Hi All.

I recently came across the following photo that illustrates how one might make an octagonal box, perhaps for a banjo or similar instrument. This series of photos was taken by David Beede to document how he built his banjo, and the method he used looks to be very simple. Here's what David has told me regarding this technique:

"I borrowed this technique from the boat building community where it's used to make hollow tapering masts. There is a good article on Duckworks magazine that addresses more sides and even has an on screen calculator that tells you the angles to use for the "mouth."

    http://www.duckworksmagazine.com/04/s/articles/birdsmouth/index.cfm...

The up side of the octagon is that you only need to set a blade to 45 degrees - as the number of sides increases you need to know two different angles."

The name for this technique, "bird's mouth" come from the two 45 degree angles you cut into one end of each of your side pieces. So, the square end of your next side piece fits into the "bird's mouth" of the previous piece and this continues on around until the "bird's mouth" of the last fits into the square end of your first side piece. Once you glue them up, you can use a piece of rope, or flat strapping and make a quick tourniquet to clamp it all together. The resulting octagonal box frame will have some bumps that will need to be cut or filed down, but the process looks easier to do as you are making 45 degree angle cuts rather than 22.5 degrees as you would using the standard approach.

Any comments?

-Rand.