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OK, archive search function sucks (or at least I can't figure it
out). So here goes.
Finn
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Finally got
around to finishing my cooling inlets. (pictures attached)�
Up until now they were simply round pipes sticking out of
the cowl.�� The pipes are still there but they have properly
shaped bellmouths on them.�� The shape and contours were
derived from a NASA contractor report (NASA_CR3485) that you
can find via Google.� Lots of math & formulas in it but
I just copied the best performing inlet picture of the
contour.�� Apparently there is an optimum radius for the
inner and outer lip of the inlet.�� There was no change to
the inlet diameters of 5.25" on water cooler and 4.75" on
oil cooler.
The simple pipes performed adequately in level flight at
moderate cruise settings even on hot days but oil temps
would quickly hit redline at high power level flight and in
climb.�
The significant change with the new inlet shape is that they
appear to capture off-axis air flow� (like in climb and
swirling flow� induced by prop at high power)� MUCH better
than the simple pipes. �� First flight test was on a 94 deg.
F day and I could not get the oil temp above 200 degrees in
a max power climb. �� They may have gone higher if the air
temperature remained constant but at 3500 fpm the rapidly
decreasing OAT kept the temps well under redline (210 deg
F).
I have an air pressure instrument reading the pressure in
front of the oil cooler and was amazed at the pressure
recovered from the prop wash.� At 130 MPH the pressure would
almost double when the throttle was advanced to WOT. � That
did not happen nearly as much with the simple pipes.��
These inlets ROCK!
Tracy Crook
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