Kort Nozzles

["Marsee Skidmore" <heyred@email.msn.com>]

I looked long and hard at ducted props when I was working on Lockheed's
entry in the 1st "Annual" Human Powered Submarine Race. The conclusion that
I remember reaching at the time was that adding a duct ("Kort Nozzle") only
reduced the diameter of the optimum prop. Care must be taken in maintaining
the foil section of the duct, and minimizing the prop to duct clearance.
Ducted props are typically used by tugs, that have a high engine-to-boat
ratio, where an unducted prop may have an unwieldy diameter. :-o Joe