gordonjudd wrote:His sonic golf approach would be interesting to apply to fly casting so you could get some auditory feedback on how to make a good fly cast.
somebody's already put it on the market, Gordy and it's called The Casting Glove !
These kind of statements show you do not understand the constraints given by the effective mo, k, and added tip mass on the loaded frequency used in the car/spring/brick model. You cannot just replace mo with PPF. ...
Gordy, personally, I don’t give a rat’s ass about any car/spring/brick model. I am just trying to present a graphical solution which works for trout rods.
I’m afraid you are just too tied up with your precise mathematical formulas and calculations to recognize that when I say “replace mo with PPF”, I am not speaking of numbers, but rather of the concept. I have no idea, nor do I care what would be mathematically involved.
Merlin's approach is much more complicated than some mythical fixed PPF value as the loaded frequency is going to change with the length of line being cast on a given rod.
Yes, However Joe’s PPF can be considered essentially a constant for typical trout rod applications. Why else, do you think anglers “over line” a rod when casting shorter distances? In my world, they do this in an attempt to match their PPF so they don’t have to change their casting style (tempo, frequency).
It will come as no surprise that that a competent caster is going to adjust his tempo when casting different line lengths. Consequently he will have a wide range of casting tempos rather than some fixed value of 83 CPS (sic) that supposedly matches up with the tempo use to cast 30 feet of line.
I heard that same story several years ago from Paul and it is still of little consequence. The fact of the matter is rod companies do not survive on the purchases by competent casters. They prosper from the sales to the likes of Joe. Experimental evidence is abundant which indicates Joe wants a rod and line with a frequency of 83 CPM. This is confirmed by Merlin’s previously proposed rod which would have a frequency of 82 CPM. All successful rod manufacturers know this, but few writing on the subject have ever expressed it to the public.
One single PPF does not apply to my casting experience, so I do not see any utility in applying your graphs to my needs, since I for one do not have a single PPF.
Fine, you are a competent caster. Don’t use them. However, whether you do or don’t use them has precious little to do with their value to others.
I do not always casts 30 feet, so I do not see the usefulness of using CCS to give me an idea of what rod I might want to use to cast from 20 feet to a hundred feet.
As I told you long long ago, at the beginning of these discussions, YOU won’t find a fly rod which will fit your requirements. Look into spinning rod blanks. You want power and high frequency (highest efficiency) for your distance and a fast action (very weak tip) for short range where you will cast with only the tip.
Your mileage might differ.
Yes, and I believe this thread has run out of gas.
What I was suggesting is a kind of PPmo. Let's take my example: I use 3 different 9 feet #5. One is mo = 3 and loaded frequency is 1.31 Hz (30 feet of line), this is my favorite for trout stalking. The second one is mo = 3.2 and loaded frequency 1.42 Hz. I use it for medium to long distance and bigger flies. The last one is mo = 3.4 and loaded frequency = 1.56 (faster that the TCR, and you would rate it as a #10 with ERN), for long distance and big flies. Each one has its specific line profile.
If you add ESC in your CCS, then you need ERM (equivalent rod mass, this is mo) since you need ERM to compute ESC. ERM comes from the frequency curve with load.
One step again, and add MOI. Then the three components of CSS are in, welcome to the club!
I understand what you mean by PPF, but you see with my example that things vary from situation to situation. I'm glad you understand one point now:
In my world, they do this in an attempt to match their PPF so they don’t have to change their casting style (tempo, frequency).
You know you don't have Jerry Siem casting style.
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
Do you have some documentation on the physics of golf? I always wanted comparing that with fly line casting.
Merlin,
That is the other half of my library.
Golf is such a huge market that there is an annual conference with a 100 papers on the subject each year. You can see they have priced their proceeding out of my price vs curiosity point. I think there are more technically inclined people who golf than fly fish so there are countless papers analyzing the dynamics of the swing, and ball flight.
Another more recent book is The Science of Golf by John Wesson. Wesson applies centrifugal force (the outward directed force you get in a rotating frame) to explain the forward bend in the shaft of a driver that had puzzled me for years.
Most recent papers have gone to a three pendulum model for analyzing the swing which could be adapted for fly fishing as well. They do not have to deal with a shaft that bends in those models, so they could not be directly applied however.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
I think I can wait, given the size of my library about fly rods, design, custom building, fly fishing, but I shall have a look sometime.
