People can choose to use whatever model they want. They can pick up a rod and wiggle it. They can ask Bubba, the fly shop owner. They can blindly "trust" the rod manufacturers rod number. The ideal situation would be to actually cast the rod with the line intended or desired. Lacking that, they COULD choose the rod based on real-life performance measurements based on the line weight they might use.
- Really………hammers and earthworms!!
It is all about the model. Models are tools, simplifications of another, more complicated state that either cannot be directly measured, or predicted, or not easily measured, or predicted. Like any tool, they might be indispensable, useful, or in the worst cases, inappropriate and damaging. They don’t even have to make sense. They just have to work.
For me, a useful fly rod model would need to both predict that I could severely overload a 30 year old Graphite II, “slow” (by modern standards) rod with a 12 weight line and still cast nearly 100’…AND why that is within 2% (roughly) the same as a vastly different…modern…..stiff…..fast rod, AND why the older rod is consistently marginally shorter. AND it had better explain why, although I haven’t actually run the test, I am NOT sure that using any of my 12 wt rods…I can do any better. I would have thought, offhand, that the 12 wt rod would be seriously longer. Again, without doing it, but I would not even bet my 12 weight is AS long as either of these rods. Shades of distance competitors using 5 weight rods!!
In a larger sense, the above paragraph sums up the questions I have asked for many years in these discussions. Given 40 years of continuous “improvement” in materials, resins, graphite, modulus, taper, even…. “suspending gravity”, why am I not noticing any serious difference in casting length? Why does the current Loomis Crosscurrent 8 wt weigh 4 ¾ ounces and yet my old, abandoned Fenwick fiberglass 9 wt weighs 4 7/8 ounces? Why does, if anyone stoops to actually cast it, the old fiberglass rod cast as marginally close to it’s graphite equivalent as the two rods above?
And therefore why is there such a high dollar value attached to those “improvements”. And why (parenthetically and rhetorically) has this all made me such a cynic?
A good model, to get my attention, had better answer all of the above, excepting that last paragraph. Only then will I believe it has a greater degree of validity in predicting the behavior of some new, unknown rod.
As often happens, it turns out that the answer to all the above questions has been staring us all in the face.
Force = Mass x Acceleration