A parafoil as light as a kite with a inflated spar and draw strings to inflate (or deflate) the air chambers. I'd like six per hub please one set CCW for the right hub and the other CW for the left hub. Some different flavors of Tyvek (that's a Dupont plug cause they were nice enough to send me the sample swatch of ALL the currently produced non woven fabric. Have you ever tried to rip up one of these envelopes? Tough Stuff), including some of the breathable knit.
The later I thought of surrounding the exhaust ports at the trailing edge and vibration to energy converters and coils interlaced in layers. The more vibration removed at this trailing edge or a valid harmonic received to get the airflow relaminerized and give the next blade an advance informational vibrational analysis to what air vibration (AUDIO -by product of all rotational flight or thowp-thowp-thowp-thowp-thowp.) to expect to and can maximize leading edge V2EC to create a truly silent rotor system and have it make electricity for external load of motors or battery charger. Or a tickler to the linear induction rotor hubs, and transferred to the frame's V2EC for stacked resonance drive and highest conversion of harmonics. Rotor differential speed is the other source of power in this system.
A parafoil for a slow efficient rotor blade? Only in Ceriva's dreams. Better than woven rattan.
An ultrasonic wielder, an air knife on a XY CNC (to get the patterns cut) and a big bench would make this vision a tested experimental rotor system that could change the image of rotational flight to the world.