Mike Wills wrote:

At 04:33 PM 12/20/1999 -0800, you wrote:

If the shape of the bottom of the duct is curved properly you
don't need guide vanes. Guide vanes generate aero losses all on their
own. Use a wind speed meter to check the uniform airflow through
the rad to be sure you have the right duct curve under the rad.
The duct should be bell shaped.
Paul Lamar

Paul,

  I went back and looked through my own personal archive and also looked
around on the ACRE site. I couldnt find any pictures/drawings depicting the
appropriate diffuser shape that you came up with a couple of months back.
Everything I found showed the wedge shaped duct with the sharp angle at the
rear. Do you have a drawing (preferably with some dimendions) of the duct
that you tested with the curved rear wall? If so could you post here and to
the ACRE site?

Thanks,

Mike Wills

This is the turbo version of the Rv6 from the web site.

This one has a very subtle curve. It may not be enough.
I would fab and adjustable version for your airplane much
like the test rig and experiment a little bit in the air
with flow sensors. There should be room in the cowl as
the bottom is convex instead of concave.

The ideal would be a 3D bell shape of course.

Also even a straight 2D wedge shape would cool 
pretty good.

The trick to get it to fit is get it as far up under the
front of the engine as you can. Move the motor mount
back a wee bit if necessary.

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