Wet or Dry rope SRTing ???
- Thread starter Geoff R
- Start date
jarvist
New member
Dry rope creeps through stops, makes scary noises (crreeeaaakkkk!), and sometimes seems to slip more on jammers (I think because mud engrained caving ropes are more pliable when wet, so are easier for the cam in the jammer to start compressing).
Dry / sun baked ropes can also be incredibly fast on abseiling (though that's more a surface abseil problem, as soon as anything is underground it's always slightly damp).
Supposedly wet rope is less strong.
Dry / sun baked ropes can also be incredibly fast on abseiling (though that's more a surface abseil problem, as soon as anything is underground it's always slightly damp).
Supposedly wet rope is less strong.
Bob Mehew
Well-known member
jarvist said:
Very definitely in terms of drops survived dynamic testing. One test we conducted found a brand new sample of 10mm SRT rope straight of the real survived 26 drops when dry whilst another sample only survived 14 after being soaked for over 2 hours. (But the peak forces seen by both rope samples were roughly the same drop by drop.) This loss of drops survived has been documented by others as well.
I am away from home so can't dig into my references but I don't recollect seeing similar claims for static strength or more correctly using a slow pull. (I guess not many people do this as you get rather wet when a wet rope breaks or in Jarvist's case dirty from the muddy ropes!)
I have not come across an optimum wetness but I guess it might be where the sheath is wet whilst the core is dry, bearing in mind it is the core which provides the strength in a kernmantle rope. I have never tried to measure how much water a rope takes up with time; I just use the requirement passed onto me by Owen Clarke which was to soak it for at least 2 hours.
AndyF
New member
IIRC the article I read compared over-dried rops with just normal conditions, such as having come out of a drying room... you know rope that stands up on its own.
I think they found that an ambient dampness rope was strong than the over dried, but then went weaker by 10% or so when really "wet".
Sorry to be vague, ican't remember even where I read this or vouch for its validity...
I think they found that an ambient dampness rope was strong than the over dried, but then went weaker by 10% or so when really "wet".
Sorry to be vague, ican't remember even where I read this or vouch for its validity...
Bob Mehew
Well-known member
AndyF said:
I have not thought to follow this area up since for most cavers, the rope will be wet. The British Standard for testing requires that the rope is previously conditioned in a fixed humidity temperature oven (75% & 25C IIRC) and that the testing has to start within 5 minutes of being taken out of the oven. So I have no doubt that water at relatively (compared to a cave) low levels has an impact. I don't recall coming across variation of static strength w.r.t. water but if any one does know I would be very interested to hear.
JasonC
Well-known member
Bob Mehew said:
Wet ? Yes, as in a bit damp, through having been dragged through puddles in a tackle bag. But not normally 'wet' as in having been soaked for two hours as in the test you mention above ?
Going back to the original question, I'd guess that any routine wetting to improve SRT performance would only be superficial so would have negligible effect on overall strength, though I'd be happy to be corrected.
ChrisJC
Well-known member
Quite regularly we find that the rope is mostly dry with the odd wet patch. When one whizzes through the wet patch, there's a 'tssschhh' noise. I find this alarming personally, so I would always go for 100% wet if I could.
My stop can be pretty hot too, and we have deformed ropes in the past through overheating them.
Chris.
My stop can be pretty hot too, and we have deformed ropes in the past through overheating them.
Chris.
SamT
Moderator
I think the whole strength issue is a red herring. The OP did not question the strength of ropes. I can see a whole bunch of people thinking "I'm gonna keep my ropes dry because it'll be stronger" (the same folk who are convinced that P bolts will pull out if they look at them too hard).
Wet or Dry, part wet or part dry, the ropes are plenty strong enough.
I think the issue that should be paramount in the Wet or Dry rope debate is the effect of heat from your racks/stops/bobbins/fig8/HMS krabs (italian hitch)/ID's/GriGri/stitch Plates/ATC's or what ever you preferred descending device.
