Without giving away trade secrets, could one of you blank mfgrs tell me how the modulus of the composite in the actual rod relates to the modulus of the graphite fibers? Is it 80% or 50% or what?

The above information would be useful to me in selecting material for hybrid graphite/bamboo concepts that occasionally surface.

TIA
Jim U

While you are waiting for replies from the various manufacturers, I will toss out this tidbit for you to mull over. The stiffness of a rod/blank comes from two places; the modulus of the individual fibers in use AND the particular structure they are used in. As an example, you could use the exact same fibers in the exact same amount but create two blanks of differing stiffness by altering the diameter/wall thickness of each. One would have a larger diameter with thinner walls, and one would have a smaller diameter with thicker walls. The amount/weight of material used would be the same, but the two blanks would possess quite different characteristics.

This is somewhat simplistic and there are certainly other aspects of blank construction to consider as well, but it is something to consider.

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Thanks Tom,
I'm well aware of the effects of the geometry on beam stiffness, been there; done that. I'm just puzzling over the materials themselves. As far as I know a published number like 43 mpsi applies only to the graphite fibers themselves.

I believe you are correct. The figure for the prepeg would be a bit less, if the makers even rate it at all. I am sure one of the manufacturers will fill us in on this.

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You are exactly right Jim. The number that some manufacturers use to market there rods in terms of modulus, only refers to the carbon fiber itself. However, the resin and the scrim used in a blank also have a modulus, but they don't market that number, because it is so low. It's an easy out for some people. In terms of the percentage of each it can vary. However, without disclosing to much the following is a good rule of thumb. Fiber (50-55%), resin (35-40%) and scrim (6-12%). Really from here, it's the quality of each, the design process, and the manufacturing process that seperates the good from the bad. Good comments Tom, it's nice to see you guy's checking into this stuff. Let me know if I can help anymore.

Now if ST. Croix would just bite the bullet and build some blanks that match the Seeker CSU surf rod specs they would have a winner!!!!!!!!

Thanks Jason,

So if the fiber content of the prepreg is say 55%, would it be safe to say that the MOE of the composite is somewhat over 24 mpsi using 43 mpsi fiber, assuming that scrim and resin contibute only slightly to the bending modulus?

Hey, I really liked that new short spey blank even though I'm a lousy spey caster.

Jim U

OK, here is another question.

Is the scrim part of the prepreg cut sheet they roll up to make the blank or is it a separate sheet rolledwith the main pre peg sheet fibres?

Thanks

Your not to far off with that Jim. You would be looking at around 21-23MSI. Again, there's more variables to keep in mind, such as scrim type and resin type which can alter the equation slightly. Most prepregs used today have a cured part modulus of half the value of the fiber modulus. Playing with the content of each as a percentage, and the type of each like I said will change things. To answere Chris's question, the scrim is part of the raw material. It is not seperate entity. It can be if we wanted it to be, but it's much easier to process if its built into the resin and fiber. Typically prepreg is manufactured like a sandwich is made. A controlled amount of resin is distributed onto a sheet of paper. A layer of fiber is spread out over top of the resin, and then a layer of scrim is added as well. All three components are somewhat compressed together to make a pre-impregnated composite. Hope this helps.

Thanks again, Jason.

FYI I'm not a spy from a competitor. Bamboo guys occasionally talk about converting tapers from other materials, or laminating reinforced materials into bamboo. I sometimes mess around with composites in handle sections-considerable weight saving in heavy rods.

BTW are those proportions typical for S or E glass also?

They can be Jim, but you'll commonly see the resin content in glass prepregs to be higher. E-glass is a good example. It generally has a very tacky feel to it.

Jason,

thanks for your enlightening answers.

It has been mentioned that the scrim is normally of lower modulus thus lowers the overall figure of the blank. Why couldn't a higher modulus material be used for the scrim? Is it because the scrim roll around to sharply for a high modulus material to be used?

In graphite rods, is the scrim normally graphite or glas?

Blank manufacturers typically use a glass scrim because of its availablity and it's lower cost. You can use carbon as a scrim, but it is much more expensive, and at times harder to work with. We do use a carbon scrim in our Legend Elite series. This is one of the very few blanks in the world that is truely all carbon. Most do use glass.

Graphite scrim has to be used a bit differently as it won't take such a sharp bend as the glass variety. Many manufacturers have solved that problem by laying it up in an angled fashion so it is not exactly 180 degrees to the linear fibers.

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