Paul, I have had some time to get back to my CAD education with Alibre.
I'm working out the cowl profiles, and was wondering if you had some simplified models of
the 13b in combination with the RD-1c and Doddridge plate. I was hoping to kinda stick
them in to make sure everything clears. I'm using the extended mount dimensions for the
lightweight version of the 13b on the Zenith CH-640.
C. Smith

Try some of these.

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Here is what the jpgs renderings look like from that igs file I just
sent.

I have a model of your engine and motor mount.
Send me a sketch of what you want the cowl to look like
and I will send some renderings and igs if you wish.

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Here is the Rhino model I have.

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More views.

Looks like the best place for the rad
is underneath  with your extended MM.

PauL Lamar