Hi, I am currently attempting to loft curved air foil sections around a central axis for an engine air particle separator. I have two projected profile sections (one on the outer cylinder, one on the inner cylinder). I've tried various connecting lines between them. No matter what I try I get the error in the subject line. In the attached IPT the last three 3d sketches are of interest. They are derived from the 2d "Front fin profile" sketch via a few projections. For the design of the device it is particularly important these blades remain perpendicular to the central axis of the device and curve/scale down (as handled by the surface projections) to properly spin the air entering the device. I've tried everything I can think of to get this to work: -Moving rail lines -changing how the 3d sketches are oriented (all in one sketch, all in separate, as it is now) -Using a cylindrical surface rather than the current, incorrect cylindrical extrusion -using the split tool to create two surfaces and lofting these surfaces along the rail lines. Thank you in advance for your help.