cap n chris
Well-known member
Found it! Blimey, ten years ago aaaagh!! Around 2m30s mark. Quite chuffed my trip report videos still seem watchable, to me at least.
which carabiners for anchors
- Thread starter michael.11
- Start date
rm128
Active member
I tend to alternate between the massive y-hang (more fun) and the deviated smaller y (easier) each time I do Sell Gill. Variety is the spice of caving after all.
I have done all variations in Sell Gill numerous times, my conclusion is the Right hand route on the second pitch is considerably easier to negotiate than the lefthand route. No big Y hang and no deviation Courses for horses I guess.
This a great post and the discussion has doubtless helped many.
Just to add to the technical parts.
I was one of the team working with Lyon Equipment that produced the HSE report into Rope Access Equipment in the early 2000's that has revealed points referred to in both Sport and Industry..
One of the big findings was how different knots for cowstails offered dramatically different levels of shock absorption.
As most will know the barrel knot as commonly referred was found to be the best performer due to the way it drew slack from the turns into play when loaded.
All knots have some absorbency potential, but finding such big differences between knots made it quite obvious that their condition was also important.
Once the knot had been loaded and the slack used up the benefit was gone and it was this result that then lead us to the conclusions that knots need re tieing to ensure the capacity for shock absorption is there in case it is needed - It was not the French.
You can re tie as regular as you wish, but the key is that if you have tightened it in use, then slack it off if you want absorbency.
A separate point relating to thin Maillons and rigging, is that radius issues can occur when rope is passed round a bar that has a tighter radius than the rope diameter. This is a really well known issue in lifting and applies equally in this context.
As there are generally pretty big safety margins (in some parts of our systems) and this is not necessarily the weakest point, then it may not be worth worrying about, but it does exist nevertheless.
There are however some situations where it has been revealed in caving.
One example was the ropes at Euro Speleo that had high traffic and were rigged on 7mm maillots - the rope folded as the radius was too tight. This also in some cases resulted in ruptured sheaths as some of the rope had a sheath and core that were interwoven - this is good in case of cuts to the sheath - but in this case it prevented the sheath being able to move to the stress point and so the folded area ruptured. It is unlikely this would have occurred without the high volume of traffic and even then if a larger radius connector was used.
Another was the Bill Stone San Augustin trip where they used 13mm rope and 7mm Maillons - again the rope over time went from running over the bar to folding around it and rupturing of the sheath occurred at these of the folds.
If the rope is rigged and only used by a small group and then de rigged it is unlikely the issue will be revealed or become an issue, but if tested the rope would break at a lower load on the thinner bar size.
The use of a Karabiner (generally 10mm bar size) for rigging will provide a better radius for most SRT (9-11mm) ropes than a thinner Maillon and IMHO are easier to use, but again it is choice.
Both of these scenarios - Knots and re tieing and thin Maillons for rigging are issues identified by testing.
The testing may point to better practice that can increase safety factors / margins just by personal care or making informed decisions.
The other point of view could be that if the issue has not become a problem then maybe we do not need to change as the margins are maybe adequate and any risk acceptable.
The choice is yours, but I believe it is better that people are informed and make decisions based around the facts.
Currently I do re tie cows tails, but not every trip - I keep an eye on them and gauge it from experience.
I also rig with Karabiners with locking gates.
My cowstails biners are screwgates and have been for over 30 years.
Great discussion though.
Just to add to the technical parts.
I was one of the team working with Lyon Equipment that produced the HSE report into Rope Access Equipment in the early 2000's that has revealed points referred to in both Sport and Industry..
One of the big findings was how different knots for cowstails offered dramatically different levels of shock absorption.
As most will know the barrel knot as commonly referred was found to be the best performer due to the way it drew slack from the turns into play when loaded.
All knots have some absorbency potential, but finding such big differences between knots made it quite obvious that their condition was also important.
Once the knot had been loaded and the slack used up the benefit was gone and it was this result that then lead us to the conclusions that knots need re tieing to ensure the capacity for shock absorption is there in case it is needed - It was not the French.
You can re tie as regular as you wish, but the key is that if you have tightened it in use, then slack it off if you want absorbency.
