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Dennis, pay attention to the inlet air first, but looking at your install
the exit air has to turn 180 Degrees to exit the bottom of the cowl. You may
want to put in a deflector shield between radiators and engine after you're
done with inlet air. I have an under the engine radiator installation
(water) as well but my radiator is much different ... 20" x 5" X 5" ... will
send photos later.
Jeff
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Dennis Haverlah
Sent: Sunday, May 27, 2007 2:11 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] James Cowl - RV-7a - Renesis - Cooling
I had very marginal cooling on my first and second flight - RV 7A, James cowl, Griffin Scirocco aluminum double pass water radiator with a Mazda 1989? RX-7 oil cooler. Water radiator fin size - 22LX13WX2.5T inches. Oil - 19LX4.5WX 2T inches. The radiators are mounted side-by-side under the engine and are at about 25 - 30 degree to the inlet air flow. (The air must turn 60-65 deg to flow through the radiators) See photos 1 and 2. After my first 2 flights, I constructed a divider/duct to provide a duct for the engine combustion air to make the sharp turn 90 deg. up after the inlet to get to the filter. The bottom of this duct was also supposed to provide a duct wall for the air going to the radiators. See photo 3. Two flights demonstrated this really hurt - not helped - my cooling. Now I can barely take off and fly the pattern before getting up to 210 - 215 on oil and water. The divider duct took out about 8-10 sq. in. of inlet area but removed the engine combustion air requirement form the remaining inlet air going in the larger inlet.
My inlet is about 50 sq. in. and the outlet is about 67 sq. in. This cowl was used successfully on the Power Sport a/c so I believe the inlet and outlet are at least big enough for 160 + hp. When I first posted pictures of the radiator installation someone suggested I may need turning vanes to improve flow to the radiators. I am now ready to try the turning vanes below the radiators.
Does anyone have info. I can use to design the turning vanes? The K&W document on page 273 mentions guide vanes but does not go into detail. I am thinking of 2 inch wide vanes long enough to go from the left to right side of the radiators and spaced 4 inches apart with the top of the vanes about 3/4 inch below the radiator fins.
Comments or -- Any other ideas? Dennis H.
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