I hate thinking on a Saturday.
When a sport kite is flying in a straight line, all the forward forces come
off the trailing edges (think shaken up bottle of soda).
When a kite is turned, some of the exhaust (forward) forces flow over
the spine onto the far side where they in turn spill off both the far
leading edge and far trailing edge.
As an example, let's assume 10% exhaust forces flow sideways during a turn.
Near side forward forces = 100-10 = 90%
Far side forward forces = 100-10 + .9*(10) = 99%
Near side side losses = 10%
Far side side losses = 11%
Total forward forces before turn = 100 + 100 = 200
Total forces during turn = 90 + 99 + 11 = 200
So the far side should go "forward" faster causing the turn AND,
the far side side losses should actually cause the kite to slide a bit
perpendicular to the turn. Note that the near side side losses do NOT
contribute to the sideways motion of the kite as they are recovered
by the far side sail and redistributed. So only 1% of the near side side
losses contributes to the sideways motion while all of the far side side
losses directly effect the sideways motion.
Wow, I wonder if that's true.
Remember, I was just guessing on the 10% part, but the math should
still be the same with a different number.
Sorry for using the word side so many times.
I still prefer Steve's Kite Faerie explanation.