I drove over to watch a large wind turbine in Minnesota and just sat there and watched and listened. It was very quiet, woosh....wooosh.... wooosh as each blade passed. I was entralled. They should build more.
But it took some time to understand the blade pitch angles. I think it had blade twist unlike a helicopter, but rather had less angle near the hub than at the tip. This is the apparent negative pitch Matthew referred to above.
But the blade sections are flying at a positive angle relative to the wind.
I see the windmill as a sailplane optimised for rotation. The windmill tower provides the same force as gravity in the case of a free glider.
Be careful, they are tall obstructions for low flyers. The windmill will win.
Last edited by slowrotor; 5th October 2006 at 20:23.
Reason: edit for spelling