There is some advantage it seems to being able to test windmills, close to the ground, and find out exactly their output, and durability. We built a simple bracket of wood, and tied it onto our '30 tudor. This way we could monitor exact windspeed, and take down information. So far we used it to test only a 7' diameter 3 bladed prop, attached to a alternator built from an induction motor. 
The results were definitely interesting, and the ride exciting. I didn't feel safe much over 20 mph, at which point the output was about 12 amps into a 12 volt battery. I doubt this prop, or the hub to which it was attached would have held together much past 20. At any rate, it's fun, exciting, and an excellent way to get information about a systems performance. It helps to have a co-pilot to monitor speed, voltage and amperage, and to jot down measurements.
The results were definitely interesting, and the ride exciting. I didn't feel safe much over 20 mph, at which point the output was about 12 amps into a 12 volt battery. I doubt this prop, or the hub to which it was attached would have held together much past 20. At any rate, it's fun, exciting, and an excellent way to get information about a systems performance. It helps to have a co-pilot to monitor speed, voltage and amperage, and to jot down measurements.