Emory,
I’m looking forward to seeing the next article on SENSITIVITY that you and Mike are collaborating on. I hope that you will include rod length as one of the factors affecting sensitivity.

Emory and I are hard at work already on an article that will cover a lot of the things discussed in this thread. We are challenging each other back and forth, and working through the things we don't totally agree upon to make sense out of this complicated topic. I know it has been very educational for me to spend a lot of time thinking this through, and I hope Tom finds it to his liking and decides to publish it.

I have noticed that most want to apply the thought to all rods and techniques. There are specific areas that the concepts are highly important and others where it does not matter a hill of beans. As a custom builder I found out long time ago that I was making a bad move when I tried to coach a customer to use what I thought were proper techniques. Now I try to listen to their desires and build what they ask for - this is very important in the bass rod area. At present they will pay for lighter more sensitive and back off somewhat on warranty to get it. The information I need are the words to quantify sound practices to combat the "hype" of production marketing. I can not wait to see what you two come up with! I understand that math and science are involved but please make a summary at the end with simple stuff that can easily be understood.




Edited 1 time(s). Last edit at 03/19/2007 12:58PM by Bill Stevens.

Jim,

That's an interesting question about rod length. If we're talking purely rod movement, then a longer rod is going to be less sensitive because for any given amount of line movement on the fish's end, the butt of a longer rod will move less than that of a shorter rod.

However, in terms of what we call "feel," the longer rod will be more sensitive due to the fact that it gives whatever is on the other end more of a mechanical advantage in terms of leverage. So any force at the tip will register higher or greater at the rod butt of the longer rod than it would on a shorter rod.

Remember that to the fisherman, a fishing rod is a third order lever, but to the fish, it is a second order lever. This creates conflicting aspects of the sensitivity issue with regards to rod length.

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Emory - I read the article and had some serious questions/comments/concerns - but I left them to myself, as there was quite a debate already going on :-) I'm an engineer myself, a Civil type :-) So, I have a decent mechanics of materials/dynamics background, but likely not as strong as other engineers on this board. Anyways, the one thing I really enjoy about this craft, and most specifically, this board and Rodmaker magazine, is the attention to detail, and the quest for knowledge. Your article has raised some very intelligent, meaningfull discussion that is helping to seek out the definitive answer in what results in sensitivity in a rod. Equally as importantly, we are starting to see that to various areas of the sport, and to various people, sensitivity can mean two polar opposite things! Your work is important, and good. I respect and admire you coming on here to point out what you feel is your error. That takes guts and class. No need to apologize - only one perfect human has walked this earth. I'm impressed - and I can't wait to see what you guys come up with for the next article!

Emory,

I expect that you will issue the same correction over on the BFHP.

And I think it’s important not to confuse semantics with clear definitions and descriptions of exactly what you are measuring.

The article contains other errors which you should consider correcting as well. We’ve already discussed the ideas of mechanical impedance, resonant frequency and Q, and that these are concepts defined for continuously driven systems. This objection has been termed a red herring, but I think you would want to be correct in your description based on your proposed experiments and avoid some pitfalls in the qualitative descriptions that follow. For example, an energy pulse from either a bite or the lure tapping along the bottom would produce a different tip deflection in rods with varying tip stiffness. This is altogether different when compared to a tip which is either continuously driven, or one which is taken to a constant offset and simply released. If you take the tip to a predetermined offset it will take more energy to deflect one that is stiffer compared to one which is more flexible….in this case the energy of the input will vary. Also in the article, the description of the effect of mass density of the material on the vibration transmission would be more accurately described by the mass effect of the object since density is a material property. This is just as in the case of the modulus vs. the stiffness.

Also, your description of the damping effect is backwards. The damping is not the amount of time it takes for the vibrations to damp out, but rather it is the amount of energy dissipated with each cycle of the oscillation. So the assumption that a rod with higher damping would be more sensitive is not correct, it’s the opposite. A rod with higher damping would mean that it would take less time for the vibrations to damp out, not longer. And a rod with higher damping would be expected to be less sensitive to vibration, should damping play a role. It can be argued that the damping factors are low and the vibrations travel very quickly down the rod. But consider that it might not be just the first half cycle that your hand feels since the vibrations can last for a few seconds and bounce around for a number of cycles. In addition, if the rod is tapped or struck rather than simply pulled, higher frequencies are a delta input and the high frequencies are attenuated or damped out rapidly due to the even greater number of cycles compared to the natural frequency of the rod.

