Rob's advice sounds good, not that I have used Rhino, but in general principle he is correct.
I would question exactly how you forced a sweep that included the wing tip. IMO, the wing tip does not likely share the airfoil shape in the sense that a profile could be swept around the end without creating a wrinkle in the resultant surface. Having worked on a few models of wings made by other people before I machined the molds, the wing tip detail was always a seperate set of surfaces, perhaps made by 3 edge surface construction. I do not know what this method would be called in Rhino.
Another option is to forget about doing the boolean operation, and simply use half the wing profile to create the airfoil surface, and then create a face frame around the countour, representing the surface of the block of stock. If necessary, the under side and the 4 outside edges can be constructed as individual surfaces (of a rectangular cube) and then merge everything, and voila, one half of the mold is complete.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)