Road Gypsy Math 101

  1. If you don't already know your radius, use the following formula:

2. Swing your radius using a strip of wood screwed down on one end with a screw protruding at the other end to scratch your arc.

3. Cut your arc with a circular saw, not a jig saw. Use a small blade diameter saw, the smaller the blade the tighter the arc you can cut. Adjust the cutting depth so it barely clears your wood.

4. Like so: