The ageing of ropes

Thanks Dave,
Pit seems to have produced a very similar graph, but not with the rope over an edge.

Does anyone know if the main issue with respect to wear is the number of pitches and raps, or minor falls on routes and in the climbing gym?

If I give a rope a hard life in the hills it ends up a furry. Indoors it might take 1000 falls and look fine. I guess I'm damaging different bits but different processes. Although indoors I'm also lowering a lot.

well each time you rap and lower off a rope it stretched out the rope ...

for your particular reference its not the falls but simply climbing, rapping, lowering with the rope ....

A J McLaren, Design and performance of ropes for climbing and sailing Proc. IMechE Vol. 220 Part L: J. Materials: Design and Applications

;)

does this mean that, even if you don't weight the rope, the rope ages while you are climbing? i don't really understand how it would put wear on the core if you don't even weight it. obviously rapping and lowering will put weight on it, so i'm not including that.

eli poss wrote:does this mean that, even if you don't weight the rope, the rope ages while you are climbing? i don't really understand how it would put wear on the core if you don't even weight it. obviously rapping and lowering will put weight on it, so i'm not including that.

For one 30% or more of the strength is not in the core, and the outer areas get worn from being dragged over rock.

yes but the sheath isn't what elongates to absorb energy and the core doesn't ever touch the rock.
also, slightly off topic but, my limited understanding was that the rope doesn't actually absorb energy but increase the duration of time that the load is applied so it applies a smaller force over a longer period of time. am i wrong?

eli poss wrote:yes but the sheath isn't what elongates to absorb energy and the core doesn't ever touch the rock. also, slightly off topic but, my limited understanding was that the rope doesn't actually absorb energy but increase the duration of time that the load is applied so it applies a smaller force over a longer period of time. am i wrong?

sure it does, how else to does the rope stretch if the core doesn't elongate. The sheath provides some portion of the strength of a rop

eli poss wrote:yes but the sheath isn't what elongates to absorb energy and the core doesn't ever touch the rock. also, slightly off topic but, my limited understanding was that the rope doesn't actually absorb energy but increase the duration of time that the load is applied so it applies a smaller force over a longer period of time. am i wrong?

The sheath has to stretch, otherwise nothing would stretch. The core may not touch the rock but is still affected by being bent and weighted over edges.

The rope absolutely absorbs fall energy. The mechanism for absorbtion is that the falling climber stretches the rope, and the work done stretching the rope has to account for the climber's loss of potential energy. Other work may also be done, eg against frictional forces, tightening of knots, and this too contributes to fall energy "absorbtion."

The business about distributing the load out over time is often cited but is a side effect of the rope stretching, not a mechanism for reducing peak load, which is determined by the maximum elongation of the rope, not how long it takes to get to that elongation. It may well be that the effects of loading on the human body are easier to take if the load is stretched out over time rather than applied all at once, but I don't think gear really cares much about that aspect.

Speaking of the reduction in number of UIAA falls held as a "reduction of energy-absorbing capacity" is a very confusing way to describe that phenomenon, confusing because it seems to me to confound the rope's ability to absorb the energy of a single fall with the ropes ability to absorb fall energy over and over again. I think what happens is that the rope "stiffens," which means that it can still absorb fall energy but the peak loads get higher and higher for the same FF fall. Eventually, those peak loads exceed the rope's breaking strength and the rope fails.

So, the effect of climbing and rappelling on a rope is to make it stiffer and stiffer, and so less able to pass multiple drop tests. Perhaps more important, since it is unlikely that the rope will ever get to the point of actually breaking in the field, is that the stiffening of the rope over time means higher loads to the gear and the faller.

I suspect that one of the best things you can do for your rope is to reduce the amount of rappelling, by climbing down and/or walking off when possible.