On Dry ropes, descenders can get incredibly hot, enough to melt the plastic fibres on the sheaf. It trashes rope very quickly, making them stiff and hard to handle. Since the strength is in the core - I'm not sure what effect a scorched sheaf has on the strength of the rope, but I'm willing to bet that since its stiff, the knot will be weaker.
For the reason of scorching of the sheaf, IMHO, SRT ropes should always be wet. Full Stop.
Other than the increase in strength over the (already plenty strong enough) wet rope and the fact that its a bit lighter to carry, can anyone give me an advantage of dry rope that trumps not scorching your ropes with your descender.
Wet or Dry, part wet or part dry, the ropes are plenty strong enough.
I think the issue that should be paramount in the Wet or Dry rope debate is the effect of heat from your racks/stops/bobbins/fig8/HMS krabs (italian hitch)/ID's/GriGri/stitch Plates/ATC's or what ever you preferred descending device.
On Dry ropes, descenders can get incredibly hot, enough to melt the plastic fibres on the sheaf. It trashes rope very quickly, making them stiff and hard to handle. Since the strength is in the core - I'm not sure what effect a scorched sheaf has on the strength of the rope, but I'm willing to bet that since its stiff, the knot will be weaker.
For the reason of scorching of the sheaf, IMHO, SRT ropes should always be wet. Full Stop.
Other than the increase in strength over the (already plenty strong enough) wet rope and the fact that its a bit lighter to carry, can anyone give me an advantage of dry rope that trumps not scorching your ropes with your descender.
Chocolate fireguard
Active member
SamT said:
Fusing the outer layer might make it more abrasion resistant?
Sorry, poor joke. :spank: :spank:
After having had a new 60m length of 9mm Edelrid glazed on Elizabeth in Nettle some years ago (and my mate pick up a very nasty blister from his Stop while it was happening), and cursing for some years afterwards every time I tried to pack it into a sensible size tacklesack, I always wet rope. SamT`s post is spot on.
The ability of a knot to absorb the energy of a fall will depend on how tightly it has already been pulled and so a knot in glazed, stiff rope may absorb more energy than one in a well-looked-after rope. So far as I know no work has been done and it would be a poor reason for wrecking the handleability of a rope anyway.
I feel SamT is spot on 
Like others, Im not worried about the potential for a slight loss in ability on drop-tests as the rope (in good condition) is more than strong enough IMHO. My thought is only to do with damage due to rope glaze.
I first read about rope glazing in old club trip reports and a complaint of too fast abbing down a very short drop into a local sand quarry (mine) or incorrect Stop technique.
Some time later when ?into SRTing? I noticed glazing on my new 50m rope our small team was ?correctly? using and began to suspect that it occurred ?very easily? with dry rope.
It was Dave in Ingleton who pointed out that they all cave with wet rope to prevent glazing and to get a smoother ride, wetting it the night before and allowing it to drain, or soaking it at the cave.
Its indeed real surprising just how much ?hiss? and steam happens from even a short moderate descent, so Ive ever since taken to ensuring that even my shortest ropes are only used wet, but wondered about others thoughts and what they did....
Like others, Im not worried about the potential for a slight loss in ability on drop-tests as the rope (in good condition) is more than strong enough IMHO. My thought is only to do with damage due to rope glaze.
I first read about rope glazing in old club trip reports and a complaint of too fast abbing down a very short drop into a local sand quarry (mine) or incorrect Stop technique.
Some time later when ?into SRTing? I noticed glazing on my new 50m rope our small team was ?correctly? using and began to suspect that it occurred ?very easily? with dry rope.
It was Dave in Ingleton who pointed out that they all cave with wet rope to prevent glazing and to get a smoother ride, wetting it the night before and allowing it to drain, or soaking it at the cave.
Its indeed real surprising just how much ?hiss? and steam happens from even a short moderate descent, so Ive ever since taken to ensuring that even my shortest ropes are only used wet, but wondered about others thoughts and what they did....
first-ade
Member
Question to anyone who answered definitely wet: are any of you a rack user?
