I am attempting to create a thin plate for the purpose of composites analysis, and to do that, I'm trying to make a thin shell using the Midsurface tool. The problem that I'm running into is that midsurface appears to be extremely finicky in choosing it's two planes; it frequently tells me "the second face of the pair must be an exact offset from the first," even though I'm using the Offest drawing tool to create my panel. I've only gotten Midsurface to work for perfectly circular cylinders, and perfectly flat plates. It will not work for ellipses, partial ellipses, or spline shapes. I've attached a picture of the issue I'm having for a partial ellipse plate.
Could anyone give me advice on how to use the Midsurface tool correctly? Or if there's a better way to model composites than this shell method, I would like to hear about that as well.