I needed a great big doughnut-shaped piece of plywood sixty inches across I could lay a curve of railroad track on. The easiest way to do this is: Get a sheet of plywood sixty inches wide, draw a big circle on it, cut the circle out with a jigsaw – done!
But that leaves you with a big sheet of plywood with a sixty-inch hole cut out of the middle that you can’t do much with, if anything. To use the plywood up as completely as possible, I figured that I could cut it into nine-inch-wide strips, then cut the strips into much shorter blocks with ends angled so that, when I put them together, they would make an almost-circle. I figured a twelve-sided shape would give me the best circle, and I knew that I would have to cut the ends at a fifteen-degree angle, but the part I had the hardest time figuring out was how long to make each piece.
You’d think the internet would have the answer to this, but it doesn’t, or at least it doesn’t have an answer I can understand. Most of the forumlas I found had cosines and square roots and all that geometrical crap I didn’t understand when I had a teacher to pester with stupid questions. No teacher hanging around my house today, though, so I had to come up with something on my own.
And what I came up with was this: The big circle was sixty inches in diameter. That means the circumference was almost one hundred eighty-eight and a half inches. I wasn’t building a circle, I was building what is technically known as a dodecagon, but twelve sides is so many that it almost looks like a circle, so I figured each piece of it should be fifteen and three-quarters inches long on the outside by dividing 188.5 by twelve and calling it close enough.
And you know what? It worked. I started getting kind of worried as I cut up the plywood pieces because they looked too short, but after I pieced it together I laid a tape measure across the whole great big thing and what do you know, it turned out to be sixty inches across. You’re as amazed as I am, aren’t you?
