Pawel,
That is a very good question. There is no inconsistency or I hope that I did not create one with my wording. A stiffer rod will be less sensitive. But for any given blank when building the rod you want to try to build it to get as high a resonant frequency as possible with that particular blank. Does that tie the two together for you? If not come back me.

Mike,
For a given input the stiffer rod will be less sensitive. The amplitude of the movement at the fisherman's hand will be less for a GIVEN INPUT. Now if we move the tip the same amount with a stiff and a less stiff rod, which I think is what you are suggesting, then yes the stiffer rod, depending upon the mass of each, may result in more movement at the fisherman's hand but it will take more energy or a larger force to get that movement. Do we agree now?
I went back and read what I said and I can see how you might conclude that the comment about resonant frequency was a red herring. I only mentioned it in the context of damping because the rod damps out vibrations at the rods resonant frequency and many believe that damping has a significant effect on sensitivity when in fact it has very little. The point that I was attempting to make, and must have done it poorly, it that the velocity of any vibration through the materials that rods are made of is so high that the vibrations get to the fisherman's hand long before the damping has had time to have a significant effect on the amplitude of the vibrations.

Jim and Mike,
I have thought quite a bit about how to measure sensitivity. If what we want is absolute measurements it gets even more difficult especially if we want to measure both the longitudinal and the transverse vibrations or displacement.
But I think that what we as rod builders are mostly interested is only the transverse vibrations and we are also only really interested in relative measurements, is a stiff rod less sensitive than a less stiff rod, is cork a better handle material than EVA in terms of sensitivity etc. If that is the case then I think that it will take a lot of measurements but the measurements should not be too difficult. I believe that I can get everything by just putting a strain gage where the fisherman's hand will be and then deflecting the tip a fixed distance and releasing it and measuring the strain. I hope that I do not get any big surprises.

Boy, you guys are tough so early in the morning

Let me answer this question about stiffness and sensitivity in a little different way.
Mechanical impedance is by definition the resistance to the transmission of vibrations or in other words the amplitude of the vibrations at the fisherman's hand will be a function of the mechanical impedance of the rod. Another way of looking at it is, the higher the mechanical impedance the higher the attenuation of the vibrations will be. The formula for mechanical impedance is the square root of the stiffness times the mass density. So as the stiffness increases the mechanical impedance increases and therefore the amplitude of the vibrations decreases and as a result the sensitivity decreases. Is that better?
Another interesting implication of this is, the stiffness of a rod increases from the tip to the butt of the rod. The more the stiffness increases the more the vibrations will be attenuated. So a faster action rod with with a larger increase in the stiffness from the tip to the butt with the same power as a slower action rod will be less sensitive. Agreed?

Another interesting question is, which is the most sensitive a graphite or a glass rod? If we look back at the formula for mechanical impedance of a material, not a structure, it is the square root of the elasticity times the mass density. Glass has lower elasticity which would result in lower mechanical impedance and therefore higher sensitivity but it has higher mass which will in higher mechanical impedance and therefore lower sensitivity. When you go through the numbers for the difference in elasticity and mass it turns out that there is not a lot of difference in the sensitivity of graphite and glass. It will depend more on the design of the rods and the type of glass and type of graphite used in the rod.



Edited 1 time(s). Last edit at 03/01/2007 10:41AM by Emory Harry.

You concede that a stiffer rod will move more, but still maintain that the "amplitude of movement" can be more with the soft rod. The first law of thermodynamics is clear on this point. When that rod tip flexes, it's absorbing and destroying the energy it was given by the line (unless that rod has a battery). The more it flexes, the more energy is destroyed and the less left over for your hand to feel. Conversely, the stiffer the rod, the more energy is passed down the blank (mass being equal, of course).

Tell me this, what transmits vibration better, braided line or monofilament? The braided line does, of course. There is a night and day difference in line feel between braided and mono lines. Why is this? Because braid stretches less- it's stiffer. Stiffer line is far more sensitive because it conserves energy (i.e. it does not absorb/waste energy in stretching or vibrating). To use your language, the velocity of vibrations through the line are higher because the line is stiffer.



Edited 1 time(s). Last edit at 03/01/2007 10:31AM by Mike Naylor.

Harry,

:)

do you realise, that if you are right, what we are talking now is one of the most important breakethrough in the way we think about the blank/rod construction in the last, I would say at least 10 years?

Boy, Harry, what have you done ;)

Okay, back to the question. It ties.... only little bit to me. First, I need to know wheter I made a good preasumption that:

high-angle (stiff) blank = higher resonace frequency

low-angle (soft) blank = lower resonance frequency

I think the preasumption is okay, because when I compare 2 blanks: fiberglass (low-angle, soft) and high modulus graphite (high-angle, stiff) , When I put a pressure upon tips of such two blanks and then release, stiffer blank should have higher resonance frequency.

