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Analysing loop propagation 2

Moderator: Torsten

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Graeme H
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Re: Analysing loop propagation 2

#21

Post by Graeme H »

Torsten,

Mends must be a constant source of frustration for you. The idea of a mend is to transport the line away from where it would otherwise land. Place a wave in the line and transport it sideways. But for you, a wave can't transport the medium, so there is a paradox.

I've said it a hundred times, but once again, the direction of of the wave path is perpendicular to the oscillation. Since we observe oscillation in the horizontal direction, the wave path is vertical.

Oh, I see you've got some of it already. You don't seem to be grasping the full concept though.
Torsten wrote: Mon Oct 19, 2020 9:05 pm Transverse wave
https://en.wikipedia.org/wiki/Transverse_wave
"In physics, a transverse wave is a moving wave whose oscillations are perpendicular to the direction of the wave or path of propagation."
FFi CCI
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Graeme H
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Re: Analysing loop propagation 2

#22

Post by Graeme H »

Merlin wrote: Sun Oct 18, 2020 2:33 pm Graeme,
I'd like someone to explain why the angular momentum in the loop disappears when the tension in the rod leg is removed.
It does not disappear since the loop is able to roll over even if the rod leg is falling down (zero tension). The string like approach is unable to catch a zeroing of the tension during the flight since it directly depends on loop rotation/tangential speed. Here is an example of a push forward and you can see that tension at loop ends varies significantly by comparison to a string like approach.
The rod leg falling down is not zero tension unless it's in free fall.
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Merlin
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Re: Analysing loop propagation 2

#23

Post by Merlin »

The tension in the rod leg must be zeroing if you want to make it fall, even if that fall is not 100% free. Gary's push forward with release is a typical example of a practical kill of tension. In the example I gave, the string like approach is unable to put the tension down unless the rollover has ended. A better description of the mechanics does show a zeroing in tension during the flight, and that confirms the possibility to kill tension at will in suitable conditions.

Merlin
Fly rods are like women, they won't play if they're maltreated
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Torsten
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Re: Analysing loop propagation 2

#24

Post by Torsten »

Just a short summary, we have collected the following terms/concepts etc.:

Classical mechanics
Newton's laws of motion
Mass
Momentum
Velocity
Acceleration
Force
Tension
Work
Energy
Euler's laws of motion
Angular velocity
Angular momentum
Torque
Lagrangian mechanics
Dynamics
(Statics)
Gravity
Aerodynamics
Drag
Form Drag
Skin friction drag
Lift-induced drag
Hooke's law
Internal friction
Damping
Wave
Transverse wave

But we have here a challenge: Newton's laws of motion apply only to point masses and Euler's laws of motion only to rigid bodies. The fly line however is a *flexible* body, thus we need to look further for yet another ways to describe it. One possibility is to subdivide the loop into shapes that are easy to compute and solve energy related equations for these simpler shapes. Spolek did this in his paper:

"The mechanics of flycasting: The flyline"
Graig A. Spolek, 1985
https://core.ac.uk/download/pdf/37776458.pdf

The simplified model has three parts, a traveling line, a stationary line and a the loop as cylinder in crossflow. Aerodynamics was included using skin friction and form drag for cylinders.

With such a simple model we can determine the effect of various line tapers on the acceleration of the line. But it has severe limitations, e.g. we can't explain loop morphing.
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Merlin
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Re: Analysing loop propagation 2

#25

Post by Merlin »

Good idea Torsten, and this is just what I am doing (N laws for variable mass systems). By the way look at the end of the paper written by my good friend Graig:
Graig's biblio.JPG
Graig's biblio.JPG (21.81 KiB) Viewed 2889 times
Sounds familiar to me :pirate:

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life
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James9118
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Re: Analysing loop propagation 2

#26

Post by James9118 »

Torsten wrote: Sat Oct 31, 2020 7:01 pm

"The mechanics of flycasting: The flyline"
Graig A. Spolek, 1985
https://core.ac.uk/download/pdf/37776458.pdf
Once we've finally condemned the lift paper to the great steaming dung pile in the sky, we should start on this festering heap of mammalian droppings.
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Re: Analysing loop propagation 2

#27

Post by Torsten »

Yeah you like to create work for me ..
I don't want to see such postings. I don't have any issues with criticism, but I expect a minimum amount of respect for works of others. What a shame for a physicist.
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Paul Arden
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Re: Analysing loop propagation 2

#28

Post by Paul Arden »

Hi James,

I know it’s no doubt intended partly in jest, but it does make things rather difficult to invite authors of these papers on to the Board with such descriptions. Apart from which, I’m sure these guys put a lot of work and time into their studies and so Torsten is right. Even if someone is completely wrong I think they should have our respect for trying. Especially so because they might be very sensitive about these things!

I made that mistake in the past with some of what Lefty said for example and I’ve often regretted it. I was light hearted about it but it was certainly misunderstood and not personal at all.

Cheers, Paul
It's an exploration; bring a flyrod.

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Walter
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Re: Analysing loop propagation 2

#29

Post by Walter »

“ But we have here a challenge: Newton's laws of motion apply only to point masses and Euler's laws of motion only to rigid bodies. The fly line however is a *flexible* body, thus we need to look further for yet another ways to describe it. One possibility is to subdivide the loop into shapes that are easy to compute and solve energy related equations for these simpler shapes. Spolek did this in his paper:”

One of the long running problems on the technical analysis board is that nobody lays out their assumptions before doing an analysis. Is the cast being done in a vacuum? Is gravity considered? Is line being shot or not? What are we actually trying to analyze in this particular study- affects of loop shape on the cast, drag induced lift, which line colour gives the best energy transfer, is the loop a wave, etc.?

Then the endless discussions begin around how the analysis is wrong because of form drag, gravity, loop shape, line colour, line shot, line tethered, some irrelevant analogy, etc., etc. After that the whole discussion is written off as a huge, frustrating waste of time and then often reborn a year or two later.

Scientists (the ones outside of this board) have been trying to solve unified field theory for over a century now. That doesn’t mean that any scientific papers that don’t solve unified field theory are automatically wrong, missing something or pointless. It just means that the paper is one more tiny piece of the puzzle. We got to the moon using plain old Newtonian mechanics but we decided where to place the James Webb Space Telescope using Lagrangian points. They each have their purpose just like relativity and quantum mechanics.

I’ve seen simulations of fly line motion, including one by Torsten, that look pretty darn close to what I observe in real life and, as far as I know, they use plain old Newton and a lot of computing power.

One thing I learned in studying math was that there are many, many solutions to any problem and that we are constantly discovering new ones. That doesn’t mean that only one is right and the rest are all wrong. It means that there are many ways to solve any problem but if you never decide what the problem actually is then every solution is wrong.
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.
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Paul Arden
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Re: Analysing loop propagation 2

#30

Post by Paul Arden »

Excellent post Walter. Some of Torsten’s recent simulations have been fascinating.

Cheers, Paul
It's an exploration; bring a flyrod.

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