Date:	Sun, 17 Apr 1994 20:40:48 -1000
From:	andrew@tug.com (Andrew Beattie)
Message-Id: <CoFzw1.3u8@tug.com>
Organization: /usr/lib/news/organisation
Subject: Why does a stunt kite turn?

Why does a stunt kite turn?

This is a question which comes up on r.k from time to time and which recieves
answers of variable quality and accuracy.  It is a lot less obvious than
it at first appears.

Things to consider:

1) When I pull on both lines, the whole kite goes faster.
   When I pull only on the right hand line, the right hand side of the kite
   goes *slower* and the left hand side speeds up, causing a turn to the right.

2) "Push left" works the same as "Pull right"

3) The turning mechanism works the same with different kite cross-sections:

   Diamond: \    /
              \/

   Delta:   /\    /\
          /    \/    \

   Peel or Flexifoil:     /-------\
                        /           \
                      /               \

I suspect that we won't get a definative answer, but there are a lot of
new people in r.k of late, and we might make some progress.

Andrew
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Date:	Tue, 19 Apr 1994 05:52:59 -1000
From:	BA03686@bingvmb.cc.binghamton.edu
Message-Id: <16F9DDF62S85.BA03686@bingvmb.cc.binghamton.edu>
Organization: Binghamton University
Subject: Re: Why does a stunt kite turn?

In article <CoFzw1.3u8@tug.com>
andrew@tug.com (Andrew Beattie) writes:
 
>
>Why does a stunt kite turn?
>
 
 
Well, you asked...
    -Here's what I remember from Physics class:
   (This seems basic but will take some explaining)
 
A kite flies up because the wind blowing past it is split:
 
    (top)  ==================>
           ========>\  This creates a low preassure above the kite,
           =========> \
           ==================>
        and a high preassure below the kite. These create lift which is a
force upwards in this figure.
     When you pull a line you angle the kite's plane into the wind in the
horizontal dimension. Yhis creates the same effect as before, resulting
in a sideways force. (Picture the same figure as above but replace "top" with
"right" or"left")
     Forces are added like vectors:
                           __
                     /\    //:
                      :  //
                      ://
                      -------->  (Pull right)
 
Thus the final force is diagonally up and to the direction pulled. As the
the kite moves into its new direction, it turns its nose to match
the final force. This happens because the final force is greater than both its
constructing forces. And as long as a kite is moving, drag will adjust the
kite's natural plane to line up with the strongest force acting on it.
The reason the opposite wing goes faster is because the actual pulling motion
increases the force of the wind. It increases lift which pushes the kite up
and creates the horizontal force which makes the pulled side slow down.
     Then, as long as you keep pulling,the horizontal force remains, acting
horizontally to the plane of the kite.
So the final force keeps "falling" away from the kite as it turns. This will
result in pulling the kite into a circling  motion.
 
 
Does this make sence? Is it right? Am I wasting your time :-(?
 
Love some feedback
 
A.L.


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