Hi Bill,
The shape of an aero object depends a lot on its use. While a teardrop
shape does have a very low drag, when measured by itself, remember a
bellytank car is running very close to the ground ("ground plane"). That,
plus the wheels interfere with the air flowing around much of that body.
Having said that when you hang that tank under a wing, the wing would act as
a ground plane as well, so ... My question about bellytanks involves their
angle of incidence. It would seem to be pretty sensitive to the angle of
the tank relative to the ground as far as stability goes.
The rear of the vehicle is VERY important. Air can only stay attached
(laminar)at rearward taper of about 7 degrees before it becomes turbulent.
One other thing to consider in the rear is a rounded shape there can be very
unstable. This is because the point at which the smooth flow separates from
the surface is not consistent and can move the center of pressure around on
the body (think of a knuckle ball).
I think it was Howard that mentioned the roostertail. This can be the poor
man's wind tunnel. The smaller that dust trail the better your aero package
is.
Dale C.
Subject: Aero Effects
Hi Folks, the discussion about aero leads me to wonder if the classic
lakester with a body made from an aircraft drop tank isn't the best. I
assume many dollars were spent by the plane makers to find shapes that
are aerodynamically neutral, no lift forces in any direction, and
minimum drag.
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