So, what I am trying to understand is the ralation of 1)resonance frequency 2) blank stiffnes 3) sensitivity

If resonanse frequency increases with the increase of stiffness, then sensitivity goes down

Now, you wrote:
"(...)when building the rod you want to try to build it to get as high a resonant frequency as possible with that particular blank (...)"

- my question, why ? To have stiffer (less sensitive) rod ?

Especially, if damping factor is of so little importance as you wrote. "(...) that the velocity of any vibration through the materials that rods are made of is so high that the vibrations get to the fisherman's hand long before the damping has had time to have a significant effect on the amplitude of the vibrations. (...)" So far, I considered weight the main damping factor.

Harry, do sth if you do not want my rodbuilding believes go to peril :)







Best regards,
Pavel

Pavel,
I did not say that damping factor is not important, or I hope that I did not. I said that it had very little affect on sensitivity.

Mike,
No, I did not mean to concede that a stiffer rod will move more. A stiffer rod will move less for a given input than a less stiff rod.
I do not think that I have violated the first law of thermodynamics. You are really pushing me but if I remember correctly the first law states that energy cannot be created or destroyed but only converted or words to that effect. The input kinetic energy in the rod is converted to heat energy but that takes time. That is what is happening when the vibrations drop in amplitude or damp out, the kinetic energy is being converted to heat. But the damping takes place cycle by cycle exponentially at the rods resonant frequency. But the rods resonant frequency is only going to be on the order of a few Hertz so it will take seconds for the majority of the kinetic energy to be converted to heat. But the vibrations will travel through a graphite rod at 10,000 to 20,000 feet per second so the vibrations get to the fisherman's hand before there is any significant loss to heat.



Edited 1 time(s). Last edit at 03/01/2007 11:14AM by Emory Harry.

In very general terms, it might be best to say that for any two rods with the same stiffness, the lighter of the two will more than likely be the more sensitive of the two. But we'd also have to assume that all other aspects of the rods are equal.

Earlier I had argued with Emory that for two rods of the same weight (and weight distribution), the stiffer of the two rods would be the more sensitive. More thought has me thinking that is not necessarily the case.

Ultimately we'll do some actual tests - the set up is really not all that involved, but it will require things the average guy isn't going to have in his shop. But we can prove out some of the things that appeared in the article. Then we'd like to take the same blank and set up various reel seat and grip arrangements and see what's what. I think we pretty much know what to expect, but the information won't be complete without the data to go along with it.

...............

Emory Harry Wrote:
-------------------------------------------------------
> Mike,
> No, I did not mean to concede that a stiffer rod
> will move more. A stiffer rod will move less for
> a given input than a less stiff rod.

Emory Harry (also) Wrote:
-------------------------------------------------------
> Now if we move the tip the same amount with a stiff and a less stiff rod,
> which I think is what you are suggesting, then yes the stiffer rod,
> depending upon the mass of each, may result in more movement at the
> fisherman's hand but it will take more energy or a larger force to get that movement.



Assuming equal mass and length, deflection follows the simple formula

D = F / K

D is deflection distance, F is Force, and K is stiffness

As stiffness increases, deflection distance decreases (i.e. a stiff rod deflects less). Deflection- the bending of the rod- as Emory said results in less movement of your hand. But Emory added that it would take more force- this is not the case. The same force would move a hand holding a stiff rod more than a hand holding a soft rod. Less hand movement means less felt transmission and less sensitivity. Stiffer rods are therefore more sensitive.




Edited 1 time(s). Last edit at 03/01/2007 12:30PM by Mike Naylor.

Doesn't Mr Newton enter here somewhere. Fast or slow, stiff or limber, you have the other end of the rod in your hand. I should also think that the easier a rod is to bend, the less leverage it gives you.but also the more direct a connection you feel (after subtracting out what the bend required).
Seems to me a fair bit of sensitivity is relevant to the person and the application as well. You might want to feel every little thing on a panfish, but do you want every shock from a 300lb tuna unimpeded.
The biggest change I've seen for sensitivity was going to braids. And I suspect many of the folks screaming for sensitivity are dong do because their lines are stretchy and little feeling is left by the time a vibration makes it up to the rod.

Emory Harry Wrote:
-------------------------------------------------------
> Another interesting implication of this is, the
> stiffness of a rod increases from the tip to the
> butt of the rod. The more the stiffness increases
> the more the vibrations will be attenuated. So a
> faster action rod with with a larger increase in
> the stiffness from the tip to the butt with the
> same power as a slower action rod will be less
> sensitive. Agreed?


Frankly : ????

