Michael Danek's investigation into and his measurements and findings regarding rods' "True Natural Frequency" helps push the objective observation and fact-based data of the most important tool we use to fish -- the rod blank.. Unlike Michael, I am not an engineer, but have built fly rods and golf clubs as a hobby for many years and, at age 66, I have seen the evolution of fishing rods move from low-grade fiberglass to high-tech graphite, all to the distinct advantage of the angler, as rod performance has improved greatly. The same thing has occurred in golf shafts, though with much more fact-based analysis and testing, particularly publicly available.

There are many parallels to TNF in the golf industry, where golf shafts, also a long and tapered tube like fishing rods, have been having frequency measured for many years, and manufacturers, club builders and tour van shops at PGA tournaments have had digital readout frequency machines in use for decades. And those machines unequivocally and accurately measure a shaft's frequency. And anyone can buy a golf shaft frequency machine for a bit more than $500. There are also digital MOI machines used in golf, as well as laser mechanisms that will quickly determine a shafts FLO (Flat Line Oscillation), what we on the Forum would call a rod's straightest axis. Thus many of the things debated here, and much of this work around it, has already been accomplished and is a long-realized fact in golf, which Michael and I have discussed -- he the qualified engineer, me the fact-finding layman. Michael has provided a rather simple and inexpensive way to measure a rod's TNF, a valuable piece of data to have.

To date, in angling, we have pretty much relied on weighting a blank and then maybe hanging some weight from the tip of the blank.

As in carbon fiber fishing rods, graphite golf shafts, particularly for drivers, which use the longest shaft with the longest taper and thinnest tip, have become high-tech, high-modulus, highly-refined instruments. Top of the line driver shafts now sell for $300 - $800. The capabilities of these shafts are one reason why Rory McIlroy can blast 360 yard drives. The shafts overall weight, its flex/bend profile, its bend point (sometimes called kick point), and the weight distribution within the shaft's wall are all factors. And high handicap golfers can benefit from high-tech shafts also, the shafts are simply designed for slower swing speeds.

Pro golfers use very stiff driver shafts, as their swing speed is typically 110-130 mph, and they test their swing results on highly-sophisticated doppler radar analysis machines that measure all the factors of their swing. An amateur can have the same analysis done at a variety of golf retail outlets and be custom fit for a shaft. At some point, someone will commercially make such analysis and fitting available to anglers, I think at least on the high-end fly rod side of the sport. By the way, many pro golfers have to limit the length of their driver shaft in order to maintain accuracy and keep the ball in the fairway. A longer shaft equals greater club head speed, basic physics, but also results in less accurate shots on less than perfectly hit balls.

In general, the higher the tapered graphite tube's frequency, the stiffer overall that rod or shaft will be. Golfers with low swing speeds find stiff golf shafts to feel like "boards." Rory would find a golf shaft rated as "regular" in flex to be a whippy mess. Similarly, those who crave high line speed casting tend to like a fast action rod. Golf shafts are rated in Regular, Stiff and Extra Stiff, just as a rod's action is rated as Slow, Moderate or Fast. Stiffness equates to higher frequency.

In golf, sensitivity is also a factor, and many golfers, particularly those who are accomplished, can feel 1 to 2 gram variations in the weight distribution (swing-weight) and overall weight of their clubs. Clubs can vary in weight from from 260-390 grams. So golfers can feel a swing-weight differences as small as .0051. If that is a data proven fact, which it is, then anglers can certainly feel minute differences in a rod's sensitivity, for which there can be a number of factors, frequency being one of them.

A key point in all of this is "fact-based." Why? Because what a human thinks they feel or perceive often is not supported by the test data. A tapered graphite tube's frequency is an irrefutable fact, and certain performance characteristics will result from that frequency. Of course other factors come into play.

In golf, if you find a shaft you like and that performs well for you, and you measure and know its weight, bend profile and frequency, you can be fairly certain that you will like other shafts that share the same 3 basic characteristics. And that's why a fly fisher who prefers a slow action, deep-flexing cane or glass rod tends to loathe a super-fast fly rod that demands fast tempo, high-line speed casting.

Thank you, Michael, for helping to push the envelope.

Very nice, informative, post, David. I'm very glad you did it. I have found your observations, references, and comments interesting and valuable. I certainly have learned from them.

