"cavelamb" wrote in message
ink.net...
Peter Dohm wrote:

"T o d d P a t t i s t" wrote in message
...

"Peter Dohm" wrote:


The Embry-Riddle link leads to someespecially fascinating discussion,
including that some efects of the dimples are related to Reynolds
Number.
However, I clearly have a distance to go before understanding this
subject--even enough to safely apply any rules of thumb.

If you are interested in the aerodynamics of spinning balls,
or want to try to extend the state of our knowledge of
aerodynamics as applied to aircraft design, then by all
means, keep on looking at dimples.

However, if your real interest is in reducing the drag of an
aircraft, you'd be better off studying up on laminar flow
and interference drag. There is enough information out
there in the glider community on fairings, control seals,
inexpensive laminar flow testing techniques (old motor oil,
pieces of yarn, microphones or stethoscopes) to keep you
busy for a long time and which will really produce drag
reduction.
--
T o d d P a t t i s t
(Remove DONTSPAMME from address to email reply.)

Make a commitment to learn something from every flight.
Share what you learn.


Well, I already know a lot of the rules of thumb for drag reduction,
especially with laminar flow, and that is my first choice for choosing
or
building an airplane.

I am also interested in general aerodynamics, and am somewhat intrigued
by
the issue of dimples. Particularly, grooves and dimples could be quite
interesting as related to propellers. Regrettably, there is a /very/
finite
limit to the percentage of time I can devote to that, so my progress may
be
gradual.

Regards,
Peter



All we need is a wind tunnel...

You're right. Then we could prove a lot one way or the other--especially if
a little smoke was part of the system. There would still be the effects of
scale and Reynolds number, which are supposed to be quite significant, but a
lot could still be learned. At least it should be possible to either verify
or deny the assertion that grooved or dimpled props produce a virtual
"switch pitch" effect.

Maybe next year.

Regards,
Peter