Whats the difference in rods with IM6, IM8, IM10, etc.???

Thanks

the amount of graphite in the rod

A little about graphite. For our purposes, graphite is rated by "Modulus of Elasticity," referring to the relationship between stress and strain. It usually defines the stiffness to weight ratio of the fibers used to construct the rod blank. Generally speaking, the higher the modulus of the fiber used to make the blank, the lighter the resulting blank can be for any given stiffness. A graphite fiber called IM6 pretty much revolutionized the industry. With IM6, you had a high modulus, high strain rate graphite that made it possible to produce a lighter, more sensitive rod.

The modulus of graphite used in rods keeps getting higher and higher, making for more sensitive, lighter and more efficient rods. With that comes a trade off. There is no doubt that the higher the modulus rod , the easier it is to break and the less (angler) abuse that it can take. Graphite in of itself is very strong and the increasingly high modulus of top end graphite enables rod blanks to become lighter and more sensitive due to the ability to make blanks with thinner walls. Of course, the downside to this is they are much more susceptible to angler abuse. The thin walls just cannot stand up to rough handling and being banged around in the boat, truck, etc. The type of fishing that you do and the way that you treat your equipment should determine your rod choice, NOT company hype or status.

Is there any benefit to using a high-modulus, top of the line rod for bottom-bouncing? Probably not. Is there benefit to using one for jigging? Probably. Only you can decide if the benefit increase can justify the large cost increase.

I did not think there was a "true" industry standard on this rating? No way to compare appls to apples.

So basically its just a manufactures way of differentiating and marketing the quality of graphite in their models of rods?

the modulus can be important, yet deceiving. Also different resins, additives, and manufacturing processes add strength to rods, making it where and IM8 graphite from one company is a different weight with the rods have different tendenancies to break as well. Also the IM6-10 can be somewhat arbritrary, but I think the "million modulus" is a better comparison from rod to rod.

I remember seeing a posting somewhere of the exact #'s but here's a guestimate to the IM(X) to million modulus (and yes some overlap, that's why I said "guestimate):

IM6 33-40
IM7 38-44
IM8 42-50
IM9 48-55
IM10 55+ Highest I've seen advertised on a rod is 92 MM


Bass Pro rods are a good example of being different. They have really high modulus graphite rods, but their manufacturing process adds a lot to strengthen rods while adding weight. That's actually what I DON'T like about them (being heavy for such a high modulus), but they resist breaking (IMO) better than most any rod of stated similar graphite.

Also, don't be afraid or suaded into thinking that IM6 rod from company A that is $30 is equal to IM6 rod from company B that is $90. There can be huge differences in rod weights, feel, and overall quality.

Confused yet?

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.

Thanks for the information guys.

A great question Doss, and some great answers guys, thanks

Why would you think there is no IM 10 blanks? We buy them and they are IM 10 but then again I only own a rod company?

never mind

Grant,
Hexcel is the company that invented and sells the IM series of fabrics. They do not sell IM10 carbon fabric. IM10 is a made up designation by some rod or blank company marketing guy somewhere. Unlike IM4, 6, 7, 8 and 9 which have specific meaning, IM10 means nothing. Unfortunate as it is, it's the marketing people praying on hype and ignorance.

You can buy a Polex Submariner on nearly any street corner in China Town, but that doesn't mean it's made the same as a Rolex.

BTW, You should check it out for yourself, www.hexcel.com . They are the largest manufacturer in the world of carbon fabrics.

I won't use anything less than IM15 on the rods I build and prefer IM20 plus. If you're using anything less, you're missing out on what it's like to fish with the very very very very best.

Take Care,
Robert

Excellent read of your post Sir. I would however subsitute the phrase "Angler Abuse" in favor of "Real World Conditions".

This ain't golf.

OK

So how do you explain my IM10 to be lighter than the IM8 if they don't make it? But they make IM15 and IM20 but not 10? Most of what I read on this is about composite not graphite yes they are fibers but they are diffrent.