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.
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
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.
I have no problems at all with my Sage rods and I have put them under some serious stress.
Larry —sagefisher—
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?
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
From Emory Harry :
[LEFT]“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.”
[/LEFT]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:
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.
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
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.
Hi Ray,
I watched a video that showed a group of folks discuss fly rod breaking. Among them were folks who dealt with quality control complaints from customers of rod companies. They had to deal with broken rods.
The consensus was that the overwhelming number of rods were broken near the tip. As an illustration they put a relatively heavy weight on the line through the rod, and then lifted up the weigh, in fact lifting it until the butt section of the rod was pointing about straight up, and the rod tip was pointing straight down toward the suspended weight. The bend in the rod was primarily in the butt and lower mid section, and by comparison the tip section was pointing straight down toward the weight and was not bent at all, since the weight was such that it had straightened out the tip section of the rod. Thus in this test it showed that under very heavy loading the real stress of the load on the rod was on the butt section and lower mid section, it was not on the tip.
The fellows who had done the testing found that the main source of broken tips was a bunch of small hits to the rod with such things as bead head flies, etc. The cummulative effect of a bunch of small small hits damaging the fibers and resin over a period of time eventually lead to failure of the rod when one spot got to the point that it would fail to handle the strain and break.
It was a very convincing discussion and demonstration.
Regards,
Gandolf
Speaking of breaking rods, a friend of mine is a die hard bamboo rod person. He owns a number of boos, several made by the same person who made one for me. Anyway, my friend was at a show last year and someone was selling bamboo rods. He asked if he could cast one of them. He likes to and can cast a lot of line (he cast 90 feet using my rod and did so easily). So, he stripped out a lot of line and started false casting and broke the rod. The seller supplied him with an other rod, (bad mistake) and my friend also broke that rod when he had a lot of line out. Obviously the seller needs to make a better bamboo rod.
Larry —sagefisher—
Oops.
I think I found a mistake in Harry’s paper.
From Wickapedia "Toughness can be determined by measuring the area (i.e., by taking the integral) underneath the stress-strain curve and its energy of mechanical deformation per unit volume prior to fracture. The explicit mathematical description is:
Energy/volume= the integral from 0 to failure of σ dε
Where ε is strain a σ is stress
Another definition is the ability to absorb mechanical (or kinetic) energy up to failure. The area covered under stress strain curve is called toughness.
If the upper limit of integration up to the yield point is restricted, then the energy absorbed per unit volume is known as the modulus of resilience. Mathematically, the modulus of resilience can be expressed by the product of the square of the yield strain times the Young’s modulus divided by two."
The curves shown by Harry are wrong because he assumed the failure stress is equal between the different modulus’s. It is not.
E.G. Do the math and the IM6 the Modulus of resiliance is essentially equal to the S glass. So the lower modulus does not have a theoretical advantage as stated.
I have only broken two rods. One when I slipped and fell on some rocks. I had not yet learned to sacrifice my body for the rod…
The other one was an Orvis Silver Label 4pc 8wt rod. I was lawn casting it and it broke just above the middle ferrule. The ferrule was tight and the break was about an inch above where the butt section would have reached, so I chalked it up to a manufacturing defect. The rod was replaced without a problem. Defects do happen and it is good to have a good warranty when they do.
Ted
Ted,
I broke a 9 wt. Silver Label in exactly the same way at exactly the same point. I think it is a design flaw in that series rather than a manufacturing defect.
Bob
Bob,
Thanks for the info and idea that it was a design flaw in the rod. I was really surprised when the rod broke and have never really felt the same way about Orvis rods since. The new Hydros and Helios rods are getting great reviews though. A friend used the replacement Silver Label rod on a multi-day float in Alaska to catch numerous silver salmon, so the replacement seemed ok.
Regards,
Ted
Some rods don’t take to being bent a certain way. I’ve seen several rods break when the owners were stringing them up and a knot caught on the tip section, in freeing it they bent the tip back on itself and ‘snap’.
High performance rods need to be treated as such IMHO. Loomis once said he could build a rod that wouldn’t break but no one would buy it.
The late JC would always remind us that more rods are broken while stringing than any other way. He would tell us to aways set the rod butt down on something forgiving and walk the line out to the end.
Bob