When air moves past a rotating sphere or cylinder the surface friction
can induce a rotational component into the airflow. This shifts the
pressure distribution and causes a net lift. The lift allows a golf
ball to achieve a longer flight. The dimples 'dirty' the surface and
increase this rotational effect.

Lift on a wing can be considered in different and equivalent ways. Some
of the ways to look at lift from a wing a
-Deflection of the ambient air is a mass pushed down which results in a
force up on the aircraft.
-Faster airflow on the upper surface and slower airflow on the lower
surface create a pressure difference and lift.
-The wing induces a circulation in the ambient air which can be
directly related to lift.

It is interesting to note that a vortex in free air must be closed.
Just like a common smoke ring. But the wing is finite. The vortex peels
off the wing in an approximately elliptical distribution across the
span and is left behind both wing tips as the aircraft flys away. Aside
from friction eventually stopping the circulation a few minutes after
the aircraft is passed, theoretically the vortex continues back behind
the flight path all the way to the runway where the plane took off
where the first inch of movement of the wing began a very small vortex
and very small lift.

A baseball pitcher gets a similar effect when the spinning ball does
not sink as fast as it should thus fooling the batter. On the other
hand a knuckle ball appears to stagger like it was drunk and makes the
batter queasy. eww!

James

Dancing Fingers wrote:
Hi all,
I always wanted to build my own airplane but the time and money has
eluded me. So I've decided to design and build my own recumbent trike,
with farings. This brings me to my question, if golf balls have
dimples, to help them sail further, why don't wings -- especially for
STOL aircraft? Would putting dimples in my faring reduce my wind
resistance?
Just curious.
Chris