Some beautiful geometry there Mr. Red. Actually it is possible to get a reasonable approximation of rope or other helical structures just using an image mapped to a cylindrical extrusion. It gets a little dodgy on the tighter curves, but in a large model serve its purpose pretty well.
Link

@mlammert said:

My next desire is to create curves and circles on the TIN surface and "bend" those...
Mark

This was done quickly with a low-poly count so the curves are not as smooth as they could easily be. It was made by placing TIN beams on a vertical TIN surface and then using Smoove to curve the beams in the vertical plane. When I had the curves I wanted I rotated everything together back to the horizontal plane... did the various other steps in the tutorial, etc.. For other shapes you could either build them from TINs or use intersect as described in Alan Fraser's original response. Good luck!

curved lines small.jpg

curved lines on surface.skp