HOW DO KITES FLY?
A kite will fly if it finds enough wind to lift it and keep it in the sky. Successful kite flight depends upon establishing and maintaining a balance between the upward force of lift, the downward force of gravity, and the backwards force of drag.
Wind blowing against the kite’s sail is blocked by the sail and is forced to move around the kite. If the kite is positioned at the proper angle to the wind, more air is deflected down from the sail than is forced up and over the kite, thus creating lift. This lifts the kite upward, overcoming the force of gravity. Turbulence swirls around the kite, reducing the lift and increasing the drag. Drag pulls the kite backward but the kite line prevents the kite from moving backwards, and the net effect of these forces – gravity, lift, and drag — is to move the kite upwards until it reaches a point of equilibrium.
“Getting any kite – from the most basic to the most complex – to fly is a matter of achieving a successful lift-to-drag ratio; that is, the lift must exceed the drag. Naturally, the kite must be constructed properly and maintained in perfect balance. Assuming these prerequisites are fulfilled, obtaining the correct lift-to-drag ratio depends on angling the kite to the wind properly, a task which is accomplished by a carefully constructed bridle.” [Create-a-Kite]
Particularly evident with maneuverable kites (dual-line, quad-line, fighter, or power kites), the wind window is an important aspect of kite flying – the angle of wind on your kite changes as you fly around the wind window, decreasing or increasing the power and control depending on a number of other factors such as the weight of your kite or lines.
Dropping grass, sand or letting a ribbon move in the wind should give you a sense of where the center of your window exists – from there, it’s mostly a matter of observing both the visual and physical feedback your kite is giving as it moves through the window.
(Images below by reeddesign.co.uk)