Re: Screw size and speed

[Greg Teiber <wolfe19@megsinet.net>]

Well I would debate you on that one :)  Kort nozzles are used as a rudder device on tugboats, It has the tendancy to turn the whole stream of water instead of just trying to use a rudder in backwash.  Though the nozzle would have most of the effect of a duct, it isn't as close fitting of a device, and pivots independant of the propellor.  if you want to find good information, Look up what you can about ducted fans used in some homebuilts and in RC airplanes.  99% of what you find there will transfer directly if you compensate for the lower shaft speeds and the smaller props.

*********** REPLY SEPARATOR ***********

On 7/21/99, at 1:05 PM, SFreihof@aol.com wrote: 

>In a message dated 7/21/99 6:58:50 AM Eastern Daylight Time, 
>wolfe19@megsinet.net writes:
>
><< For ducted fans, both undrewater and above water, if the cowling is 
>relitivley close fitting, efficancy can be markedly improved.  the propeller 
>don't have the spill off at the tips creating those wingtip vortecies.  >>
>
>The propeller shroud is called a "Kort Nozzle."  I haven't been able to find 
>much information on design or sources for supply.  Anybody else?
>
>Stan