Paul,
I'm looking at your diffusser picture on p23 of your book on cooling and
would like to know two dimnensions which would be used for say a 20 "
square radiator core
 1) height of the wedge diffuser opening
 2) dimensions or area of the trumpet diffuser inlet opening.

John P


That had the 2" wide by 20" long 2nd gen oil cooler mounted along side the rad so the total
core dimensions would be 25" wide by 20" long or 500 square inches of core frontal
area. 25% of the core area is a good rule of thumb for a 200 MPH airplane.
If the core frontal area is 500 square inches 25% of that is 125 square
inches or 10" by 12" or 6 inches by 25 inches in front of the wedge. Larger
if you are building an airplane that is never going any faster than 150 MPH
such as a float plane or STOL bush plane.  In that case you can use 30% or 35%.
Smaller if you are building a 300 MPH racer and you don't mind climbing out
at a modest angle and higher speed. Cooling drag at cruise will be reduced
in any event if you use well sealed cowl flaps as they reduce the air flow into
the intake and cause a phenomena called external diffusion. In effect a self
streamlining volume of high pressure air build up just in front of the intake
opening.


Paul Lamar ...No rotor no motor.

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