Hi Anthony

There is nothing wrong with your data, as far as I can tell. (except maybe the tangent points, see below :-( ) I just wanted to confirm that I had identified the points correctly.

I believe that the spline needs to start and end on the "tangent" points, which is why I put an extra copy of them back in the array, in the order in which the spline is created. So the "tangent" points have a dual purpose.

Attached is an updated Prop_DesignGeo, which incorporates your data as of 12/29/2011,
also creates and shows the control points for the rails.
To see the control points for the Airfoil, do "show points."
The control point spline runs from upper "tangent" point, to lower "tangent" point.
The user still needs to add the two arc radii.

Unfortunately, it appears that the two "tangent" points are just a little bit off, the arc radii do not quite intersect them...(zoom in).
(Or maybe I've made a mistake somewhere...)
(I've read how to calculate the tangent points manually, using either arctangents, or simple algebra, as a right triangle is created.)

Anyway, I think it is progress :-)

With the help Michael gave a few posts back, I think the "tangent" points can be created in the scripts, using either your "point line tangent to circle" method, or else the Thales method....