Those who doubt the validity of the lever arm argument for sensitivity without having tried it need to try it. And they need to remember that Tom K has stated that the rods used in the comparison don't have to be identical except for length; the difference felt is significant. I don't doubt that it is a significant subjective test. It is not an unproven theory; it is scientifically correct that one has to apply more force with a lower mechanical advantage. . The problem with it is that it is not predictive. It can only tell one the subjective difference between two rods. It cannot predict whether a 7 foot rod will be more sensitive than a 6 1/2 foot rod with quite different or unknown characteristics. I was hoping that TNF could do this, and while it has been (sort of) proven (without TNF data) that there are exceptions to the direct correlation of sensitivity and TNF, I still believe that it usually has good correlation. I think testing with more similar blanks than those used in the YouTube demonstration might do that. But it would take quite a bit of testing. Having said that, I don't think it has been adequately proven that the table transmissibility test correlates directly to what one can detect in the hand. There are discussions about adding rod loading with a line. Those who have researched Trika's claims and equipment will note that that is what Trika does. I know that St. Croix has a process which they contend measures sensitivity, and it proved to them that the objective test correlated with their long held subjective conclusions. I might mention that their high end blanks have pretty high TNF's.

My comments on keeping the other variables as constant as possible is fundamental to good and valid experiment design. If the other variables are too far off then there is no way of knowing which variable caused the observation.

David pointed out to me the hazards of subjective conclusions. He pointed out numerous tests on golf clubs in which there appeared to be an "expectation" factor. Similar to a "halo" factor where the conclusions are influenced by other factors. That is sort of what I was talking about with the "great wine" notes. This is a real hazard in subjective evaluations.

I have to comment on "vibrations" and the references to electricity. I have not seen or heard anyone claiming that they were talking about electricity. There are things called "mechanical vibrations," and that is what everyone is really talking about. I submit that a single tap, or thunk, or pull, is simply a single cycle of a low frequency vibration. If one believes this then the next question is this: Do rods that transmit higher frequency vibrations better also transmit lower frequency "vibrations" better? Like the tap of a fish on the line.

I remind those who are still struggling with the definition of "sensitivity" that it was well over a year ago that I introduced a post in which I asked for opinions on whether sensitivity and natural frequency correlated. I at the time defined "sensitivity" for the sake of the discussion as the ability to feel a bite. After that subject was chewed on for a while I introduced TNF and stated that I thought it correlated with sensitivity as I had defined it. In January a direct challenge to that position was made. Since it was a direct challenge the definition of sensitivity would be assumed to be the same. Sensitivity for the sake of all this directly related discussion should be considered the ability to feel a bite.

Finally, to answer the question of what practical difference does all this make? If it means nothing to you, forget it. Go on to other things. But for me and some others curiosity into how things work has value itself in providing challenges, pleasure, and knowledge. I doubt very much if I will ever not be curious.

david taylor Wrote:>
> In golf, sensitivity is also a factor, and many
> golfers, particularly those who are accomplished,
> can feel 1 to 2 gram variations in the weight
> distribution (swing-weight) and overall weight of
> their clubs. Clubs can vary in weight from from
> 260-390 grams. So golfers can feel a swing-weight
> differences as small as .0051. If that is a data
> proven fact, which it is, then anglers can
> certainly feel minute differences in a rod's
> sensitivity, for which there can be a number of
> factors, frequency being one of them.

What? I agree, there are some really talented and amazing human beings on this planet, but I'm calling someone out on this one. I don't know where that information came from, but I just did a little experiment of my own. I just read that the average zinc penny when newly minted weighs 2.5 grams. 8 tenths of that penny weighs 2 grams.

I took a shot glass, took a zinc penny, and to the best of my ability felt the weight of the shot glass with and without the penny, and if I had to save my life by identifying the shot glass whether with or without the penny in it 80 times out of a hundred, I will die at the end of the trial. I couldn't tell, and I was looking! Remember, the law of averages states that in a blindfolded experiment of this type, one can expect to be accurate 50% of the time. So unless you can nail it closer to 80% or more of the time, it's baloney.

