Nice looking table Marco! Darn near everything I make has arced rails or something. Years of fighting Murphy have taught me that bowing the thin strip of wood is "not good", inconsistenet results, maybe due to the grain in the wood affecting the elasticity of the wood along it's length. Drawing arcs with strings is "not good", because string will stretch. I have some ~1" wide strips of vinyl siding that I use a lot to mark curves. The vinyl is static and won't stretch plus it's light and easy to deal. Just punch a nail holes where you need them. I also make a "gadget" for a steel tape measure that clamps the tape measure body to a pivot on a board; the scribe end attaches to the tape and, and you vary the arc radius with the length of the tape. Works pretty good but you need help to use it. As for cutting the arcs, cut shy of the line with your bandsaw, jig saw, coping saw, gnawing, or whatever. The REAL secret to nice smooth curves is to use a circular plane. Put the piece in your bench vise, curve up, and using your circular plane, plane toward the center from each end of the arc. The finished arc will be mirror shiney and absolutely smooth without even the slightest bump or hump. Just my $0.02 from cutting a bazillion arced rails.
