Gordon bug?

 From:  Michael (MMHS)
592.5 In reply to 592.2 
This is really cool, i didn't even realise that you could do a two-rail sweep with the two rails touching in a tanget manner, so that you end up with a closed shell-type form that's completely smooth where the rails meet. I had some fun experimenting with shifting the pole-point around. (i used one closed loop at the bottom as profile and the two upright curves as rails.)