For a while Bob Mehew has been advocating that we should all relax our cowstail knots between trips. I have been meaning to discuss this with him for a while, because I have concerns about it. I apologise to Bob for posting this here rather than talking to him first, but I think it is probably worth a "public" debate.

Imagine this: I've just arrived at the first pitch underground having been a good little caver and relaxed my barrel knots after my previous trip. I clip my cowstails to the traverse line and soon find the footholds disappearing, so I gently lower myself onto my short cowstail. Unfortunately the barrel knot was not properly tightened - because I'd loosened it as per instructions - so it came undone and I am now falling onto my long cowstail (assuming it is also connected), or to the base of the pitch if the long cowstail was not connected.

I think I understand Bob's rationale ... a tight knot absorbs less shock, so the rope (or more likely the caver!) will be more likely to break following a fall. However, in my view, the advice fails to take account of the fact that barrel knots in particular need to be body-weight tight against the krab to stay done up. On any normal trip cowstails probably only have about 1Kn of force on them anyway (i.e. body weight), and I can't imagine that this is going to have much of an impact on the peak shock loading in a fall. Of course, there is no benefit in having loosened them between trips from the point at which you have hung on your cowstail on the next trip (which is often pretty much the 2nd anchor of an SRT trip).

Any thoughts?

Indeed; I have had very similar thoughts but still have a high respect for expert studies and consideration.

My main gripe with the "loosen after every trip" advice is that I'd be spending a LOT of time in the course of a month doing this (I don't begrudge the time if the danger/benefit is significant! The practice-makes-perfect result of which would be to always be able to tie a barrel knot super-fast (win!) but a secondary result would be to do away with traditional cowstails completely (due to the ball-ache/hassle of untieing cranked-up knots) and either purchase yet more spelegycas (despite their heinous shock load characteristics, and expense) or make up my own dynamic loops for use as cowstails which wouldn't have barrel knots or fig-8s and thereby do away with the problem altogether.

New cowstails invention pretty much sorted now. Thanks for the motivation!

I did use to loosen the barrel knots after every trip and then stuck a bit of tape on the rope where the short end of the knot should come as a reminder to check my knots were sound.

Once the tape wore off I stopped bothering and replacing them every year I think makes it not a big issue on the amount of caving I do.

Every year? I wear mine out in about 4 months.

I had heard about loosing them after every trip but having had the knots come undone before (thankfully I actually checked before trusting my life to them) then I would rather not do that. Infact I have gone to the extra length of using cable ties to ensure they don't come undone, as well as my hand jammer. I did this after getting off a pitch head clipping into the traverse line forgetting my hand jammer was still attached and moved away successfully, which I should not have been able to do, realising of course that my hand jammer was no longer attached to me as the knot had untied it self while I was prussicking (I checked it at the bottom and it was fine)!

So I tie the lengths to my liking, do em up as tight as possible by hanging off of them and cable tie the lot. No issues since that approach.

Funnily enough I was fingering my 'tails earlier today pondering the same question and decided not to loosen them. I am fully aware of the issue and advice.

Mine are tied in the middle with an overhand knot which is rock solid so maybe a compromise in loosening this might be a possibility? It is definitely advantageous to have the barrel knots snug.

I reckon that awareness of the fall factor issue, and a careful caving style in ensuring that I don't get into FF2 situations onto Cowstails contribute more to safety than loosening knots, but I'm open to ideas.

Surely the solution, if you wish to slacken a knot, is to re-tie it and seat it as carefully you did when you initially made the cowstail? 

And leave a decent tail so when loaded it doesn't pull into the knot...

Chris - some of your points from the original thread:

>>>First of all, cowstails are dynamic rope so a fall factor of 2 should be easily absorbed, whether or not the knots are recent, loosely tied etc.. Is this correct?

It will be absorbed (as in the rope won't break), however the impact force is reduced by the extension of the rope. Cowstails are less than 1m so this is not much extension so the impact force transmitted to the body can still be enough to damage your pelvis or internal organs. Hence knots with a little "give" in them help further absorbency - every little helps!

>>>Secondly, if we want to minimise the shock load, could we not encourage the adoption of dynamic loops, instead of 1:1 rope, to increase the shock absorbency (admittedly this is bulkier but narrower diameter rope would improve the situation)?

A loop is in effect 2 pieces of dynamic rope side by side, which actually doubles the impact force (the extension on each rope is halved).

>>>Thirdly, presumably it is standard practice to clip cowstails into rope loops instead of anchors, to increase the absorbency of any potential shock load?

It does increase the shock absorbency, but consideration needs to be given to whether you fall further, incurring more injuries by hitting things as you fall (e.g. if you fell when clipped into a slack traverse line). The short cowstail clip on descending rebelays is better into the anchor or maillon for ease of removal (loaded rope loops "pinch" the cowstail krab). Plus shock absorbency on the short cowstail length (if it is actually short) is negligible.

>>>Finally, how many people actually fall onto their cowstails? (I never have. Is it common?)

Slightly spurious argument - How many people have had a crash where the airbag has been needed in their car? doesn't stop them paying for an airbag.
you make a decision based on the practicability of relaxing the knots against the severity and probability of the risk of falling.

cavermark said:

Slightly spurious argument - How many people have had a crash where the airbag has been needed in their car? doesn't stop them paying for an airbag.
you make a decision based on the practicability of relaxing the knots against the severity and probability of the risk of falling.

