Update April 14, 2000
Note: If you didn't get here from "A Circle of Drums" website, then maybe you should go here to get the whole story.
On the first Friday of every month we have a drum circle. The goblet drum is usually placed in the center of the circle for anyone to play. If there are young ones about, they usually go straight for it and beat on it with some of my home-brew drumsticks (These are wooden spoons with solid rubber balls attached to the handle).
In 1997, the goat skin got a little stressed and I decided to change the head. I decided to use the dual tension ring method. This method is easier because you do not have to cut holes in the skin and the ropes can be looped very neatly around the top ring. The drawing below should help:
I was not specific about the actual angles that were used in cutting the circles. I think that this was because I had a vision of the completed project and did not pay attention to the exact angles when I adjusted the saw blade.
If I did this again, and planned ahead, I would get a large piece of paper and make a simple out-line drawing of the drum and then draw in parallel lines across this image. The lines would be spaced out at the same distance as the thickness of the wood that will be used to cut the rings. At the point where each line meets the contour line of the drum body I would measure the angle (see drawing below) and use this angle to cut the ring. The same angle would be used to make the inside cut.
An alternate method would be to number each "slice" on the out-line drawing and then cut out each section and use the curved end to approximate the angle cut on the band saw. (You have to imagine butting up the angled piece of paper to the band saw blade and adjusting the cutting angle-- I've never done this, but I bet I could if I was careful.