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LONGITUDINAL STABILITY OF FLEXIFOIL?


In article <1u0bpm$9v2@charm.magnus.acs.ohio-state.edu>, byang@magnus.acs.ohio-state.edu (Been-Der Yang) writes:
>WHY THE FLEXIFOIL CAN MAINTAIN THE LONGITUDINAL STABILITY?

This is a really good question. If you get a definitive answer, then
be sure to tell the inventors why it works, they would be really
interested.

Ray Merry, one the inventors has often said that he doesn't know why a
flexi should fly, just that it does. They have done experiments to
determine the best shape of the airfoil, the best aspect ratio, etc. I
imagine that if an engineer or a scientist were to spend enough time
examining things they could come up with an answer, but so far no one
has taken the time.

>I saw someone mentioned the "lightweight" spar. Does it mean the
>weight or the flexibility?  In which situation we should use the
>lightweight spar?  The quality of the spar seems to have great
>influence in the flying of the flexifoil.  Would it be weight or
>flexibility?

The lightweight spar is both lighter in weight, and more flexible. One
thing that is clear is that the spar must bend in order for the flexi
to fly. In light winds you need a more flexible spar in order to have
the kite form the correct shape.

>  But, no matter what the
>answer is, I admire the person who invented the flexifoil.  From the
>history of human flight, man can fly always after he really understand
>the reason.   

The story goes that the flexi's inventors were playing around with
airfoils and flexible and rigid spars. They had problems with
stability, but kept at it. One day, the kite turned "inside out" and
flew like a dream...
--
Marty Sasaki            Harvard University           Sasaki Kite Fabrications
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