how do I create this surface?

[Inoram]

This seems basic, but I haven't figured it out yet. What looks like a radius top and bottom, is 2 different size radii that have been stretched (so not radii any more).

[Inoram]

If boundary blend worked, this would be the chain.

[Inoram]

Well, I got it, but I'd still like to hear suggestions. Thanks!

[dgschaefer]

Why doesn't a Boundary Blend work? Seems like a perfect place for one.  What error does it give you?

[Inoram]

Boundary Blend worked after I converted the top 2 chains to one via ref curve.(4 total versus 5)

I will say I rarely use Boundary Blend. But anytime I have ever used it and been successful, it's with maximum of 4 chains.

The error is, it fails, and the adviser says add more curves. Maybe it want me to break the lower one into 2? But this would have been more work then doing the ref curve like I did.

[kdirth]

If you don't mind geting more surface sections, you can skip making the ref curve and hold the shift key to easily add tangent lines to a chain.  This can also be done by opening the chain details.

[Inoram]

Ah. shift key was the simple part that I was missing.

[dgschaefer]

Think of a BB as creating a mesh.  At minimum, you need  to create a boundary for the surface.  4 chains is the best situation, but you can sometimes use 3.  They need not be trimmed at the corners, but they need to cross.  You cannot join 2 chains in the same direction like you initially did, you need to make it one chain, either by creating the curve ahead of time or by doing it within the BB tool, as Kevin Dirth mentioned.

You can more chains in each direction, but they have to cross the area and be "parallel" if you will to the boundary chains. Again, you're creating a mesh.

There are other nuances that come into play (and some exceptions to those rules), but that's the general gist.