the all-seeingeye Pangur Ban: Mast Shapinge-Part 5
Mast Shaping: Part 1 Mast Shaping: Part 2 Mast Shaping: Part 3 Mast Shaping: Part 4 Mast Shaping: Part 5 Mast Shaping: Part 6

Mark for trimming to an octagonal section. Saw cut almost to the line, rough cut with axe, adze, or chisel, and plane the octagon smooth.

Laying out an octagon marking tool.

Prick marks made with octagon marking tool.

I'm sure there is a mathematical method for laying out an octagon marking tool. I was always better at geometry. So, I drew an octagon slightly larger across the flats than the widest part of the masts, and used the drawing as a template to make this simple marking tool. The tool is a scrap of wood, two 16 penny nails, and two screws.

You can use this marking tool by dragging it along the mast to scratch lines. It's a lot of work, it's hard to keep the two side guides flush against the spar, and the points want to dig in and follow the grain. I prefer pressing the tool into the spar to make prick marks every few inches. Connect the lines with a pencil and straightedge.

Chopping the square/octagon transition.

Smoothing the octagon.

Hole saw modified as a tenon cutter.

Masthead tenon.

Adapter for masthead light.

For the main mast I needed to cut a tenon on the masthead for the navigation light. I had a hole saw with the right inside diameter, but the pilot drill was less than half the diameter of the CPVC pipe built into the mast as an electrical conduit. I turned a section of dowel to fit the inside diameter of the pipe and bored it to match the pilot drill. This acted as a pilot, and let me center the tenon on the electrical conduit.

The navigation light has a bottom diameter of just under 2-3/4 inches inside a little raised lip. The top of the mast was just over an inch and a half. I turned a mount for the light from a 3 inch delrin rod section I found in the cut-off bin at my favorite metal and plastics dealer.