To integrate the chart plotter, radar, and autopilot, an electronic compass needed to be installed. I chose a Precision-9. In addition to reporting direction, the device also reports pitch and roll, and so it should be mounted at the center of gravity in the boat, preferably at the waterline. After exploring possibilities, we decided on mounting the compass on the mast below deck. The problem was the mount was designed for a flat surface. We started by tracing the contour of the mast where we wanted to mount the device.
We then used a table saw to cut the mount out of a block of wood.
Note the contour is rough-cut with the table saw. That surface was filled with epoxy (combined with an epoxy filler), and it was sanded and painted with enamel (on the right, the block on the left is a spacer for the wind instruments).
The adapter was used in combination with the compass mount to install the compass on the mast.