Rod ratings
There is no way to find a perfect rod rating system for fly rods. Provocative isn’t it? But there are reasons why this ideal situation cannot be. It does not mean that nothing is possible in this domain; it just means that this is not something unique. There are rod scaling systems, they reflect the way rods are designed and cast by their maker. Individual systems from rod makers are publicly unknown; they are part of intellectual property. The most popular ones have been derived by independent people with the goal to achieve a universal system. Let’s start by a historical review.
The oldest reference I found comes from a book published in 1946 by Joannes Robin. The author tried to rate rods using the classical horizontal rod with a weight at tip (around 150 grams). His work started by 1935 and he finally considered rating rods by the mass needed to get an angle (see scheme A) of approximately 24 degrees between horizontal and a line joining the handle to the tip. Interestingly, he tried to link this characteristic to the line he could cast, but at that time, lines were classified by their dimension, not their weight as it is today. So he measured the weight of line he could cast! The corresponding line length was about 45 feet. At that time fly lines were still made of silk and quoted in diameters defined by a letter (example: HDH means a double taper with the diameter H for the belly and the diameter D at the tips. He finally gave up given the difficulty to find a clear fit, but had just discovered the basic problem without successfully solving it. He just lacked a little bit of knowledge in mechanics since he tried to evaluate rod stiffness and speed by complex combination of horizontal and vertical deflection under load, while there are other means to do that experimentally (he designed a smart specific test bench for his experiments). A remarkable work for that period of time, with little means by comparison to what we can use today.
This type of methodology can be qualified of a “relative deflection scale”. You imagine that, for a given line number, rods of various length would correspond to the same weight at tip to reach the 24 degrees line. At first sight, this makes sense.
The second oldest one was published in 1948 and was inspired by the way one used to rate spinning rods (scheme B). I guess it was created before. The ideal weight to cast is 1/50th the weight which makes the tip of a rod bent to the vertical position, the rod being clamped horizontally. For example, if you need 400 grams to achieve that, your rod is supposed to cast 400/50 = 8 grams nominally. Spinning rods were quoted in grams, referring to the full weight (e.g. a 400 grams rod) by the mid of the 20th century. It may have been used for fly rods but there is no evidence of that. As you can imagine, detecting the exact position for which the end of the tip is vertical is subject to uncertainty.
By comparison to J Robin’s method of rating, this scale does not need to take the rod length into consideration. It is an “absolute deflection scale”. We now have just reviewed the two basic methodologies but we cannot tell yet which one is the most appropriate.
A new line rating, based on the weight of the first 30 feet excluding the tip, was launched by 1961. Then line numbers appeared on the shaft of rods and the discussion about if rods were quoted right took place. This scale in weight is more relevant since it is the weight of lines which influences the behavior of a fly rod during casting (on top of the casting style), we shall come back on that point later.
Historically, the rod rating challenge has been met by Europeans first, when Dr Ludwig Rheim proposed his methodology by 1997. In fact he inspired what is known today as the “15 degrees” method, for when he presented it, it was based on a dynamic test (scheme C). The 15 degrees angle was the one he chose to release a load corresponding to a 3.75 degrees static test and measure the time for the rod to cross the 3.75 degree line after release. It was changed for a pure static one afterwards, by Theodore Matschewsky, who realized he could match the dynamic values derived by Dr Rheim by static ones. There is a database of measurements with the specific calculations corresponding to the method (Theosky.com). The rods are also quoted in terms of range of speed.
The second method was published in USA by 2003 (scheme D). William Hannemann (Dr Bill), developed his own from experience, starting from the observation that some people were not satisfied by ratings proposed by manufacturers, and that amateur rod builders needed something practical. It is based on the principle that rods of the same line get a 33% length vertical deflection if loaded with a given weight (using a small bag of US cents to tune the deflection, hence the name “Common Cents System”). There is also a database to which anyone can contribute. Another parameter is given by the angle of the tip from vertical in the deflected position, the higher the angle, the more on the “tip action side” the rod is. It is quite comparable to the 15 degrees method; the deflections are just larger than for that one. A close comparison would give 27% deflection for the “15 degrees”, 37% for the CCS (based on effective length), and 44% for J Robin. The CCS method has got some refinement on the dynamic side (CCF, F for frequency) at the end.
Soon some casters noticed that “relative” methods are relevant for a small range of rod length, and that their prediction was not adequate for long rods for example. This is due to the fact that assuming that rods for a given line have the same relative deflection (%), short rods are significantly stiffer and long rods are significantly softer. Given the general trend between stiffness and speed, the scale tends to “underline” short rods, and “overline” long rods. Nevertheless these methodologies constitute some reference point and even if you do not believe completely in their ratings, you may just find what rating his best for you for any line and look for comparable rods.
Incidentally, some experiment had been conducted by 1996 in USA to compare rod characteristics and their rating. The stiffness measurement for small deflections appeared to be a good estimator of the adequate line number. Measurements were conducted by Jo Hoffmann (Cal Poly University) and his team, while the ratings were done by Al Kyte, a renowned caster and casting instructor. At the end of a couple of days of experiment, it came out that there was a pretty good correspondence between the stiffness measurement for small deflections and the line ratings performed on various rods. Rod length (tested from 7”6 to 9”6, lines from two to eight) was not influencing that fit (see scheme E). Apparently this did not spread out while in fact comparable methods were in used by that period of time. I found one on the web, unfortunately without reference to its inventor. It may have been released in the late 90s but created earlier (peche-mouche-seche.com).
So why would this last technique, an “absolute deflection scale” better fit reality? To understand that point we must capture the basic mechanism governing the fly cast, which considers that a fly rod and line is comparable to a “spring and marble” system. In one case we rotate the rod, in the other we push on the bottom of the spring. Reality is more complex than this simple model but the basics are interesting in a sense that the single characteristic explaining the behavior of the spring and marble system is a dynamic one. It is the “speed of the tackle”, in more technical words the vibration frequency of the marble/line attached to the spring/rod. It means that one may prefer a certain range of frequencies and others another one, obtaining similar results (line speed) for various rods and lines. Tackle speed is related to the stiffness of the rod and the mass at the tip: increasing the line number (mass) must be followed by an increase in rod stiffness to keep the frequency level in an appropriate range as load is changing (with line length during the cast). So it is not by chance that a correspondence has been experimented between line number and rod stiffness, it comes from the underlying mechanism of casting. This was the subject of the last article about CCS (the CCF concept), but the author did not want to consider the mechanics of casting as relevant for his relative rating system.
Ok, we may have a clearer idea of what a rod rating should be, but why can’t it be universal? There are multiple reasons:
- First, the way we fish, our physical capabilities, our casting proficiency. I remember a friend of mine (wrist) casting his 9 foot Fenwick rod built for a #6 line with a WF3.
- Second, the role of other mass (rod shaft, guides and wraps, line in the guides) which influences also the speed of the tackle and contribute to the lack of universality.
- Third: the fact that rods are hard springs, increasing their stiffness as they deflect. This is a matter of design and it also contributes to scatter the rod/line fit.
Although imperfect, the current system is quite fair for rating rods, and it should be all right if you cast like the chief rod designer. If not, you know how you can adapt the line. This is cheaper than changing the rod.
