How can I get started on a winglet design for a small remote controlled aircraft? I'm a member of a student competition team, we design light aircraft (total airplane overhead area is limited to 0.9 m²) capable of carrying higher payload. The competition also limits the takeoff distance (this year's limit was 70 m).

Coming from the last event, we decided that winglets are probably a great introduction to the project, but we have no idea how to design one.

My question is basically: with this kind of aircraft (weighs about 2.3 kg empty, carries about 13 kg, wingspan is 2.8 m), what should we look for in a winglet design?

We are mostly in doubt about what kind of airfoil should we use. Should we look for less drag? More efficiency? How can we maximize the traction vector, and should we do that in first place?

We have been reading papers on the subject, but with little luck. We also don't think it would be wise to just randomly test things until we get right, so a little bit of direction would help a lot, even if it's an article that we should work around.

Thanks in advance!
For best results, put good flaps on the wing and forget using a winglet.

If you insist on bending the wing up at its end, just continue with the tip airfoil and select the incidence such that your circulation distribution over the wing and winglet will become elliptical when you plot it in a straight line. The small size of your airplane implies that you will not need to unload the tips to reduce root bending moment.