I base much of my rod taper design on the work of Letcher Lambuth.  For me to understand the design of a rod taper curve I must make a fishing rod and test cast it.  It’s what I refer to as “trial-and-feel”.  My method of developing and understanding a taper may be a bit unorthodox, but it works.  There are five areas of the hexagon rod taper that I tweak and compare to feel how the rod action may vary.  (The five areas are based on Letcher Lambuth’s, The Anglers Workshop, 1979.)  The same graph template is used for all plotted tapers for this reason of comparison.  The five areas compared are the Straight Line Taper, which is the primary source of the rods’ strength and power, or stiffness.  The length and fastness (steepness of the slope = steeper the slope, the higher the tip frequency) of the Tip Zone, which I feel plays into the “detail”, or the “sweetness” of a dry fly presentation.  The Spring Zone in what I refer to and interpret as the “ballast”; and how a change in the mass distribution profile along this section of the taper may affect the loading and overall feel / action, or frequency of the rod.  The Transition Zone or hinge placement along the taper.  And the Handle Zone or grip sections’ degree of sensitivity; or power depending on whether a gradual swelled butt is designed into the taper.  There are a few tapers I’ve developed that I prefer above the rest.  And will make 2 or 3 hexagon blanks of the same taper design and tweak only one of these five areas to feel its effect on the performance between the rods when test cast.  And much of the time I discover that even a five ten thousandths of an inch modification between tapers will change the feel of a rod’s line delivery and presentation when test cast.  The following diagrams and examples help illustrate each of these areas of taper analysis.