Back to the table. A boomerang is a set of wings put together in a certain way. Wings are profiled, and flattened towards their ends. To understand why and how boomerangs behave, you’ve got to know some basic principles.
Boomerangs do not just go away and come back. The main reason they do so is that they turn very fast around their axe after being thrown. While throwing a boomerang the right way, you’re giving it the necessary rotation. This movement is counterclockwise (for a right-handed boomerang), the leading edges (steep wing-sides) cutting the air, just like airplanes, birds etc. The rotation gives them uplift, and the setting of the wings causes a spin. This spin forces the missile to flow not just right away. Translated: your rocket is coming back home. Get these basics in mind while setting the profile or download the picture. This drawing-thing isn’t exact science, sanding and feeling will do the rest.
Shaping the profiles is sanding, sanding and especially sanding: heavy (electric) sanding with coarse grain at the beginning and manual sanding with finer grains to finish. This phase is pure instinctive, so try to make the best wing-profiles you can get. And take your time.
Note: I never throw away the sawdust and woodchips because it’s perfect stuff to smoke fish.