Moderator: Tim White
ek wrote:...it is still possible to have a knot that should never be used because it is so weak. (I believe that the double-loop and directional/inline figure-nines--unlike the regular figure-nine--are examples of this.)
[color highlighting in original]A Directional Figure-9 exists, as shown in the photo, but is not to be used. Contrary to common sense, it’s weaker than a Directional Figure-8 when end-to-end shock-loaded - the problem is that the emerging rope (heading left in the photo) doesn’t follow the entire pattern, and just bends around one turn as it leaves. Combined with the extra slip inside a Figure-9, this makes a rope-on-rope rub point at the worst position. The loop of the knot is fine, it’s what it does to the straight-through strength of the rope that’s the dangerous bit, and if the loop itself isn’t loaded first the knot can be damaged by a severe shock load.
Also in the same “nice but deadly” camp is the Double Figure-9 (the Bunny-9). You’ve probably never seen one, but it exists (and here’s a photo!). As with the Directional knot, it’s impossible to make the inter-loop turn of rope follow the pattern of the knot, and it creates a very slippy rope-on-rope rub point. The Bunny-9 under a careful, equal load is the same strength as a Bunny-8, but if one loop is slack and the knot is shock-loaded, it can melt.
ek wrote:If you plan to take big falls on your Spectra footloop, I think you should be afraid.
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