A separate point relating to thin Maillons and rigging, is that radius issues can occur when rope is passed round a bar that has a tighter radius than the rope diameter. This is a really well known issue in lifting and applies equally in this context.
As there are generally pretty big safety margins (in some parts of our systems) and this is not necessarily the weakest point, then it may not be worth worrying about, but it does exist nevertheless.
There are however some situations where it has been revealed in caving.
One example was the ropes at Euro Speleo that had high traffic and were rigged on 7mm maillots - the rope folded as the radius was too tight. This also in some cases resulted in ruptured sheaths as some of the rope had a sheath and core that were interwoven - this is good in case of cuts to the sheath - but in this case it prevented the sheath being able to move to the stress point and so the folded area ruptured. It is unlikely this would have occurred without the high volume of traffic and even then if a larger radius connector was used.
Another was the Bill Stone San Augustin trip where they used 13mm rope and 7mm Maillons - again the rope over time went from running over the bar to folding around it and rupturing of the sheath occurred at these of the folds.
If the rope is rigged and only used by a small group and then de rigged it is unlikely the issue will be revealed or become an issue, but if tested the rope would break at a lower load on the thinner bar size.
The use of a Karabiner (generally 10mm bar size) for rigging will provide a better radius for most SRT (9-11mm) ropes than a thinner Maillon and IMHO are easier to use, but again it is choice.
Both of these scenarios - Knots and re tieing and thin Maillons for rigging are issues identified by testing.
The testing may point to better practice that can increase safety factors / margins just by personal care or making informed decisions.
The other point of view could be that if the issue has not become a problem then maybe we do not need to change as the margins are maybe adequate and any risk acceptable.
The choice is yours, but I believe it is better that people are informed and make decisions based around the facts.
Currently I do re tie cows tails, but not every trip - I keep an eye on them and gauge it from experience.
I also rig with Karabiners with locking gates.
My cowstails biners are screwgates and have been for over 30 years.
Great discussion though.
andrewmcleod
Well-known member
I think 7mm maillons are the standard size? Whether they _should_ be is a different question, of course...
This is a summary of some of the cowstail work:
and this is the French work (carried out later than the Lyon work):
The French used 80kg instead 100kg (because they are less fat) and preloaded to 3kN instead of 2kN (because they are more energetic, presumably). They suggest 3kN results in knots that look like 'real' caver knots.
Takeaways for me are:
1) after a FF1, the shock load for a subsequent fall (for typical 9mm dynamic barrel knot cowstails) increases by up to 30%, so I would definitely want to retie or replace, but that's not catastrophic,
2) loads are still comparable to other results (~6kN) for barrel knot cowstails after heavy pre-loading (3kN), and
3) unfortunately they do very few tests with non-pre-tightened knots for comparison... but two they did had <15% extra shock load on the pre-tightened knots, and <1.5cm of slippage.
"From the point of view of shock absorption, Cow's Tails made from dynamic rope and knots at both ends achieve the best results. The effect of the diameter and of the weave of the rope on this shock load is not significant. Furthermore, the results are similar for knots that are well tied and knots that are badly tied, that is when the ropes cross over each other, and also whether they have been pretightened or not."
This is a summary of some of the cowstail work:
and this is the French work (carried out later than the Lyon work):
The French used 80kg instead 100kg (because they are less fat) and preloaded to 3kN instead of 2kN (because they are more energetic, presumably). They suggest 3kN results in knots that look like 'real' caver knots.
Takeaways for me are:
1) after a FF1, the shock load for a subsequent fall (for typical 9mm dynamic barrel knot cowstails) increases by up to 30%, so I would definitely want to retie or replace, but that's not catastrophic,
2) loads are still comparable to other results (~6kN) for barrel knot cowstails after heavy pre-loading (3kN), and
3) unfortunately they do very few tests with non-pre-tightened knots for comparison... but two they did had <15% extra shock load on the pre-tightened knots, and <1.5cm of slippage.
