I've been climbing on an Edelrid 8.6mm Canary rope and many of my partners did double takes the first few times they climbed on it, calling it spaghetti cord and sketchy. Despite seasons worth of cragging, trad climbing, and some fixing and jugging on it, the thing looks practically new. I've tried to explain to folks that thickness of the rope does not directly correlate to the durability of the rope. I think that it is true when you look at older makes of thin ropes, such as the Beal Opera, which is notoriously trashable, but modern rope making technology is breaking this assumption. Sheaths can be woven significantly tighter, meaning we can find ropes with equivalent sheaths and huge weight improvements over thick ropes.

It's very easy to say that because a rope is thicker, it has more material, and therefore lasts longer. I'd like to introduce an easy way to estimate general durability of a rope in relation to another rope. In order to quantify material, we can take the rope's weight per meter and calculate the approximate sheath weight per meter.

Using the above table, we can see that the thickest rope does not have the most sheath material. When we compare the Canary to the Mammut Workhorse, we find that it actually only has 5.5% less sheath material despite weighing 22% less. That's incredible!

This doesn't tell the whole story. Sheath can give an idea of the general durability of a rope, but 25% more sheath does not mean 25% more cut resistance. According to Edelrid,  it takes 12.3cm to cut an 8.9mm rope and a 14.3cm to cut a 10mm, both loaded with 160kg of weight [1]. That's only an additional inch, or a 14% difference. The weight loaded is pretty exaggerated for this comparison though. If we look at their number, 54cm, for an 8.9mm with 80kg and extrapolate the number for the 10mm rope, we'd expect to see the 10mm cut at ~63cm. That's only four extra inches. In my opinion, four extra inches between my rope cutting or not is just not enough margin to make up for the weight difference between rope diameters. Basically, if a rope is going to cut, it's going to cut regardless of thickness.

I think this makes the Edelrid Swift Protect interesting, and I'm curious how they hold up long term. They do have a quarter less sheath than our top rope, but allegedly have way higher cut resistance. According to [1], they have about 1.5x the cut distance than a 10mm rope, or about 14 inches. I'm not sure how that will translate to cragging and fixing durability, but it will be cool to see as long term reports come out.

N.B. All of the numbers used are from the manufacturers. How each determines weight per meter or diameter differs, so the numbers do not exactly reflect reality, but give an approximation.

[1] https://www.youtube.com/watch?v=IL2r_f2g4Sw