Hi all, back into caving after a 10 year break. Loving it. So, my SRT kit is all fitted with 10mm static rope on all bits. I am obviously replacing all this, but what's the recommended cord diameters? I have a retired 8.5 meter ice climbing rope (that is in good condition) that I am keen to make use of. Is 8.5mm ok for cow tails?

Anyway, what diameters are you guys using?

I would recommend a dynamic 'single' rope (rather than a half or twin rope) for cowstails; they are at risk of surprisingly high fall factors in normal caving. I have 9mm, but they do wear out reasonably quickly; 10mm would last longer.

Thanks. Good point - the 8.5mm is a twin rope.

Personally I use a 9mm dynamic unicore rope, there is a noticeable difference in bulk between the 10mm and 9mm especially at the knot.
8.5mm or even 8mm would work but be a little exciting for my liking.

Don't forget to un-tie and re-tie cowstails knots after every use, in accordance with BCA E&T diktat. You quickly get used to doing it until it becomes automatic, especially after a few thousand times.

welcome back 
Don't go for stretchy footloop with that 8.5mm, you'll be stretching it down rather than pushing yourself up when ascending.  I went for some 5mm dyneema cord to make a footloop and glad I did.

matisok said:

Thanks. Good point - the 8.5mm is a twin rope.

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A bit pedantic, but it's unlikely to be a twin rope. A twin is designed to be used and fallen on as a pair, all clipped through the same gear. It would be labelled with two overlapping circles.

More likely to be a half rope, which is the normal kind of rope used for climbing with two ropes, clipped to alternate gear.

A half is similar to a full rope, just tested with a smaller weight (55kg rather than 80kg). In most circumstances, it will actually take the full load in a fall.

You can buy ropes that are rated as twin, half or full. Also a combination of the three.

I personally have 10mm but the knots are chunky. 9mm unicore sounds a good idea.

If I knew that ice climbing rope was in good condition I would certainly use it for my cows tails.
The fall factor idea is fine for long drops, but for drops of a metre or so the energy absorbed by the knots (and body?) produce a significant reduction in the force over what would happen in a longer drop.
A barrel knot at the krab and a fig8 at the central maillon will absorb several hundred joules, hopefully keeping the load below what would really hurt and meaning that the rope is never really challenged.
I use thin dyneema for the footloop as recommended earlier - I reckon it saves several metres on a 100m pitch - but use 9mm dynamic for the safety. I would happily use the ice climbing rope for that too.

Chocolate fireguard said:

If I knew that ice climbing rope was in good condition I would certainly use it for my cows tails.
The fall factor idea is fine for long drops, but for drops of a metre or so the energy absorbed by the knots (and body?) produce a significant reduction in the force over what would happen in a longer drop.
A barrel knot at the krab and a fig8 at the central maillon will absorb several hundred joules, hopefully keeping the load below what would really hurt and meaning that the rope is never really challenged.
I use thin dyneema for the footloop as recommended earlier - I reckon it saves several metres on a 100m pitch - but use 9mm dynamic for the safety. I would happily use the ice climbing rope for that too.

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I would suggest consider using 9 0r 10mm caving rope (semi static) for the foot loop and safety, tied with bowlines. In an emergency this will give you 2.5m ish of spare rope which you can use to super impose a Z rig hauling system on a pitch WITHOUT having to do a dead lift. Or any other situation that needs a bit of string...
For cow tails I would opt for dynamic single rope at 9 or 10mm

If you are (or your club is) a member of BCRA have a read of Speleology, Issue 12, April 2008, seehttps://bcra.org.uk/pub/speleology/index.html?j=12.  Else pm me.

10mm dynamic rope for cowstais, barrel knotted at the ends and a figure 8 loop to attach to your central maillion, just keep the long end a bit shorter than your full reach. On my hand ascender a short (about the same length as your long cowstail (that way you can use it as a "3rd" anchor)) with one of those Petzel tape footloop (packs away nicely when wrapped around the ascender). Simlples!

