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Old 04-26-2009, 10:13 PM   #1
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Default How-TO: Foam "NACA" Ducts

Here's another picture laden thread cause I love my phone as much as my DX-7 (:

Last year(?) I posted a thread about NACA Ducts and didn't get any answers.
While cutting on a new plane I had an epiphany:

Cut your NACA duct out in one piece, Important it's one piece and not carved.
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The photos were taken after I had the idea so the 1st photo has the line were I cut an angle on the rear of the opening.
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At this point it's pretty easy. Bend a small curve in the cut-out piece so the nose is back in place but the rear is at the bottom of the scoop and CA in place.
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I opted to be a little fancier and cut the piece in half so it would be flush. The curve can be seen in this photo.
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And that's it!
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Whether this has any real NACA duct effect I don't know but it looks better than a hole in the fuselage.
Gotta be a little more aerodynamic too.

While surely not a scientific test I blew across the duct at different angles.
Blowing into the hole didn't produce much airflow under the foam but blowing ACROSS the duct gets a fair amount of flow.
I'd say if has some actual ducting ability!

-edit2: There's a slight revision I do now.
I don't cut the nose of the scoop completely free.
Once the sides and rear of the scoop is cut, it's bent, the bevel is cut then the scoop is CA'd in place.

"If you stand behind me... You gonna get kicked." - Zebraman.
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Old 04-27-2009, 06:39 AM   #2
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Nice description of your process.

I agree with you - it doesnt have to be perfect to be a lot better than any old hole

I think I need a signature.
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