The method TIMBEAL found on the net:
http://books.google.com/books?id=V8L8y1J...p;q&f=false
Works really well for us. we use it all the time.
you dont need to fint the center of the circle so it doesn't take up a lof of space. in theory it is matematically accurate, in practice it is pretty damn close to dead on. Closer than the accuracy of a bandsaw cut.
All you need is a distance and a top pint in the middle (i need a curve on a 4' brace that is 2" tall in the middle)
If you need a specific radius (to match the arch of a window) it takes a little calculation or a different method
