John wrote:

Morning Paul,
You made a comment that you knew the oil cooler NACA ducts on Nemesis NXT wouldn't work. I've been trying to improve the NACA ducts on my BD-5 and wonder if you could send me data on why the Nemesis ducts are not working? My BD-5 has three NACA ducts (see photo), two on either side of the fuselage "keel" to feed the rad and one further back for the oil cooler. They work fairly well but on hot days (above 90ºF) climb rates are down around 300 fpm to keep things in the green. There was an article in Sport Aviation in Nov 03 describing the installation of vortex generators ahead of NACA ducts. They were supposed to DOUBLE the airflow. I've tried that and they do seem to help but not that much. Any information would be appreciated. If the price of a rotary engine I'm looking at doesn't go "through the roof" I may be joining the Rotary community by converting my BD-5 to rotary power.
Regards,
John Lewis
N501BD

The NACA inventors of the scoop said do not use it with heat exchangers.
Any significant pressure build up in the duct will cause the air to bypass
the scoop opening.

The NACA scoops have been around so long people fail to read the original tech
papers and that includes Boeing engineers and Jon Sharp, Nemesis Nxt designer, who works 
for the Lockheed Skunk works no less. They use them because they look kool but
they don't cool :)

Paul Lamar
 
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