Kite Aerodynamics

[Kite Aerodynamics -- How Kites Fly]
Kites, as heavier-than-air tethered crafts logically should fall like all other objects under the influence of gravity. But kites fly, and the obvious question remains: how is the kite able to fly? This section will discuss some of the physics of kite flight.
Kites are airfoils:
An airfoil is any object that can alters or redirects the flow of air so as to cause differing pressure around it. The wings of airplanes, sails, bird wings, parachutes, and kite are all considered airfoils.
Air naturally resists all physical objects passing through it. If you sweep your hand you can directly feel air resistance. Airfoils are objects shaped and angled in such a way that they can redirect the flow of air around them unevenly so as to create pressure differences.
The angle of the kite diverts the flow of air unevenly over the kite. Air passing over the kite moves faster than air passing under the kite. According to Bernoulli's Principle, the faster a current of air moves, the lower it's pressure becomes. We see then that because the air flowing over the kite is moving faster than air flowing under the kite, the air pressure above the kite is lower than the pressure below the kite. The higher pressure below the kite pushes up on the kite to create lift.
Forces in Equilibrium:
A kite (single line kites) will fly suspended in the air, that is, in equilibrium. We have mentioned two forces operating on the kite thus far, gravity and lift. Gravity tends to pull the kite down, lift counters by pushing the kite up. There are, however, a total of four forces at work simultaneous on the kite. The other two forces are that of drag or resistance from the wind and the tension of the kite line. All these forces must cancel out in order for the kite to remain suspended in equilibrium. Objects, because of their dimension naturally resist any flow of air passing through them. This resistance is called drag. Drag tends to push the kite horizontally back. So there must be some force pulling the kite forward so as to keep the kite in steady position. This force is provided by the kite line pulling on the kite. When all four of these forces are in equilibrium, the kite stays buoyed.
Lift-to-drag ratio.
It is an inherent fact of physics that all airfoils have both drag and lift.   Ideally, a kite would have only lift and no drag, but this is impossible since lift is generated due to the drag.  That is to say, the shape and position of the kite resisting the wind cases pressure difference above and below the kite which in turn causes lift.  Lift is always inversely proportional to drag.  One of the main principles in kite construction then is to maximize this lift-to-drag ration; to maximize lift and minimize the drag. 
Kites that fly high have good lift-to-drag ratio.  If the lift-to-drag ratio is low, then the kite (as measured by the angle of the kite line to the ground) will fly at a reduced angle.  Of course if the drag is greater than the lift, the kite will not fly at all.
http://www.thehighwaymen.co.uk/