With all this science, can anyone say in English how much more sensitive something is over another? Is there that much of a difference to worry about?

I would think the harder & lighter the material used, the more you will feel. So the tubing materials being harder than cork, if you used a graphite arbor - you would feel more than with cork because cork is "softer".

I'm glad I don't need as much sensitivity as others when I fish.

Roger,

What type testing apparatus did you utilize?

Billy,

Cork isn't as soft as we might think. In fact, for the weight involved, it's relatively firm. How much difference does one make over the other? A little bit. How's that for a scientific answer.

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

Billy,
Did you read the posts above? How well a material transmits vibrations is not a function of the hardness or softness of the material. It is mainly a function of the mass density and modulus.

Todd,
The cork that I used was 1 inch in diameter. Were the corks that you compared the Texalium to larger than 1 inch? I know that some of the ones that you use are 1 1/8 inch. I also assumed with the cork that it was reamed to fit the blank. If the cork that you compared the Texalium to had any sort of arbor or shims that is heavier than cork that could also make a big difference, masking tape for example.

Emory,

The vibration amplitude will be controlled primarily by the mass (inertia) and the damping factor. The elastic modulus is sometimes called the storage modulus because of the way it reflects energy stored in the material. But rather than impacting the amplitude, the primary effect of the elasitc modulus will be on the frequency of the vibration.

BTW, I did make some measurements on the handle materials you sent me. The follow-up experiment will be to mock up the same rod to test on each (Ti vs. CF), but the trick is to get the Ti straight handle mounted with something other than a significant amount of epoxy filler.....that and getting past the 40 open projects I have!

OH, and thanks for the weights! I'm surprised that the CF isn't lighter, but of course the wall thickness will be a key factor as well. I think I reacall that the Texalium is built on glass?

Billy,
I measured some the damping properties of a some various handle materials a few years ago so I'll look those up and post them.

mark

Mark,
It is not the total mass or the resulting inertia but the mass density. The mass density and the modulus actually determines the impedance that the vibration sees (Z=sq. rt. mass density x modulus). The damping factor will only have an affect on the amplitude over time. The vibration at the tip of the rod travels down the rod very rapidly and gets to the fisherman's hand before the damping factor has any effect.
I will agree that the mass, actually the distribution of the mass, and the modulus have an affect on resonant frequency along with the length, taper and wall thickness but we are not really referring to the resonant frequency. We are referring to the transfer function for vibrations that the fish introduces when it bites and may be introduced by the fish in either the time domain or the frequency domain.
I am glad that you are finally being able to test the graphite and titanium that I sent you. That must have been six months ago. I thought that you had forgotten. The titanium is not really handle material. It is used by Lamiglas in the lower end of the rod through to the handle. It sometimes extends almost out to the first guide. I thought that I also sent you a piece of graphite blank that fit tightly into the titanium in which case I do not see any need for much if any epoxy.



Edited 1 time(s). Last edit at 04/13/2006 11:09PM by Emory Harry.

Hi Emory,

I'm using mass as in a generalized system. I'd have to look up the equations, but I think the form of impedance that you've got there is for a perfectly elastic system. And that would probably work well for metals and such, but in the case of the CF composite, you've got a viscoelastic component in the resin matrix, and in that case there should be a damping component in your impedance. Although small, I'm fairly convinced that the damping has a significant effect on the "feel" of the system.

The air cavity is an extreme case and when you model these systems you assume that they're mechanically linked. But what you run into with the air gap is what amounts to an open circuit because the damping from the air is so large that it's effectively infinite. In that case, even a semi-elastic fluid with more mass would out perform air…..you might feel something come through the handle. But of course using a lightweight, elastic material as a handle fastener is ideal.

mark

Mark,
I do not have any argument with what you have said except with regard to the damping. Any vibration introduced at the tip of the rod will travel down the rod to the fisherman's hand so rapidly that the damping factor will not have time to have come into play. The vibration will get to the fisherman's hand faster than the period of a single cycle of the input and the damping will not have a significant affect until after a number of cycles. That is of course in the frequency domain. If you would rather think of the fishes bite as an impulse or in the time domain then naturally the rise time of the impulse will determine the amplitude and number of harmonics ( Fourier Transform) but the inherent resonant frequency of the rod will limit the rise time and therefore the amplitude of the higher order harmonics so the same thing is true. Thsi is all assuming the frequency of the fishes bite being roughly from 1/sec. to 10/sec. The key is the velocity that the vibration travels down the rod. The velocity C is equal to the sq. rt. of the tension (elastic restoring force) divided by u (mass per unit length).

I am also not sure about your statement about a light weight elastic material being the best as a handle fastener is true either in terms of transferring vibrations. I think that a material that had a mass density as close to mass density of the blank would be ideal. That would result in the smallest discontinuity, highest energy transfer and smallest reflection.

Sensitivity or feel really gets to be a messy but interesting problem doesn't it? I have looked on the internet for a paper that someone has written on the subject or some reference source but have not found much. If you run into anything let me know.