Now, the average golf club ( I don't golf...I'm using your numbers ) weighs a lot more than my shot glass does, so adding another 2 grams of weight to the business end of the club seems to me to likely have far less of a detectable difference than adding it to my shot glass. Now, for those of you who DO golf, think of swinging that club as you might usually do, and feel what you feel. Then, try taping eight tenths of that zinc penny to the business end of that same club, and swing again. Do that with the help of another person in a blinded experiment, and tell me that you are going to be able to tell the difference between the two 80% or more of the time. I know where my money is going.

>A key point in all of this is "fact-based." Why? Because what a human thinks they feel or perceive often is not supported by the test data.

Yup...and vice versa! If there is something about a particular rod that you like, and someone else is unable to appreciate that which you are finding so desirable, does that property not exist? Of course not. Of course it exists, and whether or not someone else can appreciate it is neither here nor there. On the other hand, if someone tells you that they have conducted an experiment that indicates that you should be able to detect this and that with that rod, and you do not, does their test matter? Certainly it doesn't matter to you.

>A tapered graphite tube's frequency is an irrefutable fact, and certain performance characteristics will result from that frequency. Of course other factors come into play.

A hundred percent true. But if one cannot take the information gained and utilize it for some SIGNIFICANT advantage, then why get crazy? There's no reason to reinvent the wheel.

Ernie, forget it. Go on to other things.

A golf club's swing-weight can be measured on a very accurate, highly available and not too expensive swing-weight scale. It is a measurement that's been around a long time, but measures the weight (or really the feeling of a club's head weight) from a fulcrum point 14 inches down from the end of the grip.

A typical driver head weighs 200 grams, a driver shaft from 55-80 grams, and a grip about 50 grams, so you can quickly add that up to a driver that on average weighs around 320 grams. If one adds 2-3 grams to the head weight or places it inside the tip of the shaft that will change the swing-weight of the club 1 point. Many players, even those not skilled, can detect a 1 to 2 swing-weight point differences. Virtually everyone will detect a 3-5 swing-weight difference, whether they golf or not.

Go to a friends house or into your garage. Take out a driver and feel it in your hands or take a swing. If you taped a penny to the top of the driver head you will likely feel a difference. If you taped two pennies to the driver head I can tell you that many, if not most, people would feel a dramatic difference, even though you are changing the club's overall weight by a tiny percentage. A few grams place on the end of a 45" golf club makes a big difference in feel.

A 240 gram club can have the same swing-weight as a 350 gram club, as it is a matter of balance, not overall weight.

Sensitivity? How much does a house fly weigh? You can certainly and instantly detect a fly the moment it lands on any part of your body. Humans are acutely sensitive to tiny changes in an object's swing-weight and, often, to its overall weight.

In terms of weight and swing-weight or balance of a sports tool, think about the type of bat you used to like in little league or whenever you played baseball. 32 ounces was too light. 34 ounces was too heavy. 33 ounces was just right. And the handle needed to be a certain diameter and the width of the barrel was a factor in how the bat balanced or felt balanced in your hand. You had your favorite bat, and when you picked up your friend's favorite bat it felt terrible, even though in ounces it was quite similar to yours.

So go ahead and remind you wife you are a highly sensitive man!

One more example. How much does a BB shot weigh? Nymph fish with a 9 foot fly rod with one BB shot on the tippet. The rod weights 2.5 ounces, has a reel on it, and a line running out of it. Place a second BB shot on the tippet and you will be sensitive to the difference and the feel through the line and rod. Put 4 BB shots on the tippet and you would think you had an anvil at the end of your line. Yes, you are a sensitive man, indeed!



Edited 1 time(s). Last edit at 10/29/2023 04:26PM by david taylor.

You forgot you need to place the shot glass or penny on the end of a 48" to 108" tapered graphite tube. Fulcrum. Balance.

As to raw weight, go to the gym. Try a bench press with 100 pounds and with 105 pounds, you will perceive the difference, and that is in holding a weight two feet above your body. Then put a five pound weight on the end of a 5 foot broomstick and see how easy or not it is too lift.

OK Dave, I will take your word for it for the time being that the average human being can detect the weight of a penny added to the top of his golf club when swung. I played a lot of ball, and I fully get the difference in bats example. Although I never fished flies with split shot in fifty-five years, I understand what you are saying, and I agree.