"From the point of view of shock absorption, Cow's Tails made from dynamic rope and knots at both ends achieve the best results. The effect of the diameter and of the weave of the rope on this shock load is not significant. Furthermore, the results are similar for knots that are well tied and knots that are badly tied, that is when the ropes cross over each other, and also whether they have been pretightened or not."
andrewmcleod
Well-known member
The French work certainly suggests the rope choice is fairly unimportant (not massive difference between dynamic, static, 8.1mm, 11mm) and the knots are everything.
"In order to compare only the types and diameters of rope, we have produced averages of the results for each type of rope. These come from the tests on the 60 cm Cow's Tails knotted at both ends (taking exactly the same tests for all the Cow's Tails), except of course for the Spelegyca Cow's Tail, which is made from tape.
[...]
The results are very close (average of 6.01 kN and standard deviation of only 0.15 kN or 2,5 %) although these ropes display very different characteristics and have varied diameters."
The French work demonstrated that by far the biggest factor affecting cowtails was usage/age, not knots or type of rope. Static strength could be nearly halved after a few years, and the fact that a weakened rope might be more stretchy is hardly a comfort as the static strength can fall below the FF2 load. This is why I buy new ones every year or so, and I use 10-10.5mm. The larger rope does not generate more force but has more contingency. This age result is in line with work done a long time ago on lifting slings. It’s a small amount of money for the piece of kit likely to get by far the most abuse and seems a no-brainer to me.
Still, it’s not climbing where people take these falls all the time, so the incident rate is non-existent. There are without doubt people using cowstails that will not take a FF2 load given the multi-decade age of their gear, but luckily they have yet to fall badly on them and very probably never will. All good then.
I think you should get everything going for you, use dynamic rope, use barrel knots, look after your kit and try not to get above your anchors. Falling is no fun at all.
It's actually quite difficult to get truly static rope, most is semi-static which extends 5 to 10% under load, UIAA stipulate that dynamic stretches no more than 10% under static load & no more than 40% under dynamic, so on a 60cm cowstail you don't get much benefit compared to a 50m rope! However, knots do normally grip themselves noticeably better on dynamic...
The other thing to consider is that UV light affects materials, so if you dry kit outside then slings won't last as long as ropes (as most of their strength is protected in the core)
The other thing to consider is that UV light affects materials, so if you dry kit outside then slings won't last as long as ropes (as most of their strength is protected in the core)
But we also don't know how much of that is due to the knots, or the elasticity of the rope not having time to recover? What we do know is that differently tied knots (even the same knot tightened more or less) give variable results.
cavetroll
Member
The advice to retie your cowstails is fascinating. I’m really not sure what I think is more risky, but what I’d say is that for me, we’re targeting the wrong hazard.
Avoid (at all reasonable costs) falling onto your cowstails in anything approaching FF1 let alone 2. If you’re level with or above your cowstails, you’re doing something weird. Get yourself on a dynamic belay or re-do the rigging, but don’t think “oh it’s fine I loosened my cowstails in prep for this moment”. If you’re digging something grim and badly bolted or doing something a bit left-of-field perhaps you need something more specialist for the extra risk you choose to take on. For most of us I doubt it.
Also there is a risk, call it 1% (or 0.1%?) that you tie your cowstails incorrectly. The more times you untie/tie them the greater your exposure to this small risk. It happens to all of us, except of course anyone who claims they’re immune from mistakes... Perhaps not a big problem, but is this risk bigger than the gain of a bit of stretch given the primary concern should be avoidance of FF1+ falls on cowstails anyway?
I tie mine once, check them twice (or three times!) and use them for a year. Then I replace them for the grand cost of £3-4.
But mainly, I politely decline to get into situations where I might fall on them where there’s no additional rope in the system.
Avoid (at all reasonable costs) falling onto your cowstails in anything approaching FF1 let alone 2. If you’re level with or above your cowstails, you’re doing something weird. Get yourself on a dynamic belay or re-do the rigging, but don’t think “oh it’s fine I loosened my cowstails in prep for this moment”. If you’re digging something grim and badly bolted or doing something a bit left-of-field perhaps you need something more specialist for the extra risk you choose to take on. For most of us I doubt it.