I think that maybe a more practical approach is to forget the theory and just get some strain gages and make the necessary measurements.

If I were a betting man, I'd be pulling my sensitivity "chips" back, until Mr. Forhan reveals his hand ...............

Emory,

You know I like the practical experiments better, so I'm hoping not to have to look the equations up. lol I'm treating it as a pulsed system that goes into free oscillation (decay) where the impressed force has gone to zero.....it's a transient condition. If you solve for amplitude the primary variables will be mass and damping. If you want to ignore the damping, then you're still left with the mass effect and hence my comment on the arbor material. You could fill the void in the handle with a solid carbon fiber composite, but I think you'd find that the weight of it would be detrimental.

The concept of mechanical impedance is usually applied to driven systems. And the solutions to the equation of motion for forced oscillations and the solution for the steady state (unlike free decay) will involve the forcing function and impedance....there can still be a damping factor which you take or leave, but the driven system, it's still a bit of a different beast compared to free decay. I'll see if I can find a paper or another reference if that helps?

mark

Mark,
Yes, I understand the effect of the mass, actually it is the inertia, and the elastic restoring force and the damping. But the period of the damping is going to be on the order of seconds while the time it takes for the vibration from the fish bite to get from the tip of the rod to the fisherman' hand is going to be on the order of milli seconds. So once again I suggest that the damping will not have a significant effect whether or not it is driven or in free oscillation.

I agree with you about the arbor material but I would suggest that in this case it is not just the mass but the mass density because the closer the material of the arbor matches the mass density and modulus of the blank the closer the impedance matches and the smaller the discontinuity and therefore the more of the vibration that is transferred through the arbor and the less that is reflected. For this reason I completely agree with you that a carbon fiber arbor or an arbor made of exactly the same materials as the blank would be best in terms of the transmission of the vibrations but as you say it would tend to be heavy. Thin carbon fiber ribs or arbors that are close together would probably be a decent compromise.
For most rods though I think that the blank through reel seat with your finger directly on the blank is a more practical solution because it does not add the weight and even though you only have one finger on the blank it is certainly better than an arbor that results in most of the vibration being reflected right back down the blank or an arbor that adds a lot of weight.
I had not thought about it before just now but an improvement over what we have now would be a reel seat whose modulus and mass density were as close as possible to the modulus and mass density of the blank. There are literally thousands of plastic formulations so I am sure that there is one that has a mass density that is close to the blank but being plastic they are all going to have very low modulus and of course you still have the weight issue.





Edited 3 time(s). Last edit at 04/15/2006 09:58AM by Emory Harry.

Mark,
Something just occurred to me that I have not thought through yet in the context of our discussion that also affects the transmission of the vibrations through the rod of the fish biting and that is the Q of the rod.
A carbon fiber rod has high Q which means that it is going to tend to attenuate all of the frequencies of vibrations, or all of the harmonics if you think of it in the time domain, that are not at or very near to the resonant frequency of the rod. The resonant frequencies of rods are in the same ball park as the frequency of fish biting but they are going to have to be very close to travel up the rod unattenuated. Plus the weight of the guides, wraps, reel seat, and handle, especially the guides are going to lower the Q resulting in the rod transmitting a wider range of frequencies. The amplitude will be lower but the range of frequencies or the bandwidth will be wider.

In the past we have thought that the lighter a rod is for a given stiffness the more sensitive that it will be and I think that we also know this to be true from experience. But this argues that this is true but only for a relatively narrow range of frequencies. Or a rod that was heavier for a given stiffness and had lower Q might actually be more sensitive for input vibrations or frequencies that are not close to the resonance of the rod.
Am I missing something here?



Edited 2 time(s). Last edit at 04/15/2006 11:36AM by Emory Harry.

It may be that you fellows are talking about two different damping systems. One is the force created by the system (rod in motion) itself which inhibits the oscillation of the rod itself and the other would be that which inhibits the transfer of vibrations by the nature of the material it's traveling through.


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

Mark,
Forget my last post. I think that I am off on a tangent there.

Tom may be right.
Let me put it differently and see if you do not agree. A vibration introduced into the rod by a fish bite travels down the rod and sees discontinuities at the reel seat, arbors and handle and there are reflections and changes in amplitude based upon the differences in the materials, differences in impedance (mass density and elastic modulus). There are also internal loses in the material (damping). The loses get larger and larger with each cycle, or with time, but the fisherman will start to initially feel the vibration on the very first cycle before the damping factor has had time to significantly reduce the amplitude of the vibrations.



Edited 1 time(s). Last edit at 04/15/2006 08:17PM by Emory Harry.

My thought here is that what you refer to as "damping" is, in this instance, "insulation." Perhaps a problem in terminology.

I would think that damping is the force created by the system which then inhibits the very motion that created it. So we'd be talking about damping oscillations, not signal input (similar yet different things in some respects).

I need to run this around in my head a bit more, but I'm not sure that these two things are the same.

........

