re: Drawing bow

If these fail to yield a perfectly smooth curve (draw a line, flip it end for end, and see how close it comes to the line), you can sand/shave a bit of wood from the stiffer side.  Archers call this tillering a bow.  

On the other hand, if you are looking for an asymmetric curve, exaggerate the effect by thinning the thinner side - think of it as a redneck French curve.