The reason for the lack of a clean interface at the ends of the wing is because the two planes are not aligned to the block of air. If you measure the two planes, they are not parallel. This was because the two edges of the STL file were not perfect planes.

This is easily repaired by creating two new planes from the Z axis and placing them slightly inside the solid body so a clean cut can be made.

Now in SpaceClaim, on the Prepare tab, an Enclosure can be created with 0 mm on each side. The edges are now very clean.

Even though there are many surfaces around the wing, this was meshed with only a few minutes setting up some simple mesh controls.

Improvements can be made if more time is spent on meshing.

The image with no edges is just the same surfaces with the edges turned off.