Moderator: Tim White
JSDunham wrote:One factor no one has mentioned yet is that webbing is easier to inspect; rope with questionable history may have deterioration of the core that isn't visible from the outside. I would never trust rescue rigging to a rope that just happened to be in the cave myself, unless I knew its history. Webbing, by contrast, I could inspect and be more confident about.
Something I've wondered about: does anyone know how fast a rope deteriorates when left in a cave? I know, various conditions--but any ideas?
JSDunham wrote:Something I've wondered about: does anyone know how fast a rope deteriorates when left in a cave? I know, various conditions--but any ideas?
I've seen fixed ropes in caves that have been there for 15-20 years that appear to be in good condition.
If a rope stays too long underground (i.e. several years), it can have serious effects on the rope, even resulting in breakage during normal use. We have already seen this with a dynamic climbing rope left in a cave for seven years. While it had only been used twice in those seven years, it broke on the third use under the weight of the second person to climb up that day!
paul wrote:An interesting and relevant story from an old newsletter from my caving club: The strange story of orpheus rope number 10.
Mike Hopley wrote:I've seen fixed ropes in caves that have been there for 15-20 years that appear to be in good condition.
Appearances can be deceptive. A cautionary tale from Alpine Caving Techniques, about leaving ropes underground for too long:If a rope stays too long underground (i.e. several years), it can have serious effects on the rope, even resulting in breakage during normal use. We have already seen this with a dynamic climbing rope left in a cave for seven years. While it had only been used twice in those seven years, it broke on the third use under the weight of the second person to climb up that day!
This issue applies to nylon rope and webbing/slings (polyester ropes might not be affected in the same way, because they don't chemically absorb water). On expeditions, we've often left ropes (derigged and coiled) in the cave for the next year. We limit this to about three years total, and then replace the ropes -- but of course it depends on the situation, and we take advice from an expert...
Dynamic rope is really not a good choice for caving, except for belaying climbers. Abrasion resistance in a rope is proportional to its elasticity; that's partly why Dyneema, which is static, is so hard-wearing. Semi-static (caving) ropes stretch a lot less than dynamic (climbing) ropes; therefore semi-static ropes resist abrasion better than dynamic ones.
On top of this, caving ropes tend to have a thicker, stiffer sheath that is more abrasion resistant.
Extremeophile wrote:While I agree that dynamic kernmantle is not a good choice for caves, I'm not sure I understand the anecdote from ACT. So a rope left in a cave for 7 years lost roughly 95% of its original strength? This story, and your explanation after, suggests that this loss in strength was due to chemical degradation (maybe just from exposure to moisture?).
It seems more likely that the rope mentioned in ACT failed due to abrasion, and in this case the lesson should be don't use dynamic rope as fixed line in caves because of lower abrasion resistance, not that fixed ropes need to be changed every 3-7 years because of chemical degradation.
Again, it seems like someone has probably tested Nylon rope under controlled conditions to determine the loss of strength over time. I'm all in favor of regular inspections of fixed ropes and retiring ropes based on visible attributes (e.g. sheath wear), but I believe a decision to change ropes on age alone should be based on data showing the change in strength over time.
Mike Hopley wrote:Extremeophile wrote:While I agree that dynamic kernmantle is not a good choice for caves, I'm not sure I understand the anecdote from ACT. So a rope left in a cave for 7 years lost roughly 95% of its original strength? This story, and your explanation after, suggests that this loss in strength was due to chemical degradation (maybe just from exposure to moisture?).
They seem to be blaming it on the loss of strength due to water absorption, yes.
Of course, for the furtherance of knowledge, it's helpful to have people like you around to test old ropes through real-world use.
I'm also not sure why static ropes are being tested in FF2 scenarios. I believe most brand new static ropes won't survive a FF2 test with an 80kg weight. And even if the rope survived, you probably wouldn't. Seems like static pull tests would be more meaningful.
Extremeophile wrote:Again, if 10 years is the period of time to allow a sufficient margin of safety then why not share the data showing what that margin is?
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