Finding the Center of a "Pipe"

Rhino Rhino for Mac
#1

Problem Pipe.3dm (89.8 KB)
In the attached I have a sweep created from two circles and a path. Oddly, the plans dimensioned from the outside of the pipe, rather than the center.

Is there any simple way to create a curve that forms the center of this “pipe.”

#2

Hi Jim - ExtractIsocurve the long direction isocurve that is opposite the seam of the pipe - Int OSnap will find the one you need. TweenCurve this curve and the seam edge curve.

-Pascal