Posted: Fri, Jun 29 2007, 05:21 AM
I guess kite flying is rocket science...
Fig. 14 Stability angles of 180Â° lead to an aerodynamically unstable system
Connect two matches by two strings (Fig. 14 upper left). The left match could now symbolize one of the handles and the right match could stand for the corresponding vertical spreader spar of the kite. If the kite rises (Fig. 14 upper right) matches and strings still form a parallelogram. The angle of attack is therefore not dependent on the altitude of the kite.
If, as shown in Fig. 14 middle left, the kite has rolled on its back () and the handles did not roll (), according to Eq. (12) a stability angle between kite and handles builds up (). If now the kite rises (Fig. 14 middle right) the angle of attack is decreased, thus the lift is increased and therefore the kite rises even more. No stable equilibrium is possible. The pilot persistently has to actively control the kite to stabilize it at a certain altitude. This aerodynamical instability is one of the main reasons, why it is much more difficult to fly a REVOLUTIONÂ® on its back than in its normal flying position.
If the kite has rolled one (or more) full turn(s) (), the stability angle becomes a multiple of too (Fig. 14 lower left) leading to a stable configuration. Even though the lines are crossed the kite rises parallel to the handles with a constant angle of attack (Fig. 14 lower right). Neglecting the friction of the lines the handling qualities are identical to the unrolled case.