It is a good idea to clarify the damping. I'm referring to damping as the fraction of the input energy dissipated through internal friction in the material. If you ping the system (signal input), the amplitude of the vibration(s) will decay exponentially with time. The damping in a fishing rod is fairly low, but if it were undamped, it would ring for a long, long time. You could also consider the losses from other external factors like friction from air.

Emory, I think the ideas of impedance and Q are generally used for systems that are externally driven to a steady state condition, and in that case you're controlling the frequency as well. This case would probably relate to something like false casting, where you're driving the rod as opposed to plucking it and letting it go.

One key variable here is the frequency though it depends a little on how you ping the rod. If you hit it and let it go into free decay, the high frequency cycles will get damped out fairly quickly and the low frequencies less affected initially. When I think of sensitivity and feel, it's somewhat like a musical instrument or sound that vibrates with a tone to it.....think about something like a string or a drumhead that develops many multiple modes when you hit or pluck it. In an underdampled system the high frequencies will be attenuated fairly quickly, and you'd likely be able to feel the difference in systems that are damped differently. Say an unfinished rod vs. one with a layer of some polymer coating on it, or one with a high fiber density compared to one with more resin in it.

Anyway, back to your thought about the Q factor. Again, typically thought of in the context of a system driven to resonance near it's natural frequency.... but what's interesting is, you can think of it in a very general way as the ratio of the energy stored in the system to the energy lost. The quality of system could be thought of as high if it’s looses little energy over time…. you could equate this in a general way to sensitivity.

The vast majority of the damping that takes place with a fishing rod is external - air friction/resistance. The internal damping, while there, is minimal compared.

In any case, the amount of energy dissipated, assuming an equal amount is present on both systems (glass and graphite we'll say), must also be equal. So any oscillation/signal that is damped more quickly must also then be much stronger in terms of transmission to the angler. You could not have a system that damps more quickly and also sends a weaker signal (vibration or whatever you want to call it) to the angler.

This is why a graphite rod that does indeed damp more quickly than a glass rod (and assuming we're talking about similar tapers and powers) will also convey a stronger signal to the angler. The same signal in a system that requires more time to damp, will be less strong in terms of what the angler can feel.

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

Tom,

I'm not sure I agree, although I think it has a bit to do with definitions. When I think of the sensitivity of a blank, I'm thinking about how the blank transmits vibrations internally….the efficiency of the material to store and transmit the energy. So take the case where you simply hold onto and tap on the end of the rod without really moving it ....much like running into a rock on the bottom. In that case, there's little to no effect of air friction. Take that in comparison to resistance in casting or how long it takes for the rod to settle after casting and the air friction can play a larger role. In either case, though if the spring is undamped…… take a perfectly elastic spring in a vacuum and the amplitude of the signal will be equal to the input, and it won’t decay over time. In a damped system, the amplitude, or strength of the signal will weaken or decay exponentially with time.

Yes, the internal damping in rods is low, and CF blanks are even lower than comparable glass blanks…typically less resin and less mass overall…but what I’m eluding to is the high frequencies in the spectrum are going to be knocked down quickly in a system with a bit more damping and that could change the feel you get from something distinct, to something more dull at the hand.

Damping aside, one of the main reasons the carbon fiber rod has a faster settling time (for a large scale deflection) compared to glass, can also be due to a difference in mass (given the same power).

mark




Edited 1 time(s). Last edit at 04/19/2006 05:03AM by Mark Gibson.

Mark,

We agree on all counts except for your second paragraph. You can't simply "lose" something. A system that damps quickly is also going to transmit the vibrations more strongly while they are there. A system that damps more slowly and allows the vibrations or oscillations to continue for a longer period of time is not going to transmit them nearly as distinctly.

Your statement in that paragraph would seem, to me, to indicate that a green hickory shaft will provide more feel to the angler than would a rod made from high modulus graphite. This isn't the case.

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

Hi Tom,

Thanks for the note and sorry for the long delay in responding. I'm not quite sure I understand what you mean when you say you can't simply loose something. The damping in the system controls the energy lost per cycle of oscillation. And the amplitude (over time) of an energy pulse is a function of both the mass and the damping together. In the case of the fishing rod, you've got an underdamped system and the amplitude of the oscillations decay exponentially over time. Here's a reference for an underdamped system compared to something that's critically damped out in less than one oscillation:

[www.efunda.com]

There are two main variables that control the amplitude with time, and the mass is a big key. Take a heavy steel bar compared to a thin steel film of much lower mass. The damping is exceedingly low and the same in both systems since it's a material property. But put an energy pulse into each and the lighter film will vibrate at a much higher peak amplitude.

I'm not sure what to expect out of a green hickory stick although, I think some dry woods might have some reasonable efficiency. Again, I'd add that mass might be the important difference since the green stick will out weigh the CF composite of comparable power by quite a bit.

The terms "feel" and "sensitivity" can mean different things to different people, but I tend to think in terms of the damping relating to the efficiency of the material, the mass largely controls the initial amplitude, and the stiffness (modulus and shape) controls the frequencies.

mark