"Dancing Fingers" wrote in message
...
Last night the Mythbusters put about a 2 inch layer of clay a a sedan
and drove it at 65 mph and recorded their mileage. They put dimples
in the clay, like a golf ball, and repeated the same test and got 11%
better mileage. This again begs the question why don't wings have
dimples, especially for STOL type aircrat, where you still have
laminar flow? Heck, hexagonal dimples might reflect radar better for
all I know?
For conversation
Chris

Something along this line has been discussed here from time to time, and we
did not all agree at that time.

However, even ignoring the possibiliyt of measuring errors in the
Mythbusters tests, an automobile does not need to produce lift in order to
operate--and may work best if all lift can be eliminated.

The most classic case of dimpling, of which I am aware, is a golf ball.
There, the dimples provide a relatively clean breakaway of the airflow--so
that, even thought the cross section of the wake appears larger, the total
energy level of the wake is reduced.

There have also been some potentially interesting experiments involving
propellers, although I have never personally seen the sort of conclusive and
complete data that a really well designed experiment should be able to
provide. For example, there was an initially interesting article in
Experimenter several years ago--but the experiment was not sufficiently well
planned, and the aircraft was not sufficiently instrumented, to provide
really conclusive findings. (Actually, changes in the relationship of
engine RPM to airspeed without accurate monitoring of manifold pressure and
fuel flow can be extremely misleading--but that is a subject for nearly
endless future threads.)

So, the bottom line is that the results of dimpled wings could be
interesting--and there has been some successful experimentation of gliders.
But seemingly small changes in the installation be better or worse, might
have a softer or more abrupt stall, etc.

Peter