I looked at Dr Robson issue. If you take into account an effective length which translates the way you handle the rod, then you can estimate the equivalent inertia at 0.0027 * 2.54^2 = 0.0174, which is 0.24 times the SW of the rod (I think Magnus and Grunde took into account the position of the hand on the handle, but I did not checked).
Remember the 1/4 ratio for beams?
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
I understand what you mean by PPF, but you see with my example that things vary from situation to situation.
Let me recall for you an earlier exchange.
Bill Hanneman wrote:
Do you also have a different PPF for the same rod when you are casting 5 meters of line versus when you are casting 25?
Not being ambidextrous, I do not cast both lengths of line simultaneously. Consequently, these are two separate sets of circumstances—(you call them situations). One’s PPF is a nebulous and ever changing value depending on many undefinable factors, including perhaps how badly you want a beer.
This is the point where I “lost” Gordy. You, and most anglers, recognize the problem and simply solve it by using a different fly rod. Gordy, on the other hand wants to do everything with one “universal” rod, and he can accomplish this only by drastically altering his casting style for each situation.
On the other hand, what I gather from your example is you define a #5 rod as one which is “strung up” with an AFTMA #5 line—irrespective of its power. One cannot take one of those rods and describe anything about the properties of that rod by saying it is a #5 rod. If I string it up with a #4 line and use it, doesn't it now become a #4 rod? That, in a nutshell is the problem the CCS was developed to solve, i.e., to provide a means of unambiguously describing the power and action of any rod.
Essentially, according to CCS, you are using three rods having ERN values of about 3.5, 5.7, and 10 and calling them all #5 rods because you are using a #5 line on them. CCS says you are simply overlining or underlining rods of those ERNs, which each of which actually has a CCF value close to 83 cpm. (i.e., when ERN=ELN).
If you add ESC in your CCS, then you need ERM (equivalent rod mass, this is mo) since you need ERM to compute ESC. ERM comes from the frequency curve with load.
One step again, and add MOI. Then the three components of CSS are in, welcome to the club!
Have no fears, I am not going to add ESC and/or MOI. I’m afraid Joe wouldn’t understand.
---------------------------------
Now, let me explain a new concept. You should have no trouble understanding and recognizing what I am doing.
As I have always said, this is a “first approximation” and the question I need answered is “Is this close enough to be useful to Joe’s rod builder? I believe that answer will depend on the influence of mo on the result in the region of this interest. I would expect some engineer could calculate the size of the error.
Procedure:
1. Take the chart in Post 85 and give it a new title such as “Dr. Bill’s Feel Fixer Chart.”
2. Remove the k values and simply number the lines from 1 to 11, starting at the bottom.
3. These lines now have no mathematical significance so I shall call them Dr. Bill’s Isofeels.
To use, locate the pertinent isofeel by determining the frequency of the sample, after adding sufficient weight to the tip of the sample to bring it within the bounds of the chart. One can use the rod blank, the rod in any intermediate state of construction, or the finished rod. This establishes point A
Point B is defined by the PPF and ERN desired by the client. If one wishes to construct a “generic” graphite fly rod, use the line f=83 cpm.
To find the “feel fixer” (actually the minimum weight) necessary to reduce the “efficiency” of the sample so as to match the desired point B, follow the isofeel down until it reaches the 83 cpm line or the desired PPF. The weight required is determined by the additional weight required to go from point A to point B
In practice, this weight will be supplied by anything one adds to the sample in the process of finishing the rod (handle, guides, thread, glue, etc.), the line which will be used, and a new and lighter “feel fixer”.
In order to obtain the most efficient rod from any blank, it is desirable the new “feel fixer” have a weight of zero. If this is impossible, seek a less powerful blank (or spread the weight more evenly along the length of the rod, however, this will make the rod heavier as more weight will be required).
The builder should recognize the purpose of a fly line is to allow the angler to adjust his “fishing outfit” to match his own PPF. Consequently, one must accurately know the ELN and ERN of one’s rod and line. One can calculate changes by recognizing a change of one ERN or one ELN will change the frequency of one’s outfit by about 5 cpm.
