After numerous attempts to find a time to schedule, we were lucky to have Emory Harry up to the plant recently. We wanted to hear all about using frequency as a tool for consistent blank production and he did not disappoint. You can read about his visit and some basic concepts on our blog.

[northforkcomposites.com]

Jon

Hi Jon,

Are you guys measuring the Flex (Frequency) of the Rod ? I think the rating is somewhere 8.0=Stiff down to 1.0=Soft ? Just curious.

Ben

Ben,

I think that is an Orvis scale, but I'm not sure, can you give me more details?

Jon

Jon,

The DigiFlex Frequency Meter is used for measuring Flex of the golf club. It seem that you can also measures rod as well, illustrated on your webpage. i may be wrong ?

Ben

Jon,

I think this is great tool for measuring frequency of rods. The system and scale is user-friendly. Does anyone else use it ?

Ben

Ben,
It is the rods or blanks natural frequency or resonant frequency or first harmonic. Different disciplines often use different terms but it is the rate that the blank or rod will oscillate if stimulated (deflected and released).
The resonant frequency of golf clubs are also measured using the same technique as is used with blanks or rods. It has become fairly common for the shafts in a set of golf clubs to be frequency matched. The small device shown in the last of Jon's photos is a device designed for measuring the frequency of golf club shafts that Gary Loomis had. I guess it was left over from the days when he was making graphite golf club shafts. Jon and I found it to work very well. In fact, it was much easier to set up and use than all of the equipment that I brought.

Ben,

Right now we're just using the frequency measurements to make some basic comparisons. We aren't using a frequency scale to label things. We use CCS, URRS and all other acronyms just to give objective data. What everyone does with it is what makes rod building fun.

Jon

Emory,

LOL ! would the frequency be differ if you tested on granite rather than concrete floor ? Just curious. Anyhow, it was fun and educational to read on NFC website. I think Gary's idea of using this device for creating his rod is "genius".

Thanks again !

Ben

Jon/Emery

With all due respect, what is all this new information going to do for us poor uneducated rod builders? Are we supposed to accept this as 'fact' and charge on as if we had all the answers, or are we supposed to wait until there is some kind of confirmation from unbiased sources. Real science takes time you know, and I don't see any unbiased scientific background in your statements.

Personally, I accept Emery' thesis (kind of) but it leaves most of us with nothing more than "two peoples opinion". Is this just more 'hype' intended to sell more blanks or is it a preamble to some greater understanding of the hobby we enjoy?

I agree with one thing, the internet is the greatest tool ever devised for spreading """"facts""""".

Bobby Feazel

[www.shockwaverods.com]

Conventional wisdom will not open the box.

Bobby,
This is not some sort of new scientific theory that requires peer review for confirmation. It is just straight forward engineering. Every physical structure has a resonant frequency, a pipe, a beam, a two by four, a bridge or a carbon fiber blank and the measuring of the resonant frequency of physical structures has been taking place for I would guess a couple hundred years.
Some resonances are fairly simple. The resonant frequency of a beam or a pipe is simple, just the square root of the spring constant divided by the mass. The resonant frequency of a carbon fiber blank, mainly because it is tapered and has varying wall thickness, is much more complex but much of what we as custom rod builders are interested in and that determines the rods ultimate performance shows up in the resonant frequency, stiffness, length, action, the mass, distribution of the mass, and even the material. And other performance factors are very closely related to the resonant frequency and accurate inferences about them can be made from the resonant frequency like sensitivity, casting distance, and damping.

Emory, the idea of "resonant frequency" in rod blanks intrigues me. As far as the "feel" of a rod goes I tend to like the overall feel of a 2 piece fly rod over a 4 piece rod. An engineer friend (non fisherman) said that it could have something to do with the resonant frequency of the blank. In your opinion, would the number of pieces of a rod blank have an impact on the resonant frequency of that rod?
Thanks..JH

Jeff,

If we were only concerned with performance, we'd fish one piece rods, which will be lighter and lack the flat spots created by ferrules. I don't know if the ferrule mechanism itself influences frequency, but the additional weight a ferrule requires certainly decreases frequency and performance.

If only a nine or ten foot one piece was easy to pack.

Jon

Jon are you saying a multi piece blank could possibly not perform as well as a one piece? Heresy!

