need to find 13 equal points along a 35, 40, and 45 foot circles is there an easy way to calculate this?

Question

I have to lay out 13 flag poles in a circle (3 possible sizes given) just need easy way to figure this out when in the field

Answer 1

A way to do this would be to take a piece of surveyor's string/twine and mark it at lengths equal to 1/2 your diameter (or you could have 3 separate pieces of string that are 17.5', 20', and 22.5' long).

 

In the field, drive a stake down in the center or your circle. Tie one end of your string to the stake then take the other piece of your string out to the edge. As you walk in a circle you can put down your flag locations with stakes or marking flags. Repeat this for the other two lengths of string and you'll have your 3 circles.

 

It would be easiest to use one string with 3 different lengths on it because then you can mark the 13 locations at the same spot, just at different lengths from the center.