I had a brain storm today on a roadable aircraft.
It is always in the back of my feeble mind :)
I realized one of the unique features of the rotary
is its very simple e-shaft. If one makes it longer and
larger in diameter on the front end one can get power out of both
ends. One end is mated to a stock VW transmission and the
other end uses one of Ken Welters 3:1 cog belt reduction drives.
You take off in first gear and get much better acceleration to
flying speed. This is due to the traction you get out of tires
as opposed to a highly slipping prop. As soon as you run out of
RPM in first you push in the clutch and shift into neutral.
the prop takes over.
For road work you remove the canard and main wings
and tow them behind you. The only drawback here is the weight
of the VW gear box and drive shafts.
Its a motor cycle on the ground as that circumvents a load of
EPA and DOT rules.
Paul Lamar
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Roadable airplanes ARE flyable. There are no technological
break throughs required. The vast majority of the
parts are off the shelf.
The main challenge is minimizing the weight penalty.
Most roadable aircraft designs use twin booms for the tail but
the Ruttan Canard configuration is a better fit with roadable
requirements IMHO. To my knowledge nobody has tried the canard
configuration yet.
Paul Lamar
Paul,
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With modern high
strength to weight ratio materials and the canard configuration
the aircraft performance does not have to suffer that much.
There are a zillion VW rear suspension and drive line, three wheel
custom motorcycles on US roads and they suffer no performance penalties
what so ever. Particularly with Mazda rotary engine power.
Sure it won't be as fast as a Long EZ but it will get you there
a lot faster than a car. Especially to remote areas like Baja.
An honest person could make some money selling well designed
kits.
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With the gear retracted there will be near zero aerodynamic
penalties.
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One of the design parameters one needs to pay a lot of attention
to on a roadable is the weight of the wheels and tires.
I suggest dragster forged aluminum front wheels and tires at 15 by 3 1/2
for the rear. You need diameter as the cruise RPM on
the ground using the VW tx requires a rather large diameter
tire.
The front tire can be a light weight motorcycle wheel
and tire. Motor cycle disc brakes will also keep the weight
down.
Paul Lamar
My suggestion for the structure is to use 3/4 inch thick foam carbon fiber sandwiches
in a box like structure. 1 to 10 layers of carbon according to the stress
and one layer of glass to insulate it from metal attachments.
The engine is cantilevered from an aluminum plate between engine and gear
box. The prop shaft is large diameter carbon fiber Charlie Airsmen
style. Prop is carbon fiber Perry Mick style large diameter hub.
Front suspension will not be the traditional motorcycle type. I have
a new design I used on a Breedlove 3 wheel land speed record car that
distributes the loads better into the structure. Went 400 MPH no
problems.
What do you think of the structure Vance? Got any suggestions for
improvements or changes?
Paul Lamar