You have just described what is believed now to be perfect blank for jigging application = stiff butt and delicaste tip [large increase in the stiffness from tip to the butt ]

Emory Harry Wrote:
-------------------------------------------------------
>So as the stiffness increases (...) the amplitude of the vibrations decreases and as a result the sensitivity decreases. Is that better?

Frankly: ????

How amplitude of vibrations referes to resonant frequency and the test for resonant frequency you applied in "Weight versus performance article" ? I would say, as the stiffness increases, the renonance frequency increases

To sum things up - I am still confused, as present discoveries seems to me contradictory with former statements.

However, this discussion indicates clearly, how invaluable Rodmaker Magazine articles are. This is truly a place where the wisdom is born, even if it is sometimes a painfull process. Harry, I would like to let you know that I appreciate your efforts very much, even if sometimes I can not confirm them myself on the basis of my own experience.




Best regards,
Pavel

Italo I know your are reading this and using a translator - lets get together and make a tasty gravy for the "noodles" everyone would enjoy!

stiffer rods result in a higher resultant moment at the hand. this is evident by attaching a line to a broomstick (stiff) and an ultralight (soft) of the same length. place the reel between two supports such that the rod lays horizontal, hang an equal load from each. the broomstick will fall over first because the moment generated by the force at the rod tip results in an equivalent force that is distributed farther from the hand than the softer rod (stored in spring force) that is distributed throughout the rod and the resultant force would be closer to the hand (shorter moment arm). theres a reason that they don't make shark rods 14' long, the moment arm would be way too long and it would be an unreasonable moment formed at the hand.

anyways, these are my two cents after thinking about it for a few minutes.

disclaimer: my two cents may actually be worth less. if I read more arguments I am willing to change my mind, LOL.

Mike,
Yes, D=F/K. What I meant to say and what I thought I said is that for the SAME DEFLECTION it will take more force if the rod is stiffer which is what the formula says. Or for the SAME FORCE there will be less deflection if the rod is stiffer which is again what the formula says. I do not think that there is any disagreement between us on this. I think that maybe the disagreement is on how much of this deflection at the tip of the rod gets to the fisherman's hand.
Maybe this is the disagreement.
Previously I said for a GIVEN INPUT and I meant and should have said is for a GIVEN KINETIC ENERGY INPUT at the tip of the rod there will be less movement or deflection at the fisherman's hand if the rod is stiffer.
You are suggesting that for a GIVEN DEFLECTION at the tip of the rod there will be more movement at the fisherman's hand if the rod is stiffer.
Both statements are correct all other things, Mass, line, rod action.
But for a GIVEN ENERGY in the fish's bite there will be less movement or deflection at the fisherman's hand and therefore lower sensitivity the stiffer the rod is that the fisherman is using.

By the way, I am not a scientist like you. I am just a poor old retired, retarded electrical engineer so lighten up on me. You push me a little farther into thermodynamics and you will have me in real trouble.

Pavel,
Yes, you are right, as the stiffness increases the resonant frequency increases. What I should have said in the previous article if I did not is that for any given blank with a given stiffness we should attempt to keep the resonant frequency as high as possible. Another way of saying this is we should try to keep the added mass as low as possible. In other words, all other things being equal, including stiffness, the higher the resonant frequency the better in terms of sensitivity. Does that make it clearer?



Edited 1 time(s). Last edit at 03/01/2007 02:54PM by Emory Harry.

Emory I am struggling along.

For any given blank what has a measurable stiffness the resonate frequency should be a maximum with the blank bare - no mass added anywhere. You can measure the stiffness using the CC for comparative purposes.

Can you measure the base resonate frequency for the blank with no added mass?

Start adding mass in reverse order - wrap a few tip guides next.

Will the addition of thread, guide frame /guide, epoxy change CC numbers at all? If they do stiffness has been altered by added mass. If stiffness is changed due to mass addition there can be no comparison of numbers because the stiffness then becomes a variable for that one blank.

Measure the resonate frequency after first addition. What would you predict?

Repeat the above in increments saving the seat and grip for last.

This should develop a set of test numbers for THAT blank that might explain the overall effect of added mass at different locations.

What your explanation tells me is that a blank has its highest sensitivity and resonate frequence when nothing has been added. This is basically the build technique described by Rich Forhan - remove get all non functional mass of the rods you build when sensitivity is of concern.

Bill,
You have forgotten or did not read the article in RodMaker Volume 8-Issue 3 titled Guide Weight and Rod Performance that I wrote about a year ago in which I did just what you are suggesting. I measured the resonant frequency of the bare blank and then the resonant frequency with several different guide configurations and guide locations. I also weighed the guides, thread and epoxy separately. If you read it again, assuming that you did read it, and have any question let me know and I will try to answer them.

