If routing flutes into a straight board is what you want to do, a number of store-bought or home-made jigs for your router will help you get the job done, but Eagle America’s Combination Arched Fluting Jig & Edge Guide will also allow you to route flutes on curved or arched pieces.
The 3/8″ polycarbonate jig replaces your router’s existing base plate. In their straight position two wings ride along both edges of boards from 1″ to 12″ wide, and in their curved configuration rollers follow the board edges of pieces from 1″ to 5-1/2″ wide. You can also remove one of the wings to use the jig as an edge guide.
Made in the USA, Eagle America’s Fluting Jig will run you $60.
Fluting Jig [Eagle America]