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Thread: Graphite composite versus fiberglass

  1. #1
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    Question Graphite composite versus fiberglass

    What is the true story about high modulus graphite being more sensitive to impact failure. I have a lot of stories about rod tip fractures where the "better" the rod the more susceptability to fracture. Thanks.

  2. #2

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    Ray,

    My guess is that this question would be difficult to answer for even a plastics expert. You might get an answer for a test sample subjected to what is called an Izod test for either knotched or unnotched samples. But this would mean little in the real world. Things like resin type, surface treatment, scratches, section, reinforcing material (graphite or glass), age, temperature, scrim type and angle, load application, and much more would influence the outcome in an acural rod. But I bet, in the real world, whatever breaks a glass reinforced rod would most likely break a similar rod with graphite reinforcement with all other items being equal. I would be careful with both and if I broke it, I would blame it on me rather than the reinforcement type.

    Bob

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    Ray,

    I seems you and I have come to the same conclusion cheaper rods are more foregiving of rough handling that higher end rods. I don't know but have thought perhaps there's more resin and less fiber in lower end rods and resin is tougher, but does not have the desirable qualities, of fiber. Not being given to following the development of the technology of fishing rods, etc., I wonder if there has been much development in a stronger resin to go with the higher performance fiber and better protect them.
    Want to hear God laugh? Tell him Your plans!!!

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    I have no problems at all with my Sage rods and I have put them under some serious stress.

    Larry ---sagefisher---

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    Could it possinly be that the more frequent complaints about graphite are based on the fact that their owners have paid much more and therefore expect superiority in all regards?

  6. #6
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    I listened to a podcast featuring Gary Loomis and he said that although graphite has a higher modulous than fiberglass, it has much less hoop strength. Modulous is the resistance to bending whereas hoop strength is the resistance to crushing. the higher the modulous the less hoop strength. So that said fiberglass rods will almost always be more durable and the higher the modulous of graphite used in building a rod, the higher chance of rod breakage. I imagine resins have improved graphite and so has rod construction. That being said I can't imagine a graphite rod being as tough as a fiberglass.

    Wayneb

  7. #7

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    From Emory Harry :

    "All other things being equal, a blank constructed of lower modulus graphite will be tougher because there is more area under the modulus of elasticity curve. It will also be less fragile for the same power because more of the lower modulus of elasticity material will be required to get the same power in the blank and therefore the blank walls will be thicker. Conversely, as the modulus of elasticity of a composite gets higher less material can be used to get a given amount of stiffness or power. This results in thinner walls and therefore lower weight. However, the lower toughness and thinner walls also means that the blank will be more fragile. It should be noted that how fragile a blank is will be greatly influenced by the design of the blank. For example, a high modulus of elasticity material could be used but the diameter of the blank reduced resulting in more layers of material used to get the desired power resulting in somewhat more weight but a blank that is just as durable as a blank constructed of lower modulus of elasticity material that is larger in diameter but thinner walled. (If two blanks have the same wall thickness the one with the larger diameter will be stiffer or have the most power). However, because the outer most layers of material are under the most stress and resulting strain when a blank is flexed, this approach has limits. As the blank walls get thicker and thicker the point is rapidly reached where the inner layers are doing very little but adding weight."
    So technically, lower modulus has some advantage but a lot depends on design. If you break a rod, it's probably your fault, not the rods.

    Article is below:

    http://www.rodbuildingtutorials.com/...ry%20Harry.pdf

    Bob

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    Quote Originally Posted by Bobinmich View Post
    If you break a rod, it's probably your fault, not the rods.Bob
    I would agree with that whether it was a high end rod or something you picked up at Wallyworld. The only rod I ever had break with a fish on was one I found in the middle of the highway.
    Want to hear God laugh? Tell him Your plans!!!

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    Quote Originally Posted by Uncle Jesse View Post
    Ray,

    I seems you and I have come to the same conclusion cheaper rods are more foregiving of rough handling that higher end rods. <snip>
    I think there is some variant of "the cockroaches will always survive" law at play here. Back in my younger days, when I spent a bit of time working livestock, I usually wore jeans and t-shirts. (Actually two pairs of jeans, to protect against getting kicked.) My "nicer" t-shirts got ruined quickly. I bought a bunch of the most unasthetic t-shirts the campus bookstore had to offer (and UT Martin had some ugly t-shirts). They were worn hard but not worn out. I still have the ones I didn't gratuitously discard. So it is with cheap fly rods. (I still have all of them, too.)

    Ed

  10. #10
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    Well, I can tell everyone from experience that both fiberglass and graphite fly rods will break right at about the very tip when you walk into a tree with them.

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