Dissecting the haul

[Graeme H]

In bold above, there is no "wave turning the loop over". The wave is the loop. That's the point I'm making. Your statement reads to me as "it's the wave turning the wave over".

Surely a wave travelling through a flyline is not the same as the flyline taking the shape of a wave? A wave moves because it’s a wave. A loop unrolls because the fly leg has momentum.

Unfortunately it’s very difficult to make experiments that appease everyone. As can be seen by Lasse’s comments on mine. I find it very difficult to stall an unrolling loop. It needs to be cast at a very slow speed to begin with. Lasse on the other hand is still wrong.

Cheers, Paul

A loop is a bend travelling through the fly line from the rod tip to the fly.

A mend is a bend travelling through the fly line from the rod tip to the fly.

A tail is a bend travelling through the fly line from the rod tip to the fly.

A dolphin nose is a bend travelling through the fly line from the rod tip to the fly.

Every part of the fly line that is moving has momentum. The line particles in a wiggle mend have momentum too, because they are moving. How do you think a wave propagates if not for the momentum of the particles of the line? (Not directed at you in particular Paul - this is just something that is true but rarely stated.) Indeed, this is exactly why Merlin and Gordy and others are able to present the loop as a classical Newtonian Physics solution. The forces acting on the rod leg and the fly leg resolve and can be shown using those complex equations, but my students (and I) grasp the concept of wave motion more easily than integrals and derivative calculus. It's easy to demonstrate without a blackboard.

Yes indeed - the line does need to be moving very slowly to stall the cast. Exceedingly slowly! It's close to impossible in the wind or with short lines or with lines that have a long front taper. When I'm trying to demonstrate the slowest possible casts to the students, I need to make between 6 and 10 attempts before I can get it to collapse. Even then I cheat more often than not - I reveal the cheat after they've had a go, the cheat being dropping the rod tip and making slack! That's why the exercise is such an "ah ha" moment for the students. They realise exactly how slowly they can cast and still make the cast work - provided they maintain tension in the rod leg. It is almost impossible to stop the loop if the rod tip is high, which is a great lesson to provide any student.

Cheers,
Graeme

[Paul Arden]

To my way of thinking, which is obviously highly questionable , I think that by eliminating things such as air drag, gravity, etc, in order to try to understand a mechanism, it has a tendency to make our thinking very polarised. Which becomes a problem when our tool doesn’t explain everything.

Waves do help us understand certain phenomena; mends, overpowered curves, tails, possibly the dolphin nose?

A whip is often referred to as a “whip wave”. A flycast has been described as a “loop wave”. I have seen the whip wave physics papers. So I suspect that this is part of what we do. I don’t think it’s the primary mechanism, but with something like a Snap Cast, it may very well be.

The way I look at physics, is that we have a number of different tools, that we apply to the cast that work as filters. We use the most appropriate filter to comprehend a mechanism. You would be pretty crazy to have a toolbox with just one tool. And if you are going to have just one tool then make it a hammer.

Cheers, Paul

[Bernd Ziesche]

Hi Graeme,
Thanks for your fine answer, Graeme. Sounds plausible to some degree. Thinking about pull back, tension (I prefer resistance) in the rod leg has impact on the movement of the fly leg, yes.
However when I cast a short headed fly line out of my hands (no rod), the head unrolls just fine. I can cast upto 70 to 80 feet that way. So its quite a bit of flight time.
And then Lasse and I had the free flying heads filmed proving proper unrolling. We also shoot heads on monofilament shooting lines without any trouble in unrolling the head.
It seems this somehow collides with your video here. Whats your take on the why?
Maybe its in the relation of the resistance the rod leg provides relative to what the fly leg needs.
Whatever the details are, we have both collapsing casts and none collapsing ones. I dont think tension applied by the rod tip during unrolling is THE answer/key.
Regards
Bernd

[Graeme H]

Do you or don’t you see a transverse wave in this video?

Graeme,
You no doubt disagree with the answer to your question I gave back in post 143, but I do not see a transverse wave in that cast since the line itself is being transported (i.e. its position changes) in that video.

but with respect to your question about angular momentum (presumably within the loop and somehow driving turnover). I think it’s wrong

Now why do you think that COAM cannot be used to explain why the loop diameter of that cast with a sink tip line decreases as the higher rho_l of the the sinking line goes around the loop. Just as a test of your technical understanding of how to calculate the angular momentum of the line going around the loop what do you think the angular momentum of the line with a linear mass density of rho_l going around a semi-circular loop of radius R and a tangential velocity of V would be?

