Here is something I'm sure Bob and my dad will not leave untouched. In
today's LA Times, in the "Science" section they had the following:
"Q: Is a fan with five blades more effective than one with three blades?
A: The more blades a fan has, the less efficient it becomes because each
blade is moving in the turbulent wake of the blade preceding it. But a fan
with fewer blades has to turn faster to move the same amount of air, so it
will have a higher tip speed and thus be noisier. The same principles
apply to airplane and ship propellers. The optimum efficiency is achieved
with a single blade attached to a suitable counterweight, and some planes
have actually flown with such a design. The primary reason for multiple
blades is to reduce the diameter and the noise."
Jay
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