Some questions about thickness and AOA

[Niggo]

HI! I don't know so much of aerodynamics but looking to some images of rc models some questions pop up in my mind.

About depron parkflyer i see some wings with very little thickness (just 3mm) curved but not closed (undercambered) : this choice what brings? why they simply dont' use a flat bottomed or semi-simmetrical wings?

In this kind of planes, the AOA of the wings attached to the fuselage is important or a 3-5° positive is useful?

thanx for any answer ^_^

[Ollie]

The smaller the wing chord and the slower the airspeed, the thinner the airfoil needs to be to work well. The mean camber line of the airfoil shape (the line half way between the top amd bottom curves of the airfoil) determines how much lift the wing can produce for its size and airspeed. The greater the curvature of the airfoil's mean line, the slower the plane can fly without stalling. Park fliers are relatively small and are intended to fly slowly. That's why they have thin airfoils with highly cambered mean chord lines. If one were to cover the bottom of such an airfoil to make the bottom flat, it would halve the camber of the mean line and increase the stalling speed.