Why do windmills typically have 4 blades, yet all modern wind turbines have 3?

Question

Why do windmills typically have 4 blades, yet all modern wind turbines have 3?

In: 9124

Answer 1

Windmills with wooden spars need to have even numbers of sails – one on each end of each spar. Wood construction technology demands this because of the huge forces involved. Modern turbine blade technology allows the three blades to be mounted on a central boss because the strength and resistance to lateral forces of the materials are much greater than wood. There were, of course mills with six and eight ‘jib sails’ each one being much smaller and only suitable for sites with nearly constant strong winds.

Answer 2

Windmills with wooden spars need to have even numbers of sails – one on each end of each spar. Wood construction technology demands this because of the huge forces involved. Modern turbine blade technology allows the three blades to be mounted on a central boss because the strength and resistance to lateral forces of the materials are much greater than wood. There were, of course mills with six and eight ‘jib sails’ each one being much smaller and only suitable for sites with nearly constant strong winds.