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More acid rope testing 2-Jun-2012 At 10:33:11 PM ARidgley

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On 31/05/2012 Olbert wrote:
>On 31/05/2012 mikllaw wrote:
>>Lots of stuff and mentioned the 'bowline effect'
>
>What is the 'bowline' effect? Is it the effect of reducing the breaking
>strength of a rope because of the bowline knot? If so, is there a corrasponding
>'figure 8' effect?
>
>The strong ropes broke at ~12kN, this seems very low. Is this what a
>real rope out in a real climbing situation would break at? If I go for
>a big factor 2 whipper on a bowline, am I going to generate enough force
>to potentially break my rope (assuming nothing else breaks) ?

I think Spelean did quite a lot of testing of knots, mainly static, during the 80's. This is from memory and Dr Law may know better, but if my memory serves me correctly, the humble bowline breaks well below 50% (maybe as low as 35%). The Alpine Butterfly is not much better and should be avoided at all costs too. A Figure 8 is indeed up there at around 80% or more with the best knot being a Figure 9 at above 90%.

What I found most interesting was that a Figure 8 tied in line (i.e in an Alpine Butterfly application) is still stronger than an Alpine Butterfly even though it looks ugly and stressed. It's all about the diameter of the tightest bend. All knots should bend around at least two strands.

If you use a Figure 8 for everything you'll do OK. Makes life simple too.