The builder has the option of either first defining the desired ERN and action of the rod and building so as to match the PPF, or building the rod on the blank available and then determining what line weight is required to match the client's PPF.
Merlin,
I have tried to derive that divisor factor, but do not get the 4 value. Do you have a reference for how that value is derived for the cantilevered beam?
The m/3 factor for the linear spring comes about because the delta x at some position is linearly related to the total deflection of the mass at the end of the spring. The delta y deflection in the cantilevered rod is not linear relative to a position along the beam, and I have not been able to come up with the solution to that problem.
In his book on Vibrations and Waves French also states that the m/3 factor only applies when the mass of the spring is << less than the mass of the tip load, so that is another complication since the mass of the rod is relatively large compared to the mass of the tip load.
I would expect you would have to take into account the shape of the deflection of the first bending mode to come up with a good estimate, but I would like to see how it should be done.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
To find the “feel fixer” (actually the minimum weight) necessary to reduce the “efficiency” of the sample so as to match the desired point B, follow the isofeel down until it reaches the 83 cpm line or the desired PPF. The weight required is determined by the additional weight required to go from point A to point B
Bill,
I do not really understand your procedure, but know that the "feel fixer" mass would add to the mo value, and that would required a different set of curves since they are so sensitive to m0.
From this description it sounds like you are changing the mass of the line which implies that if you want to slow down the response of the rod, then you would want to cast a longer distance, but you cannot assume the effect of adding a fixed tip mass to increase the mo value is the same as adding a line mass.
You would need another graph for a different mo value to see how the relationship between the effective spring constant and the line mass would impact the frequency of your "outfit".
Adding mass to the tip of a rod is a really horrible thought to a rod designer, so you might ask Merlin what he thinks of adding a 5 gram weight to the tip of one of his rods to "fix" its feel. "Destroy" is more like it.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
The first mode pulsation for a beam of uniform thickness is (believe me here it is the "exact" value calculated by people better than me):
12.36 EI/(rod mass* L3)
Since its stiffness is K = 3 EI /(rod mass * L3) you can say its pulsation is K / equivalent mass mo
Then you find mo = 3/12.36 * rod mass = 0.243 rod mass
Nearly 1/4
It is not as easy as in the case of the spring.
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
Point 2 of the procedure: this is not so straightforward, because those Isofeel correspond to a given stiffness (in N/m here), and that a given stiffness corresponds to various rod and line combinations, for example, to a 9 feet #4 and a 10 feet #5 at the same time.
I understand the procedure after, but the starting point raises a problem: you should have a set of curves per rod length.
In order to obtain the most efficient rod from any blank, it is desirable the new “feel fixer” have a weight of zero.
Absolutly! It must be zero.
If this is impossible, seek a less powerful blank (or spread the weight more evenly along the length of the rod, however, this will make the rod heavier as more weight will be required).
Correct. In the TCR example, the first trial gave an increase in swing weight of 40%, we can go a lower value (26 %) by using the original TCR with 2.9 grams at the tip (12 grams minus 9.1 grams, you follow me?). If you do that, you are stressing the tip at each flex and counter flex. You know that the tip of such rods is rather supple (which means it sees high level of stress), so there is a danger that fatigue will shorten its life. Hence my reluctance to see any “feel fixer” at the tip top of a rod.
The builder should recognize the purpose of a fly line is to allow the angler to adjust his “fishing outfit” to match his own PPF. Consequently, one must accurately know the ELN and ERN of one’s rod and line.
Well, this is where the misconception is. I think you put yourself in a particular domain, which corresponds to casters who do not want to change their habits (I know one of them, he his lost if he cannot fish with his GLX). But after all, this is your decision.
One can calculate changes by recognizing a change of one ERN or one ELN will change the frequency of one’s outfit by about 5 cpm.
For trout rods: one line number = from 0.06 Hz to 0.09 Hz
The builder has the option of either first defining the desired ERN and action of the rod and building so as to match the PPF, or building the rod on the blank available and then determining what line weight is required to match the client's PPF.