All those things said and examples given, at no time did you incorporate the importance of the material and the properties of that material in either the golf club example, the bat example or the fly rod example. The examples across the board it seems center around the lever arm principle regardless of what the clubs, bats or rods were constructed of. How about this? If you took one of those fancy golf clubs made of the finest kryptonite and whatever else they are made of, and tape that penny to the end of the handle, would all that fancy kryptonite still allow the user to detect the weight difference?

How about the 9' "fly rod"? You told me how long it was to make a point, and a good one. You didn't seem to care about what that fly rod was constructed of. How much would it matter if was bamboo, glass or graphite....and just what graphite? And what about the bats? Are they wood? Are they aluminum? You were more concerned about how they were actually constructed in terms of weight distribution, diameters in certain places and the balance those parameters ultimately resulted in than the material they were composed of.

And last but not least, that fly example was killer! But the issue is not the weight of the fly, but the integrity of the normal human nervous system that makes the difference. That's where a HUGE degree of subjectivity comes into play. Some people just might not feel it. And if that fly happens to land on the little band aid you applied to your arm, I dare you to look me in the eye and tell me you felt the weight!

First off, in regards to the leverage arm argument, Tom K alluded to the rods not needing to be identical, they just had to be sufficiently different in length. And if so, then the difference felt will be significant.

Secondly, as sensing weight is one of the ways a bite from a fish is detected, a bite from a fish being your definition of sensitivity, the lever arm effect is about as predictive as you can get Using the length of the lever arm, you can calculate how much weight an angler would feel based on how much weight is added to the end of the lever. You don't have to predict how much difference there is in the sensation of weight between a 6 1/2' rod, and a 7' rod ...... you can calculate it !!!! And if you can calculate it, that means it's objective, not subjective.

I'm curious as to what quite different or unknown characteristics of a rod blank would affect the ability to calculate its' mechanical advantage? Could it be ........ none?


As far as the reference to the testing that Aleks did in relationship to the A Sensitive Topic thread. I will only say that I found the results of his testing, quite predictive. And my prediction came true.

Anyhow ..... I'm done here. I'm going to go see what Ernie is doing. Maybe he wants to go fishing ........

Using the lever arm method Is a glass 9 foot 3 weight fly rod more sensitive than a 7 foot high modulus graphite spin rod with ERN 17 and AA 77?

I know the same sized fish would feel larger when fought on the fly rod so I would surely think the fly rod would be more sensitive for the same reason. But what is the ERN and AA of the fly rod? If the fly rod is a super slow action and just folds right down to the handle then maybe not.

Feeling larger and detecting a tap of a fish bite by feel are not likely the same thing, may or may not correlate. One is static, sustained, and the other is dynamic, instantaneous, not sustained. If tip deflection were to be considered, then the fly would likely be more sensitive, but this whole discussion has been taken with the detection of the bite being felt, not seen. That's certainly the direction I've been taking.

Most fly rods have ERN's on the high side of their stated weight, so it would probably be about 4 ERN and 60-65 AA. But what if it were weaker and slower? I think it would be even less sensitive to feeling a bite. And this is where the lever arm argument weakens for predicting sensitivity. It does not take rigidity, weight, material characteristics into account. It can only be predictive when all the other characteristics are fairly close together. Not exactly the same, but fairly close. Exc for length.

Michael Danek Wrote:
-------------------------------------------------------
> Using the lever arm method Is a glass 9 foot 3
> weight fly rod more sensitive than a 7 foot high
> modulus graphite spin rod with ERN 17 and AA 77?

The horse isn't quite dead yet. I don't know the answer to this question, but you pose it I believe because you think the answer is going to be the shorter rod because of its calculated action and power. If that is the case, I don't know that that is going to necessarily be true.

Now, apples to oranges comparisons aside, as a fly fisherman of fifty-five years, I cannot think of a single advantage a more "sensitive" fly rod is going to afford me at the end of the day. There are only so many ways to fish with a fly. In as much as fishing in streams for various species of fish is likely the most common, again, I have a relatively short list of possibilities. If I am fishing dry flies regardless of the type of water I'm in, the only sense I need is my eyesight. If a fish decides to gobble that fly, the next thing I need is a reflex quick enough to set the hook before he figures it out. Nothing about what the sensitivity rating my rod is has changed a thing. I didn't need it to see the fly, nor did it change my ability to set the hook.

