: overlaying the points with parabolas? could you please explain in a little
: more detail how this proceedure works? what points did you choose as each
: group of three that would define the curve?

A parabola is a curve that starts as a straight line that curves at a constantly increasing rate to it's midpoint and then at a constantly decreasing rate until the line is straight. They can be defined by algebraic function, but I'm no mathematician.

: ...using the straight edge to
: draw the curve -- does one form an angle based on the three points and
: draw lines from one side of the angle to the other allowing the tangents
: to form the curve or is there another (better) technique. i appreciate
: your patience in this for those of us who don't understand these kinds of
: things. thanks. j

j,

For any three points, divide the two legs into equal parts. I usually use 8 parts, because it's easy to divide in two three times and get 8 equal parts. Start at one end and draw a line from the end of the first part to the end of the first part after the mid point on the other leg. Repeat, this for all seven parts, advancing one part for each line. The inside of the curve created by the lines will be a perfect parabola.

For fitting the parabolas to existing curves, I draw the tangent lines first, then try to fit in the mid lines of the parabolas to the curve as well. By setting dividers to the distance between the apex of the lines and where the mid lines intersect the tangent lines, the dividers can be swung to plot the begining and end points of the parabolas. Often these will overlap on the first try, so some fitting is required, and often the tangent lines have to be moved. I've never been able to do this kind of work for more than a few hours straight as it requires a lot of concentration.

Hope that answers your question.

Al