I did some research about IM series rods. Here are my results:
Modulus - a term that describes the stiffness to weight ratio of the graphite that’s used to create the rod blank. Modulus is the ratio (expressed in millions of psi, "pounds per square inch", a measure of a force on an area) between stiffness and weight of the graphite blank. Modulus is most commonly used in the terms to describe the performance properties of prepreg tape* made from fiber such as carbon, or graphite, but does not relate to the actual performance design of the blank pattern.
*
Prepreg Tape- tape roll of fibers woven, weave, or layered. Then impregnated and coated with resin. Rod Patterns are cut from prepreg and rolled onto a mandrel to form the shape and taper of the rod blank.
Tensile Modulus - measurement of shear strength or stiffness of a part which is made from fiber, relates to stiffness of a part made from that fiber. As modulus increases, stiffness increases.
Graphite - the most common rod material today
IM = Intermediate Modulus
HM = High Modulus
The originator of the IM series of graphite fabrics is US based company Hexcel. This is what you can find about fishing rods on company site:
"Fishing rod manufacturers were quick to recognize the improvements that composites could bring to the sport. Early composite rods had a glass/polyester prepare construction, which then evolved into glass/epoxy prepreg with the quest for higher performance and a cleaner manufacturing environment. However, when cost pressures drove the glass/epoxy business to the Far East in the late 1970’s, Hexcel remained successful by developing higher performance carbon/epoxy solutions for market leaders including Daiwa, House of Hardy, Garbolino and many other Italian manufacturers. Carbon fibre prepreg* enables manufacturers to fine-tune the rod performance. Carbon fibre rods have the strength to lift heavy fish from the water and to cast long distances, whilst retaining the sensitivity for the angler to feel the slightest touch on the end of the line. The development of extremely high modulus prepreg tape allowed significant breakthroughs in the design of competition roach poles. The damping characteristics of the composite enable the rods to flex deeply without oscillating. They provide the ideal combination of power and sensitivity, lightweight and durability."
Source:
http://www.hexcel.com/Markets/Recreation/Summer+Sports/
IM6 = 40 million (psi tensile modulus)
IM7 = 41 million
IM8 = 45 million
IM10=?.
None of major carbon fiber materials manufacture are listing such product as IM10 but more and more fishing companies are advertising IM10 based rods.
Example: Shimano Cumara
Shimano Cumara
It looks just like marketing.
General example of modulus ratings using G Loomis classes:
GLX - 65 million modulus
IMX - 55 million modulus
GL3 - 47 million modulus (IM8)
GL2 - 42 million modulus (IM7)
IM6 - 38 million modulus
Standard Graphite - 33 million modulus
***
The first thing you should know is there is no industry standard for IM6, IM7and IM8. Rather, it’s a “range” that manufacturers use to classify their rods according to the “modulus” content.
Here’s how it works….when you cast a lure, the rod flexes with the weight of the lure, storing energy as it flexes. When the motion of the rod stops, the rod flexes and releases all of its stored energy to propel the lure. When you increase the modulus of the graphite, you increase the ability of that graphite to store and release energy. You also increase the speed that the rod releases the stored energy. That in turn, increases the lure speed that is generated in the cast. Increase the modulus and you increase the reaction speed and power of the rod blank.
Unfortunately, increased modulus results in increased costs. The highest modulus graphite material costs as much as ten times more than standard graphite. The drawback with increased modulus is the rod blank tends to be somewhat “brittle” and more likely to break from impact fracture, such as dropping the rod on a hard surface. If you tend be abusive with your gear, it would be wise to back away from the top modulus rods and choose something in the mid range that will offer more durability. Before you purchase a rod, especially the high priced, high modulus, be sure that it is backed by a lifetime warranty.
Graphite is the most common rod material today, and is the lightest and strongest material. However, there are many varieties of graphite, depending on manufacturing quality and process, and thus graphite rods range widely in cost. Graphite rods, especially higher-end models, tend to be thin and a susceptible to breaking if they are chipped, scratched, or cracked. Lower-end graphite rods, these days, are probably almost as durable as fiberglass rods. Most high-end rods have lifetime warranties, partly because they do tend to break more often.
Below are some explanations of rod materials:
From Ralph Heidecke: Types of Graphite (IM6 etc) [from Brian Costlow, posted this back in April 1998]
IM6 is a 'Grade' of Magnamite, a graphite product of Hercules Inc. BASF makes a similar product, as well as others. The important thing about IM6, IM7, IM8 ratings for fishing applications is the tensile modulus. Most dept. store rods that are graphite composites are around 30-35 million psi tensile modulus. The IM is a shorthand for that tensile rating. IM6 = 40 million IM7 = 41 million IM8 = 45 million Tensile modulus briefly is: (Courtesy Owens-Corning) "When a bar is pulled in tension, it has to get longer.
