I am trying to make a shank for this ring. I have tried using multiple sets of curves. Split, single span, etc. and none give me a great surface to work with. Network surface was able to generate something, but it was very heavy (even though I used the same type crvs for cross sections) and I had trouble making a transition surface that matched. Here is the file.
ProblemSrf3.3dm (633.0 KB)
Eric, is what you are after something like the attached? I can’t tell if you need that transition to be completely smooth there, which looks like asking a lot, off had, if you also need to hit the angled lines.
ProblemSrf3_Maybe.3dm (573.0 KB)
-Pascal
I know it’s asking a lot, that’s why I posted it 
I need it without a kink. If only Rhino had a match command for trimmed edges.
I figured it out last night. I just hit record and started modeling.