Paul wrote:

Face it Tracy! You are going to have to provide this 2.85:1 option sooner
or later :-)

"Perry J. Mick" wrote:

Like when Renesis arrives.

You guys can't have it both ways, if small ducted fans are "bad" then
big slow props have to be "good".

--
Perry Mick
Duckt N7XR
http://www.ductedfan.com

Let me clarify. I am not advocating a big slow prop. The landing gears
we have to work with are too low to the ground for that. I am 
advocating a slower
prop of the same diameter using the 2.85:1 psru. As Don Bates stated
we are only looking at a 2 to 3% prop efficiency loss while picking up
20 to 30 HP normally aspirated by running the engine up to 7500 RPM
or so.

Paul Lamar

The prop program by Dokus and Dubner shows a 2.2% loss of efficeincy
between a 76.4" prop (at 2700 RPM) and a 64" prop (at 3225 RPM).
This would indicate that there is not much difference between the 2.17
ratio and the 2.85 ratio.  These numbers are for a tip speed of 900 ft
per second.  900 ft per second is 80% of Mach at sea level on a 'normal'
day (1114.4 fps).  This also explains why the canard guys go so fast
with small diameter props.

Ken Powell

I'll let Bill explain the chord factor because I  don't understand it yet.
I think this is for a 16 series.

The second chart is lift to drag ratios at Mach .78 for different airfoil
sections.

Paul Lamar

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org