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Re: Ceiling fan design



On Fri, 13 Feb 1998, Neil D. Adams wrote:

During Christmas, I spent a week in Honduras visiting my daughter who is
in the Peace Corps. We saw a number of ceiling fans, mostly older ones,
where the blades were horizontal, or nearly so, with the tips bent
upward at a 70+ degree angle. My knowledge of aerodynamics is limited
resulting in my failure to understand the function of the bent tips.
Can anyone help me?
Thanks in advance.

I've seen these in films. I've heard that on aircraft it's done to
stablize the tip vortex so lift is not lost when the vortex migrates
towards the fuselage. Maybe fans suffer from this effect, so a bent tip
increases effective fan area.

Since fans are sometimes very close to the ceiling, perhaps the bent tip
aids in the radial airflow along the ceiling surface.

Or, perhaps its some sort of marketing meme. If some manufactuer of old
produced a bent-tip fan in order to gain product recognition, and other
companies copied it to aquire bent-tip customers, then an "infection" of
bent-tip fans could progress through the fan market, even if the bent tips
have no function. A "fan-culture phenomenon" rather than pop-culture
phenomenon.

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