What is the average thickness of wings now days? I am thinking 17% t 20% including flaps. I don't get much on a search. Anybody have a link to some recent discussions?
More-or-less, if everything else is right, it doesn't make much difference. Mine is 26% (including flaps), and the Trivial Pursuit is slightly thinner. But I have seen very good results with as little as about 14-15% (Diva, etc). The key takeaway from the entire situation is that the lift is not the limiting factor if you have the rest of the shape right, and that the lift coefficient is only weakly related to the thickness.
You have to have the LE bunt enough, and you do not need large flap percentages, and probably want as narrow a flap chord as you can get away with. You want the high point relatively far forward, but you also need at least some curvature in the aft section, DO NOT make it a straight line. Round off all the corners near the hinge line, and seal the hinge line,
Beyond that, choose it for your desired other properties of parasitic drag and structural qualities (thicker stiffer for a given mass). I would use a relatively thick wing for very powerful IC engines, and it's particularly important to get the right amount of parasitic drag VS horsepower available for 4-2 break IC engines and 4-strokes.
It's much less important with tuned pipe engines, assuming you know what you are doing, because the lack of parasitic drag from a thin wing, which would cause large speed variations in the wind on a 4-2 break engine, you can instead control with the engine response. That presumes, of course, that you know how to make the engine do what you want - for which there is abundant information, although no one pays any attention to most of it, preferring their barnyard bullshit theories on the topic to both analysis and extraordinarily successful contest record by those who developed and propagated the information.
For electric, I am far from an expert, but while you have infinite control over the power delivery with Igor's feedback system, or similar, you still have to consider drag because you have to carry a big enough battery to make it through the flight with margin to keep them from self-destructing. Given that the lift is more-or-less a non-issue, I have opted to have a relatively thing wing compared to my current airplane, around 20%.
As in the "best airfoil" thread, the answer is something close to the Imitation airfoil (which was considered thick at the time, but not so much any more) is a good compromise.
Brett