The rudder ribs are bent from .025″ sheet metal. The bend radius is 1/16. The rib is shaped like a triangle with three flanges.
Approach (1) The flanges can be bent on the brake and the last will need a form.
Approach (2) Create a form block and back up block for the whole part, clamp the metal and use the hammer to form the flanges. This method requires you to drill a couple of clamp bolt hole in the rib.