Harmonic Oscillator

[Merlin]

Walter,

From my files, I can get an order of magnitude of the "braking torque" used to stop a rod. It is based on casts inspired from Paul's long distance casts, but let's see the order of magnitude in that extreme case: something between 80 an 100 N/m.

To make things simple, if I assume that the torque applies to the elbow, and that my hand / elbow distance is around 0.4 m, that would correspond to a force on the hand equivalent to something like 90/0.4 = 225 N (like the weight of a 23 kg mass). May be half of that for a normal cast, or even less.

Merlin

[Bernd]

Hi Tom,
not sure what you mean by frozen loops. Let me know what is on your mind?

Hi Merlin,
if I remember right it was Echo rods Lasse were using. But I can't remember which ones exactly.
And no, I don't have them available.

My short conclusion after all was:

"Adjust arc, stroke & force application to line length, rod stiffness & the type of cast."

Greets
Bernd

[Lasse Karlsson]

Hi Merlin,
if I remember right it was Echo rods Lasse were using. But I can't remember which ones exactly.
And no, I don't have them available.

My short conclusion after all was:

"Adjust arc, stroke & force application to line length, rod stiffness & the type of cast."

Greets
Bernd

Hi Bernd and Merlin

Rods used where
Medium fast: Echo classic 590
Fast: sage XP 590
Extra fast: Sage TCX 590
Extra ultra fast: Streamstix T5

And the premis was to keep the speed and loopsize app.the same but with different rods. All clips shot in 210 fps
Linelength the same for all casts naturally too

Cheers
Lasse

[Bill Hanneman]

Now, wouldn't it be great if you had some CCS data to describe those rods?

You guys are still back where you were 4 years ago.

"Adjust arc, stroke & force application to line length, rod stiffness & the type of cast."

[gordonjudd]

From my files, I can get an order of magnitude of the "braking torque" used to stop a rod. It is based on casts inspired from Paul's long distance casts, but let's see the order of magnitude in that extreme case: something between 80 an 100 N-m.

Merlin,
And just to show the difference for a less "heroic" cast with a much smaller deceleration factor here is the plot of the estimated torque applied to stop the rod using the data for the "Expert 50" casting analyzer file.

As shown below the maximum deceleration value for that cast was -4764 deg/sec.^2 (-83 radians/s.^2).


Assuming the MOI of the rod/reel/line system was .155 kg-m.^2 gives the estimated applied torque curve below.

That had a maximum reversing torque of -12.8 N-m so would require a force of 12.8/.4=32 N on the hand applied from the elbow. That is equivalent to holding a 3.2 Kg mass which is more in line with what you could expect for a non-distance cast.

Gordy

[Bernd]

Hi Bill ,
let me give you an example of what I see quite often.

Changing from a soft to a stiff rod:

Student A: Shortening the arc in order to maintain SLP. Using almost the same force application.

Student B: Using a bit more force application in order to get a bit more bend than he would have with the same force application used on the soft rod. Shortening the arc slightly, too.

Student C: Using the same (favourite) arc size. He doesn't feel comfortable with changing his arc size to a smaller one. Increasing force application in order to get the right bend to maintain SLP.

Student D: Using the same (favourite) arc size and force application. If his arc was quite huge his loops may get more open than they could be. But on a short line this doesn't mean a problem to him.
If his arc was quite as small as it could be for the softer rod, he might be throwing a tighter loop with the stiffer rod cause now he has significant less cf (also depends on how much bend he creates / how fast he is casting).

Student E:
Using less force and less arc. Casting pretty relaxed with the stiff rod.

Student F:
Now he is human and he is simply using all these figures (unintentionally) and being inconsistant on each one from one cast to another one. I see this student in all slomos! (he looks different all the time ... could look like Lasse, Paul, Aitor, Bernd or who ever )

Student G:
He is a sexylooper and using them all INTENTIONALLY. :p

I could go on with this ...

We can also change rod hand path to maintain SLP...

So in my book there are so many key figures which can be adjusted that it is inpossible to put out one short thing which covers them all.
Only if you leave it that much open as I did in that short one.
I did not aim for saying how it should be adjusted in detail but making people think about the key figures and starting to get into them...

Does that make any sense to you?

Greets
Bernd

[Lasse Karlsson]

Now, wouldn't it be great if you had some CCS data to describe those rods?

You guys are still back where you were 4 years ago.

"Adjust arc, stroke & force application to line length, rod stiffness & the type of cast."

Hi Bill

All the rods are in the base just look them up if you are confused

And Bernds quote makes more sense than your reply...

Cheers
Lasse

[gordonjudd]

Now, wouldn't it be great if you had some CCS data to describe those rods?
and
All the rods are in the base just look them up if you are confused

Bill,
We need to know what the k and m0 of those rods would be in order to predict how they will respond to different forcing functions and line masses.

Can you tell me how to derive those needed values for Merlin's and Grunde's model from the ERN, CCF, and AA values that are listed in the data base for those rods? To complicate matters I see very few CCF values in that database.

It would be a big help if you could figure out how to make those conversions for us so that your CCS measurements could provide the rod input data used in the model. As they are now CCS measurement do not give us squat in terms of providing any useful data that can used to predict how a rod will respond to different casting motions.

Thanks,
Gordy

[Tom]

Hi Bernd.
What I mean by a frozen loop in a no shooting situation
is if I move the tip/rodleg back (pull back) with the same
velocity as the flyleg the loop will not move forward.

Tom.

