Hi lorem - for the Network tool (this same tool is labeled "Gordon" in the French UI) to work, it needs to be able to determine a 2D grid layout for the curves.

Think of it as latitude and longitude lines on a world globe that correspond to horizontal or vertical lines on a flat map.

In order to provide this kind of organization, your single outside loop will need to be split into 2 pieces, so that you will have 3 long curves that touch at at 2 "pole" points at either end.

With that layout you can then see that the long curves will be like longitude lines on a map, and the shorter curves will be like latitude lines.

To split the long curve up, select it and run Edit / Trim, then select your center long curve as the cutting object.

After that then these curves have a suitable arrangement for Network. Except Network doesn't seem to behave properly with them still, that seems like it may be a bug in Network, I will take a look into that.

One other thing you can try right now would be to use Sweep instead - select the shorter curves as profiles, then run Construct / Sweep, then pick the 2 outside curves (the ones that were split from the long closed curve) as the rails.

- Michael