Also there is a risk, call it 1% (or 0.1%?) that you tie your cowstails incorrectly. The more times you untie/tie them the greater your exposure to this small risk. It happens to all of us, except of course anyone who claims they’re immune from mistakes... Perhaps not a big problem, but is this risk bigger than the gain of a bit of stretch given the primary concern should be avoidance of FF1+ falls on cowstails anyway?
I tie mine once, check them twice (or three times!) and use them for a year. Then I replace them for the grand cost of £3-4.
But mainly, I politely decline to get into situations where I might fall on them where there’s no additional rope in the system.
andrewmcleod
Well-known member
Indeed 
if we _really_ cared, we be using VF-type lanyards with shock absorbers...
if we _really_ cared, we be using VF-type lanyards with shock absorbers...
cap n chris
Well-known member
Because it's in print and published in the public domain by the national governing body for caving I believe that the correct/insurable thing to do is to follow the diktat. Obviously there was an innate resistance to having to add the workload to the routine daily grind but having done thousands and thousands of safety connector knots it's become a non event chore which takes no time at all in the general scheme of things and probably serves to make things safer due to the ability to tie perfect knots every time, now it's entrenched.
Sorry caving last night so the thread has moved on.
If you think of the % stretch in dynamic rope and then apply that to the relatively short length of a long cowstail, then there is relatively little dynamic effect available.
If you then load the knot and draw the stretch out - of both a barrel and a fig 8 at the harness end - it is depending on how tight the knots are likely to add more length than the stretch as it progressively tightens.
The additional rope should add more than the rope stretch, but will depend on tightness of knots.
This is what the French report is confirming and hence why the type of rope is less important.
The key to loading prior to re tieing is unlikely to be from a fall and in my opinion more likely to come from suspending on them during manoeuvres. This will gradually tighten them over time rather than in one fell swoop and hence why I use experience as some trips or activities incur more static loading of cows tails.
Happy to do a little testing if here is a consensus on what we are interested in - we should be able to carry things out professionally and in a controlled manner using proper test equip.
If you think of the % stretch in dynamic rope and then apply that to the relatively short length of a long cowstail, then there is relatively little dynamic effect available.
If you then load the knot and draw the stretch out - of both a barrel and a fig 8 at the harness end - it is depending on how tight the knots are likely to add more length than the stretch as it progressively tightens.
The additional rope should add more than the rope stretch, but will depend on tightness of knots.
This is what the French report is confirming and hence why the type of rope is less important.
The key to loading prior to re tieing is unlikely to be from a fall and in my opinion more likely to come from suspending on them during manoeuvres. This will gradually tighten them over time rather than in one fell swoop and hence why I use experience as some trips or activities incur more static loading of cows tails.
Happy to do a little testing if here is a consensus on what we are interested in - we should be able to carry things out professionally and in a controlled manner using proper test equip.
Most tests I've seen don't replicate a typical underground fall.
We rarely if ever face a fall onto an anchor, though we may well hang off them.
A fall in a traverse will be onto a rope fixed to two anchors, by two knots. I.e. will have a lot of rope stretch and knot slippage.
A fall at a Y hang will be onto the Y hang system.
The ranking for different types of cows tails will be the same whatever the test, but the forces involved will not be.
By all means test, but it has been done , many times. Do it again by all means, but not on to fixed anchors.
And allow for harness/body absorbing some of the shock too.
TC
We rarely if ever face a fall onto an anchor, though we may well hang off them.
A fall in a traverse will be onto a rope fixed to two anchors, by two knots. I.e. will have a lot of rope stretch and knot slippage.
A fall at a Y hang will be onto the Y hang system.
The ranking for different types of cows tails will be the same whatever the test, but the forces involved will not be.
By all means test, but it has been done , many times. Do it again by all means, but not on to fixed anchors.
And allow for harness/body absorbing some of the shock too.
TC
Mark Wright
Active member
As a fully paid up member of the IGKT I would argue the more times you untie/tie Cowstail, or any other such knots, the less likely you are to make a mistake. They say (whoever They are) that if you tie a knot correctly 150 times you should never forget how to tie it.
It's also rare to see a freefall onto cowstail. Problem is that you can't measure anything useful in a multi link system as there are too many variables. Testing directly on bolts gives you a comparable result & a worst case scenario...
