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A question on doubles 13-Aug-2010 At 10:42:52 PM voodoo

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On 13/08/2010 ajfclark wrote:
>On 13/08/2010 hargs wrote:
>>First, they test half ropes with 55kg (instead of the 80kg used for singles)
>-- and I'm well north of 55
>
>I assume the difference in weight because they assume that part of the
>load will be taken by the other strand.

This exact question came up in Rock & Ice Issue 181. Jim Ewing (product manager of Sterling Rope) provided the explaination. The weight discrepancy has absolutely nothing to do with what weight the rope will take and everything to do with testing procedure. Originally they tested half-ropes with the standard UIAA 80kg test mass (as per standard ropes) - if it withstood that drop, it passed. But one single drop doesn't produce enough test data for it to be accurate. So they lowered the mass to 55kg and raised the standard to 5 drops.

Why is this? Because a labcoat-wearing, calculator massager worked out that 5 drops at 55kg has the same mass value as a single drop at 80kg.

So essentially if your rope is rated to 5 drops at 55kg you know, with a much better degree of accuracy and reliability, that it is capable of withstanding a single UIAA 80kg fall.