The reason I asked repeatedly earlier what specifically you were measuring is because the measurement best defines the system, the variables and their effects. The equations for a resonant (driven) system are not exponentials. Also, just defining the sensitivity, as energy in energy out isn’t quite enough detail as evidenced by many of the disagreements here and when this was discussed over on the BFHP.

If you pulse the rod with an energy input, some of the work will go into translation/rotation and some into internal vibrational motion. And the system response for translation/rotation vs. vibrational motion will be different. In the case of translational motion, the optimum response (displacement) in the limit will be from a rod with infinite stiffness and zero mass. For the case of internal vibrational motion that response is a bit different. The effect of mass will be the same as in translation/rotation, but the effect of stiffness will be such that the amplitude of the internal vibration will be lower as the stiffness is increased. In both cases, the stiffness will resist motion in a general sense. In the case of internal vibration in the limit, the amplitude can be reduced to zero if the stiffness is infinite. Picture a string of constant mass where the tension is increased resulting in a lower amplitude and higher frequency of vibration….The idea is that in springs of equal mass, the one with higher tension is more difficult to set into vibratory motion.

As for the device for sensing either the translational/rotatational or the vibrational motion from an input, I would recommend the use of an piezoelectric accelerometer over a strain gauge for sensing motion, especially for low frequency measurements. It’s also very critical to strain relieve all the connections to your device.

Good luck,

mark

Damping factor plays almost zero role in rod sensitivity. The role of amplitude is much, much greater. With regard to the materials that are used to build fishing rods, the longer it takes to damp vibration, the lower the amplitude will be. The more quickly the vibrations are damped, the higher the amplitude will be. Nothing is lost in nature - you can quickly damp vibrations but such will require a harsh reaction (amplitude), or you can damp them over a longer period of time, but only a subtle reaction will be felt.


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Damping factor plays almost zero role in rod sensitivity. The role of amplitude is much, much greater. With regard to the materials that are used to build fishing rods, the longer it takes to damp vibration, the lower the amplitude will be. The more quickly the vibrations are damped, the higher the amplitude will be. Nothing is lost in nature - you can quickly damp vibrations but such will require a harsh reaction (amplitude), or you can damp them over a longer period of time, but only a subtle reaction will be felt.

Emory and I have already discussed the use of piezio-electrics. I have some experience with them and they could certainly be used in rod sensitivity tests.


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My background isn’t along these lines so I never know when somebody who comes along and uses the big words and equations is tossing @#$%& or actually knows something about what they’re speaking about. Awhile back somebody around here said that when you really know what you’re talking about you can explain it to your grandmother. Well I don’t think many of you guys could explain any of this to your grandmothers. No offense intended but surely a lot of what’s being said here is so far out in left field that it has little to no value to the simple issue at hand.

There are some things we know for sure. Graphite rods tend to be more sensitive than glass or bamboo in terms of what we’re able to feel with them out there at the end of the line. What Tom just said about the time it takes to get rid of vibrations coupling with how strong or harsh the signals will then be in the hand makes good sense to me. It backs up my personal experience as a fisherman of several decades. I know my graphite rods don’t bounce around like my old glass rods but when something ticks the tip or the line you damn sure feel it more strongly than you did in the old glass rods. The longer a rod vibrates the softer the vibrations that you feel seem to be. The more quickly the rod stops vibrating the more strongly you tend to feel those vibrations. And anybody who has fished enough with the different types of rod materials can tell you this is a fact. They might not be able to provide any equations for it but they know what they feel and know what they’re seeing.

This is what I’d like to see in an article; the effect of the different materials, the effect of the length, the effect of the weight and the effect of different handle constructions. All the rest of this rigamarole is just idle talk that isn’t impressing anyone or proving anything.

Hi Emory,

I'll look forward to the corrected math discussion because intuitively, the slow action rod would be less sensitive to the touch, but more obvious in detecting deflection by sight. This was why I questioned you earler regarding blank details and properties that would yield a more sensitive rod, based on your research and years of steelhead fishing experience. The correction makes more sense to me now so thanks for being so open about this.

We'll see you in a couple weeks in Woodland, I hope.

Terry

Ken,

When you impart a signal or introduce energy to a fishing rod at the tip, you immediately set a certain mass in motion. There are various factors that determine how long that mass will remain in motion. The amount of mass involved certainly has a great deal to do with things. Damping, within the confines of a fishing rod operating in our normal atmosphere, is going to be accomplished mostly by external air friction. The more surface area you have the quicker it should stop vibrating or moving due to greater friction with the atmosphere, but again, how much overall mass must be stopped also plays a very large role in this as well. Once you get it moving, a rod with greater mass will generally take longer to stop moving or vibrating. This is the reason your graphite rods tend to stop oscillating more quickly than your older glass rods even though they possess less surface area for the atmosphere to act on - for a similar stiffness and structure design, they contain less mass. Of course, a lighter rod can be set in motion by less input than a heavier one.

