I loved the design for the 4 blade turbine. I scaled it up slightly, gave the blades a slightly different attack angle to the wind, which I think will work better, and added another four blades. I also re-made the hub, and changed the hole size to suit my little motor, but am printing near 100% infil, so I can drill out if required.

Ideally, I think the front of the blade should have more of a scoop, or hollow to increase efficiency, but this design looks pretty good the way it is.

Thanks morrowwm!