Your curves are broken up into segments and Loft wants to use whole curves. There is a command called "Merge" that is not in the UI, but it did not fully work here when I tried it. If you use the Join command once you selected all the edge curves on the shape, you'll get one closed curve that Loft likes.
Play around with Loft's settings to figure out what kind of point matching works best. When I tried with Profiles: set to "Auto" the loft result had a funky shape to it.. "Exact" worked better.

Two other methods include grabbing all of the edge curves and Joining them as single rings in their respective objects;

1) You can then perform a Loft on each ring. Make sure to use the "Exact" setting on the "Profiles:" list. So that the shapes use the existing curve points. (middle)

2) You can also place a curve at any point to bridge the two shape rings. Then perform a Sweep, selecting the two rings when asked at first. (top)
I made the bridge curve (which is really called a "Profile") with a FreeForm curve. The ends have to snap to somewhere on the rings of your shapes and should be adjusted to be more tangent or flat with their respective edges. The Sweep takes the shape of the curve and swings it around the "Rails" or the edges of your shapes.
Then you can go back using the History state of the Sweep to tweak the bulge as you can see below:

Network is a very good choice.

Note: Blend can be done, but is tricky. Could be done piece by piece if the two sets of edges have curves that start and end in the same relative places.

Hi cc,

> Apparently loft doesn't work on curved surfaces.
> Network didn't work either.

Both Loft and Network take curves (or edges) as input and build surfaces from those curves.

Since Loft or Network do not take surfaces as input if you just select an entire surface object as the input into the command it will just be ignored - you've got to select curve objects for Loft to use instead of surface objects.

You can duplicate any edge into a curve object by selecting it and doing a copy/paste (ctrl+c/ctrl+v) or also like Pilou mentions you can select a bunch of edges and use the Join command to make a new curve from them that is all joined together into one piece.

Since your objects have fairly different shaped outlines, to make a good surface in between your 2 objects there you'll need to control how things are segmented so that you have a good match between each outline - this will mean using Join and/or Trim to configure the pieces into segments that match up nicely.

- Michael

Hi cc, so your smaller profile there is segmented into 8 pieces with 4 long side edges and 4 smaller rounded corner segments. So to control how those segments will match to the outer profiles, I drew in some line segments from each segment's endpoint like this:



Each of those lines goes from the end of one of the smaller curve's segment endpoints to a perpendicular snap on the larger curve. Then I trimmed that outer curve by those lines and joined together pieces, and used the Rebuild command (link) to reconstruct a few joined pieces so they were made up of one single smooth segment.

So after that rearranging, I got the outer curve to be set up to have 8 segments same as the inside curve - now when lofting each of the segments will match up in the loft so that gives you some more control over how different shaped things get connected together.

The 3DM file is attached - to loft it, select these 2 curves:



and then run Construct > Loft to build this result:




That can then be joined with your other potato chip surface pieces to make a fully closed solid.

Your objects are a little small in size, and you may see some kind of odd things that are related to that since the default fitting tolerance of 0.001 units is not a very small distance compared to your object's size - if you see things like stuff sagging away noticeably from your curves it means your objects are too small in size and try scaling them up by 10 times so that the fitting tolerance is not too large in comparison to your objects.

- Michael

Thanks, everyone! I got it to work.

It's great to have such a responsive community here.

BTW, I'm here by way of Alibre. One of the reasons I upgraded to Expert is so that I can have MOI to do these complex shapes that Alibre kept choking on.