ducted fan design questions

[Bob Chiang]

Hi all,

Didn't know whether to post this here or in jets, but I've seen great information in this forum, so....

I am designing a sport model to be powered by a GWS 40 and six 300 or 700 mah nimh cells. The GWS fan unit will be located in the middle of the fuse, with a tube running forward to the intake in the nose. The fan outlet will be exposed on the bottom half of the fuse.

Will it hurt the system efficiency if the inside diameter of the tube fits the outside of the GWS intake lip? or do I need to make the intake tube so the inside diameter matches the inside diameter of the GWS duct?

Is my target weight of 7 ounces too high? Any recommendations for wing area?

Thanks in advance,
Bob Chiang

[John Boren]

For a intake design you would be better off if the intake matches up with the inside diameter of the fan unit. You can build up a over lap joint on the intake tube with thin ply or balsa so it fits over the outside of the fan unit but allows the intake tube and front fan shroud to share the same diameter.

John Boren

[Bob Chiang]

Thanks for the response and information John. I figured it would be better to have a smooth airflow from intake tube to fan unit.
I guess I was hoping for an easy to build duct system.

I took a look at your web site: impressive fleet (my condolences on the turbine).

-Bob Chiang