As far as the strength of the signal you feel in your hand, keep in mind that for any given input into any given rod, the same amount of energy must be dissipated. So, you can do it over a longer period of time (heavier glass rod) but at a lower signal strength, or... you can do it much more quickly (lighter graphite rod) but at a higher signal strength. This is precisely why your graphite rods allow you to better feel what’s going on at the end of your line.

This is a very simplistic explanation and only regards a few of what are actually many, many factors that all play a role in what we call rod sensitivity. Jim’s mention of rod length has some things going around in my mind this morning. Length certainly plays a role as well, and it’s one that is far more easily adapted than say, stiffness which is typically dictated by what the angler needs for the fish he’s after. What I think will be interesting, will be to see which factors play the larger roles in rod sensitivity from a practical aspect that can be controlled or manipulated by the rod builder.

I’d hope your grandmother could understand this, but frankly I doubt she’d be interested. Unless, of course, she fishes. As far as all the big words and equations you mention, I try my best not to use them in such an arena as this. But sometimes if you want to get deep enough into the matter at hand, the guys who want to discuss such things are left without much recourse. I'd suggest that when something comes up that you don't think is pertinent or somehow a bit "over the top," just skip it. The board is for everyone and it represents a very broad demographic of backgrounds and interests. There is a place here for everyone.

Nevertheless, we will have an article at a future date where we actually construct various rods in various ways to see (prove) what actually does contribute to building a more sensitive rod in a practical sense for the rod builder. I think it'll be quite interesting.



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Mark,
I agree with you that the basic conceptual error that I made and Mike corrected me on led to other misleading statements which we will correct.

No, I will not be posting any corrections on the BFHP board. In fact I do not plan to post there again. It has been my experience that there is a less knowledgeable audience there when it comes to rod building issues but more importantly the posts there seem to quickly degenerate into personal attacks.

I used the term damping factor and if you look it up damping factor you will find that damping factor is the ratio of the amplitude of the first cycle to the amplitude of the 535th cycle. You will also find that the amplitude drops off exponentially so after just a very few cycles the amplitude will be very low, normally unless the input is very large, the amplitude will be too low to be felt by the fisherman. But yes, obviously if the rod is continuously driven the amplitude will not drop. However, you are in error about reonant frequency, mechanical impedance and Q being concepts that are only valid for driven systems. For example, when the vibrations in a rod, non driven, damp out they damp out cycle by cycle at the rods resonant frequency or natural frequency if you prefer. How rapidly they damp out in a non driven system is partly a function of the Q of the rod. The definition of mechanical impedance that I used was the square root of the mass density times the elasticity but this can be converted to the mechanical impedance being the Force Wave divided by the Velocity Wave. You will notice that this says nothing about either the force wave of the velocity wave having to be of constant amplitude which would be the case if it were only true for a driven system.

I also agree with your point that when a rod is deflected unless it is infinitely stiff that some of the energy will result in motion at the fisherman's hand and some will be stored in the rod and later dissipated into heat.

As far as the device used to make the measurements is concerned I have considered a number of different approaches. Both strain gages and accelerometers have advantages and disadvantages. The accelerometers that you suggest tend to be larger with higher mass and therefore can introduce a larger error. Yes, obviously any leads will have to be strain relieved but even if they are strain relieved they still have mass. I am considering just mounting a small, low mass, mirror on the blank, focusing a laser on the mirror, and then measuring the amount that the light is deflected at some distance from the blank. I think this could result in the lowest added mass but I am still trying to figure out how to calibrate it.

Tom,
The length has a surprisingly large effect on stiffness just as it does on the resonant frequency as I think that you are suggesting. It turns out the stiffness increases inversely propotional to the square of the length, double the length and you get 1/4th the stiffness, triple the length and you get 1/9th the stiffness etc. I was frankly a little surprised to find that length had this large an effect on stiffness.

Rich,
I agree that sensitivity used in the way that we are using it has not been previously defined very well. And I would argue that we want to remove all the subjectivity possible. If you have any ideas about a better definition than "energy in the fish's bite to the movement at the fisherman's hand" I would sure like to hear it.

