rope age

[cap n chris]

It never ceases to amaze me that the more one looks into a subject, the more one realises (a) how huge that subject is and (b) how little one knew about it in the first place!

On a kind of seaweed-hanging-on-a-bit-of-string basis I feel happy on a 2 year rope replacement cycle. It's about as scientific as witchcraft, granted, but the psychology wins the day.

 

[Peter Burgess]

It never ceases to amaze me that the more one looks into a subject, the more one realises (a) how huge that subject is and (b) how little one knew about it in the first place!

On a kind of seaweed-hanging-on-a-bit-of-string basis I feel happy on a 2 year rope replacement cycle. It's about as scientific as witchcraft, granted, but the psychology wins the day.

But you never let your ropes cool down between uses so perhaps you are a special case?

 

[Downer]

Tent fabric can certainly fail after exposure to UV, but tent fabric is rather thin.

How far into a rope would UV actually penetrate?
Would it *ever* reach the core in significant amounts, and even if it did, assuming there's at least some significant attentuation going on with depth, would the sheath be close to falling apart by that point due to the much higher UV it would have encountered?

That would be my expectation. Also there are different grades of nylon and I somehow doubt the same one is used for tents, ropes and combs...

 

[wormster]

Here's a link to a vid of a simulated rub point:

http://www.swaygogear.com/hotknife/11mm%20rock.mov

It takes frighteningly little to severely damage a rope where a sharp edge is involved. I think everyone should try cutting an old piece of rope with a blunt knife, its scarily easy to do !!

Not *quite* in the right area I know, but worth stressing nevertheless.

 

[Geoff R]

It takes frighteningly little to severely damage a rope where a sharp edge is involved. I think everyone should try cutting an old piece of rope with a blunt knife, its scarily easy to do !!

Cutting old 10mm rope under my body weight load in the gym, its also surprising just how few fibers of a rope will support you. Amazing just a few fibers are strong enough. 

However it is indeed surprising how easy a knife slices tensioned 10mm rope and the shock when it finally breaks.
Well worth experiencing !


 

 

[ianball11]

I was going to say for those of us who aren't boffins, the usual 5 year store and 3 year useage replacement cycle is nice and comforting but when dangling above Alum Pot main pitch or Eldon Hole I always start thinking that I should make the effort to understand it more. I've not tested a rope for a very long time though.

Ian B.

 

[cap n chris]

I can thoroughly recommend getting your rope tested by Mr. Bob M at Hidden Earth using the rope testing rig! - it'll either reassure you.... or it won't.

 

[dunc]

I can thoroughly recommend getting your rope tested by Mr. Bob M at Hidden Earth using the rope testing rig! - it'll either reassure you.... or it won't.

Hmmm. Been waiting a year to have a piece tested from the last HE.
Should I wait for the results before deciding whether or not to carry on using it or do what I have done and will continue to do in the future - use my own judgement.. :doubt:

 

[Downer]

It never ceases to amaze me that the more one looks into a subject, the more one realises (a) how huge that subject is and (b) how little one knew about it in the first place!

On a kind of seaweed-hanging-on-a-bit-of-string basis I feel happy on a 2 year rope replacement cycle. It's about as scientific as witchcraft, granted, but the psychology wins the day.

I am fairly used to discovering I know nothing about a subject  But what does piss me off right royally is being told I must do this or must do that when there is no "audit trail" back to evidence-based science at all. Drink five glasses of water a day or you will die! Eat five portions of fruit and veg a day or you will die! Don't go near a radio mast or you will die! Keep your ropes out of sunlight or you will die!

Ho hum, I'm guessing that no-one here knows much about it, better keep throwing those ropes away

 

[Peter Burgess]

I'm with you there, Downer. I used a 28-year old steel krab at the weekend as part of a lifeline set up on a shaft entrance. I didn't die.* No doubt there are folk who would say I should have thrown it away years ago. Also, if old ropes are such rubbish, why are we so happy to relegate them to use as car towropes, given that they are supposed to be so much weaker, yet they will be subject to severe snatch loading if you are unfortunate enough to have to be towed out of danger, and possibly end up in the path of another vehicle as a result of it breaking. Perhaps towropes is not a suitable end use for old caving rope.

