It seems to me that you could use a router with bushings to make some of the templates. Just run the bushing against a right angle template. For example for 1/4" radius, use a 3/4" bushing and 1/4" straight bit. You might be able to make larger rings to slip over the bushing and get larger radii. It would definitely be tangential at the ends of the curve.
edit: and you could get 1/2" by using the 1/4" template to make the next template. So, in fact, you can make any radius template that is a multiple of your smallest gap between bit and bushing lip. Might be a bit of work to get to 3" radius 1/4" at a time though!
Last edited by PhilBa; 05-13-2015 at 11:01 AM.