Ed - I am building intakes right now and noticed in your photo many tangent lines you used to derive your shapes.  I'd love a quick lesson on what you are doing.  I've been simply mocking what I think sorta' looks the same. Since I am taking AutoCAD classes I could design stuff to any accuracy.  I'm guessing that your lines are some type of maximum curvature limits to avoid separation?  I always wondered how one measured degrees of curvature on a curve.  I know, like you don't have enough to do ! :-)
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net