To make the stop section of the dome I first needed to create two more discs. Since the top of the head slopes in I needed to cut the discs with edges beveled to that angle. To do this I used the same fixture I used in my last post to create the two next discs.
I cut these discs out of 1/2 plywood. I added a stop block to the fixture to set the finished diameter of the disc. The angle of the fixture will control the angle of the bevel on the edge of the disc. I used this technique to cut both the bottom and top discs.
Next I drew the layout lines on the disc. I first divided the disk into 10 equal segments. The sides and back of of R5’s head have pockets in them so you can see the wider layout lines in those positions. The remaining segments have layout lines for plywood pieces that will form the frame of the head.
With the layout complete I could cut out the inside of the disc to form a ring. Since this edge will not be seen it could be cut free hand or on the router table.
The support ribs are cut out of 3/4” plywood with the ends cut at the same angle as the angle cut on the edge of the disc. I rounded the outside edge of the ribs slightly so that the styrene skin will go on smoothly. To do this I just put the edge on a belt sander and gently rocked it back and forth to knock the edges off.
Here is the top ring that was made the same way as the bottom ring.
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