Let me try to explain a little better. I use an airfoil generation program to create a bunch of DXF curves for each rib (they get smaller as they get closer to the wing tip).

I ultimately do want to loft from one rib to the next to generate that leading edge skin, but the problem is that I need to get a solid wall - let's say 1mm thick. The question is how do I produce a loft or extrusion that is consistently 1mm thick all around?

For example, if I try to duplicate the curve of the rib and scale it to extrude the leading edge out of the space between the curves, the scaling doesn't keep the spacing between the points. What I'm looking for is the ability to scale down a curve, scaling each point 1mm in perpendicular to the tangent of the curve at that point. To complicate things, since it's a DXF import the 'curve' is represented by a bunch of points and lines.

Here's a pic of what happens if I try to copy the curve and inset. You can see that there's a bigger gap between the curves at the front than there is at the top and bottom: