My Biplane Propeller

Recently listened to a lecture on regenerative electric flight. Electric motor and propeller airplanes are actually flying these days in 2011. Electric motor glider can take off using electric motor and propeller, and fly into an area of lift there to circle and gain altitude in the regular way as a glider flies. During glide to landing, the propeller could function as a windmill and the motor could function as a generator, recharging the batteries during descent.
More after the cut. 
A slotted propeller might be made from two windmill blades. The gray windmill blades could compliment the white windmill blades in Propeller Mode. These two blades together, not quite overlapping, constitute a propeller blade.

Windmill mode remains the same as before.
Here is a style sheet for ya.

Fin

Here is an idea regarding a way to combine the windmill function using many blades, and the propeller function using fewer blades. The drawing Blade4.GIF shows the closed position two blade Biplane Propeller and the open position four blade Windmill.