Gordy

I do not see the answer to the question I asked in #143. It's well hidden in deflections and evasion if it's there.

But here, I see you have answered it and I'm disappointed that you are not being honest. You say you don't see a transverse wave. Fine. I'll post the screen-shot images of it again. I don't expect you to change your answer, but at least I know how well you are evading the question when I see this image. That you don't recognise that wave as a transverse wave is truly unbelievable.





But you have answered the question and I see you do not recognise a transverse wave when it's blindingly obvious to all. That tells me a lot and I can move on, knowing that I can't trust your answers to be made in good faith.

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Semi-circular path? This is not a line path - this is a series of digitised locations of the line as the loop progresses.





The line paths for the particles of line in a loop are this shape. Not a circle or ovoid to be seen in the real world frame of reference, where the momentum is being applied.

Why do I think COAM cannot be used to explain anything in the loop? The A in that acronym stands for Angular, and there is no rotation of the particles about any point in space. (Try the moving frame of reference if you like, but please move the world in that frame too.)

You might also say "let's examine the snap casts in that video". If it's applicable there, explain why there is no evidence for the loop swelling as the line exits the loop into the rod leg? What force is holding that in place? How is that not apparent as a deviation in the line in any videos at the exit of the "semi circle" you claim is there?

And how much angular momentum is contained in a piece of 3X tippet through which a loop is passing?

Enough answers for you at this time. Maybe I will see what other questions of yours I can address later.

[Graeme H]

I shall repeat myself Graeme,

You start by creating a transverse wave in a vertical line. By the way did you notice that you need a large piece of slack to create a loop? Could it be considered as some kind of horizontal piece of line? In the end you find a transition to come back to a somehow normal cast by dropping the end of the line.

Thanks Daniel. That's a start but you haven't answered the question I asked about the type of wave it became once my friend dropped the line. Was it transverse or longitudinal? (I will accept "I don't know, which makes me curious to find out more." That's how a scientist would answer.)

I prefer the wiggle example, it is easier to follow and less complex in approach. Again you start with a transverse wave. But I have some problems with that approach. If I was the caster, then the line would lay in front of me at start. As I wiggle the rod, I create transverse waves along the line. Then I increase their amplitude whilst I reduce their tempo. Finally I make a transition to a normal cast as I stop and pause to wait for the line to unroll. At the end, the line is now lying on my side, 90 degrees from its initial direction. Does that change in direction by 90 degrees question you?

You can start with the line out to the side rather than in front if you like. The results will be the same. Side casts are valid casts too.

Now it’s my turn for a yes or no kind of question: do you acknowledge that you cannot forecast morphing from your analogy with a transverse wave?

It is Oct first, 14h15 French time, and I wonder how many hours, days, weeks, months, it will take to get a “yes” or something like an approval to my question.

No. (See, it's pretty simple.)

You're worried that I went out and experimented before giving you an answer on Saturday, claiming that's not science. For me, science is about testing a theory before publishing the results. Are you saying your models are not tested before you publish?

PS: I was not aware that you are the authority allowing people to use expressions like “wavy thing”. I’m a French rebel, you know, you cannot constrain me. If one tries to do so, I’m ready to take a guillotine out from the cave.

Merlin

If you want to make definitive statements in physics, use terms that are found in physics. Using undefined words leads to confusion and can be misleading to the reader. French rebel or not, your message must make sense. "A wavy thing" could just as easily be referring to this thing ...

[Graeme H]

Gordy

You make an interesting point about medium transportation. In Graeme’s videos the situation at start is close or fits mechanical waves, but it moves progressively towards transportation waves. Naming those waves is likely possible, and I take one example in a paper you sent me as I was inquiring about the physics of the whip:

Now I cannot tell if Australian authority will allow that wording.

Merlin

I was really hoping you'd offer the whip wave Daniel. That wave is the one we produce for roll casts and I love demonstrating how roll casts work and why tension is vital in them. A video of my favourite "running rabbit wave" would have been perfect ...

However, I knew the response would be cold water from Gordy. The whip wave is a transverse wave that transports the medium and we can't allow that.

Better luck next time.

