Why do traditional windmills have four fins on them whilst modern wind turbines only three?

What are the reasons for the original four fin design and why has modern engineering moved to a three finned design?

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  • 1 decade ago
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    A four blade design is easier to make and balance, but fewer and longer blades are more aerodynamically efifcient. This is because the airflow coming off the back of one fin creates resistance for the following fin. In old windmills, the blades turned very slowly, so this effect was not significant. Also, the builders were limited in the length of the blades that could be made. The shorter the blades, the more you need to get the same power.

    Electric generator windmills need to turn faster under less load. You can be sure somebody did a lot of high tech aerodynamic computer simulations to determine the optimimum number, length, speed and shape of blades to get the most power. This kind of technology was obviously not available to the old windmill designers.

  • 1 decade ago

    Four fins are used to drive the heavy wheels to grind corn into flour ,the three fins are only driving a light turbine to make electricity .

  • 1 decade ago

    Less fins are more efficient, one fin with a counterweight is the most efficient but doesn't have the power density to make it worth using.

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