This is not the way rods are designed. They are designed for a particular job and the compromise is depending on that job. Remember my own example with my three rods? For a given series (a given job) you can then design a rod for each line, and most of the time in several lengths (not so easy). If you compare two series, they do not match in terms of stiffness. And as surprising as it appears, my “big” number five is designed for a number five. I could make it for a number 10, but the design would be somehow different, and the stiffness the same: this #10 rod would then turn out to be a rod for “another job”. Of course, we all know the can of worms: a graphite fly rod can take a number of fly lines. Pick up the one you prefer if you disagree with the designer. I do not think a designer think about what builders will do with his blanks. And it is highly likely that for the same “job”, Grunde, Lasse, Gordy or I would not agree on the best line fit for a given rod. Should we blame rod makers for that?
It’s a holy grail, you know.
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
I do not really understand your procedure, but know that the "feel fixer" mass would add to the mo value, and that would required a different set of curves since they are so sensitive to m0.
You would need another graph for a different mo value to see how the relationship between the effective spring constant and the line mass would impact the frequency of your "outfit".
Yes, that is why I asked you for two curves in Post #85. I was trying to estimate “just how sensitive”. My interpretation was the difference between mo of 38.6 and 30.9 amounted to about 3 cpm, or a little over half an ERN or ELN and that was pretty darn good for a first approximation.
From this description it sounds like you are changing the mass of the line which implies that if you want to slow down the response of the rod, then you would want to cast a longer distance, but you cannot assume the effect of adding a fixed tip mass to increase the mo value is the same as adding a line mass.
I can assume anything I want. The question is: ”If I use this assumption (premise), will the calculated results (my chart) be of value to a rod builder? The question I am asking you engineers is, “If it is not, then what is the magnitude of error indroduced by this assumption?”
Adding mass to the tip of a rod is a really horrible thought to a rod designer, ...
Of course it is. that is why I wrote:
... If this is impossible, seek a less powerful blank (or spread the weight more evenly along the length of the rod, however, this will make the rod heavier as more weight will be required).
I assume you recognize this is accomplished by using heavier hardware.
If you really want to continue this discussion, it would be great if you would reconstruct the chart in Post 85 as I described previously to Merlin.
Bill.
If you really want to continue this discussion, it would be great if you would reconstruct the chart in Post 85 as I described previously to Merlin.
Bill,
Does that mean you want to change the K values given in N/m that have some physical significance to Dr. Bill's Isofeel numbers 1-11 that have no meaning?
That might make sense to you, but I do not see the point of substituting a value with a well defined dimension (N/m) to a one that does not. Don't chemist worry about working out the dimension term balance in a problem? That is the first step any physicist or engineer would do to check the solution to a problem.
You need to pay more attention to what Merlin is saying, as your concept is just meaningless BS to any competent caster who will adapt his stroke to meet the needs of the cast he is trying to make.
Your approach sounds like you need a fishing ghillie at your side with a bevy of rods in toe, much like a golfer carries a number of different clubs to hit the ball different distances.
I can see it now. After working a fish that was 20 feet away you see a rise at 60 feet. You turn to your trusty ghillie and say, "Here Magnus, put this 2 weight away and hand me my 8 weight. I have a new fish to go after, and therefore have to change my outfit to be able to make that cast." What a silly concept.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
Merlin,
What do you mean by Pulsation factor in your equation? I find several references where the 1 st mode natural frequency of a uniform cantilevered beam is equal to;
f=1.875.^2/(2.*pi*L.^2)*sqrt(EI/rho*A) Hz.
Where rho is the mass density (kg/m3) and A is the area of the cross-section. Thus the rho*A factor is the kg/m linear mass density not the mass of the beam. You would need to multiply that linear mass density factor by L to get the total mass of the uniform beam.
How is that modified to come up with your pulsation factor of
12.36 EI/(rod mass* L3).
Given that the deflection at the end of a uniform stiff beam for a tip load of N Newtons is:
deflection=N*L.^3/(3*E*I) meter I would get a corresponding K factor of
N/meter=3*E*I/L.^3.
But that does not include the mass factor in your equation.
If I use the K value above and assume the frequency of the mass spring system is f=/(2.*pi)*sqrt(k/m0) then set that equal to the first mode frequency for the beam I end up with:
m0/(total mass/L)=3*/12.36.
That has 1/ L term in the denominator since the rho*A factor in the frequency equation is a linear mass density value not the total mass of the rod.
That results in a (effective mass)/(total mass) value that is equal to:
m0/(total mass)=3/(12.36*L). for a stiff, uniform beam., and for a beam 2.5 long the m0/(total mass) ratio would be .0971 which corresponds to a divisor of 1./.097=10.2 for that stiff, uniform beam.
