Hi Ed,

As usual I didn't pay attention when I should have.
I'm now replacing the right radiator for the 2nd time (this time with a new one) and am starting to look at proper ducting.

Bernie Kerr suggested pointing the inlet in the direction of the slipstream from the prop to increase ram effect.
Looking the the inlets on some turboprop installations it seems the clearance between rear side of prop and tip of inlet lip is quite small. My RV-3 cowling tapers back from the center to maybe 5" at the outside of the cowling.
Would there be any negative effect on prop efficiency if one were to extend the outside of the cowling out close (1" or less) to the trailing edge of the prop?

Which brings me to the next question: With proper ducting, what is your currently recommended mininum inlet area? I'm considering a circular inlet as in Dave Anders RV-4 (see the Mustang II in Feb 2004 Kit Planes").
The advantage of moving the inlet forward would be a longer duct, closer to the optimal 7 degree maximum.
Would having the inlet real close to the prop also increase pressure in the duct?

Others are welcome to chime in here too :)

Finn