Radius and arch question

I designed an arbor with an arched top. When it came time to transfer that info to my wood I had to plot it all out because I didn’t know the radius. If I had, maybe I could have used string and a pencil to make a big protractor of sorts to draw the arc. As far as I can tell, Sketchup 2 point arc tells me the bulge, but not the radius of an arc. Is there a way to determine this?

If you haven’t edited the arc in a way that breaks it apart, you can select it and entity info will tell you the radius.

Steve’s right, of course that you can get the radius of the arc from Entity Info. You could also use the Dimension tool, again, as long as SketchUp considers it an arc.

If I were going to do what you describe, though, I think I would be more interested in the bulge distance as that won’t require locating a point somewhere in space in the shop. The arc I drew above has a 1-1/2 in. bulge. My shop isn’t big enough to be able to set up a center point to strike the arc with a string. Instead I would trace a batten held at the ends and pushed up the inch and a half.


If you are using a flexible rule and simply pinning the ends, the curve is not part of a radius, but a cubic equation:

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That’s true but it’s close.

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I was thinking it was something other than an arc, but you “nailed” it.

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Thanks all and thanks Dave R for both tips.