I am all for eco-friendly materials but there may be more to the equation than simply replacing carbon fiber.
Epoxy gives the material its stiffness. Carbon fiber serves as the reinforcing material. This leads me to believe that the type of epoxy makes up a very important part of the sound.
Ekoa is a combination of flax and bio-resin. I suppose there are other materials that could be used for reinforcement? Or other types of epoxy? Or is it possible to create a guitar out of pure epoxy without any reinforcements?
Questions, questions...
But anyway, perhaps more important is the weight of an acoustic guitar. In general I have noticed that the lighter a guitar, the better it sounds. It must be why air guitar always sounds great to the player.
All kidding aside, with their soundboards Blackbird seems to have found the right balance between lightness and stiffness. In addition the hollow neck reduces the weight even more and enhances the resonance.
I believe this is where Emerald and Rainsong could really learn a thing or two from Blackbird. Especially when it comes to nylon string guitars.