 # Arc creation assistance

I have the length of the Arc I want to create and I have the radius of the Arc. The length of the Arc is 136.5 inches and the Radius is 68.75. Is there a way for me to create this in SketchUp? I do not have the bulge or angle.

Any assistance would be greatly appreciated.

With a bit of maths, you can calculate the angle, and use the Arc tool which draws an arc from centre, start point, and angle. If you don’t want to do the calculation, draw an approximation, look at the arc length in Entity Info, and make successive approximations to get it near enough right.

To get greater accuracy, make your trials with a lot of segments in the arc, then redraw with fewer according to the resolution you need.

By experiment, using 192 segments, the angle is close to 114°. The calculated segment length is 136.79"

By calculation, 136.5/68.75 = 1.9855 radians or about 114 degrees - more precisely, 113.771°.

Try that input to the Arc tool.

It gives an arc length of 136.515 with 192 segments, and the same with only 24 segments. Looks as if SU is actually calculating the true arc length, not the length of the segments in the drawing. If I explode the 24-segment arc, SU shows the curve segments’ combined length as 136.476.

How accurately do you want it?

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You can also use an online arc calculator.

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The circumference C of a circle is pi * D or 2 * pi * R.

From your radius, C = 2 * pi * 68.75 or 431.9690 (approx.).

The length along the arc is 136.5.

136.5 / 431.9690 = 0.3160 or 31.60 % of the circumference (360°).

The angle is 0.3160 * 360° or 113.7582°.

This can be easily drawn using the Pie Tool. See this SU file.

Arc with length and radius known.skp (84.0 KB)

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this is super helpful. Thanks!