On Monday, May 18, 2015 at 3:56:47 PM UTC-4, Jonathan St. Cloud wrote:
Can an aerodynamicists explain the reasoning behind the bent up wing tips of the Schempp-Hirth and Jonkers gliders. I thought Schempp first started this on the Nimbus4 purely to keep the outboard tips from getting scraped, but now the tips are bent on shorter wing birds. Someone fairly knowledgeable once told me the the bent tips actually hurt performance in the run but help in climb. I just wanted to get a bt more educated not the reasoning. I noticed the Quintus has bent tips but the same wing on the Antares 23 were straight.

Here is a theory: When you are banked at 40° when thermalling the inside
wing tip is closer to the core than the outside wingtip. With the strong dihedral of the wingtip this puts the bank angle of the wing tip closest to the center of the thermal at say ~28° instead of the ~40° so the lift vector is closer to perpendicular to the lift = better climb rate.

What i don't understand is that when flying straight/level with an effectively high dihedral the lift vector of both wings are pointing perpendicular to the wings, so the vectors are not pointing up, but rather inward. They balance each other out of course but seems like if they were perpendicular to gravity they would be most efficient. Isn't dihedral costly on performance, but helps on handling?

Curious if anyone else makes any sense of this. I'm more asking than telling.
Chris
Not an aerodynamic expert!