thanks burrman,

that is helpful. i don't personally have an issue with changing the leading edge in order to keep the points straight. what i have been saying is the ler and data do not agree and something has to change. since for me it is pretty obvious what the ler and ter mean, i have been changing the data points. the difference is minimal. one thing to keep in mind is that the airfoil points you were working with have one point removed, because it was way out there. i can try just giving you something with the exact data points and see how the ler you are doing works out. this whole thing is rather silly to me. but its not a big deal to try out what you are doing. thanks for actually showing a working example.

the airfoil info is ancient, done before computers, most likely with slide rules. so a little bit of an issue with comparing computer generated data to the old data is no surprise to me.

anthony