[Merlin]

Graeme,

I’m not going to answer again about your video, I did it several times so it’s enough, you can re read the thread if you wish, and you know the answer since a transverse wave does not transport the medium. You keep on stating that you can link loop morphing to a transverse wave analogy, which is physically impossible. You never explained how to come to your conclusion and finally used your own experience to answer. The demo is done, fair enough, you can keep saying no to my question. Now we learn that angular momentum does not exist in a fly line:

… analysing them shows there is no angular momentum to be found because none of the particles are travelling in an ovoid or circular path, much as it might appear that way.

That is a new dimension in physics; you tell us that the line does not roll over. I wonder if you understand something in the application of Newton’s laws to a fly line. I think I know the answer, no again.

Merlin

PS: whip wave. The authors never mention the word “transverse”. Guess why.

[Graeme H]

To my way of thinking, which is obviously highly questionable , I think that by eliminating things such as air drag, gravity, etc, in order to try to understand a mechanism, it has a tendency to make our thinking very polarised. Which becomes a problem when our tool doesn’t explain everything.

Agreed.

Your way of thinking is highly questionable.

More importantly, I agree completely with the problems introduced by removing air drag and gravity. Especially gravity here!

Consideration of gravity is essential for this concept. It is the force against which we provide much of the tension and it causes the direction of propagation to be vertically upwards. The motion of the medium is perpendicular to the direction of propagation. When we are moving the medium horizontally, the direction of propagation must be vertical. The waves "want to go up" but the line is "falling through the waves".

An example I've noted in the last day was the tail in my "successful cast" in the recent video. It's moving back to the right along the line but the line is moving to the left. In other words, the wave is moving left-to-right in the line, but the line is moving right-to-left at a faster rate. (All the time that's happening, the tail and the loop remain separated by pretty much the same distance until the taper is encountered by the tail and them the loop.)

And also agreed about the tool we prefer not always working on all problems. I have come from the "momentum and linear forces" side of this discussion. It was a discussion with Vince (much as he will hate to know this) that made me examine other options like wave motion to explain the loop more fully. We were examining the Tracker data when he noticed the fluff accelerating rapidly at the end of the cast. That set me off, because that was not something I predicted and I wanted to know more.

Then I watched Christopher Rownes with critical eye and it fell into place for me.

(And here we are 23 pages later on one of too many threads about this shit. At least it's staying contained here and people who don't give a shit can avoid it. )

Cheers,
Graeme

[Graeme H]

PS: whip wave. The authors never mention the word “transverse”. Guess why.

Would it be because the whip wave transports the medium?

That leaves us with the mend as the ONLY transverse wave that transports the medium, doesn't it? Its only purpose is to transport the medium so we better come up with a new term for that wavy thing. We can no longer think of it as a transverse wave because it breaks the rules.

[VGB]

It was a discussion with Vince (much as he will hate to know this) that made me examine other options like wave motion to explain the loop more fully. We were examining the Tracker data when he noticed the fluff accelerating rapidly at the end of the cast. That set me off, because that was not something I predicted and I wanted to know more.

I’m always happy to inspire creativity

I have no problem with talking about waves in a general hand wavy sense if it helps my instruction, it’s just lies to children. For insurance purposes, I always carry some pixies in my waistcoat for the really technical guff.

From a mechanical perspective, I’m more than happy with Newtons Laws to explain stuff, the wave equation is just describing how a bent piece of string behaves under the influence of a restoring force is a derivation of N2. I don’t believe in semi circular loops,so don’t see any point in using them for calculations, but that doesn’t mean that angular momentum isn’t involved in casting. Tension is only self generated in sport and horror movies.

However, many of the artefacts that attract the wave labels aren’t waves in accordance with the wave equation because the restoring force is too feeble. As James said, the loop isn’t wavy enough to meet the physics criteria and I haven’t seen or heard anything to change my mind.

Personally, I have had minimal returns in terms of casting improvement for the effort that I have put in to get my head around the deeper mechanics and I commend anyone trying to improve their casting to spend more time practising casting than gazing at graphs, if they want to get better. By all means carry on if you want to be able to have deep and meaningful conversations at the bar but you might end up drinking on your own for long periods of time.

It’s still the trout season in Wessex, so the physics shite can wait for the long winters evening when it’s too cold to fish for grayling.

Regards

Vince