If I am fishing streamers, wet flies or nymphs, the game changes a little. If I am fishing them across and down stream, or just plain down stream, if a fish decides to bang the fly, I don't care how sensitive the rod is, I'm going to know it. If I cannot, it's not the rod's fault, it's me needing to be off the water and home eating oatmeal. If I'm fishing a nymph upstream and guiding it down with the current, I'm likely never going to feel anything at all. Again, I don't care how sensitive the rod is, because there is nothing really happening that is allowing me to take advantage of its sensitivity. What I'm likely going to do is detect the deviation of line movement indicating some likely disturbance at the end of the line. Maybe a fish...maybe a rock or a branch...but not necessarily the tug I would need to have to engage the sensitivity factor of the rod. What I nee once again is the ability to see and react in a timely manner. It's all me.

What is undoubtedly important to fly fishermen is the ability to present a fly to their target efficiently, with the presentation appropriate for the current situation. If you're teasing up bill fish out on the ocean, you need not worry about a delicate presentation. If you're on a small creek with barely running water trying to trick some rising but wary trout, it's a different story. The sensitivity of your rod is meaningless. Assuming a competent fisherman, what's important to him or her rod wise is the action of the rod. In either case however, what difference would it be to either fisherman to have a more sensitive rod?

As far as spinning or casting rods are concerned, those who primarily fish artificial lures of any type are usually not going to gain any particular advantage from rod sensitivity when it comes to practicing their art. The action of the rod will make all the difference in the world. If I toss a paddletail under some overhanging mangroves and it gets attacked by some devious snook on the way back, it happened regardless of what the rod's sensitivity may be. The lure doesn't care, the fish doesn't care, and I don't care. The action of the rod helped me get the lure to where it needed to go, and the action of the rod may have a significant bearing on whether or not I get that fish landed. I'm not much of a bass fisherman, though I would like to be, but I can think of one circumstance where rod sensitivity might come in handy with a distinct advantage. Guys who fish artificial worms might very well feel those taps better with sensitive rods.

Greater and better are words usually associated with a price hike when it comes to most goods. If rod companies are becoming sensitivity mongers, they can keep the new goods. Greater sensitivity just doesn't seem to be advantageous to the average angler in any way shape or form.

The fly rod example was only used as a tool in the discussion. There was no intent to state that sensitivity is or is not important to fly fishing. Or baitcasting cranks, or spinnerbaits, or paddletails or anything else.

If you like it better, consider a 9 foot ERN 3 AA 60 glass SPINNING rod vs a 7 foot high modulus graphite ERN 17, AA 77.

Please correct me if I am wrong, Mick, about any of this since I am interpreting your words, concepts, and theories.

You defined sensitivity as "the ability to detect/feel a bite" from the very beginning, right?

Did your initial definition of sensitivity imply that "a bite" is a mechanical vibration that is transmitted through the line, through the rod, and to the hand of the fisherperson? (I seem to recall you have said that before.)

Have you refined your definition of sensitivity over time and through discussion and debate? Any nuances added? If you were starting over again with introducing TNF, would you make any changes to how you presented it?

I have always held in my mind that TNF was about an apples-to-apples comparison of frequency to the efficiency of mechanical vibration transmission. The theory: the higher the frequency, the more efficiently it transmits mechanical vibrations. Also part of the theory as I understand it, higher modulus materials transmit mechanical vibrations more efficiently than lower modulus materials in a rod blank. A key assumption I made was that these ideas could be compared with all things/variables being equal. And finally, data could be reliably and repeatedly collected. (I never in my wildest dreams imagined using TNF to compare fly rods to bass rods of any length as proof or dis-proof of concept.)

It seems to me there have been different definitions of sensitivity introduced into the mix. One is the "lever arm" - which I understand as a different, though related, set of data to the sensitivity discussion. I don't dispute that I can feel the difference when lifting/holding the same weight with a lever arm of varying lengths (no matter which side of the fulcrum I am on). This can be measured with numbers, too; it just hasn't been with fishing rods (?). I see that lever arms play a role in the 'lever arm length vs sensitivity' discussion. It's a different discussion in my mind.

