Do I need an airfoil?

[Bythebookie2]

I see slowflyers with no airfoils occasionally.

How is the flat stab airfoil causing lift?:confused:

[vintage1]

By having an angle of incidence.

That causes a partial vaccuum behind the plate and also and part of te same process defelcts air downwards at teh back.

Almost anything will give you lift. Its all a matter of hpw ecfficiently it does it. Spinning balls will give lift too. Put enough backspin on a shot and watch it soar...

[robbie]

so is the "angle of incidence" the same as the "angle of attack"?
one example i have been looking at / thinking about building is the und-nu, or and-now.
so if the wing is a flat plane with no curvature or airfoil, is the angle of attack created by the downthrust of the motor?
what about "decalage"? isn't the tail group supposed to be angled the opposite way from the wing? (prop points down, wing points up, tail group points down?)
looks like this plane appears in these threads with a flat plane wing, or a circular curvature airfoil wing like on some of the rubber power indoor designs, and the "TLAR" airfoil. rub the foam across the edge of a table or something, step back and say "that looks about right", then go for it! sounds a little unscientific to me. but they all seem to work ok according to the reviews. flat plane for less "lift" meaning faster overall speed? curved airfoil for more "lift" and a slower overall speed?
the only specs on the plan is that the highest point in the airfoil be about 12mm.
these are probably dumb questions since i'm new at this. sorry if i got off subject, but thanks in advance anyway.

[steve lewin]

Angle of incidence is built into the plane. Angle of attack is what it is currently flying at i.e. when flying slowly fuselage may be pointing up so AoA is high. AoI is still what it always was. Decalage relates AoI of wing to AoI of tail. Usually tail incidence is lower than wing but not necessarily negative.

The Und-Nu is built with an airfoil. It may not look very scientific to you but fortunately the air doesn't know that so it actually works very well ;).

You can get quite a lot of lift from a flat plate but it has to fly at a greater AoA than a curved surface and usually creates more drag for a given value of lift. It also has other undesirable characteristics like a very unforgiving stall.

Steve