im trying to make a octagon flower bed at home. what i need to know is what would the angle cut be and the length of the 8 boards for a 80 inch across octagon. thanks for any help
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Isn't this a taxidermy site? Maybe I'm wrong but...
There are 360 degrees in any enclosed shape. You are going to have eight sides so divide 360 by 8 which equals 45 degrees which gives you the angle at each corner. Because that angle is madeup by two sides now divide 45 degrees by 2 and you get 22.5 degrees your cut.
Now for the length of the sides. The height of the octagon is 80", take that number and multiply it by the constant .414213 which equals 33.13704 inches or about 33 3/16".
Since you're wanting it 8 feet across, then the diameter is going to be C= pi D or the circumference is equally to 3.14 times 96 inches. That comes to 301.4 inches. Dividing that by the 8 points where the corners touch the circumference, you will find that the arch between each of those points is 37.68 inches. From there, you're on your own. A guy my age forgot the rest of those formulas last century some time.
Actually to get the angle the formula is (n-2)180/the number of sides
or (8-2)180/8 or the inside of one angle is 135 degrees. The length of the boards would be approx. 31 7/16".
At time like this. Figuring 8ft. (96") across each side would measure 36.738 at its longest point. It would be easier to cut if you rounded up to 36.75 (36 3/4) which would make your bed alittle oversized.
Lay them landscape timbers or boards out like you want then, set them off the ground on bricks, overlap ends, take a chainsaw and cut through each corner...remove bricks, nail together...Done
that's what i would have done joeym...