Hi bemfarmer,

A lot of that is way over my head. But the reason for the control points aspect of the airfoil curve generation is because of the leading and trailing edge circles. The NACA data points do not agree with the radius they specify for the le and te. If you were to strictly follow everything they specify in the document, you would end up with a lumpy airfoil. The picture you attached with the red and blue curves do not have the leading and trailing edge circles in there. So that may be why you aren't sure why I'm deviating from the data points at this step.

The hard part is going to be coding all that from your aspect. I don't know how you script MoI to generate a model, or if it can be done. So I can only speak about how I am doing it manually. I don't know if that translates to the way it would be coded. But it should become pretty obvious to you when you start to try and generate the whole airfoil, that you will have to use the control points option for the airfoil data points.

To get the whole airfoil curve that you need for the sweep, I do the following:

1) make circles at the leading and trailing edge, using the naca defined radii
2) make a line from the last naca point defined near the le and te to points tangent to the circles
3) make points at the intersection of the lines and circles
4) delete the lines and circles
5) use the new points as the start and end of a spline that runs through the naca defined points, using the control points option
6) mirror that spline
7) make arcs at the le and te
8) select all four curves and join them

Now you have a smooth airfoil that closely follows the naca document. You can sweep it using the le and te rails. The 1/4 chord rail is for reference. You can create the hub cutout with it, measure the radius, and apply loads later on with a different program if desired.

I hope that helps some.

Anthony