| A fly rod's performance is a function of many elements, but nothing is as important as the maker's ability to determine the overall "slope" and shape of a taper. Our objective in designing rods for a given length and line-weight is always to obtain maximum strength for minimum cross-sectional mass, with weight always present as the enemy. "Strength," in our case, might be described simply as a given rod's relative ability to resist the forces of bending -- a widely varying consideration. |
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Typical fly rod tapers, unlike the "convex taper,"
incorporate what I consider to be a fundamental and unnecessary design flaw. These
tapers do not run straight from butt to tip, but progress, instead, in a series
of steps and dips -- now narrowing, now running straight, then narrowing
again -- "telescoping" downward in this manner over spans of ten inches or so.
The negative effect is that every dip in the rod's taper will function, when
flexed, as a "hinge," causing the rod to yield more easily at those points.
These weak areas must then be compensated by designing relatively stronger areas located nearby, thus forming a "controlled" series of steps distributed along the shaft, with each portion meant to compensate for (or to compliment) another. The net result, however, is that a fly rod designed in this manner (to a given line weight) will be somewhat heavier than need be. |
Good Friends Make Short Days
Photography by Michael Simon |
| The appearance of a "step-and-dip" taper is not discernable to the naked eye, but when measured, foreshortened and plotted on graph paper, the details in the design can be seen very clearly. In the illustration below, greatly exaggerated, the drawing demonstrates unequal forces of compression/tension present in more typical taper designs. |
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The convex taper, by contrast, is an engineering
principal as old as the Greek columns, spars of a sailing craft or a fletcher's
arrow. In a fly rod, as Marinaro developed the idea, the convex taper discards the
usual progression of steps-and-dips by maintaining a relatively uniform, curved trajectory
along the length of each shaft. Thus, there are no "hinged" spots within a section,
and every area is buttressed, just behind, by the "shoulders" of gradually
increasing dimensions. The design challenge, however, looms large (as Marinaro
explains in his "In The Ring of The Rise"), as one must search for the optimal distibution
of that trajectory -- and each of a rod's sections calls for a different
set of considerations.
One tremendous advantage of the convex taper is that, because no local area of a rod section need compensate for a neighboring, weaker portion, the rod is free to flex with more uniformly distributed forces of compression/tension throughout its length. This, in turn, ensures that the linear wave energy imparted through the caster's hand can travel more smoothly down the rod, and each cast feels crisp and responsive. The real pay-off, however, is that with all these factors working in concert, a fly rod properly designed to a convex taper can be built to somewhat finer proportions than its step-and-dip counterpart -- thus, helping to defeat needless weight while retaining comparable strength. (Recall, that's a rod's relative ability to resist forces of bending.) The illustration below, again, both simplified and exaggerated, demonstrates the uniform forces of compression/tension inherent in the convex taper. |
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| I no longer believe, as I once did, that makers should work only with their own tapers. While it is true that convex tapers fulfill my idea of how a fly rod should perform -- one of the hallmarks of a Harms rod -- it is also true that, since every caster's style and rhythm is necessarily idiosyncratic, the "ideal" action of a fly rod will remain a highly personal issue. So, if a customer has a particular rod taper in mind and wishes me to duplicate it on a custom basis, I would be very happy to do so. |
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