How to Design an Efficient DIY Propeller for a Homemade Car?

[goorioles747]

Hi,
I need to make a propeller using either soda bottle plastic or cardstock. I think I can come up with a mechanism to spin it with a rubber band, but, I need an efficient propeller that creates enough power to move the car I am building. Any ideas/possible designs?

 

[russ_watters]

Two concepts are critical to propeller efficiency:
-Camber: The propeller blades have to be curved to re-direct the airflow.
-Twist: The propeller blade has to be twisted to provide a steeper angle of attack at the center than at the tips (the tips are almost flat in the direction it spins). this is so that the velocity distribution along the blad is constant.