Elastic Modulus

[Traditionalist]

Thomas Young, an English Doctor and physicist, coined the term "Modulus" in the early 1800´s.  The term is used as a constant in equations, as "Young's Modulus", to calculate specific properties of certain materials.

In simple terms, it may be seen as a mathematical description of a material's property of resistance to bending.

Calculations using this are essential for developing the fibres used in many modern composite constructions. The fibres, such as carbon fibre, boron, glass fibre etc, provide the stiffness, at the same time reducing the weight which using other materials would involve ("standard" carbon fibre is about 30 % of the weight of aluminium, and roughly 250% stiffer) and the epoxy resins used hold the whole thing together.

So what does this have to do with fishing rods?, and why is the term "Elastic Modulus" so often bandied about?

IM6

It has to do with them, insofar as the term may be applied to the materials used in their construction. IM6 Graphite for instance. IM6 has a modulus of about 35 million, although many rod manufacturers use fibres of much higher modulus.  IM6 is actually only a trade name for Hercules fibre in any case, Hercules being the largest producer of carbon fibre.

However this may be, the fibres used in rod construction are only a part of the story. The taper, wall thickness, and of extreme importance, the weaves and resins used, and the actual manufacturing process are at least as important. In actual fact, of even greater importance than the modulus of the fibres used.

Rod designs vary considerably, and this may be controlled by any and all of the factors above.  Using a suitable design, resins etc., practically any rod action may be obtained, anything from a floppy noodle, to as stiff as a poker. This really has little to do with the modulus of the fibres used, and is mainly the result of other design factors.

Although higher modulus fibres may be used to produce stiffer lighter rods, they may also be used to produce noodles if desired.

Light, heavy, stiff, soft

Although light rods are generally desirable, they do have some disadvantages.  Some light rods will not load very well at close range, as they lack the mass to "pre-load" themselves, which a cane rod for instance has, and will not "cut the wind" very well, and will often not be very robust. Differences of half an ounce or so, or even quite a bit more, between various otherwise similar rods, will not really make much difference in terms of practical fishing either.  Rod length is more of a factor here than rod weight. Rods of about nine feet are usually more or less optimal for most people. With much shorter rods the weight is not even a major factor.

Whether you choose a stiff rod or a soft rod depends, (or should) mainly on what you want to use it for. Nowadays, this is not considered as important as it once was, as other technological advances in lines, leaders, floatants, sinkants, etc. have made it less of a problem. Casting techniques have also improved greatly, and a good caster can produce wide loops or tight loops, indeed, some can even produce "sexy" loops at will. Once upon a time, all this was simply not the case, and specific rod actions were deemed essential for specific applications. It is still a good idea to choose a suitable tool for your particular application though, and not just rely on "feel", or advertising hype.

From cloth to blank

Back to modulus.The modulus given by the fibre manufacturers only applies to the fibre used, which comes to the rod maker in the form of special "matting", or ""graphite cloth" and once this has been built into a composite (sometimes also rather inaccurately referred to as "laminates"), it no longer applies, as the actual "modulus" of a finished rod (to which the term is not really sensibly applicable in any case, although it could theoretically be applied), is not dependent on the fibre used, but more on how it is used in the construction, wrapping, resin bonding, etc.

Hollow blanks are made by wrapping very carefully measured pieces of the matting around a steel mandrel. This is then coated with special resin, and "baked" in an oven.  Manufacturers keep their exact processes secret.

When finished, the mandrel is withdrawn, and used again for the next batch of rods.  Usually fairly large batches of rods are made at a time.  How good the finished rods are, depends on how good the design is, and on the quality control of the resulting blanks.  There are often a number of rejects in each batch, due to cloth imperfections, and various other problems.

Many marketing departments have swooped on the term "modulus", and use it quite indiscriminately for all sorts of things, basically none of which have to do with the properties of finished fishing rods. It is basically hype.

So, does modulus mean anything?

It is not possible to compare fishing rods in any meaningful way by calculating their elastic modulus, and using the elastic modulus of the fibre used in their construction as a basis for such "calculations" is just nonsense, and will really tell you nothing useful at all about the rods in question.

The quality of modern composite fishing rods is dictated primarily by the manufacturing process used, the quality control, and the hardware and cosmetics.  Practically any modern blank, even Far East  "cheapies", will make decent fishing rods if good procedures and materials are used.

Rods produced in America and Western Europe are more expensive than those produced in Korea and similar places, simply because the cost of producing them is much higher. Labour, materials, marketing, etc etc etc are all more expensive.