My next question is, incorporating the lever arm idea, what's the TNF of a rod of any length or composition? I can make better choices to fit my needs with data like TNF can provide.

Aleks is building a fish fighting machine to demonstrate something about sensitivity? Sounds exciting and like a lot of work to build and bring a machine like that! Why not also pack along the 'vibrometer' test equipment he already had for last years expo that did not make it? Let Mick play with it to his heart's content!!!

If rod speed, recovery and damping are important to a fishing rod's performance, then TNF is of value. For this fact alone, it is a very useful tool in analyzing and comparing blank characteristics.

Michael Danek Wrote:
-------------------------------------------------------
> The fly rod example was only used as a tool in the
> discussion. There was no intent to state that
> sensitivity is or is not important to fly
> fishing. Or baitcasting cranks, or spinnerbaits,
> or paddletails or anything else.
>
> If you like it better, consider a 9 foot ERN 3 AA
> 60 glass SPINNING rod vs a 7 foot high modulus
> graphite ERN 17, AA 77.


I still think it would be the long fly rod as being more sensitive. A fish pulls on the rod but so does a fly or lure. The rod would have no way of knowing what it is that is pulling on it. The lure's vibration is just a constant rythm in pull or weight against the rod. As somebody, maybe Tom said earlier, lures do not just start vibrating on their own. They only do it when pulling or fighting against the rod. And a fish bite or strike is going to also be a pull or stop against the rod. If you have a lure than is vibrating as you pull it through the water and you detect a change in the vibration due to a fish inhaling it that should also be felt stronger on the longer rod as it is still a force or pulling on the rod but it has changed timing which alerts you to a strike. Going to be more leverage against you on the longer rod.



Edited 1 time(s). Last edit at 10/30/2023 12:32PM by Mike Ballard.

The only way we will know is by trying it. I think I have an old glass fly rod of about 4 power, will try it vs a modern 7 foot hi mod graphite. Probably in the spring, now.

Of course it matters what the fly rod is made of and what the golf shaft is made of, especially in terms of weight, feel and flex profile and, in regard to those qualities, of great import is what you prefer in your casting style and type of fishing.

You could measure the frequency of each blank, which is the number of oscillations per minute. The more oscillations, the stiffer the rod will be, and the more quickly it will return to rest (rebound), which enables certain performance benefits.

I cannot speak to the relationship between sensitivity and frequency, so I must leave that to Mr.Danek. And I suspect a variable in realizing sensitivity is how developed or not an individual angler's sensitivity is. Tiger Woods and Steve Rajeff are likely to be much more attuned to their tools of the trade than we mere mortals, and they are generating club head speed/ball speed and line speed that we cannot ever hope to approach. Yet much fishing does not rely on line speed or casting distance, and Tiger's greatness often came down to his putting, the slowest ball speed club in the bag, and a "feel" part of the game.

Overall, one can agree that over time graphite fly rods have become lighter, stronger and more powerful. The rod designer determines the materials, taper and flex pattern of the rod. The angler may not want or like a stiffer or faster rod, and prefer a fuller flexing, slower action rod.

I have spent more time this afternoon thinking about this than I should have but one thing struck me --- if the lure is not moving then there is nothing to feel. It is only when the lure is moving such as being retrieved or falling on a taut or tensioned line that you can feel anything. If you feel it hit the bottom it was moving but once it stopped it is no longer moving and you no longer feel it. So movement is what we are feeling and movement against a longer rod should result in the fisherman receiving stronger inputs than he would receive on a shorter rod. I am going to go watch TV and think about it more another time. Might try a few things when we fish next week.

"The more oscillations, the stiffer the rod will be, and the more quickly it will return to rest (rebound), which enables certain performance benefits."

It is related not only to stiffness, but also to weight. The stiffness is in the numerator of the equation for natural frequency, and weight is in the denominator, so the heavier, the slower. It's about stiffness to weight ratio. I have always thought there is a correlation between ERN (or better, IP) divided by blank weight and TNF, but have not really investigated it. There should be a correlation.

I don't know what controls how quickly it comes to rest, but stiffness to weight ratio may be it. I just have not figured that out. If there is a scientific theory that predicts this, I'd like to know it.