No, the added mass of the guides, thread and epoxy will not have a significant affect on either the CC power (stiffness) or the action angle but the added mass does naturally have a significant effect on the resonant frequency and on the sensitivity.

Emory Harry Wrote:
-------------------------------------------------------
> Mike,
> Yes, D=F/K. What I meant to say and what I thought I said is that for the SAME DEFLECTION it
> will take more force if the rod is stiffer which is what the formula says.

Yes, precisely! This is why the stiffer rod will be more sensitive. Because the same force results in less deflection and thus more movement of the lower part of the rod.

I wish we could be having this discussion over a beer at a pub drawing on napkins instead of online. If we ever meet Emory, the drinks are on me. I'd love to pick your brain.

Mike,
I am sure that I would really enjoy the conversation and the beer.

If I understand you are suggesting that the less movement or displacement that there is at the tip the more movement that there will be at the handle??

There is another piece of this sensitivity issue that we haven't argued about and that I thought that you would come at me with. The formula for mechanical impedance, the square root of the mass density times the stiffness, is actually somewhat simplified. There is a frequency component as well, what you called a red herring. The mechanical impedance increases as the input frequency or dv/dt increases but then drops dramatically at the rods resonant frequency. I am actually not sure exactly how much it drops I am still looking into it. At this point I think that it is probably a function of the Q of the rod.

Harry,

without you, it would be half the fun really, you started sth tremendously intersting !

I am ashamed to confess that I still didn't get you - this is my last try I think ;) maybe I have to face the facts and admit that there are things in this world which are simply beyond my capacity of my brain :D

Some most recent quotas of you:

1/the stiffness increases the resonant frequency increases

OK, this what I can understand

Question 1: does it apply to a reverse sequence - when we increase resonant frequency, does the stiffnes increase along? If the relation is linear stifness = resonant frequency, the answer should be "yes"


2/ the added mass does naturally have a significant effect on the resonant frequency and on the sensitivity

Question 2: I preasume answer "yes" for the Question 1. From this point I derive following reasoning: we reduce mass = we increase resonant frequency = we increase stiffness = ? Up to now, I would put = we increase sensitivity, but now it seems I have to put = we decrease sensitivity (because of increased resonant frequency and stiffnes). This is where I am lost.

3/
the added mass of the guides, thread and epoxy will not have a significant affect on either the CC power (stiffness) or the action angle but the added mass does naturally have a significant effect on the resonant frequency

I can not understand that stiffness is not affected and resonant frequency is affected, at the same time, given linear relation between resonant frequency and stiffness






Best regards,
Pavel



Edited 2 time(s). Last edit at 03/01/2007 04:00PM by Pawel Tymendorf.

Like Emory's article, this is an interesting thread. i am curious about another aspect. Given that a rod is basically a multitude of molecules, and I suspect that any energy transmission passes through it molecule to molecule. When it is flexed by the strike, run, or whatever and the molecular spacing is elongated at the outside radius and compressed at the inside radius is there any affect on the energy reaching the anglers hand? I realize that beyond the flex, this displacement does not exist.

Pawel,
The stiffness of a blank is determined by the material it is constructed from, mainly the modulus of elasticity of the material, and from its dimensions,partly by the wall thickness but mainly by the diameter of the blank. To get more stiffness we must go to a different and stiffer blank, a blank that has a larger diameter or is constructed of higher modulus of elasticity material. There is really no practical way that a rod builder can do anything to increase the stiffness of a blank. And the stiffness of the blank does not change significantly when we add guides. But when we add the guides the mass does increase though so the resonant frequency does drop.

Stiffness is not linear. The power of a blank is a number because we select an amount of deflection at which we measure it but stiffness is not a number but a curve. As we apply more and more force to a blank it deflects more and more and gets stiffer and stiffer. The blank gets stiffer as it is deflected more and more approximately exponentially.

We as rod builders also cannot increase the resonant frequency of a blank. Everything that we do adds to the mass and lowers the resonant frequency. All we as rod builders can do is keep the amount of mass that we add to a minimum so as to keep the resonant frequency as high as possible or as near to the blanks resonant frequency as possible. Keeping the added mass as low as possible not only keeps the resonant frequency as high as possible but also keeps the sensitivity as high as possible.

If this does not answer your questions do not give up but ask again and I will try again to give you a satisfactory answer.

C. Royce,
You are right that energy does move through a blank molecule by molecule, actually atom by atom. But I am not sure how the tension on the outside of the blank and the compression on the underside of the blank affects the velocity and the amplitude. That is a good question. My guess is that as the tension increases the velocity and the amplitude also increase and as the compression increases the velocity and the amplitude decrease but that is just a guess. I will have to think about it or maybe Mike or someone else can answer.