Ditto Chuck's response. On one of my experimental gliders, I designed a
delta-wing using a reflex airfoil (M-178 I think.) However, I did not wash out
the tips, and I used wingtips that terminated in a sharp points. Big mistake.
When tested at high AOA's, massive tip stalls caused the wing to roll 45
degrees and yaw 180 degrees about every 3 seconds.

Curiously enough, the Wright boys (yep, them again) used washed out wingtips on
the 1902 glider.

Harry "flies under polyethylene too" Frey

PS: Funny what you can learn from watching the (stress) hawks fly. Isn't it?