Perry Mick wrote:

Paul:

I've reached a point where we can look at some real world data to see
how (in)efficient my ducted fan is.  If I'm using a normally aspriated
13B turning 5200 RPM to go 125 knots, how fast does George go in his
Eracer when he throttles back to 5200 RPM?  That would be an interesting
comparison.  I'm sure he's still going faster than 125 knots at that
point.  Also, I don't think I have the optimum prop/duct combo yet.
I also don't have the optimum prop/duct combo to get the maximum
potential out of the NA 13B (6000-6500 RPM).

--
Perry J. Mick
Mick Duckt N7XR
http://www.mickaircraft.com/duckt.htm

I was thinking about this a bit more and there is really no engine
out there with aircraft engine style power to weight ratios other
than the Mazda running at 6000 RPM and above with a PSRU suitable
for use as a ducted fan engine.

Real aircraft engines would not hold up at 4000 RPM.

The power to weight ratio of say a small block Chevy with
4340 everything and an aluminum block/heads running at 4500 to 5000
putting out perhaps 250 HP might be acceptable at around 400 pounds.

The Mazda would have it over the Chevy as far as size is concerned.
Important for a direct drive ducted fan.

Since 6000 is too high for an efficient diameter ducted fan perhaps
the only solution is pump the Mazda 13B rotary up with a turbo to
about 200 HP and run it at 4500 to 5000 RPM.

One could also gear the Mazda down 4:3 for a 4000-5000 RPM ducted fan which
might be the best solution for my roadable ducted fan airplane.
Even Pratt & Whitney and GE are considering gearing their large turbofans.
Garret is already making geared turbofans.
 
Paul Lamar
 
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