Been studying up on airfoils, reading the books, etc. Thinking about simple airfoils for low performance aircraft. Most of my designs (none of which have progressed beyond the X-plane model) just use the old NACA 4 digit series, but I have been thinking about moving a little beyond. The other day, had an idea on changing the mean line. Because the NACA 4-digit mean line is two parabolic sections, the slope is increasing all the way to the trailing edge. This means you end up with fairly high moments. The NACA 5-digit uses a straight line from the max camber point to get low moments, but at the cost of having a sharp stall due to the kink (discontinous 1st derivative) in the mean line. So, my idea is to use a hyperbolic mean line after the max camber point. For the front, use the same parabola as the standard 4-digit, then for the back use a curve of the form a/x+bx+c where a,b,c are chosen to have the peak at the max camber point, then back to 0 at the x=1 position. Worked this up in the attached spreadsheet. Just using the y+-thickness for now, instead of perpendicular to the mean line as the real NACA method, so that is also a little diffrerent, but using the NACA 4-digit thickness profile. Testing with javafoil (as it is free and easy to use) shows my foils as having slightly lower drag, the same Clmax, and about 25% lower moment than the same parameters for the NACA 4 digit. I know that what I'm doing is basically 1930s tech, and there are many better airfoils available now. But, I want something that is less critical to exact shape (working with wood or Al instead of composite) at low Reynolds numbers (1-3x10^6). Just thought I'd throw this out here for the many more knowledgeable posters to take a look at. Thanks for your comments.