Resin

[VGB]

Torsten

I think that obtaining the measurements you mentioned are fairly straightforward and taught as standard practice in the mechanical engineering world.

http://www.geocities.ws/hasanpashag/Documents/exp_7.pdf

If I was doing it at home, I’d maybe swap out the electromagnetic sensing set up for a high speed camera and tracker measurement of the amplitude. Does the Don Philips book mention why internal damping is important, my thought were that it was related to sensitivity which would provide a measure for feel or be useful for nymphing.

CTS has started a blog on rod technology and included an article on specific modulus that I alluded to earlier in the thread:

https://ctsfishing.com/hooked-on-tech-m ... explained/

Regards

Vince

[Merlin]

I'm used to measure my rods and guess their design. That needs patience since I measure deflection and frequencies for the tip section alone, the tip and tip mid section, the same with the butt mid section, and finally the whole rod. Then I process the measurements in suitable files to tune the characteristics of materials (I never had trouble with resins incidentally). As you can also imagine, you have to estimate guides and wraps weight to make reverse engineering.

I do my best to measure the dimensions of the rod shaft, both external and internal (I use my wife's knitting needles for tips). Among the last 5 (Scott) rods I bought since 2006, I could guess the design (including the mandrels and prepreg patterns) of two of them within 5% of the spec. When I think my data are correct, I send them to Jim Bartschi and he comments the results. That means that the estimate of three of them were not so good as well

I can guess the modulus of carbon fibers in the various sections of course, and I use the best theoritical approach to calculate the characteristics of layers (sometimes there are several kinds on the same section). When a couple of prototypes were made to extend an existing series of rod (about ten years ago), a #3 rod, the measurements showed that the proto built to my specs was just on the low side of the #3. Jim's one was spot on and went on production. Two protos and the rod is there, amazing isn't it Paul? This is also the result of my secret weapon for design

Merlin

[Lou Bruno]

Merlin
Designing a rod from scratch, not using a manufacturer blank takes rod design to a whole different level...pretty cool.
Looking at the Torayca prepreg data sheet I see other variables, weight, density, fiber direction, resign matrix, and thickness.

So you choose the prepeg sheet (s), with those variables, that best suits your design specifications?

Lou

[Merlin]

Yes Lou, for example thickness is important (usually specified in grams per square meter), because there is a minimum number of layers to put on a mandrel.

Merlin

[gordonjudd]

I can guess the modulus of carbon fibers in the various sections of course, and I use the best theoretical approach to calculate the characteristics of layers (sometimes there are several kinds on the same section).

Merlin,
Are you referring to the effective modulus value here ( based on the deflection of a rod section for a given tip load and its diameter profile or are you able to somehow guess the modulus of the carbon fibers based on your measurements?
Gordy

[Merlin]

I can get both Gordy, but I do not perform such analyzis very often. I guess that when I failed coming close to the original specs, it is because I have not completely understood the layer combination on some sections.

Merlin

[gordonjudd]

I guess that when I failed coming close to the original specs, it is because I have not completely understood the layer combination on some sections.

Merlin,
Did your calculation of the effective modulus show that it was only 20-25% of the quoted modulus for the graphite fibers?

Haun tried to look at different factors like the alignment of the fibers and the effect of low modulus of the resin, but was unable to explain the difference.

Has the stress breaking point failure of high modulus materials and different scrims increased the failure point much beyond the nominal 2% value that Tim Rajeff found in some of his rods?


Gordy

[Merlin]

Gordy

I never met that kind of problem, I use the calculations for layers and fibers orientation and it works. Most fibers are unidirectionnal and the order of magnitude is 60% or more of the fibers modulus. Their maximum stretch is usually just below 2%.

It is likely that Haun could not identify fibers orientation and layers combination (e.g. scrim, layers thickness, number of turns, etc). If the rod has been polished that generally deeply disturbs estimates. I think reverse engineering works better with unpolished rods like the Scott ones.

Merlin

[Paul Arden]

I assume that’s a lower modulus rod than Tim is bending - out of interest how heavy is the weight?

Many years ago in a car park in Idaho Falls, Tim showed me a rod that he could bend butt to tip.

Cheers, Paul

[gordonjudd]

Most fibers are unidirectional and the order of magnitude is 60% or more of the fibers modulus.

Merlin,
Does that mean you are getting effective modulus values that are around 60% of the carbon fiber modulus values for the rods you have tested?

I am surprised that (on a sample of one at least), Loomis only got an effective modulus value that that was 40% of the rated carbon fiber value while Scott appears to get much larger values of 60%.

Gordy