This is fun
So if the modulus of the materials does now affect the stiffness of the blank (about 95% effect with carbon fibre) And perhaps if we regard the fact that when carbon rods are the subject then Taper has almost no effect at all, (unlike bamboo) then we can talk about wall thickness.
Thin walled blanks are more prone to deformation than a thick walled blank, they are tubes after all, however if the thin walled tube is of a larger diameter than the thick walled tube then the stiffness assuming the same modulus of material, will be about the same. Elasticity of the material during the deformation affects how well it regains its shape, this is affected by the cloth, resin and scrim type used. This is where all the rod building science goes these days.
Flaws in any material subject to stress will cause problems, what you tend to find with flaws in composite is the micro cracks will propagate from flaw to flaw, the more or larger the flaws the faster the cracks will propagate, eventually they will become critical and the material will break. I can see how an assumption that a thin wall will break more easily, if it is created under the same conditions and from the same material as the the thicker wall , would work. There is less material therefore less micro cracks are required to reach the critical point.
Problems is, if the designer is building a thin walled blank then they will select appropriate materials that allow the tube to deform more readily and with greater elasticity and therefore not crack so quickly, likewise if they design a thicker walled blank they will select materials appropriate to the purpose.
So materials are the prime mover in the design of a blank and they will dictate how thick a wall is to be made and what the properties of the finished rod will be. Incorrect manufacturing of said materials is what will cause the problems. Building any carbon fibre product that is to be subjected to a variety of stresses is a very intensive and clinical procedure, the very fine tolerances required as the grades increase need very specialised equipment and i still reckon thats the problem, the machines being used are not up the requirements of the materials. Modern resins need to be hotter and under greater pressure than ever before.
Interestingly Modulus was a big issue even with bamboo/cane rods. Flaming rods increases the modulus of the material (by expelling moisture), therefore making the rod stiffer and quicker (taper staying the same) but go too far and the rod becomes brittle. Nodes are the issue with Boo, natural flaws, staggering them was the best solution to making the rod stronger, handy when you can see the flaws
Sandy