* I might add it has been cared for and never abused since I bought it.

 

[Downer]

I'm with you there, Downer. I used a 28-year old steel krab at the weekend as part of a lifeline set up on a shaft entrance. I didn't die.* No doubt there are folk who would say I should have thrown it away years ago. Also, if old ropes are such rubbish, why are we so happy to relegate them to use as car towropes, given that they are supposed to be so much weaker, yet they will be subject to severe snatch loading if you are unfortunate enough to have to be towed out of danger, and possibly end up in the path of another vehicle as a result of it breaking. Perhaps towropes is not a suitable end use for old caving rope.

* I might add it has been cared for and never abused since I bought it.

Really? I didn't know there was law about old krabs too. Well, well, I have learned something

And on another matter entirely, I wish I'd started a topic with a different name! I keep reading it as a single word pronounced "rowpidge".

 

[Peter Burgess]

I didn't know there was law about old krabs too.

I expect someone's working on it somwhere.

 

[ian.p]

if old ropes are such rubbish, why are we so happy to relegate them to use as car towropes

the trouble is that its hard to tell what sort of internal damige has been done to ropes over time from things like calcite crsytals working there way in and cuting fibers or damige from uv which is equaly dificult to detect so its not so much that the strenth is gone but that its unreliable much better to find out that actualy the core of your rope was nackered when it snaps puling somones car out of the mud then when your dangling on it 

 

[Wolf]

I am fairly used to discovering I know nothing about a subject  But what does piss me off right royally is being told I must do this or must do that when there is no "audit trail" back to evidence-based science at all. Drink five glasses of water a day or you will die! Eat five portions of fruit and veg a day or you will die! Don't go near a radio mast or you will die! Keep your ropes out of sunlight or you will die!

Ho hum, I'm guessing that no-one here knows much about it, better keep throwing those ropes away

the most things are probably overestimated, but you *MUST NOT* pour acid like from lead-acid cells (I hope that is the correct expression) over your ropes. But that should be known by now.

The most rope breaks that I heard of were by rock fall or when running over sharp edges. Another thing are preloaded cable ways, when I'm not completely misinformed the official recommendation (I think for Germany and Austria at least) is to use 11 or 12 mm ropes (and a separate backup rope).

 

[Downer]

if old ropes are such rubbish, why are we so happy to relegate them to use as car towropes

the trouble is that its hard to tell what sort of internal damige has been done to ropes over time from things like calcite crsytals working there way in and cuting fibers or damige from uv which is equaly dificult to detect so its not so much that the strenth is gone but that its unreliable much better to find out that actualy the core of your rope was nackered when it snaps puling somones car out of the mud then when your dangling on it 

Yes, but you are assuming that UV damage does occur. Internal wear is an obvious way a rope can weaken. UV damage is, on the showing so far, hypothetical. Plastic-eating bugs could destroy ropes in less than a month. If we don't need evidence that this actually happens, we'd better all buy new for each trip just to be safe.

 

[Downer]

I am fairly used to discovering I know nothing about a subject  But what does piss me off right royally is being told I must do this or must do that when there is no "audit trail" back to evidence-based science at all. Drink five glasses of water a day or you will die! Eat five portions of fruit and veg a day or you will die! Don't go near a radio mast or you will die! Keep your ropes out of sunlight or you will die!

Ho hum, I'm guessing that no-one here knows much about it, better keep throwing those ropes away

the most things are probably overestimated, but you *MUST NOT* pour acid like from lead-acid cells (I hope that is the correct expression) over your ropes. But that should be known by now.

The most rope breaks that I heard of were by rock fall or when running over sharp edges. Another thing are preloaded cable ways, when I'm not completely misinformed the official recommendation (I think for Germany and Austria at least) is to use 11 or 12 mm ropes (and a separate backup rope).

