Glenn,
>
> There is a 12" long diffuser section that expands like a bell to
> slow and pressurize the incoming air. After the rad, there is a
> converging duct that accelerates the hot air back to free stream.
> There also is a pull up cowl flap inside the converging section
> that allows most of the incoming air to be shut off under cruise
> conditions, adding 10 mph by cutting the flow and associated
> drag when its not needed.
This is the way to go.
Nice work designing and constructing your cooling duct and cowl flap.
Kchemann is indeed a excellent basis to start from.
We had long discussions with Michel Colomban, of Cri-Cri and Ban Bi
fame, who also used calculated sections similar to Kchemann's
theoretical curves.
Since I had the opportunity to build a small wind-tunnel, I chose to use
the stream-line approach (also in Kchemann's book), to exactly match
our radiator block characteristics.
The results showed that a shorter -hence less lossy- diffuser was
adequate in our case.
We also had to manage cylinder cooling air and intercooler duct.
Your cowling looks very sexy.
Congratulations,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
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