(sorry I couldn't resist - very tongue in cheek comment)

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You can prove any of this to yourself with the CCS frequency measurement. While it is not "resonant frequency" per se, it is a relative means of judging if one blank has a higher or lower frequency than another, which is what I believe the average builder interested in making routine comparisons will want to know. Not all rod builders can purchase expensive electrical equipment so the CCF is the layman's means of making those comparisons. Anybody can do it. All it takes is the instructions from that article plus a stopwatch or a good eye on a clock with a second hand. I have found it to be remarkably resolute considering the simple apparatus and procedure!

Is there any way of measuring the amount of stored energy which could potentially be delivered when a bank is flexed by a known load?
It is, after all, this stored energy that we are chiefly paying for when we buy blanks which will be used to cast for distance.

The amount of stored energy which the completed rod actually contributes to the cast will vary with the amount of weight added to the blank and the spacing and type of guides used, but these are the responsibility of the rod builder, not the blank maker.

Phil,

Emory can correct me if I'm wrong. If you take two blanks with the same intrinsic power, length, but one having a higher resonant frequency, the one with the higher resonant frequency will perform more efficiently and do a better job of transferring the stored energy into the cast.

Jo

Joe,
You're absolutely correct. A higher resonant frequency means that the tip velocity will be higher during the cast. The rod with the higher resonant frequency will release the stored energy more rapidly than a rod with a lower resonant frequency. Or another way of putting it is that the rod with the higher resonant frequency will convert the stored energy to kinetic energy more rapidly.

Jeff,
Your engineer friend is correct. A rod that has a higher resonant frequency will feel more crisp and responsive. You can feel the higher frequency and higher tip velocity plus a rod with a higher resonant frequency will also damp out the oscillations more rapidly which is part of what you are feeling. The rod with the higher resonant frequency will also normally will weigh less.
A blank with four ferrules versus two ferrules will have four spots where there is a slight stiffening, as Jon points out, which will tend to increase the resonant frequency but the four ferrules also means more weight. I have never made this measurement but my guess is that the added weight will swamp the increased stiffness and result in the rod with four ferrules having a lower resonant frequency.
I also agree completely with Jon on one piece rods. It seems to me that the only reason for a ferrule in a rod is that it makes it easier to transport. One piece rod, especially the longer ones, can be a pain to trainsport.

Emory some have taken and posted on other related "sensitivity" threads on this Forurm that the human hand cannot detect the small differences in mass between "micro guides' and other larger guides. I can grasp the concept that quality control procedures which monitor frequency can be used to optimize performance issues related to production runs of like blanks. Are you now saying that the "human hand" has the capabilities of actually feeling the small differences in frequency. Are you now proposing to equate the subjective words of "crisp and responsive" to a set of numbers?

The golf club industry also relates a precise spine alignment as well as resonate frequency of the shaft - will the subject of spine orientation for fishing rods be included before this discussion reaces a conclusion?



Edited 1 time(s). Last edit at 04/02/2010 01:37PM by Bill Stevens.

Emory,

For the Love Of Learning, is it : Vibration=Square Root of Stiffness / Mass ?

I think we can use our computer with a soundcard and a microphone to records or measures resonance frequency, is it possible ?

Thanks

Ben

Bill,
I would tend to agree with those that posted that the human hand cannot detect the difference in the mass of guides if the difference is small and IF the rod is being held steady or with no movement. However, once the rod is put into motion very small differences in the mass of the guides and the frequency of resonance can be detected. Try this experiment, shake one of your rods that has the micro guides. It will oscillate at its resonant frequency. Now tape a couple more micro guides on it near the tip and shake it again. It will oscillate at a lower frequency and will feel different to you. You will be able to tell the difference with just that small amount of added mass, not quanitatively but qualitatively.
As far as spine is concerned it is my impression that the golf club shaft manufacturers are somewhat ahead of the fishing rod blank manufacturers with respect to spine. They are working on removing the spine from their graphite shafts and have built shafts using filament winding techniques that have spines that are so small that they cannot be detected by the golfers using them. As Jon suggested go to the CSFA.com site and go to the Tech Notes at the bottom of the first page. These tech notes will tend to remove some of the rod builders myths about spine.

Ben,
Both the stiffness and the mass affect the frequency of vibration but there is a little more to it than that. If you will also go to the CSFA.com site there is a formula there for resonant frequency that I think was derived by John Kaufman. In his formula you can see that it is a function of the total mass and also of the mass distribution and the 3EI part of the formula is an expression of stiffness. I think that this formula is a little simplified but probably as good as can be done with algebra and without resorting to calculus.