



 
Hi Adam. You are right: 15 degrees separates the cells from one another. So the innermost "edge" will be 0.75 inches on each side. That forms an isosceles triangle with the center, and the central angle is 15 degrees. That means the distance from the center to a vertex is one of the common sides. If you bisect this isosceles triangle, you get a right triangle whose hypotenuse is this centertovertex length, one leg is 0.375 inches and the angle opposite that leg is 7.5 degrees. To calculate the length of the hypotenuse, you can use the Sine relationship. Sin(7.5) = 0.375/h. This means h = 2.873, or roughly 2 7/8". So that means the central "dead" space (perhaps you can use it for the rules) would be twice this length between opposite vertices of the the 24gon. To make things simple, let's say each ring is 1 inch wide. That means the overall diameter is 2[6(1) + 2.875] = 17.75 inches from corner to corner. Here's a sample (a higherresolution version is here ). If you build it, send us a photograph please! Cheers,
 


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