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Well done for spotting the skewed logic; however, "making a decision based on the practicability of relaxing the knots against the severity and probability of the risk of falling" is what I alluded to: e.g. if, say, 5 cavers have a combined logged total of 5,000 SRT trips and only one of them has ever fallen (and sustained no injury) onto their un-loosened cowstail, it seems to me that loosening and re-tieing cowstails 5,000 times is an impractical workload when balanced against the severity and probability of the risks attendant.

On a trip through yordas I had the misfortune to fall on my cowstails. 10mm dynamic rope, barrel knots at the carabiners and an overhand on the harness maillon. All the knots were hand tightened but not previously body-weighted. With hindsight I realise the cowstails were already slightly too long. As I hung in my harness (unable to progress/retreat/regain the ledge) I had plenty of time to examine how much *longer* the tails had become as the knots tightened under my bodyweight. The long cowstail in particular had seemed to be a reasonable length before being properly weighted, was now out of reach.

Lesson learned. I still relax my cowstails to hand tight but make sure that they are tied a good deal shorter than seems practical at the time.

A bit off topic  but my cowstails are over long and I've never really understood why I should be able to reach the crab on the long cowstail when it is loaded. If it's loaded you can't unclip it. If it's not loaded you are presumably able to climb up and unclip.

What am I missing?

If it's a bit on the long side you may need to prusik up it to get back to a traverse line (if you're free-hanging) whereas a long cowstail with the karabiner within reach means you'd be able to grab the traverse line with your hands to more easily effect your recovery from an exciting position.

Thing is that, although I'm not particularly short, having cowtails of the recommended length turns a lot of  rebelays at ledges into hanging rebelays and makes traverses much harder especially if rigged tightly (there seems to be a rule that bolts may only be placed by people over 6 foot tall).

Like you indicated, if the worst happens I would have to put my hand jammer on my cowstail and step up to get to whatever the cowstail is clipped to. Doesn't seem like a biggy really.

If its too long and not loaded. how are you going to reach the carabiner to unclip it ?

TheBitterEnd said:

(there seems to be a rule that bolts may only be placed by people over 6 foot tall).

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Have you not met my mate Les then....

Cave_Troll said:

If its too long and not loaded. how are you going to reach the carabiner to unclip it ?

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It's not THAT long. unloaded there is little slack in it at arms length and given that it is most likely to be out of reach while traversing/rigging I can lean over and reach it.

However if I hang from it then the fact that my harness will be higher up my body plus rope stretch  means it is out of reach.

damian said:

Of course, there is no benefit in having loosened them between trips from the point at which you have hung on your cowstail on the next trip (which is often pretty much the 2nd anchor of an SRT trip).

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I think this sums it up really.

Any idea what IRATA recommend as they probably have more data on this subject. When I did my level 1 (many moons ago) there was no mention of loosening between jobs/uses.
I'm sure it would have a benefit if you weren't hanging on them and they were just used in fall arrest situation.

Am I missing something? Unless you have really messed up, why would you fully load your long cows tail in the first place? Except maybe rigging to reach an akward bolt? In normal circumstances you only need to reach your long cows tail when its not fully loaded? If you did fully load them like someone says you can always prussick up or at least stand in the handjammer to reach the cows tail on the traverse/rebelay or Y-hang.

With the above point as your often not fully loading your long maybe you should loosen/tie that one?

Rigging high, with relatively horizontal traverse lines, with cowstails relatively tight and/or loaded means you'll never be putting a significant shock load into the system in the event of a slip. Seems to be good practice.

There is a lot of stuff talked about knots and fall factors that does not, to me, make an awful lot of sense.

So overhand knots sustained 4 drops and had a residual strength of 58?68% the ?true? strength of the rope (according to a different thread) ? so what? We?re talking (4 drops) about gross cruelty to rope and knots, here ? a 100-kg weight dropped through a distance of a metre of two. And since the breaking load of rope is up around the 2-3 ton mark, so what if it gets reduced to1.5?2 tons? That?s good enough for me.

In practice, what is a likely scenario? You slip off a ledge while rigging, and slither down ? a far cry from a 1:1 fall factor per se.

I?ve tried to envisage a plausible scenario for putting even a FF 1 onto a rope, let alone a FF 2, and find it difficult. The nearest I?ve come is the following: You set off on a traverse of, say, 3?4 m to rig a pitch, but when you get to the end of the traverse ? with no intermediate belays, mind you ? you change your mind for some reason or another, and walk back to the start of the travers with something ? a cows tail, descender or what have you ? clipped into the rope at what was the end of the traverse, and (again, for whatever reason) you forget/omit to move your point of attachment along the rope, as a result of which you reach the start of the traverse clipped into the rope some 3?4 m along . . . and then you fall, thus experiencing a 3-4 m fall onto 3?4 m of rope. Even then, you?d probably slither down the walls, and, in all probability, it wouldn?t be a kosher FF 1.

As for loosening cows? tails knots, well, I prefer to have tight knots that aren?t going to come undone in use through having been left loose.

Look, I?m playing Devil?s advocate here, and am prepared to be shot down in flames, but I?d be interested to hear what others think.