Hi Tony, so yeah you can put in an arc using arc 3pts like this:



Then prepare the rails by joining together the edges so you've got 2 long closed
curves as described above, then you can select the arc and run Construct > Sweep,
select the rails and get this result (3dm attached too):


- Michael

Thanks Michael

I did not like the sweep command because there was an unselected edge (I think I hide) I rebuilt the curves and everything is ok .... thanks again