The
lifting force of all kites is produced by deflecting the air downward,
the resulting change in momentum producing an upward force. The reason
for this is that the air traveling over the top of the curved surface of
the kite is going faster than the air passing underneath. Fast-moving
air creates less pressure; this means there is more pressure underneath
the kite, and this helps to force it upwards.
Think of the kite as a sail boat, catching the air. The air tries
to push the kite along like the sail boat. But the string the flyer
holds keeps the kite tethered. Since the kite cannot go with the wind
flow and the kite is tilted so that the air is deflected downward, the
kite has no where to go but up.
