Tandem-wing Airplanes

William Hung wrote in news:356251e4-f6d9-420e-a4d8-
:

On Feb 2, 11:59*am, Bertie the Bunyip wrote:
Phil J wrote in news:e5efb14f-c2c5-41c7-a127-
:



Here's another question for you engineers out there. *Traditional
airplane design has the tail pressing down, so the tail is fighting
the work that the main wing is doing. *A tandem-wing airplane in
which

both front and rear wings are lifting upward is a more efficient
design, which is one reason Bert Rutan chose the canard
configuration
for so many of his designs. *But in the canard configuration, the
front wing is smaller than the rear wing. *This is what I don't
understand. *It seems to me that a design in which the front wing
was
larger and the rear wing was smaller would be more stable in pitch.
The smaller rear wing would automatically damp pitch excursions
like
the fins of an arrow. *So why is the canard the most successful
tandem-
wing design flying?

Well, it isn't a tandem wing, for one thing. It's a canard. It's
front
"wing" is called a canard and not a wing. You could say it's a tomato
tomato thing, but that's the definition. A Bleriot could also be
called
a tandem wing aircraft if you used the same standard. It's tail
lifts.
So do most free flight models. These airplanes have very large stabs
(or
wings, if you prefer), and very far aft CGs as compared to a a
"conventional" aircraft and usually very long fuselages.
Aircraft like the Bleriot were not very stable in pitch, and RC
conversions of old time free flight airplanes with the original FF CG
are very twitchy in pitch if elevator is used.

*The basic principle is that more of the horizontal surface (
multiplied

by it's arm) has to be behind the CG to get the thing going in the
direction you want it to. Think horizontal weather vane.
That's pretty simplistic, but basically it's the way it works. The
horizontal weather vane principle also explains why conventional
aircraft get nasty when their CG is moved aft. Never mind any rubbish
Jepeson might tell you about the elevators making lift the wrong way.
.
I'm not exactly sure what the definition of a tandem wing is,
percentage
wise, but basically if it looks like one then it is one. That is, the
wings should be in the neighborhood of each other area wise.
The Flying Flea would be a good example.

Bertie

I was gonna mention the Flea. The Frogs seam to like the Fleas.

Definitely not my cup of tea, but the early ones have a funky look
that's irresistable! The French were fodn of Tandem wings period. There
was a guy named Delanne who made a few in the thirties and forties. and
there was a light plane called the Payen tht was near enough a Tndem
wing that made no difference. I don't know much about how either one
flew, but Delanne made a lot of different airplanes and I think a few
Payens were made and flew for a good few years.


Bertie