Bernd,
It was first shown in this thread
Gordy

[Merlin]

Brend,

It would be fine if we could have a look at what expert casters are doing when they use different tackle to adapt their cast. The options are too numerous if we consider beginners.

Merlin

[Bill Hanneman]

"Adjust arc, stroke & force application to line length, rod stiffness & the type of cast."

So in my book there are so many key figures which can be adjusted that it is impossible to put out one short thing which covers them all.

Does that make any sense to you?

Yes, of course. What doesn’t make any sense to me is anyone’s belief there is an answer to the question(s) you hope to ask. But then, you haven’t formulated any questions to be answered yet.

In my world, unscientific as it is, one first develops a premise and then tests its validity. In this case, no one doubts the above 6 factors (plus the undefinable one of “Personal Preference”) affect every cast. Is it your premise one can develop a “formula” correlating all these factors, or are you simply messing around with various physics and engineering calculations for the fun of it? What exactly are you hoping to accomplish and when can one say you have accomplished your goal? This sounds like the typical research project whose basic object is to raise enough questions to assure future funding.

Can you tell me how to derive those needed values for Merlin's and Grunde's model from the ERN, CCF, and AA values that are listed in the data base for those rods? To complicate matters I see very few CCF values in that database.

It would be a big help if you could figure out how to make those conversions for us so that your CCS measurements could provide the rod input data used in the model. As they are now CCS measurement do not give us squat in terms of providing any useful data that can used to predict how a rod will respond to different casting motions.

Now, you are breaking my heart.
CCS measurements were developed for the purpose of describing a fly rod, and it does that reasonably well. YOU chose the task of trying to predict how a rod will respond to different casting motions. It is hardly fair to damn a method for not doing something it was never intended to do.

I do feel your pain, but let me tell you one thing—You are never going to provide any useful information to fly anglers until you solve the problem of telling them what the properties of a 5-wt fly rod are and how they differ from a 4-wt or a 6-wt fly rod.

[Bernd]

Hi Tom,
thanks for the link. Interesting point of view about the frozen loop.

Hi Merlin,
I could have put "expert caster" A, B,C and so on instead of student A,B,C and so on as well to my last post.

I remember casting with Bart de Zwan four or five years ago.
He was using the Sage TCR rod and the MED line aerilizing an impressive amount of line when having a huge wind straight against his bc.
Then I asked him to do the same thing with my rod which was a much softer one.
With my eyes I couldn't see any change in his style or line length. It seemed as if he did not adjust anything.

For sure there were differencies. So a slowmo probably would have shown the details...
But am pretty much sure that he did not just change the arc for example.
He changed different things - but all very slightly.

Hi Bill,
seeing Bart that day really made me think for a while.

I don't have any open question here.
I can put out a physical based relationship for each of this 6 figures combined which each other figure...
It would end up in a long article.
Actually I have such an article on my website but unfortunatley it's only in German language yet .

However my intention about that 6 figures in one short note was about saying it is more than just adjusting arc to the length of line which I read millions of times.

Greets
Bernd

[gordonjudd]

It is hardly fair to damn a method for not doing something it was never intended to do.

Bill,
You missed my point.

I was just responding to your comment that:

Now, wouldn't it be great if you had some CCS data to describe those rods?

I was trying to show that for Merlin's purposes CCS data would be useless in terms of characterizing how different rods would respond to different forcing functions and line masses.

So rather than "being great"; in fact, CCS ratings have no useful parameters that can be used in a simple model to analyze the changes expert casters make in their stroke to get the most line speed out of different rods.

I appreciate the fact that CCS values provide some useful data on the relative stiffness, loaded frequency (for one specific line mass), and action of different rods. That is all well and good, and might shorten the search for finding a rod that fits with a specific caster's preferences.

However as you point out they were never intended to be used to predict how they would respond to different forcing functions and thus are of no use providing the data that Merlin asked for:

Do you have a record of the time history of the butt rotation for different rods used (relative to the vertical position, for example)? This would help to look at how the adaptation is made.

If you also can identify the corresponding rods, that will help.

Thus if you had any understanding of what Merlin's model and this thread was about you would never have suggested that it would be "great" to have some CCS data to characterize the rods. As Lasse pointed out that data was readily available so your comment was pointless.

I was just trying to point out that your self-aggrandizing comment was clueless as well.

Until CCS data can be manipulated to provide the data Merlin needs to compare rods, then CCS data is worthless in providing answers to the task at hand.

Now, you are breaking my heart.

That was not my intention. I was just trying to dampen your ego a bit, and show that if you really want your name to go down in fly fishing history, then you could work on a way to convert CCS values to provide data that would have some relevance in predicting the line speed different rods would produce for different casting motions.

Gordy

[Bobinmich]

Gordy,

In your torque calculations you used the MOI which is, I think, calculated at the bottom end of the rod. If the instant center was lower, say at the elbow, would not the MOI be somewhat higher? Or did you estamate a different center than the base of the rod? Seems as though the torque required would be somewhat higher depending on where the IC was for that part of the cast or am I missing something?

Bob

[Bill Hanneman]

Until CCS data can be manipulated to provide the data Merlin needs to compare rods, then CCS data is worthless in providing answers to the task at hand. ...
... if you really want your name to go down in fly fishing history, then you could work on a way to convert CCS values to provide data that would have some relevance in predicting the line speed different rods would produce for different casting motions.

Golly, golly, golly, I do. I do. Now I understand just what your problem is. You want to correlate rod properties to line speed for different casting motions.

However, before I can “contribute” anything I need to know your answers to a few questions. Since these questions are not germane to this thread, I shall start new one.
Bill