Hi Mal,

> I would still like to know why the original curve didn't work however.

It's because the segments of the curve are not not quite smooth to one another, there is a small angle (about 8 degrees or so difference) between their ending tangents instead of having equal ending tangents.

On a rail curve that has sharp corners like that, the current v2 beta will attempt to do extensions and mitering of the sweeps in those areas, but that is not working completely properly yet for rails that have curved segments instead of straight line segments. That is pretty much the last remaining area I have left to fix up before v2 will be all completed.

If you align the 3 control points where segments meet, or delete the control point where 2 segments meet to fuse them into a single smooth segment, then that solves the problem.

Here's a zoom in to one of the segment join areas of your curve to illustrate how it is sharp there and not actually smooth:





- Michael