How about an ornithopter?  ;-)

Tongue firmly in cheek,
Bill
Long EZ builder & pilot
mechanical engineer

No! No! Ornithopters are not out of the question. No
fooling. We have a
least one person on the list working on a rotary
powered ornithopter.

The X wing or dragon fly variety is particularly
attractive as the vertical
reaction forces are more or less canceled if the
wings are 180 degrees
out of phase. Very similar to this kayak propulsion
unit. There may also
be some aerodynamic advantages as the wake is less
vortex perturbed unlike a
spinning prop. Similar I would say to a counter
rotating prop.
I suspect there is useless or wasted vortex energy
in the wake of
a single prop. I have yet to see where this has been
investigated.

Paul Lamar

Vance Jaqua wrote:

There has been a great deal of study of the "vortex
sheet" which is different from the rotational loss
component behind a prop. This loss is surprisingly
small and is indeed partially recovered by the second
contra rotating prop. In most cases - except for high
disc loading turbofans - stators to recover this
rotating loss create more drag than gain.
I fear that onithropters are inherently lossy since
you are expending energy on drag and some negative
lift during the up sweep. The only reason birds flap
their wings is because God had not gotten around to
developing an organic Wankel :-) - Vance

Stators are widely used in turbofans for bis jets.
Here is a picture of stators in an Allied Signal 731-60. Also used in
P&W JT15D

Depends on the angle of attack while the onithopters wing is going up.

And a propellor I might add.

Paul Lamar

I too think that ornithopters are a viable approach.  I just don't think
the "enabling technologies" are mature enough.  I agree with Paul that the
key to making it practical is the proper angle of attack at all times.
That requires cyclicly variable twist.  The birds and bugs all have it.
The structure and actuators with our crude methods would be prohibitively
heavy and complex.  If someone could replicate the functions of a bird (or
bug) it would make one kick-ass ultralight.  I don't see high speed or even
cross-country ornithopters, however.  Vance's chart demonstrates that
propulsive disk area becomes less of a factor the faster you go.  But I
would rather have an ornithopter than a Mini-500.

Jeff Spitzer

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