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The Rooster

Graphite content in a rod

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When a rod says it has IM-6, IM-7, or IM-8 graphite, does that mean that the IM-6 rod doesn't have as much graphite as the IM-8 rod does, or is it that the IM-6 is a different type of graphite compared to the IM-8??  

Basically, does the number refer to a type of graphite, or just how much graphite a rod has??

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This is a little ditty posted a couple years back on the rodbuilding site I am a member of.

It is by a very talented and knowledgeable builder in TX.

I will quote it all....

Good evenin' folks,

I may be about to open a SERIOUS can of worms with this thread, but what the heck.....here goes anyway. Being in the blank distribution business, I get asked A LOT about the construction and makeup of the various graphite rod blanks that I sell. And, I have to say that whenever somebody asks me about modulus I just cringe! Here is why; It seems that about 90% of the folks that email me want to know what the modulus is of the blank(s) they are considering buying. When I ask "Why do you want to know that" they can't really give me an answer....they're just convinced that higher the IM rating is better. Here is how the conversation usually evolves:

Mr. Customer: What modulus is that blank made from?

Andy: Well, if you must know, it's about 40million Msi

Mr. Customer: What does that mean?

Andy: Well, it means the blank is made from the material you have come to know and love as IM6

Mr. Customer: Oh, that's too antiquated...I only fish with IM7 and higher.

Andy: Really? Did you know that the difference between IM6 and IM7 is not the modulus it's the tensile strength?

Mr. Customer: Really?

Andy: Yeah REALLY!

Mr. Customer: Eh Hhhmmm....erreer, uh, oh....well uh....well Bass Pro Shops says...

Andy: Forget Bass Pro shops...let's look at the numbers (at this point Andy whips out his trusty data chart that illustrates the differences between the different fibers that actually have IM designations). Here take a look at this. This comes from a chart put together by the folks at Hexcel (http://www.advancedcomposites.com/technology.htm)

The number on the far right is the modulus of the fiber, and the number in the middle is the elongation to failure or stretch.

Hexcel IM4 600 40

Hexcel IM6 760 40

Hexcel IM7 780 40

Hexcel IM8 790 44

Hexcel IM9 920 42

Mr. Customer: You Mean all this time I thought I was getting a higher modulus fiber with the higher IM rating, when what I was really getting is a fiber that stretches more?

Andy: Well, in some cases you are, and in some cases you arent. The fact is though that the difference between IM6 and IM7 is nothing in terms of modulus, and compared to IM8 it's only slightly higher. Wow...look at that IM9 actually has a lower modulus than IM8...go figure Now, many companies are using fibers with a much higher modulus, like 57 and even higher, however these fibers don't necessarily use the IM ratings. So, whenever you see a fiber with an IM rating...BUYER BEWARE! THE HIGHER THE IM RATING, DOES NOT NECESSARILY MEAN THE HIGHER THE MODULUS!!!

The point is this folks...just because you have a blank made from a high modulus fiber, doesn't means it's a good rod! And vice versa, just because you have a blank with a low modulus...even the original fiber blanks were made with (33 million) doesn't mean it's a bad or outdated rod. It's all about what the designer does with it.

I know there are some of you that may already know this, but judging from the amount of calls I get on a daily basis from folks who ONLY want IM7 or IM8, but can't really tell you why, I have to believe they don't really know what they are talking about at all. They've just been sucked into the marketing machine that leads people to believe that the higher the IM rating, the lighter and more sensetive the material, which is not always the case.

Be forewarned that there is A LOT more to graphite blank construction, performance, quality, sensetivity, weight etc... than just what modulus the fiber is. There are lots of other variables like flag patterns, and wall thickness, and resin systems, and mandrel design....It's all about the talent of the designer, and what he is able to do in terms of the sum of those variables...not just the friggin modulus!

Whewww...ok I feel better now...

My aforementioned explanation of modulus and IM ratings is by no means meant to be anything more than a brief primer for the folks who didn't realize what the differences with the IM ratings were. I hope this clears things up a bit, and I hope that some of you will chime in on this as well. Oh, here is a link to the Hexcel page for those of you who want to investigate the matter further. Do a search for IM6 and you'll get some interesting info. (if you're into that kind of techie junk).



Now, this gives you some ammunition...next time you stroll into BassPro, and some yahoo tries to sell you a rod based on it's IM rating, ask him to explain to you why the higher IM ratings are better. When he replies by sayin' that the higher the IM rating means more sensetivity, less weight etc....just tell him that you have a blank at home made from IM2000, and see what he says.


Andy Dear

Lamar Manf.

I hope this helps explain the IM ratings and what they mean....

Tight Lines!!!!  :(

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This pretty much tells me what I think I already knew, and that is that I have to feel a rod hands on in order to tell if it will perform like I want it to.  The numbers alone mean nothing.  Makes sense cause I was looking at a Shimano Clarus that was IM-7 and even though I already own a bunch of rods that are IM-7, that Shimano just "feels" like it would be more sensitive.  Something about the lightness of the blank and the tip being so thin compared to some of the rods I have makes me think I would be able to detect more subtle bumps under water.  

What I also got from that is that the IM numbers do mean that each one is just a different material instead of having more graphite.  

Thanks for that informative post.  I'm not quite sure I fully understand it all yet.  May have to read it a couple more times before it sinks in fully.  But thanks none the less.  It has helped me with my primary question.

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I love when this thread resurfaces.  When those articles get posted,  it is nice refresher.

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That was a great read. 8-)

Here is some more information.


Having read this I now get that higher modulus means a stiffer rod that is lighter cause less material was necessary to make it.  More stiffness results in more sensitivity.  Combining that with the previous read from up above I can see where some companies can use the identical same material and one can create a better rod than the other due to how it was made.  That explains a lot to me as to why one company can sell an IM-7 rod at 1/2 the price of another company's IM-7 rod.  

I'm glad I asked this question.  I think I understand a lot more about this now and it makes me feel better about purchasing a higher dollar rod with the same rating as one I already own.  Maybe I'll even go a little higher with the amount I put into one now that I know more about what I would be getting.  

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So now that I think about this, technically an IM-7 rod can be every bit as sensitive as an IM-8 rod, but it just has to be a bit heavier because of having more material in it in order to achieve the same stiffness as the lighter IM-8 rod that has less material in it.

But there might be something to be said for the lighter IM-8 rod maybe even being more sensitive than the IM-7 rod just because it is lighter. The graphite content of both rods may be equally sensitive but the heavier rod still might not let a person feel as much just due to the weight being more. If your hand is tired from holding a heavier rod then you won't feel as much as you might have if the rod had been lighter, no matter how sensitive the graphite blank is. I would think this would be more the case in a 7' medium heavy flippin' stick as opposed to a lightweight spinning rod though. It would also be more apparent in a sold cheap and made cheaper, IM-7 rod vs. a high quality IM-8 rod from a high end company.  

This is all just me thinking out loud and posting it so when someone reads it and thinks I'm either onto something or way off base, they can tell me so. :):( I feel like I've learned quite a bit from this thread so far. I know my rod purchasing will likely forever be changed by it all.

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I couldn't care less if a rod had IM8 or IM80 graphite.  I decide on a rod based first on the blank action and power and then the components.  Lastly, I check to see if it feels right with the intended reel.

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awesome read. glad i saw this. this puts to rest some issues ive had with graphite rods and i feel much more comfortable with purchasing a new one. good stuff.

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