I've only encountered glazing on long pitches where people have descended rather quickly and then not bothered to remove their descender promptly. As such, I have no preference. I can't say that I've ever found dry ropes to be quicker than wet ones. I am a rack user, so is this something more specific to bobbin style devices?
I've only encountered glazing on long pitches where people have descended rather quickly and then not bothered to remove their descender promptly. As such, I have no preference. I can't say that I've ever found dry ropes to be quicker than wet ones. I am a rack user, so is this something more specific to bobbin style devices?
Roger W
Well-known member
Thinking about it, using friction to slow down your descent - whatever bit of kit you choose to use - is going to generate heat. The mathematicians and physicists among us should be able to calculate how much heat will be produced when a caver weighing X kg descends Y metres, assuming he arrives at the bottom with velocity V metres/second. The problem is how to dissipate that heat.
Evaporating water from a wet rope is obviously one way. Big cooling fins on your rack might be another...
Evaporating water from a wet rope is obviously one way. Big cooling fins on your rack might be another...
SamT
Moderator
spot on Roger (was going to reply along these lines - but you beat me to it).
Law of conservation of energy and all that - O level stuff.
So - the kinetic energy of your fall has to be converted to another form. Due to friction, this is virtually all heat energy.
for the same height drop and same weight caver - the same amount of energy has to converted, no matter how fast or slow you descend.
The only factor that can change is the ability to dissipate that heat. Racks have a bit more 'exposed' metal, so probably cool better due to air flow as opposed to the enclosed bobbins of a stop/simple.
A slow descent just gives more time for that heat to be dissipated.
(well I guess the other factor is that some fatty caver has more potential energy, and therefore generates more kinetic energy, thus more heat to dissipate.
However - back to the OT. You could attach cooling fins to your descender or much more simply - wet the rope !!!
Due to its incredibly high specific heat capacity, water on the wet rope, will soak up that heat, even evaporating when things get a bit too hot. hence the sizzle you sometimes get (soaking up even more heat - latent heat of vaporisation!) .
This is all good, since it means the heat is not going into the nylon sheath and melting it!!
Law of conservation of energy and all that - O level stuff.
So - the kinetic energy of your fall has to be converted to another form. Due to friction, this is virtually all heat energy.
for the same height drop and same weight caver - the same amount of energy has to converted, no matter how fast or slow you descend.
The only factor that can change is the ability to dissipate that heat. Racks have a bit more 'exposed' metal, so probably cool better due to air flow as opposed to the enclosed bobbins of a stop/simple.
A slow descent just gives more time for that heat to be dissipated.
(well I guess the other factor is that some fatty caver has more potential energy, and therefore generates more kinetic energy, thus more heat to dissipate.
However - back to the OT. You could attach cooling fins to your descender or much more simply - wet the rope !!!
Due to its incredibly high specific heat capacity, water on the wet rope, will soak up that heat, even evaporating when things get a bit too hot. hence the sizzle you sometimes get (soaking up even more heat - latent heat of vaporisation!) .
This is all good, since it means the heat is not going into the nylon sheath and melting it!!
Alex
Well-known member
I thought I should point out one thing that seems to be missed regarding heat dissapating
Going slow despite the same energy being released will lead to a cooler bobbing/rack/rope. This is because there is more time for the heat to dissapate in to the surroundings.
Also I imagine the heat energy released would be on a curve so the faster you go the more violent the energy release will be as that energy is being released is over a shorter time, so alot more heat.
Not really relivant, but I just thought I would point that out.
I thought I would get in on the geek act lol.
Going slow despite the same energy being released will lead to a cooler bobbing/rack/rope. This is because there is more time for the heat to dissapate in to the surroundings.
Also I imagine the heat energy released would be on a curve so the faster you go the more violent the energy release will be as that energy is being released is over a shorter time, so alot more heat.
Not really relivant, but I just thought I would point that out.
I thought I would get in on the geek act lol.