Yup, the susceptibility of nylon to strong acid attack is well-known. Fortunately only a few cavers still carry Oldhams around. You can tell them by their lopsided gait, never mind the dribble of sticky tar that used to be a rope.

 

[ian.p]

err there is quite a lot of evidence that UV affects nylon look at two pieces of nylon one that's been kept in the shade and one that's been left in sun for a while say about a month and there will be a noticeable difference its why modern tents don't last that long these days admitidly its not like if you left your rope outside for a day you'd have to replace it (in which case climbers would have a significant problem) but if you regularly left it on the washing line between trips so it spent weeks in the sun then you'd have more of a problem 

 

[mak]

If you are worried about loss of strength as ropes age and the expense of early retirement/replacement then a good compromise, given that cavers need a number of ropes of varying length, is to buy new ropes with longer lengths (60m, 70m or longer) and use them for however long you feel is safe (2 years for C'n'C 5 if you follow the manufacturers guidance) NB still must visually inspect the ropes regularly.

When that safe period is up - cut it into shorter lengths (e.g halve to ~30m, ~35m or whatever other length combinations you find useful - oh and buy some new long ropes to replace the cut ones) and take a 3m section from what was the middle of the old rope (NB must be middle as the ends don't get as much use/abuse as the middle) then get that rope tested (at HE or any one of the clubs that has a drop test rig).

If it breaks after only a few falls then destroy/retire that rope, if it survives what you feel is a safe number of falls (2+) then you can carry on using the now shorter lengths for however long you feel safe (1+ years - NB it is getting older now so might want to be shorten the time period), once past its extended life repeat the process (i.e. cut in half/whatever to 15m, etc.) and test another middle section.

Following the above means you extend the life of your ropes in a safe manner (by testing them) and have a useful collection of varying lengths of rope. And all old ropes will eventually be too old/short to use.

 

[MSD]

This scheme relies on a basic assumption, that the test gives a fully representative idea of the condition of the whole rope. I don't believe that assumption is necessarily valid.

A simple counter-example is isolated damage to a particlar part of the rope. The damage might be visible and picked up by inspection or it might not. This whole discussion revolves around the basic premise that a rope can look OK but in fact not be OK. You can't simply reverse that argument and say "if one bit of the rope is OK, so must all the rest be".

Apart from isolated damaged (possibly cause by abrasion, falling etc.), ropes are not used or worn equally throughout their length. The bits near the end don't tend to get abseiled/prussiked on much, but on the other hand they get knots tied and loaded on them much more. Or they can get coiled and hung up in the sun, with the outside coils getting toasted while the inside ones are in the shade (or any one of a hundred other things which might lead to uneven deterioration over the length of the rope). Obviously we want to try and test the weakest part of the rope (a chain is only as strong as its weakest link), but what empirical evidence is available which suggests that the middle of the rope is necessarily going to be the weakest part?

Busting one piece of rope also gives you only one piece of data. Obviously you try to control the experiment and make it as "standard" as possible, but there will still be experimental variation.

So I'm sceptical about drop testing as a very useful tool for improving safety. A more pragmatic approach is to have a large safety margin and use ropes for caving which are much stronger than the loads likely to be applied to them, so that unexpected damage or wear is not disastrous. That's a practical approach which has served the caving community excellently over the years. I know of many clubs which operate around a 5 or 6 year cycle for rope replacement and the empirical data here is overwhelming - SRT ropes don't break on a regular basis. In fact they don't break AT ALL unless you do something really stupid.

Mark

 

[whitelackington]

err there is quite a lot of evidence that UV affects nylon look at two pieces of nylon one that's been kept in the shade and one that's been left in sun for a while say about a month and there will be a noticeable difference its why modern tents don't last that long these days admitidly its not like if you left your rope outside for a day you'd have to replace it (in which case climbers would have a significant problem) but if you regularly left it on the washing line between trips so it spent weeks in the sun then you'd have more of a problem 

Even if uv light does degrade rope
it will only be the sheath that degrades and you can see that.
The sheath is responsible for a small fraction of the ropes strength
not sure but I seem to remember 15%  :-\