Hi Keith;

This is another way;

-Draw a circle
-Add a point on the circle and use array circle to copy the points on the circle.
-Copy the circle and points in Z direction.
-Draw wave curve by connecting the points via freeform command (through points).
-extrude the first circle to make cylinder surface.
-use trim to cut the cylinder surface with wave curve.
-use the shell command to give a thickness to surface.


Sharif