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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