Re: 36" build in Tallahassee - AKA Bruce's Folly

I wanted to share the technique for laying out semi-circle (Roman) arches. Here's an example with arbitrary numbers

First, you need to know your span...lets say 20 inches. Draw a center line at 10" that crosses (at a 90* angle) span line ( spring line) on both top and bottom, at least 20". Now lets say your rise is 10"...mark that on your center line. You now have three points of a triangle.

Next, measure your distance starting from the center point of your rise, to one sidepoint of your span...right or left. Now, draw a line between these two points, and mark the center.

Using the line you just made, set a square on the line on the center point. The square is now crossing your center line below the high point of your rise. Draw a line along the square until you cross the center line.

This point is where you set the point of your trammel or whatever you are using to trace the arch. Now you have a perfect semi-circular shape for your form ( called centering in masonry).

If you know this already, forget everything I just typed.

I wanted to share the technique for laying out semi-circle (Roman) arches. Here's an example with arbitrary numbers

First, you need to know your span...lets say 20 inches. Draw a center line at 10" that crosses (at a 90* angle) span line ( spring line) on both top and bottom, at least 20". Now lets say your rise is 10"...mark that on your center line. You now have three points of a triangle.

Next, measure your distance starting from the center point of your rise, to one sidepoint of your span...right or left. Now, draw a line between these two points, and mark the center.

Using the line you just made, set a square on the line on the center point. The square is now crossing your center line below the high point of your rise. Draw a line along the square until you cross the center line.

This point is where you set the point of your trammel or whatever you are using to trace the arch. Now you have a perfect semi-circular shape for your form ( called centering in masonry).

If you know this already, forget everything I just typed.

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