Ken- anyone who writes anything has to toe the line between using formulas to prove concepts- which is not terribly helpful, and just citing a bunch of anecdotes- which is even worse than just using formulas. Some of these simple concepts are not as easy to write about as one might think.


Tom K wrote "However, in terms of what we call "feel," the longer rod will be more sensitive due to the fact that it gives whatever is on the other end more of a mechanical advantage in terms of leverage. So any force at the tip will register higher or greater at the rod butt of the longer rod than it would on a shorter rod."

I don't think this is necessarily. Tom is right in terms of effective leverage, of course. The question is whether this leverage advantage is enough to overcome the extra weight of the longer rod (both blank weight and the extra guide or two) and the lesser movement at the butt of the longer rod. This gets ticklish to compare, because we have been saying "weight being equal" all along. But you can't just make a blank a foot longer and keep stiffness and weight constant unless you change materials or taper. This is where testing would really be helpful- my brain hurts from trying to think through whether you might feel a stronger pull more even if it would be a lesser distance. I'll put it this way, I believe the testing would show that for any given blank the rod would become more and more sensitive the shorter you make it.

Mike, Tom
I think that Mike must be right. The leverage should increase directly with length but the stiffness will decrease at the square of the length. This says to me that all other things like mass being equal the shorter the rod the more sensitive it will be.
The only potential problem that I can see with this reasoning is that stiffness being inversely proportional to length squared is the case for a tubular structure not a tapered structure like a blank. However, the formula for stiffness that I think must apply for a tapered structure is Stiffness equals Cross Sectional Area times Moulus of Elasticity divided by Length. For a rod blank the change in cross sectional area is not a squared function in fact there is no squared function in this formula so length much dominate over leverage. Does that make sense?
This whole sensitivity issue has given me a pain in the brain as well but it has given me a bigger pain that is quite a bit lower than my brain.



Edited 1 time(s). Last edit at 03/20/2007 11:33AM by Emory Harry.

Emory and Mike,

We have to reduce this to things that the rod builder can control. For instance, if he is building a 6 foot rod and by moving to a 7 foot rod with the same general power or stiffness and no loss to the fishermen in terms of the fishing technique being employed, will he have a more sensitive rod due to moving to the longer length? I can make an argument on both sides of the issue but it comes back to what we're describing at sensitivity.

If you're talking pure movement at the fisherman's hand, then the longer rod won't be as "sensitive." But if you're talking about feeling the tug or pull from the fish, then it will be more "sensitive." Then again, as Mike points out, the longer rod will be heavier so now we go back to the issue of having to set more mass in motion and everything that happens when we do that. Which ends up playing the greater role? These are the things that some good testing will reveal.

I doubt many rod builders will move to a softer or stiffer rod based on sensitivity issues - rod power will be determined by the intended quarry or lure weight range. But the same rod builder might choose to go a little longer or a little shorter if it meant more sensitivity, provided the additional or reduced length had no bearing on the fishing technique being employed.

There is a lot of good and accurate information being presented here, but at least some of it is really immaterial in practical terms of what a rod builder is going to do, or even can do, in order to try and achieve greater sensitivity.

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Edited 1 time(s). Last edit at 03/20/2007 12:18PM by Tom Kirkman.

Tom,
If I understand you are saying that if we could keep the mass and stiffness constant so that the only variable was length then wouldn't a longer rod not be more sensitive, result in more movement at the fisherman's hand, than a shorter one due to the increased leverage. As I think about it more I do ot think so. A longer rod will give you more mechanical advantage but will actually result in less movement at the fisherman's hand for a given amount of input energy.

The rod needs to sensitve enough FOR YOU, that you can get beyond the "3 tap habit" that Rich Forhan so aptly described in one of his seminars at High Point: Tap No. 1.... when the fish picks up your lure, Tap No. 2 ..... when the fish spits out your lure, Tap No. 3 ....... when the guy next to you taps you on the shoulder and tells you you should have set the hook on the first tap! LOL

Emory: There is a phrase in latin something to the effect "tuces el decum" that attorneys throw at each other in fits of anger. It is more commonly defined as a pimple on your posterior at the mid point between your shoulders and knees. This one may be painful but think of the relief when you get it figured out!

I know enough about the subject at hand to know when somebody is just trotting out textbook information without actually knowing if it's pertinent or not. There is a poser in the crowd, probably hard at work digging up some additional non pertinent mumbo jumbo to throw at us here!

Emory,

That is exactly what I've been saying - the longer rod will not move as much at the hand per any given movement at the tip, but what movement does occur there will be more powerful.

So now we'd be back to which type of sensitivity we're discussing - rod movement or force of movement.


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