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Topic Date User

Knots 29-Nov-2007 At 11:01:03 AM AlanD

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On 29/11/2007 bomber pro wrote:
>Given that the bulk of the strength of a rope is its core, I think that
>a 25% reduction in strength is too
>much, maybe if a quarter of the core was shot then you could apply those
>figures, but not otherwise.

You're assuming that the core is only damaged by being cut in one location and filaments that make up the core do not lose strength with age, unfortunately this is not the case. If you rope gets grit into the core, that grit can start cutting the individual filaments or groups of filaments, without any damage to the sheath. It's also the nature of polymers to lose strength overtime as the between the polymer chains break, heat being a major influence.

>Also have to say that a figure of 2,3 is pretty out there, maybe even
>impossible to generate this
>but it does make your theory sound more knowledgeable to quote facts and
>figures,
>though only they were the correct figures!

Yawn. See the correction above to the 2.3 figure. Yes, by definition 2.3 is impossible to generate. Figures do put things more into perspective, even they are guessimates, to many people see that there rope or sling, beaner are rated to take a certain load, divide that by how much they weigh and thing that they have a safety factor of 40. Knots, damage to the core from cutting, age, the type of fall, loads etc reduce that significantly.

>And trying to use this situation, to then say that if you were doing a
>rescue would further reduce the
>safety margin is just plain crazy! who would climb up 60m from the anchors
>with a quarter of the rope
>shot, and then connect another climber to themselves and jump off?>

From my understanding, a 4 metre fall generates the same fall factor a 120 metre fall. Surprising anchor points fail, including those above you, while you might not delibrately jump off while doing a rescue, the situation can develop through the failure of other items.