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Re: REFLECTOR: Pictures of the air intake on my bird


When I run into a new student at the fluid dynamics lab at Fla. Tech I have
a favorite question to see if they understand the basic principles:

Which way should a 2 to 1 funnel be placed in the wind tunnel to get the
most smoke tracers through the center?  The students that don't have to
think to say "small end into the wind" are the ones I want to work with.  If
you put the big end into the wind ALL the smoke diverges out in front and
goes around the funnel creating massive turbulence.  Small end into the
wind... the smoke trails converge into and through the small hole.

Venturi and Bernoulli's principles don't make since to most of us so we just
have to go by what the lab tests have proven for years.  Scientific method
is the only way to get objective about this type of engineering.  NASA's
test in the 70's made it clear that we also need a minimum of a 3/8" thick
lip and 1" stand off from the fuselage/wing.

In Velocity intakes internal porting of the "expanding funnel" is
challenging.  Restrictive sharp bends  as we go into the cowling or up into
plentums can cause  air to "pile up" out in front of the intake.  Over the
years we have all been guilty of subjectively engineering these systems with
our cut and try.  By doing this we are looking at CHT's which is like
studying the symptoms without identifing the disease.  A multitude of
pressure censors fed into a PC would be great but an old fasioned manometer
should do the trick.

Adjustable flow is usually done with the exhaust outlet.  If your prop has
good "cusp" at the TE root and is close to the cowl it will suck more with
more rpm.   The best control I ever got of the cabin ventilation was with a
pilot adjustable cowl flap under the rear seat with the back seat area and
strake vents sealed up.

Your "gizmo" looks like something I've seen for ram air on a Mach Five Wave
Rider which has slightly different pressure dynamics (my favorite word).
Maybe you are building the wrong kit.  Do you want to go coast to coast in
45 min.?      I do.

Your friend