REFLECTOR: NACA's vs Scoops

[Al Gietzen]

Subject: REFLECTOR: NACA's vs Scoops

 

I thought of using one of the exisiting armpit scoops that will not be

needed for engine cooling, for the intercooler, but then what do I do with

the other scoop?  It be kinduv lopsided to have one armpit scoop.  Maybe a

very low profile scoop in the middle of the lower cowling?

 

I don't think you need to be concerned much about having a scoop on one
side; but I would suggest not using the stock Velocity scoop.  IMHO; it is
not a very good design, and with a bit of flow resistance downstream it is
likely to spill some air.  The drag of a well designed scoop would be small
compared to the overall drag, and it's "moment arm" a couple feet off the
centerline is small.  (At least I'm assuming all this is correct since I
have a scoop on one side).

 

When looking at one scoop or another; consider that if they exit into the
cowling, it is likely that one (the biggest, or best pressure recovery)
could control the downstream pressure inside the cowl.  Pressure recovery
minus heat exchanger pressure drop equals exit pressure.  If you have an
effective ram scoop, and a NACA scoop of similar size, you could find air
exiting the NACA scoop.

 

Al

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