Taper Research #3

In post #2, 444 tapers were plotted in a scatter chart based on the average diagonal value of each respective taper. The plot of those values indicates that there's about an equal number of taper designs on both the positive and negative side of the trend lines with most tapers falling in the 5% to -5% range. I wanted to know more about the characteristics of the tapers throughout that range of values. So...I picked a group of tapers to analyze from each of three well know Makers: Young, Garrison and Payne.

Here's a chart of the tapers that I used. These are all 4, 5 & 6wt tapers. The tapers for each respective Maker were chosen to represent 3 unique diagonal value categories. The goal of this exercise was to find the master taper that each of these Makers might have been working from. My guess is that each Maker had a taper that they always started with when developing new tapers. It was probably scribbled on a napkin and hidden at the bottom of a desk drawer...or maybe not. I figured I could back into that taper by averaging several similar tapers. The "average" tapers in this chart have been extrapolated from the list for each respective Maker.

Here's how the three average tapers look in a side by side comparison. The values in this chart are all generated by the FlexRod program written by Jim Utzerath in the late 90s. The first chart is a plot of the taper diameters. I mentioned the characteristics of the mid section in the previous post. You can see them in this chart. Next is a "Garrison style" straight stress chart. By "straight" I mean that the stress values are calculated with no allowance for deflection angles. That's the commonly used form of stress analysis in the rod making community today. But there's a fundamental problem with using straight stress values to analyze a loaded (bent) rod...the stress values change dramatically when the rod is loaded. Jim got way out ahead of the rod making community by simulating the bending effect on the stress values. If you're accustom to reading stress curves, it shouldn't be a big leap to read the bent curve (e.g. stress values go down in the tip when the rod is loaded and up in the butt section depending on the taper design).

Moving on...the diameter in inches for each taper is listed in the middle of the slide along with the deflection in inches at each station. By the way, there are several variables used to drive the deflection calculations (e.g. line weight, line length, line angle, line tension, etc...). But I'm not qualified to get into the details of all that. I just input the variables and analyze the results. Jim did all the heavy lifting.

Maybe now would be a good time to mention that I vary the line length by line weight in FlexRod. I use 10ft of line for every 1 line weight (e.g. 5wt at 50ft). As a practical matter, the heavier the weight rating of the rod the further it should cast or it should turn over a heavier fly. The rods should be analyzed accordingly. That's contrary to conventional wisdom, but I've never been much of a conformist anyway. I'm not a rebel by any means, just always asking questions and testing conventional thinking for reasonableness. In this case, there's no empirical analysis supporting the 10ft assumption. It's a seat of the britches thing. A 4wt at 40ft, 5wt at 50ft or 6wt at 60ft just seems to make sense to me.

Below the taper diameter and deflection tables is a statistics table. The primary FlexRod variables are listed along with a few metrics for comparison. The metrics should be self explanatory except maybe "Effective Length" (EL). EL is the straight line distance from the tip top to the butt of the rod when it's loaded. You can visualize that in the deflection chart on the right hand side of the slide. If you think about it a minute, the energy generated by the lever effect of the rod is determined by the EL, not the overall length of the rod. Now, take that one step further and divide the EL by the length of the rod and you have a proxy for how "fast" (stiff) the taper will be relative to other tapers. In this case, the Young average taper at 86% will be stiffer than the other two when it's loaded. If you're familiar with the Young tapers, you may take exception to the idea that a loaded "parabolic" could be stiffer than diametrically opposed taper designs. Read the next paragraph before you draw a conclusion on that point. There's a method to my madness.

The deflection chart on the right should be self explanatory. Those are fully loaded rods for the given variables. Yes, deflection and EL can change dramatically with changes in the casting stroke. FlexRod could simulate that to some degree by changing the tension variables. But I don't think that adds value in this analysis. I'm using congruent tension variables to compare taper designs. Said another way, I'm assuming a proficient fly caster can adjust their casting stroke to the action of the rod. However, it would be cool to be able to analyze casting strokes. But that might require more variables than cells in an Excel spreadsheet. Actually, casting strokes vary with personality profiles. Maybe Myers-Brigg testing could be used to match the fisherman to the best taper design.

Well...I think I've covered all the stuff in that slide. Back to the "master" tapers. I'm not going to try to describe what you should already be able to see in the charts. To oversimplify, the heavier the mid section, the lighter the butt and vice versa. The differences in the three taper designs are significant, but they're all 5wt tapers with about the same ELs and significantly different average diagonal values. They are diametrically opposed designs that are within the range of functional tapers. I think we might have found these three tapers scribbled on a napkin somewhere in the Payne, Garrison and Young shops.

In the next post I'm going to tweak these three tapers a little and create a standard set of tapers that cover the primary average diagonal value categories noted in post #2.