| This is a short one.
Generally, to achieve the maximum possible
lift, your kite should be trimmed with the highest AOA (angle of
attack) possible without causing the airflow above the kite to become
separated from the kite surface, and turbulent. Airflow separation
starts near the trailing edge, and with progressively higher AOA,
caused by tighter bar trim, the area of airflow separation increases,
working forward toward the leading edge. Total separation is called
"(aerodynamic) stall", and partial separation can be considered as
"partial stall", which reduces lift and decreases the L/D (lift/drag)
Most reasonably experienced kiteboarders can tell when a
kite is suffering total aerodynamic stall because it stops flying
effectively and begins to fall backward, as though it were a parachute
or giant Glad garbage bag. But it is virtually impossible to detect a
subtle, "partial stall" by feel alone.
"Telltales" are simple
but effective devices for detecting any degree of aerodynamic stall.
They are typically strips of ripstop sailcloth, yarn or cassette tape
that are adhesively fastened to the upper surface of the kite near the
trailing edge. When they stream smoothly backward, they indicate smooth
airflow, but when they flutter erratically, they indicate airflow
separation and turbulence. I recommend attaching about four telltales
across the top of the kite, about six inches forward of the trailing
edge. You can add more if you want to see what the airflow is doing all
over your kite, but it's not necessary.
For optimal lift (for
maximum power, speed, upwind performance, jumps or whatever), the bar
should be trimmed, or "sheeted in" until the telltales just begin to
act erratically, and then the bar should be immediately eased just
enough to make the telltales stream smoothly. If you keep repeating
this procedure, you'll always know that your kite is perfectly trimmed.
and marine suppliers like "The Dinghy Shop" sell very tidy and
effective telltale kits, but alternatively you can improvise your own.
And just because most kiteboarders don't use telltales doesn't mean for
a second that they shouldn't. For the same reason, there is barely a
competitive racing sailboat in the word that doesn't have telltales on