Given: Three Parabolic Curves, Curve 1 with n points, Curve 2 with 2xn points and Curve 3 with 3xn points:
Select Parabolic Curves 1, 2, and 3, each with its own set of Curve Points. See AutoCAD file.
Generate a Grid of TWO sets of Straight lines,
RED lines: from Curve points of 1 and 2 to each point of 3
GREEN lines: from Curve points of 1 to each point of Curve points of 2 and from Curve points of 2 to each third Curve points of 3.
Once the straight lines are generated, then:
DRAW Solid Cylinder of diameter d pipe for each straight line.
See AutoCAD file.