Knotability

Okay, so it sounds like a word made up by our friends across the pond but really, this is a measure of one of THE most important requirements for any climbing rope: flexibility.

But all ropes are flexible right? Er, actually no. It’s knot that simple.

A rope with poor flexibility is harder to tie in knots and slides less efficiently through a belay system. The result: frustration, expletives and no strength left to climb because you’ve just expended all your energy having to feed, coax and grimace your rope through your belay plate. Now, this doesn’t often happen with a new rope (although some are more flexible than others due to manufacturing processes) but as a rope ages, a number of factors can accelerate the loss of flexibility and suddenly you find yourself back on the web parting with a sizeable chunk of cash for a new one.

Zero-G ropes are lab tested by having a section tied into a simple overhand knot. A weight is then applied (10kg for a single rope) and the interior diameter of the knot is measured. The ratio between that diameter and the diameter of the rope gives the co-efficient of knotability— in the case of the Zero-G Tanga it is 0.7. The lower the number the more flexible the rope.

Of course, this measurement is done on a brand spanking new rope that has never been near a molecule of grit, never been caked in mud, never been soaked in a puddle, frozen or coated in chalk or salt so our advice is simple:

1: Check the rope you buy for it’s knotability so you know that you are getting a good rope to start with.
2: Clean your rope regularly and save yourself a whole lot of misery, energy and cash!

On a slightly different note - if you clicked through to this page expecting a tutorial on how to actually tie knots then frown no more as those lovely folks at the BMC have turned their legendary knots booklet into a free download. Just click here to read all you need to know......