Raked Tips are thin, semi-flexible extensions for curved-tip hang gliders which help roll handling when flying slow with the wing at its tightest variable geometry setting. The tips are roughly triangular, just under a square foot area, with one side convex and another concave. Picture a triangle with one side aligned with the wind and the opposite tip swept back in the wind. They attach with velcro to the aft edge of the wingtip, where the top and bottom sail surfaces meet. May be cloth & foam or carbon composite. Weight is negligible.
With the VG tight a high performance hang glider flies more efficiently in a straight line but is harder to turn at low speeds, especially making subtle bank angle adjustments while circling in a thermal to gain altitude. Raked Tips help this very specific situation by smoothing out some bumpiness and allow a good pilot to fly just that 1/2 MPH or so slower, maintaining smooth control and getting a better overall climb rate. Some say they can feel improvement from VG 1/2 on up.
One theory of how they help is that they move the center of the tip vortex outboard and aft of the wing tip, thus reducing the disruption of the airflow over the lift-producing part of the wing tip. When thermalling, the inside wingtip is usually near stall airspeed so small disruptions can have large effects.
Raked tips also add visual drama to the glider, with the wings trailing off to points at the tips, like the Batman logo or something.
(Not to be confused with vertical or upward-canted winglets as seen on many commercial jets these days. Those work a bit differently.)
Brevity Quest 2018
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