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Scoop - outlet, exit air vent

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gmcjetpilot

Aerospace
May 21, 2007
11
Hi, New guy, mech engineer degree, airline pilot and experimental aircraft builder RV-4 & RV-7.

Regarding thread 1-61524:

key words, vent, outlet, scoop, exit.

The question is about the so called NACA scoop, working in reverse, ie, for an exit air scoop, not as an inlet air scoop.

Yes it will work. Any scoop can flow in reverse. However for exit scoops the common type if you want flush is a parallel wall submerged (flush) scoop, with a ramp angle no greater than 30 degrees. With a NACA scoop you have lips and radius-ed edges as key details. As an exit it is just not that critical. So the flush ramp is very simple and as effective as any NACA scoop, at least as a exit.

Old NACA report No. 713. Although the report is for scoops as inlets, it does show the ramp type exit I am talking about. A good scoop that works well as an inlet often does work for an exit, may be better. However in the case of the NACA I think the complication of making the shape is not justified as an exit. However it looks cool.

If you need or want a external scoop, protruding a simple ramp is all that is needed, a "Flap" if you will. With a scoop sticking out in the breeze rounded corners would be a nice touch.

Looking for data on exit or outlet scoops, I really have not found much, for subsonic planes. Lots of exit or nozzle design for jets, ramjets and hypersonic stuff.

I agree with the comment in the ref thread that the execution of NACA scoops on experimental planes (amateur or home built) are often poor. They are look a likes, but the details and dimensions are poor. They are there for style points in my opinion, just like some sports cars.

What you all think. Any good exit scoop data?
 
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