[Don Kingsley]

Don Kingsley  asked the Naked Scientists:
   
Why are most wind turbines used to generate electricity three bladed. rather than four or five, as in your excellent sea fury fighter of wwII?

What do you think?

[Phractality]

Turbulence from each blade reduces the amount of torque on the other blades. You can get more total torque by adding more blades, but each additional blade adds proportionately less torque. The most efficient turbine has only one blade with a counter weight on the other side of the hub. Apparently, three blades is the most cost-effective number.