How can I create a surface from these curves?

I know its doable but I tried everything I can think of. Its basically completely curvilinear with that bulge in the middle.


Help.3dm (4.5 MB)

There is little information how the finished product shall look like, only two sections and a footprint curve, there is much left open to interpretation. Do you need G1 or G2 continuity? Is there a sketch describing the desired result?

Its basically a 3mm high watch band where middle bulges out to the middle section. Im sure the rounded caps can be done after. Sweep2 is the best I can get, but it doesn’t work well. Help.3dm (4.6 MB)

Your input curves are sloppy. One of your rails is U-shaped, the other is almost straight. The rails of the Sweep2 command should be more or less parallel. Keep different curves and different surfaces in different layers.

But if they’re parallel I won’t be able to achieve the desired shape. Would you recommend making a simple shape and using a bounding box to make the deformations?

No. Make more cross-section curves for the Sweep2 command. I agree with you that the Sweep2 command should make the middle part of the surface and that the ends should be made later. You can make the ends with the help of SplitEdge command and Loft command. SplitEdge will divide surface edges into two halves before Loft makes the ends. Match start tangent and end tangent in the Loft command.