[BabyPeanut]

$this->bbcode_second_pass_quote('', '�')��One hot Florida summer evening, my father-in-law, Shep Shepperd, and I were sitting around talking over a drink. I remarked how much cooler it felt under the ceiling fan above us. A retired airline pilot, having flown many a propeller-driven aircraft, Shep looked up and said—‘Yep, but those damn things haven’t changed since I’ve been around.’ Shep is 83. I asked him what he meant by that. ‘Well,’ he said, ‘I never flew an airplane with a flat propeller.’ That started me thinking about why ceiling fan blades are flat in the first place....”

[parainwater]

Two reasons:
Flat blades are cheap to make and the fluid
Reynolds numbers are low hence negating
the positive effects of a nice airfoil.

[jato]

My ceiling fan is reversible, the airfoil (or lack thereof) has to travel in both directions.

[Cool Hand Linc]

Jato makes a good point about the reversing of the ceiling fan.

Have you ever noticed how most things are produced in an in expensive way?

A flat blade is pretty inexpensive.