I once bought a 24" box fan at he HD. It had about 5 narrow blades and it
looked like it would throw a lot of air.

I returned it after 20 minutes. It just made a lot of noise and did nothing
but churn air. Too much turbulence and not enough air movement.

After many years of experimentation I have settled for 3 blades, low speed,
high angle of attack, like shoveling snow with a biiig shovel.

Ceiling fans are also low speed because you want to keep the noise and
vibration down. They, too, benefit from the same principle: Wide blades (3
or 5), low speed, high angle of attack (slope).

Air plane propellers are faced with different dynamics: Small planes
universally have a two bladed propeller. Makes a lot of noise and shoves a
lot of air because there is no churning. But, you don't want your ceiling
fan to rotate at 4000 rpm.

--
Walter
www.rationality.net
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"Bob-tx" wrote in message
...
I was shopping for a ceiling fan at a light store (not a big box no nothing
store), and was told by the salesman that a three bladed fan pushed more
air than a four or five bladed fan. Didn't make sense to me so I asked why
that was and was told he didn't know why, but that is the way it is. I
asked if a two bladed fan pushed even more air, but he didn't know and of
course didn't have any. I bit my tongue and didn't ask about a one bladed
fan.

I didn't buy anything yet.

Is it true that a three bladed fan pushed more air than a four or five
bladed fan, and if so, WHY???

I sure would appreciate any info you guys in the know can offer.

Bob-tx