Re: Screw size and speed

[Dave Everett <deverett@idx.com.au>]

At 09:31 22-07-99 EDT, SFreihof@aol.com wrote:
>In a message dated 7/21/99 7:10:22 PM Eastern Daylight Time, 
>deverett@idx.com.au writes:
>
><< It's only a Kort if the prop is shaved to a "square" tip and the
clearance 
>between tip and nozzle ring is minimal (like a sixteenth or so). >>
>
>Hmmm.  What if the shroud is attached to the blade and rotates with it?  Or, 
>what if the blade tips are "T" shaped, as I've seen on some aircraft props 
>and wings?  Is the same effect accomplished, to eliminate tip vortices?
>
Attaching the duct to the blades will increase the prop efficiency, however
it will probably decrease the motor efficiency because of the extra weight.
There would still be small slow moving vortices around the duct.

I'm looking at using ducts for a small flying platform I'm designing and
will be trying to make a rotatable duct as well as a standard one.

I'm not familiar with the T-tips but it sounds like an interesting idea, I
think there would still be vortices with a T-tip, more than a duct.

Dave Everett.