What's the fascination with cotton? You said yourself cotton is not the best dielectric.
I was being ironic, really. Just trying to say that under extreme situations cotton may not be the best, but in the "controlled" environment of the living room it'll be almost perfect. Cotton as dielectric (and also paper) to me makes the contour (attack and decay) of instruments and voices sound more natural than teflon and other plastics. Its downside is that timbres are not so well defined as when plastics are used. Swap any non-electrolytic capacitor in the signal path for a paper one and hopefully you'll see what I mean. There's always a compromise. Each material has its own advantages, and one must try not to be more papist than the Pope.
I think it's not just the dielectric constants that tell the whole story, much in the same way silver sounding different from copper must not be solely attributed to the better conductivity. If it was the case, using a double run of copper wires of a predetermined gauge would halve the DC resistance and should sound silvery than a single silver wire of the same gauge. But it doesn't. Why the heck it doesn't, I don't know.
Instead of cotton rope, why not try polypropylene? It has a D.C. of 1.5 and is not hydroscopic.
Been there, done that

. That's a splendid design, I must say. I did use cotton rope and cat5, though (not an issue with portuguese weather :JPS: ). I testify that geometry is one of the best around. It simply adds
nothing to the sound and stays
musical unlike other low capacity, air dielectric designs I've tried.
Weave your wire into the braid. I like Cardas tonearm wire, 33 awg copper litz.
If you don't like the counter-rotating helix you can run the wires in parallel. If you don't like yellow, polypropylene rope is available in red, green, blue, white, black, and neutral or any combination.
Use your choice of termination. I like Bullet plugs. The fused polypropylene collar provides strain relief from pulling and the setscrew prevents twisting.
Thanks for sharing. Those cables should beat a lot of commercial ones.
I advocated the use of polypropilene rope on several posts in AA and DIYAudio.com, long before SilverFi appeared with their line. They seem to use the very same ropes I did. It's the same weaving pattern. You can find them anywhere in AKI stores and the like. They're made in Spain and cost like, 3€ for 10 metres? Just be sure they're made of polyprop, not nylon, and that they're woven around a core. The basic design sounds very, very good. Take the core out and carefully insert the wire of your choice. Twist it or braid it PBJ style and terminate. This way it should measure no more than 50 pF/m. Adding more wires and complex braids like SF do will just add more capacitance and no significant benefits, I think.
To finish, j_b you got a champion there. I advise everyone into DIY to try it. You may discover the interconnect thing is done.
Cheers