REFLECTOR: Retrofit NACA from armpit scoops

[Andrew Ellzey]

Andrew,

You can keep your scoops attached to your cowl if you make mating internal scoops that stay with you engine and airframe. My internal scoops are attached to the cowling flange which is part of the lower wing. I only had to add four additional screws that have to be removed when you remove the lower cowling. It sounds like you already have the internal portion of you armpit scoops made to attach to your scat tubing, just cut them off and add flanges to attach them to your airframe. Then add as many additional screws as needed to make them re-attachable to your lower cowling. See attached photos.

Andy Ellzey 




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From: Andrew Judge <ajudge at grovenetworks.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Mon, October 26, 2009 1:18:56 PM
Subject: Re: REFLECTOR: Retrofit NACA from armpit scoops


I’m a little concerned about high temps. I seem to have them now (semi high temps) and want to get the temps right and make it easy to take the cowlings off. I also have a second oil cooler, but both cyl and oil seem a little high.
 
Maybe I can keep the scoops and cut those out of the cowling and fasten them permanently to the wing roots?
 
Thanks!
 
Andy
 
From:reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Chuck
Sent: Monday, October 26, 2009 1:06 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Retrofit NACA from armpit scoops
 
Andy, 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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