REFLECTOR: Retrofit NACA from armpit scoops

Chuck c.harbert1 at verizon.net
Mon Oct 26 13:06:06 CDT 2009


Retrofit NACA from armpit scoopsAndy, I switched from the armpit scoops to the overhead NACAs when I switched from the Mazda 20B to the IO360. It wasn't that big a job, but it does take some time to repair the lower cowl and to cut and paste the fuselage to accept the NACA ducts. Initially I had cooling issues with the NACAs until I tightened the plenum clearances and added 5/8" VG's. 

I'm just finishing adding a turbo and a second oil cooler (factory) which mounts in-between the inlet NACAs. I've added the factory 3" oval air scoop to the upper cowl that feeds directly to the oil cooler, but is not totally sealed to the oil cooler face. I did this because I was getting a pretty hot upper cowl and I think this will help force cooling air into the upper area and when shutdown will release hot air out of the scoop opening. I went with a scoop because the boundary layer is pretty thick that far back on the fuselage and I wanted to get clean air. I'll be doing taxi testing soon and will let you know how it works. 

By the way, you can get the factory scoop in either fiberglas ($35) or carbon fiber ($45). I'm using the carbon which is stringer, lighter and has a smaller opening profile.

Chuck H


From: Andrew Judge 
Sent: Sunday, October 25, 2009 9:32 AM
To: reflector at tvbf.org 
Subject: REFLECTOR: Retrofit NACA from armpit scoops




I was wondering if anyone on the list done the change from armpit scoops to NACA cooling?

I really want to make the change due to maintenance and cooling on my Standard Fixed. The SCAT is killing me every time I have to remove the cowlings.

If so, what difference in ease of maintenance, cooling and speed (if any) have you noticed? I'll probably do the down exhaust too.

I also have a second oil cooler aft. How do you route air into that?

Andy Judge
N55AJ
KTMB 



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