hey michael,

i replied to your post this morning but i notice its not here now. i was saying that i'm trying to find a definition of an ellipse that works equally well in real life and moi. nothing is wrong with moi, i love the program and the tools to make a conic section and ellipse work great. i'm just curious about defining the ellipse for both real life and moi. the reason being the airfoil i'm working with has the leading edge defined with a circle. however, it seems an ellipse is really what is in there (at least for the data set i am referencing right now). so it made me wonder, if i wanted to define an ellipse, how would i go about that. i recently found something that might help. you can define concentric circles about each foci and where they intersect is the points on the ellipse. this would fit in with the rest of the airfoil definition, which consists of points that you run a spline through. so if you add some points at the leading edge, you could run a spline through those as well. which i believe is what you were talking about before.

i was trying to use the stevens' method, however, haven't had luck with that. the premise there would be to use the line and arc tools to draw the ellipse. i'm open to how to define it. any tool would be fine, so long as you can duplicate the method in real life. back when these airfoils were created, it was done on drafting tables with slide rules and things. no calculators or computers.

hope that clears up any confusion i caused you. her are some links to interesting info about the topic:

http://demonstrations.wolfram.com/CirclesAndEllipses/ - interesting way to graphically find x,y points along the ellipse

http://en.wikipedia.org/wiki/Hypotrochoid - interesting and simple way to draw an ellipse, also simple equations to use

http://en.wikipedia.org/wiki/Ellipse - has some equations you can use to calculate points easily, i like the polar coordinates in particular