-hair-man]

A note about rope/brake-plate Via Ferrata shock absorbers:

They are designed for Via Ferrata, not for caving. Keep in mind they have not been tested with wet and/or muddy rope. When brand new, clean, etc. some of these devices do not slip at all until sustaining a load greater than around 4-6 kN, depending on the rope used, conditions, etc. Performance also varies with bodyweight. Please do not make the mistake of thinking that the test data provided with these devices is relevant to caving use.

Thanks Hank,

I'm basically not counting on any shock absorbing behaviour, any shock absorbsion that MIGHT happen is just a bonus. I can't really see how a cowstail with one of these plates can perform worse than a regular knoted cowstail so I don't see that safety is comprimised. (Would you agree?)

To me the value of these plates is in making a neater cowstail attachment to the D maillon, and making it easier to replace and set the lengths of your cowstails. Also by getting rid of the knot and covering the plate with bicycle inner tube or preferably heatshrink I should be able to avoid abrasion where the knot used to be.

[hank moon]

I can't really see how a cowstail with one of these plates can perform worse than a regular knoted cowstail so I don't see that safety is comprimised. (Would you agree?)

I have no data comparing the two, but it's certainly possible that a knotted dynamic rope cowstail would make a better energy absorber than a plate/rope combo due to moisture, mud, swollen or fuzzy rope, etc.

[kmstill]

Has anyone ever heard of the Beal dynadoubleclip.

so, if cleaning up the mallion attachment on a custom cowstail is the goal, any reason that one can't sew their own mid loop like this above? any comments regarding safely sewing rope/terminations on a custom cowtail from those that do a lot of sewing/harness making? critical errors? thread type/size?

NZ- you have any numbers data handy on the double overhand vs butterfly vs 8 for the mallion knot (9-10 mm range dynamic cord)? is the double overhand significantly smaller?

[Scott McCrea]

any reason that one can't sew their own mid loop like this above? any comments regarding safely sewing rope/terminations on a custom cowtail from those that do a lot of sewing/harness making? critical errors? thread type/size?

Do not try this at home. The machine required to sew this pattern, costs more than my truck. The knowledge to properly create a joint like this requires a degree in engineering, maybe even a masters degree, in science. Or at least a lifetime of real world experience. Thread? Don't even go there. Plus, the custom wear protector that keeps the threads under wraps. This is one joint that is best left to the experts. If it is that important for you to have such a thing, you should have no problem paying for it.

[NZcaver]

so, if cleaning up the mallion attachment on a custom cowstail is the goal, any reason that one can't sew their own mid loop like this above? any comments regarding safely sewing rope/terminations on a custom cowtail from those that do a lot of sewing/harness making? critical errors? thread type/size?

I tend to agree with Scott's point on this one, although I'm not so sure about needing an engineering or science degree just to do a little sewing - even if it is for life safety.

Looking at the sewns eyes in my Zyper, I see a bar tack pattern approximately 1.75 inches long by 0.5 inches wide. The thread thickness appears to be sightly less than that used on your average commercial climbing harness. There appears to be roughly about 60 individual strands that make up the bar tack. Of course this particular sewn eye is at the end of rope, not in the middle. I've sewn plenty of my own harnesses and slings in the past (on an industrial machine which is no longer with me), but it's unlikely even I would attempt this on my cowstail.

NZ- you have any numbers data handy on the double overhand vs butterfly vs 8 for the mallion knot (9-10 mm range dynamic cord)? is the double overhand significantly smaller?

Why, of course I do and yes the overhand is significantly smaller. Actually I believe the following test results are predominately with low-stretch rope in the 10-11mm range, but it's a start.

See the current edition of Warild's "Vertical" section on knots here, page 51. The old (Marbach/Rocourt 1980 and Corbis 1984) testing has the overhand loop retaining a mere 50% rope strength, the figure 8 loop 55%, and the alpine butterly is not listed (and was not a recommended knot in earlier editions of Vertical). These older figures should really be taken with a grain of salt nowadays - not because the testing was flawed, but mostly because rope technology has significantly progressed in the quarter-century since then.

