So, turns out the hard part of drawing a perfect 30′ circle on wood is not the circle part, but the drawing part.
The circle part went great. I drilled a pencil-sized hole in the end of a 16′ board and pushed a pencil through it, eraser-end down. The board rested on the eraser in the center of the platform and allowed the board to spin. (Paul held it in place and watched that it didn’t wobble around.) We wrapped some duct tape around the pencil to keep the board from slipping down it.
On the other end, I drilled the same hole (exactly 15′ from the first) and inserted a pencil lead-side down. I was thinking “this is so easy!” Then I tried to draw the circle.
Every bump broke my pencil. It would go a few inches and break. The second bump broke the pencil in half. Not wanting to spend all day figuring out the best way, I just drilled a bigger hole and stuck an ink pen in. The pen wasn’t great, it dug in to the boards too much, but it worked and it did leave a nice bright blue line. The other issue with the pen was that it wobbled in the hole and was off by 1/8-1/4″ depending on it’s angle. Not a big deal, but I think finding the right drill bit for a sharpie or piece of chalk would have worked better.
Even without doing it the best way, it was still pretty quick and we are ready to cut!
Oh, and to find center, we measured roughly and guessed. Then walked the compass-board around to check it before we drew.