"New-style" cows tails – comments/criticism/remarks welcome

[carpet]

If you or anyone else is interested they are welcome to a copy of the thing – it’s an Excel file of about 350kB. In fact there are several files as it proved impossible (for me) to include a big range of traverse line lengths in one file, although you can change mass, cows tail length, type of knots (or no knot at all).

I'd be pretty interested in seeing your data, would you like me to dm you an email address or would you rather share a link to a file sharing service of your choosing?

 

[mikem]

It's very rare for anybody to "properly test" their cowstails, as your mind and body will do almost anything they can to avoid falling ...

& Fall factor theory doesn't apply to cowstails - it is for longer lengths of rope, as the knots do most of the work, rather than the rope core.

Although Via ferrata set ups have snapped cowstails (sliding down a steel cable can result in many more "fall factors" than 2), hence why knotted rope isn't recommended nowadays

 

[pwhole]

I once fell down a cave wall pretty much the length of my long cowstail - not a complete free-fall, but it was definitely a proper fall. And to be honest, it didn't hurt as much as I thought it would, though it did hurt, and I was at the bottom of a Yorkshire pot, so still had to get out, which was uncomfotable in places, but doable. I definitely couldn't get the knot undone afterwards though - a three-turn barrel knot. I'm gl;ad I put three turns in though - I see some knots that would absorb very little shock as they're only two turns and haven't been undone ever.

I've posted this before, but this my 'ideal' set-up - the lengths of all the lanyards (for me) are perfect, and the central loop is always perfectly balanced - I try and keep the knots loose, especially the overhands on the D-ring.

 

[Chocolate fireguard]

I'd be pretty interested in seeing your data, would you like me to dm you an email address or would you rather share a link to a file sharing service of your choosing?

If you dm your email I shall get the file off to you today.

 

[Fulk]

pwhole: In the set-up pictured above I wonder if it would be better if you left a bit more rope in the central section of your cowstails so that you could tie a knot and clip the central krab into the knot?

 

[pwhole]

I did think about that - however, I then thought that tight squeezes with the harness on could be rather painful - or at least more difficult, with another knot right there. I quite like it like this - just feels a bit more flexible, and on traverse lines it's a dream with three points. And I've not lost a krab yet either, amazingly.

 

[Rachel]

I did think about that - however, I then thought that tight squeezes with the harness on could be rather painful - or at least more difficult, with another knot right there. I quite like it like this - just feels a bit more flexible, and on traverse lines it's a dream with three points. And I've not lost a krab yet either, amazingly.

Another advantage I found is that when I've got my long cowstail clipped to my side gear loop, clipping the middle krab and letting the rest dangle means that I don't get my knee caught up in the loop when crawling.

 

[Chocolate fireguard]

Or when stepping over a hole in the floor, as once happened to me.

 

[Tangent_tracker]

I like my short cows tail to be really short, as I find that this helps when crossing a rebelay going down; however, it has the disadvantage that in some situations it is not long enough to reach, say, a traverse line. On such occasions I resort to the somewhat unsatisfactory method of clipping an extra karabiner (or krabs) onto the safety cord . . . not an ideal solution.

So I wonder if the following would work – instead of having a very short cows tail, having a 'normal-length' one but with a second krab tied into an in-line figure-of-eight knot, so I'd have a 'two-in-one' cows tail – see photo.

What do you reckon?

My only real critism (from a non-expert mind) is tie barrel knots round those crabs, or at least a knot that grabs the crabs. The last bit of kit you want to loose is one of those in a fumbly moment with muddy and cold hands!
I also like a short/long cows setup.

 

[Tangent_tracker]

The idea is good, but I would worry that the rope is the only energy absorber and would want at least one decent knot in there.

I have been involved in work to measure the energy absorbed by the different parts of a cows tail (rope and knots).
The work has been done on a static rig rather than a drop rig, but I can't see any reason why the same results aren't applicable in a fall, up to the sort of forces likely to be encountered in a fall onto cows tails. I appreciate that there is not universal agreement on that, but I am quite prepared to argue my case.

The results show that the knots absorb far more energy than the rope.

Applying the results to a 70kg (unyielding) mass falling (FF1) onto a 750mm cows tail, made up of a krab, barrel knot, fig8 knot plus about half a metre of 10mm dynamic rope gives a peak force of about 4.4kN.

The same mass falling onto a 650mm sewn lanyard of the same rope with a krab on the end gives 7.9kN.

The force on a person would be less due to the body also absorbing some energy, but in the second case I think that might be a part of the problem rather than part of the solution!

Did you consider tying a fig8 in the lanyard where it fastens to your maillon in the usual way? There looks to be plenty of rope.

Re the OP, I would be quite happy to use that, although I have used the loop and double knot system for many years.

How often do we find ourselves in a situation that could really deliver that kind of a shock though? The only time I clip into something with no give is generally a P bolt or similar, in which case you are FF1 maximum and usually stood on a floor. Most of the time it's a traverse which would surely absorb a huge amount of shock... I have, on one occasion been FF2, and very aware of it, and hated every second... I suppose in situations of a sudden collapse and being attached to a solid anchor is a good example of a potentiall FF1 with full effect though...