Newer testing wisdom (by Long Lyon and Lyon 2001) now also published in Vertical suggests the overhand loop retains 58-68%, the figure 8 loop 66-77%, and the alpine butterfly 61-72%. Of course all this only matters if you're inclined to worry a lot about percentage points. The overhand loop is much smaller than the others, but once tight it can be very difficult to untie. Alpine Caving Techniques (English edition) shows the overhand used as a mid-cowstail knot on page 41, and also shows an alternate "metal blocking plate" used instead on page 42. I'm not sure what this plate is - perhaps there is a proliferation of DIY versions like it out there around Europe? It has a similar configuration to the Zyper device, but with 3 holes instead of 2.

[Tubo Longo]

I completely agree with Hank: please don't - DON'T - think shock absorber (dissipatore in Italian), a device thought and built for use in via ferrata, is of some possible use in a caving cowstail.

Being Italian and having lived most of my life next to the Dolomites, where vie ferrate are very common, I own and use shock absorber in my personal via ferrata set. It requires two long cowstail (both longer that my upper ascender safety loop), made of possibly 10mm dynamic rope. The all system then tied up in a proper fascion to a full body climbing harness.
Shock absorber is meant to slow down a fall in a via ferrata, an event that can easily be of ff2, so to minimize the fall effects on the body.

PPE laws now are quite restricting in Europe and in many case to use a self assembled via ferrata set may invalidate an insurance policy. Most of the European Alpine Clubs now require manufactured via ferrata set to be used in their advanced hiking and/or 1st level climbing classes.

Then, I'm sorry, I don't really get what's so difficult in setting a cowstail's lenght: where lies the need to have some sort of device to adjust the lenght of the cowstail? Personally, in 30 years of vertical caving and rebelays, I have always been well off with a short and a long cowstail. It's just me or do I miss something? Just curious...

[hank moon]

Has anyone ever heard of the Beal dynadoubleclip.

Yes, it appeared earlier in this thread - briefly - but good to see again. Gonna git me one.

any reason that one can't sew their own mid loop like this above?

The machine that makes this join costs in the neighborhood of $30,000 (new) and is a bit more than a simple sewing machine: it's more on the order of a simple robot or "automatically controlled" machine. A jig is required to hold the rope in the correct position for sewing. On some loops, the rope is tensioned in such a way as to "equalize" the sheath tension between the inner and outer parts of the loop to maximize strength.

Short of buying one of these machines, I suppose you could try to do it on a manual machine, but better be a burly one! It (almost) goes without saying that any homemade PPE should be tested to destruction statically, and in the case of cowstails, a drop test would also be in order. Or (not recommended) you could go "trad" and do as others have: sew it up and use it on blind faith or taking a "calculated risk," depending on your capacity for self-delusion.

[fuzzy-hair-man]

On a whim I decided to compare the dynadoubleclip with the results from Lyon's tests of knoted cowstails... (for a comparison of sewn loops to knots)

The results are hard to compare but with fall factor 2 100kg the knotted cowstails are getting 6.33kN (barrel knot) (Lyon test used beal dynamic rope but probably pre-dates the dynadoubleclip but hopefully dynamic rope performance hasn't gone backwards since) 60cm lanyard.

The dynadoubleclip doesn't say what weight thier testing used but they get fall factor 2 falls with 9.5kN force.

In the absence of a weight I'm guessing the Beal testing uses 100kg as this seems reasonably standard for 1 person loads (much larger wouldn't be very informative) although I remember reading (could be wrong) CE single person loads might be 80kg? Lengths 40/75/80 with the same results.

That seems like a fair difference in performance Am I reading the results correctly?

Looking at the Lyon tests again and even Barrel knots and "low stretch rope" gives ff2 loads of 8.81kN same 100kg weight.

Lyon also tested a Petzl Jane dynamic rope cowstail with sewn terminations and recorded results all in excess of 10kN (the limit of thier measuring machine). All this doesn't seem to recomend cowstails with sewn terminations.

If your interested overhand knots give higher loads than barrel and figure eight knots but out perform sewn terminations/loops. (again from the Lyon tests)
The Lyon tests are available from the 2nd link hank posted in the first post for this thread or
http://www.hse.gov.uk/research/crr_pdf/2001/crr01364.pdf

Wow this thread has been alive for a long time!

[NZcaver]

I completely agree with Hank: please don't - DON'T - think shock absorber (dissipatore in Italian), a device thought and built for use in via ferrata, is of some possible use in a caving cowstail.

Buon giorno, Renato! Long time no hear.

Nice to see you back again, and thanks for your input.