Are kernmantle ropes more susceptible to damage than 3 ply twist or solid braid?
A comment on recent answer suggests that kernmantle ropes are more easily damaged than a conventional twisted rope. This is contrary to what I learned very long ago. So far I've been unable to find a general reference on how different ropes need to be handled, and what tools can be used with each.
Please do NOT answer with generalities like 'keep it clean, don't step on it, check after each use' I'm looking for usage differences.
Example: One rope company said that double braid rope shouldn't be used where you have a running bend over a short radius, such as a pulley or carabiner, as the inner rope is 'milked' with the slack running to one end, and most of the load then falling on the inner rope. (I've had this slip happen with shoe laces...)
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Since I'm guilty of the comment in question and referring to climbing ropes in particular. The key to the comment is that they're more sensitive to damage, not that they're more vulnerable to it.
What they're specifically vulnerable to is hidden damage. If the core is damaged, the rope is significantly weakened but it's really hard to tell from a surface inspection.
Twisted rope on the other hand can be inspected much more easily.
So for example, if you accidentally penetrate a kernmantle rope with a marlinspike while trying to undo an overtightened knot, you don't actually know what damage you may have done. With a twisted rope you have both the gaps created by the twist to work the spike into and the ability to fully inspect the rope for damage afterwards.
With a mainsheet or other lines on a dinghy that's not really a problem, but for a climbing rope unknown suspected damage is a reason to get a new rope.
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In general, the answer is most likely no. With regard to (at least) one specific scenario, however, kernmantle ropes are thought to be less resilient than twisted rope.
Consider the case when one rope (rope1) is used to tie a load into the middle of another rope (rope2). Rope1 is first turned in a few coils around rope2, and then somehow fastened. Rope2 bears the load with the support of rope1, because of the friction of the numerous coils of rope2 around rope1, which effectively fasten rope2 onto rope1. Some examples of this scenario are the Tarbuck knot, Prussik knot (with load), etc. This is more likely to happen under heavy load, e.g. rescue situations, falls, etc.
The coiled rope (rope1) directly grips onto the outer sheath of the other rope (rope2), in the process pulling on it, and trying to strip it (the sheath) from anything it might be holding on to (the core). This pulls at the bonding between the sheath and core, and can in the long run damage it.
This phenomenon is known as sheath slippage. Do look it up, there are lots of posts about it in various forums. This is supposedly one of the reasons behind the development of unicore ropes, which are marketed as being immune to this problem.
This post was sourced from https://outdoors.stackexchange.com/a/24652. It is licensed under CC BY-SA 4.0.
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