Manipulating STL data in SpaceClaim is somewhat of a work of art. I have spent years developing a basic level of skill. With your wing data, if a sharp trailing edge was important, I would not use the smoothing method and the Autoskin tool because that leaves you with a rounded trailing edge. Is that acceptable?

Another approach, which is even more work than Autoskin, is to separate the leading edge, the top tail surface and the bottom tail surface.  I started on that with the first wing. It has the possibility of having geometry with a sharp trailing edge.

You can provide a link to a zip file of the STL of your second wing and I will have a look.

If you delete the trailing edge of your second wing, you can fill that in and smooth that out if you don’t care about a sharp trailing edge.

There is also the possibility of importing the STL into Fluent Meshing. I haven’t spent much time trying that out, but it might be worth investigating since it can operate on STL files directly. I expect you would have to have a closed STL body for the wing and subtract that from an STL of the air domain.