REFLECTOR: Louvers

Rene Dugas dugasd at bellsouth.net
Mon Nov 1 12:00:32 CDT 2010


It seems like Jean also added lips to catch more air on the trailing edge of
the NACAs too to increase the differential pressures.  I may be wrong.  I
can't find those old pic right now.  How close to the cowl exit is the
leading edge of the prop?  I have no temp problems with the IO 540 non turbo
with NACA's one inch larger than recommended originally.  My inlet plenum
slopes down gradually to cover the entire engine and my exits are close to
the Prop.  Two oil coolers.  560 hrs.

Rene'

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Jeff Barnes
Sent: Sunday, October 31, 2010 9:33 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Louvers

 


Hi Scott,

 

     Look at this from Jean Prudhomme.  Jean was among first to implement
the top cooling ducts/NACAs. The big hole is to exit cooling air.  Worked as
far as I can recollect.

 

http://www.tvbf.org/gallery/index.php?display=engines%2Fexhaust_jean_prudhom
me%2Fjp_exhaust_1.jpg

 

 

     The picture series was to show his improved exhaust.    

 

 

Regards,

 

Jeff Barnes 

--- On Sun, 10/31/10, Scott Derrick <scott at tnstaafl.net> wrote:


From: Scott Derrick <scott at tnstaafl.net>
Subject: REFLECTOR: Louvers
To: reflector at tvbf.org
Date: Sunday, October 31, 2010, 7:38 PM

Still trying to get my CHT's down where I like them.  I consider 400-410 in
cruise TDH.

I've been thinking about the exit for the cooling air. I've got a fairly
large engine in a fairly small cowling,  IO520 in a STD cowl. I did enlarge
the aft end of the cowl a bit but just enough to barely clear the plenum on
top and the right hand exhaust tube(#6) on the bottom. I've been thinking
maybe I have restricted the airflow out of the engine compartment?  As I
understand air cooling its all about differential pressures between the top
and the bottom.

I then started thinking of putting a cowl flap in the bottom cowl, right in
the middle.  I sketched it onto the cowl and was trying to figure out the
hinging on a curved surface, how much movement woudl be needed etc..  I was
planning on making the door and at first just bolting it on in the full open
position to see how that worked, If I saw a dramatic decline in temps I
could then install an electric actuator of some kind to operate it from the
cabin.

Then somebody mentioned a set of fixed louvers? You see them all over
Cessna's and Beech's.

Has anybody installed a set of fixed louvers in the bottom cowl and had it
improve their cooling?  Maybe a set below each side of jugs?

Scott

-- It is with our passions, as it is with fire and water, they are good
servants but bad masters.
Aesop

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