Originally Posted by kcaldwel
Yes, non-planar wakes are interesting, but VL or LL code cannot not model that. You need pretty radical geometries, like the split tip wing proposed by Smith to perhaps have span inefficiencies over 1 for a planar wing. XFLR5 shows span efficiencies over 1 for a rectangular wing, which is not correct.
Funny we were both thinking of a split tip wing. I did my thesis work side-by-side with Steve in the Ames 7x10 using the same wings. I measured the induced and profile drag of the split tip wing from wake surveys (my work is reference 24). The induced drag looked pretty good, but the profile drag at the tip junction was atrocious.