I can definitely recommend the 'two knot' system as shown in the article and used on many rope-access harnesses. Although slightly more bulky on the D-ring, each cowstail is independently-knotted, and even better, the short loop inbetween makes rebelays and traverses far easier and therefore less strenuous. if you're smart and use dynamic rope for your hand-ascender/footloop connector, you now have two long, a medium and a short. I have used all four before

Thanks for all the input - brillant. I will definitely play around with my rig. And yes, sorry, the mentioned ice climbing rope is not a twin rope but a half as was rightly pointed out. Important.

Cheers,
Mathias

Cap'n Chris said:

Don't forget to un-tie and re-tie cowstails knots after every use, in accordance with BCA E&T diktat. You quickly get used to doing it until it becomes automatic, especially after a few thousand times.

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Wow. Seriously? That will definitely be something I need to get used to. My old ones had kept the knots the same since I tied them _and_ they were made of static rope. Now that I look at then they are without any dynamic force absorption quality what-so-ever. Bad.

Thanks.

matisok said:

Cap'n Chris said:

Don't forget to un-tie and re-tie cowstails knots after every use, in accordance with BCA E&T diktat. You quickly get used to doing it until it becomes automatic, especially after a few thousand times.

Click to expand...

Wow. Seriously? That will definitely be something I need to get used to. My old ones had kept the knots the same since I tied them _and_ they were made of static rope. Now that I look at then they are without any dynamic force absorption quality what-so-ever. Bad.

Thanks.

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Yep. Tis correct. But if you're caving for fun (rather than work) then you are a grown up and can make your own decision whether to completely ignore it. I'm not allowed to ignore it so over the last few years have un-tied and re-tied multiple thousands of cowstails. I'm quite good at it now.

PS Yikes to the EN1891 cowstails, blimey!

I think the number of people in the UK who actually retie and untie cowstails in the UK is probably only double figures, if not single figures...

Equally, although a small number of people do like the two-knot system 99% of people just use a Fig 8/overhand in the middle and barrel knots/Fig 8s on the crabs (although barrel knots are unambiguously better).

As with all things, the people who do something unusual are much noisier about it than the majority who don't

By the the time I have finished bouncing up and down on my cowstails from a bolt on the garage wall, you will have to cut the knots out of mine.

If you want a lower peak shock load use smaller rope. I use 10mm these days, but I use 8mm dynamic on the top ascender to give it a fighting chance. Shock loading ascenders (ripping rope) is the only mode of failure I am objectively concerned about. Subjectively lots of things scare me, but that is irrational and weak minded of me. Age probably.

I have never heard of an incident involving shock loading of cowtails with dynamic rope. I have heard of people failing to use them or krabs disconnecting. I use the krab on my top ascender as a third cowstail for extended traverses to avoid single point of attachment with a snapgate as far as possible, hence another reason for using dynamic on it.

I use a Petzl Jane because the lengths are perfect for me and I really appreciate the lack of knots for low bulk.  {I do a lot of tight stuff}.

On a test rig they will give nasty shock loads.  Meantime, back in the real world, they are fine.  Use them correctly.

I have fallen on my previous set: a sudden drop from a wide bridge, so straight down, no body friction.  Of course, being on a traverse line between two alpines, and having c4m rope, plus body / harness deformation I felt no shock at all.

Test rigs give a graded list when comparing systems, but the figures are pretty meaningless.  Loosely knotted barrel knots will always give lower shock loads than sewn 9mm dynamic, which will be lower than sewn tape [which the French seem to use without much issue].

Know where you are on the continuum and act accordingly. 

Bulky knots are far more of concern to me.  I have had to be assisted a number of times in the early days when I was following conventional wisdom and using them.  Getting kit stuck in a crawl could be quite serious, especially when solo caving.  Compact, light and as snag free as possible is the way for me.

I have only ever seen one person loosen his barrel knots.  And I thought they were dangerously loose!

I crack the knots on my cowstails every trip mainly because Bob and he knows his onions.

Ian Ball said:

I crack the knots on my cowstails every trip mainly because Bob and he knows his onions.

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Well done. Bob and the E&T Team have reason to hope their efforts aren't a complete waste after all - an example of something BCA do for their membership but probably wonder why they bother, lol.