Pivot for swinging arm. There are two positions to define the inside and outside curves.
Cutting the curved sections of the arch using the band saw and a swinging arm that guides the curve. I tried cutting the curves freehand but it’s much easier and much more accurate to use the simple jig shown below. Excuse the mess surrounding the band saw. Where does it all come from? Its origin may be a mystery but its destination is not. It ain’t going nowhere anytime soon!