Second try :) Having difficulty using straight-line segments as rails (for a loft or sweep) ...  

Ok, so I’m modelling a flying wing and I’m at the point where I’m making the bottom mould box.  The mating surface between top and bottom moulds has many slightly angled surfaces, so I will create the bottom half and use it to cut the top from a plain box.

The intent then is to use the wing model to either add to the boxes to create male patterns on which to lay up the moulds, or cut from them to form actual moulds to be CNC cut.

The construction of all these angles has been messy so I have created two ‘clean’ sketches, one for the profiles, and the other for the rails.  I did the profiles first so that when I created the rails they were exactly on the corners of the various profiles.

I have checked all the profiles for any ‘open’ corners, but all close, as demonstrated in the pic.

I’ve tried to loft and to sweep but I keep getting the “the rails are not smooth” error.

The suggestion is always to ensure a tangential relationship along the rails, but I can’t see how that’s possible with straight line segments.

Is there some other command that I’m missing, that uses straight line rails, or is there something I need to do with the rails ???

Any help or advice will be most appreciated.

Thanks, Steve.