Do you get a similar dimension check in your values?
For a linearly tapered beam with a 6:1 taper such as a fly rod the square of dimensionless scalar to determine the the fundamental oscillating frequency changes from 12.36 to around 18.5. With the taper the total mass would also depend on the taper parameter combined with the linear mass density at the butt of the rod.
Just based on some of Grunde's MOI measurements the total mass of a rod 2.54 long was about 1.4 times the value of the linear mass density at the butt of the rod.
That would give a m0/(total mass) value for a tapered rod of
m0/(total mass)=3/(1.4*18.5)=.11.
That results in a divisor of
8.6 compared to the previously noted divisor of 11.8, i.e.
For my full flex saltwater rod blank the measured mass for just the blank was 76.1 g and the effective m0 was 6.45 grams. That gives a divisor of 11.8.
for one of my blanks.
Obviously we need some better refinement of this estimate, and a good place to start would be to get a better estimate for the k value expected for a thin flexible rod as compared to the linear equation for a stiff beam.
I will see what I can find in regards to getting a better K value. and continue this pursuit in a new thread rather than completely hi-jacking Bill's thread.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
2. Remove the k values and simply number the lines from 1 to 11, starting at the bottom.
------
Point 2 of the procedure: this is not so straightforward, because those Isofeel correspond to a given stiffness (in N/m here), and that a given stiffness corresponds to various rod and line combinations, for example, to a 9 feet #4 and a 10 feet #5 at the same time.
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I understand the procedure after, but the starting point raises a problem: you should have a set of curves per rod length.
I don’t think any of you fully grasp exactly what I am trying to do, so let’s try again.
Look at it this way.
I had a vision. In it, the great god of fly fishing gave me a golden tablet on which the subject chart was inscribed. He said this chart could be useful for custom fly rod builders in helping them choose the best rod blank for an angler who has specific requirements, e.g., it must have an ERN of 5.1, feel “good”, and his PPF for “his kind of fishing is” 79 cpm. Being an agnostic, I wanted a second opinion. Now, all I am asking you engineers is: Will this chart be of value to such a rod builder, and what is a typical magnitude of error (in cpm) to be expected if it is used?”
The builder should recognize the purpose of a fly line is to allow the angler to adjust his “fishing outfit” to match his own PPF. Consequently, one must accurately know the ELN and ERN of one’s rod and line.
Well, this is where the misconception is. I think you put yourself in a particular domain, which corresponds to casters who do not want to change their habits ... But after all, this is your decision.
I don’t think it does. Teaching someone how to do something does not equate with saying that something must, should, or ought to be done. That is their decision.
The builder has the option of either first defining the desired ERN and action of the rod and building so as to match the PPF, or building the rod on the blank available and then determining what line weight is required to match the client's PPF.
This is not the way rods are designed. They are designed for a particular job and the compromise is depending on that job. ... I do not think a designer thinks about what builders will do with his blanks.
You are missing the point. How rods (actually, I believe you mean blanks in this case) are designed has nothing to do with the options of the rod builder when converting a commercial blank into a fly rod or “outfit”.
Therein lies the problem, the designer puts his heart and soul into designing a rod for a particular job, but it is of little consequence. I would wager not one angler in a million knows what that particular job was when he bought his rod. Rods just aren’t sold with personal instructions from the designer. They are just sold because they feel good.
That is the reason the CCS is so useful. It allows one to know the properties of any rod without actually seeing it. Knowing these properties allows the experienced angler to immediately ascertain its usefulness for his own or any other purposes.
And it is highly likely that for the same “job”, Grunde, Lasse, Gordy or I would not agree on the best line fit for a given rod. Should we blame rod makers for that?
No, of course not. Blame it on your PPF.
-----------------------------------------------------
Gordy.
Does that mean you want to change the K values given in N/m that have some physical significance to Dr. Bill's Isofeel numbers 1-11 that have no meaning?
You got it! If it works, Joe doesn’t give a hoot how it was derived.
That might make sense to you, but I do not see the point of substituting a value with a well defined dimension (N/m) to a one that does not.
Fine, then use your dimension in determining the answer to the question I asked.
Bill
