Why do knots weaken a rope?

Asked by: Bob Nevis, Manchester

Anyone who relies on the strength of a rope takes great care to prevent knots forming in it, as they can reduce the breaking strength by more than 50 per cent. The reason is that knots create curved regions of rope whose outer circumference is greater than the inner part. This difference in length creates stress across the rope’s width when put under tension, undermining its strength.

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