This is better than a separate duct around the fan as the fan being
buried in the fuselage there is less total skin friction drag. It
won't be as efficient as a prop but it is more efficient than a
conventional external ducted fan.

Of course with 650 HP you may not care. It looks like a jet aircraft
and goes pretty good :-)

Another advantage is there is no gear box required so that saves 30
to 50 pounds and about $3,000. The main fan is cheaper and much
lighter as it is not running at 1400 to 1800 F temperatures so it can
be made from carbon fiber.

A further advantage is the simplicity of the turbo compound feature.
Since no gear box is required this saves weight and money. In fact
most radiant waste heat from the engine, normally unrecoverable, is
used to increase the pressure in the duct slightly. Much like an
after burner.

It also heats the cockpit.

This is well  before I wrote the book "How To Cool Your Wankel" so
some improvements can be made in this cooling system.

I should have gotten  a patent on this thing but I was way ahead of
it's optimum time :-)

I tried to sell it to Southwest Technical Institute but they had no
vision :-)

It takes a brilliant engineer to recognize a brilliant engineer :-)

I may do some 3D's if any one is interested.

Paul Lamar

Paul, so ducted fans seem to be popular, maybe you would like this,

https://www.youtube.com/watch?v=IvAToG7GZPU

Steve Carlisle

So are opiates. That does not make them good :-)

Some of the early swing wing ducted fan airplanes were designed by
engineers that did not understand the drawbacks of ducted fans.

Ducted fans in essence increase the diameter of a rotor used to generate
a lot of low speed thrust at the great expense of inefficiency. Ducted fans
are high drag when used as horizontal  propulsion. That is why the Osprey
uses large diameter rotors and NOT ducted fans.

The Wright Brothers understood the low speed thrust efficiency
of a large diameter rotor. In essence they had two of them with just 12 HP.
Remarkably it made their airplanes capably of lifting and flying two people with VERY low
HP. Years, if not decades, ahead of any other airplanes anywhere near such low
HP. It is the reason twins climb better than single engine airplanes.

It is the reason we use and 84 inch diameter prop on the TTC.

Even the vast majority of  $100 electric drones don't use ducted fans. They
use a lot of motors and props. The relevant term is called disk loading. Google.

https://en.wikipedia.org/wiki/Disk_loading

Ducted fans are less so if they are buried in a fuselage similar to a jet engine.
The outer skin of the fuselage has drag and you need that skin
anyway no mater what.

A ducted fan at 80% of that of a prop needless to say is still not as good as a prop
which is already only 80% efficient.

There is an analogy with an electric motor and a generator. The generator
is 80% efficient and the motor is 80% efficient. So the overall efficiency is .80
times .80 or 64%.

This is not just a good idea.  It is a LAW of physics.
The world would be a better place if they started teaching physics in
High School. Then maybe I would not get such questions :-)

Paul Lamar

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