Hi Steve,

> however, that curve (with gap) is actualy the edge of the
> swept surface produced from the geometry created from a
> 2 rail sweep.

I don't quite follow - from what I can see the Sweep surface you built is the one in yellow here:



But the edge that you are offsetting is this one up here, not actually touching the sweep:



As far as I can tell, that curve being offset is not itself an edge or actually touching the sweep surface directly, it seems to have been created probably by a Fillet? It seems to be a trim curve living on the top flat face, not an edge of the sweep.

I examined your sweep surface by extracting it and untrimming it, and the sweep surface itself seems to have fully closed edges.


At any rate, in v2 when offsetting that little gap is being automatically sealed so that becomes a closed curve, that's why you had different behavior between v2 and v1.

- Michael