Do you really get what you pay for?

There is indeed considerable controversy about cheap rods vs. expensive rods.  Some people maintaining that a cheap rod can not possibly be as good as an expensive one, merely because of its very cheapness. This is factually incorrect of course, certainly as far as composite rods are concerned, any composite rod built anywhere to the same specifications, under the same conditions, will be more or less identical to one built anywhere else. The price of course may vary very considerably, even though the rods are identical.  The same applies to any manufactured goods.

There are now quite a number of very good cheap rods available.  If you put good quality hardware and cosmetics on a "cheap" blank, then you no longer have a "cheap" rod. Also, the word "cheap" here is used in the sense of the final retail price. It may have nothing whatsoever to do with the actual quality of a blank.

Composite blanks are by their nature "cheap" products, as they may be mass produced easily and consistently at will, once the specifications are known. Pricing policies of various firms have little to do with the quality of their blanks, although of course may reflect good quality to some degree.

Comparing blanks

There is no generally accepted way at present of mathematically comparing various rod blanks to one another in any meaningful or useful way. Most anglers choose their rods absolutely subjectively, based on how it "feels", how it "looks", price, manufacturers name, "modulus", etc etc.  Quantifying such things is an impossibility. Some good casters, and quite a few anglers know pretty well what they want and expect from a rod, but this is the result of long practice, quite a bit of skill and knowledge, and is subjective in any case, although some may pretty well agree on some things.

Some manufacturers, and a number of other interested parties have been working on various systems of definition and comparison for some time, but as far as I am aware, nothing of general application has yet emerged. If you have never cast a rod, and have no other knowledge of the subject, then it will not help you anyway, as there is no way as yet to translate such system results into useful information. They all require some prior knowledge.

For some new information on this and related mattes;

See "Common Cents" By Dr. Bill Hanneman



Money doesn't talk

If you think that a very expensive rod is better than some other less expensive tool, then you must perforce buy the expensive one. One thing is certain, it will not normally catch you any more fish than a cheapie.

Quite excellent rods which cost ten dollars ex-factory in Korea, or Taiwan, are regularly sold in Europe and America under various brand names, for well in excess of two hundred dollars, and sometimes a very great deal more. The final price has little to do with the cost of actually producing the rods, and certainly not with the raw material cost or the inherent "quality".  Transport, advertising, several middle-men taking their profits, etc etc, all jack the price up.

This is also why comparing rods based on their retail prices is absolutely senseless, as you have no way of knowing how this price was set. It may have absolutely nothing whatever to do with the quality of the rod.

Tools like rods, must not only be suitable for the application itself, fishing of course, but have a whole range of other properties which makes them more or less desirable for the purpose, and may be used to determine their "quality" more accurately than any mathematical equations relating to the stiffness or otherwise of materials used in their construction.

"Useful life"

As far as I am aware, there are no absolutely conclusive studies about the useful working life of various composite  rod-blanks, but modern resins, coupled with the manufacturing techniques now available should produce rods which will certainly last a very long time. There is some literature on the useful life of composites in aircraft manufacture, but this is highly technical, and not a great deal of use, as any conclusions drawn would have to be based on the use to which a material is put, and theoretical projections of such behaviour, with regard to composites built and used for other purposes, would be suspect at least.

Apparently, bamboo is susceptible to "going floppy" after a while, presumably as the "springiness" of the power fibres lessens in use, to put it simply.  Similar effects in other materials are often referred to as "fatigue".  This will also occur with other fibres (like carbon fibre), but will take much longer (in normal use), and be less apparent. In fact it is unlikely that a difference may be found at all in normal use, although it may be possible to measure one after a certain time in use. I am not aware of anyone having done this however.

Although I have heard that this is often the case with bamboo, I have never actually attempted to measure or quantify it.  Bamboo is interesting for a variety of reasons, and although I no longer have any bamboo rods (at least not in use), and the only ones I ever built were really quite awful, I still read a lot about it, and listen with interest to any comments from experts.

I would have no qualms about using even the cheapest composite blanks to build on, as all I would have to lose would be the time involved and a few materials. Hardware etc may be used again, should the rod turn out to be useless, or not up to expectations in some way.

One may also save a lot of time and trouble, take some casting lessons in order to obtain the necessary knowledge and "feel", and simply walk into a shop and buy the best rod one can afford, that one feels is suitable, after trying it out.  It is then most unlikely to be a "lemon". What "modulus" fibres it may contain, is more or less irrelevant, especially if it has a lifetime guarantee!

TL
MC