I used a 1-1/2" x 1/4" length of rectangular pine molding. Molding is knot free and bends smoothly. Clamp it at one end, install small finish hails at the offset points and bend it to make a smooth cure, press it to the surface while the cure is traced with a pencil.

Small radiused curves will require a small more limber piece of molding. The 1-1/2" x 1/4" is good for the curves on hull panels with offsets up to two feet apart.