The tensile modulus is used to calculate how much longer it will get when a certain load is applied to it. Units are normally millions of pounds per square inch. Higher numbers indicate materials which will not elongate as much as others when they are being compared under equal tensile loading conditions." That elongation, or elasticity, is what allows the rod to spring and bend back.
So (grossly oversimpifying) a rod made of IM6 can be built with similar strength and flex characteristics to a rod that uses cheaper material, while making the tube wall thinner, which in theory makes the rod lighter and more sensitive. On the other hand, just because a rod is built using IM6 does not mean it's a great rod. Exactly how the material is laid up in the blank, whether any other material (other graphite composites, fiberglass, aramid and gel-spun polys for instance) the taper, length, all go towards making a good blank. These things also affect the action (fast or slow taper). Then to make a good rod, you have to worry about the seat and handle, and how it's connected, guide material and so on.
Term High Modulus Blank
Hexcel is the originator of the "IM" series of graphite fabrics. Not sure if they trademarked "IM_", but you now see rod makers use "IM" even if they don't use Hexcel graphite like the IM10 rods from many different makers. I assume if you see IM6, 7, 8 or 9, it is indeed a Hexcel fabric, but I have no way to verify this. The Hexcel fabric ranges from IM4 to IM9 (note there is no IM10). The modulus for these fabrics is between 40 and 44 million. The IM in IM6 means intermediate modulus. There is no such thing as a high modulus "IM" blank. It's an oxymoron, a high modulus intermediate modulus blank?
So the question is, what's the difference between the various grades of "IM" fabric if the modulus ratings are very close. The difference is the "elongation to failure" rating (etf is measured in KSI and is tinsel strenght) and some other technical things I'm not qualified to detail and probably beyond 99.9% of us. The lower series have lower etf/ tinsel strength. Below are the Hexcel fabrics listed with their etfs and modulus. Note that the modulus is very close but the etfs vary quite a bit. In theory the higher etf allows for less epoxy and lighter finished rod (more on this below).
Hexcel IM4 600 40
Hexcel IM6 760 40
Hexcel IM7 780 40
Hexcel IM8 790 44
Hexcel IM9 920 42
The key factors beyond what's listed above for any rod are scrim, resin and finish content. You could have 2 rods with the same graphite fabric have totally different feel, action and weight based on the difference in scrim, resin and finish. This is a key difference between the high end blanks from the likes of Loomis, Lamiglas and St. Croix and the $70 rod and Bass Pro.
Ever notice that Loomis and the other high end manufacturers listed above don't give their modulus ratings and other lower end rods like BPS, Cabela's and Berkley make a big deal of it? It is a marketing tool. One thing to remember is that as modulus increases, durability decreases. Thus, a cheap high modulus rod (think BPS Extreme which are close to double the modulus ratings of the IMs) which should be lighter is actually heavier because the high modulus fabric is thicker with more resin for durability than a comparable "high end" lower modulus rod.
Cliff Notes - IM is a series of graphite fabrics made by Hexcel that varies little in modulus, ranging from 40-44 million. The range includes IM4, 6, 7, 8 and 9 (no IM10). Where the fabrics vary is in tinsel strength with the higher numbers having higher tinsel strength. Finished rods can vary greatly even when made of the same fabric based on the scrim, resin and finish.
So what makes a "better" rod? I'll take a shot at this later this afternoon when I have more time.
HM is a generic term for high modulus. Typically anything over 50 million is considered high modulus. You'll sometimes see reference to mid modulus blanks/ rods and those are typically made with a 33 mil modulus fabric.
he sad thing is that I only know how to use a rod and not make one, but this conversation is pretty easy to follow.
It is clear that the IM10 is not a product of the Hexcel corporation (the original manufacturer of fabric for rod building) and the IM10 that is being used is from a another company. Not that I care...but someone should be able to look up the specs of the IM10 product and see how those specs compare to materials from Hexcel for IM6, 8 or whatever...
Most high end crankbait rods like Loomis are multi modulus. They use different fabrics for different sections of the rod. They may use a high modulus for the butt and a lower modulus or even a little glass for the tip section. I'm a crankbait fool and some might argue a fool in general
, so I have 4 or 5 different crankbait rods, ranging from 7' l/ml to 8' medium heavy.
Source:
http://texasfishingforum.com/forums/ubbthreads.php/topics/3080871/Whats_the_difference_in_rods_I
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