Perry Mick wrote:

Paul,

I saw your posts about ducted fans, and I don't want to rehash
all the old stuff over again, we've been over the same arguments
several times now.

I agree the ducted fan has to be less efficient.  But one more
time I'll say that my goal is KISS, my goal is not to have
the most efficient or the fastest airplane.  There are a lot
of planes out there that are not very efficient.

I asked George to send me some airspeed numbers for his plane
when he throttled back to 5000 RPM, which is where I cruise at.

Here is his raw data:
Indicated airspeeds:  115 knots at 6500 ft., 125 knots at 3500 ft.
GPS Ground Speeds:  166 mph with a tailwind, 145 mph with a headwind.

As a quick and dirty comparison I just used his average GS of 155 mph.
Well, I cruise at 145 mph at 5000 RPM (GPS verified), at a guesstimated
7 GPH, or about 20 mpg, about the same as I get with my RX-7.  Not a
whole lot of difference there between George and I (10 mph), the drag
of the duct can probably account for it.

George's static RPM:  5000
George's RPM at rotation:  5100
Perry's static RPM:  4800
Perry's RPM at rotation:  5000

Where George has the advantage, he can increase RPM over 6000 and go
faster (and burn more gas), whereas mine seems to max out at 5300.

What I've done is not for 99% of the people out there, but I sure enjoy
flying it! (slowly)

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

Well Perry compare it to Tracy's not George's.  George has a very crude
carb set up. His manifold is a piece of four or five inch square tubing
bolted to the block with holes for a two barrel carb and intake ports.
Carb on top side, engine on back side 90 degree away. Filled 
with foam and the runners hollowed out. I don't think 
George
can lean it out at altitude. I could be wrong. Mixture distribution? 
Yes .... maybe. Its KISS all right :-) 

BTW have you gotten around to changing the stock intake manifold for a lower
cowling yet? That ought to be good for more thrust and a few more MPH. 
What are you going to do about the thrust bearing? Have you checked 
the e-shaft end play? Rodger Hilyard mentioned something about that.

How is the new rubber-bushings-in-the-firewall motor mount coming? 
I am real curious about that as I am considering doing it on my 
Cruiser.

Sorry for all the questions.

Paul Lamar
 
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