The practical side of considering loops as waves: Teaching and Self Improvement

[Graeme H]

Which direction are these waves propagating? Am I doing anything with my rod tip direction that makes them go that way? What are the forces acting on the line?

[Paul Arden]

Hi Graeme,

Yes they are very similar but that doesn’t mean they are the same. That’s why we are studying the differences of course. At some point we might very well say that it’s too different to be the same.

For example propagation of a transverse wave in a string is determined by tension. Propagation of a “transverse wave” in a flyline is determined by gravity.
That’s a significant difference.

The tension can be caused by gravity in the case of the string (hanging down). A fly line will respond in the same way (in which case I would undoubtedly call these transverse waves). However when the flyline is not hanging down as for example when the casts are in flight, then we have a significant difference.

It may even be one of those soft fuzzy borderlines where you say it makes more sense to analyse this as a transverse wave vs a casting loop.

As a casting drill for beginners - great! Absolutely. Get them to play with waves. I do. The roll cast is even closer. The line is hanging down. I teach it using Brian Henderson’s method of throwing a wave down the line. But at some point, when the anchor lifts off the water, flies through the air in the direction of the force, then we have a significant difference.

I think it’s mostly determined by propagation. In the case of the transverse wave in string the wave propagates through the string at 90 degrees to the applied force ie “transversely”. In the case of a fly casting loop, the line unrolls through the air, in the direction of the force. If it’s travelling in the direction of the force then it’s not transverse since it doesn’t fit the meaning of transverse.

That’s how I see it anyway. Waves can be handy for teaching. But to call a loop a transverse wave I think is a step too far. It’s just too different.

Cheers, Paul

[Graeme H]

Try standing on the roof of your boat and making those waves. Gradually increase the length of pause at the end of each impulse and then try to work out when it became a cast.

[Torsten]

Hi Paul,

regarding #162, thumbs up, very nicely written.

Graeme,

But please remember that physics was never meant to be discussed in this thread. It's about teaching, remember? Of course, this is all too hard to calculate (as Torsten admitted earlier) so just forget I ever tried to help people understand something. It's probably better that you guys think the loop is witchcraft or some sort of physics that's unique to fly lines.

Why such theatrical comments Graeme, you don't want to write in the physics sub-forum, but even you first posting contains a lot of physics terms. The moderators have to decide and to intervene, if it's going to much off-topic. I'm quite sure that you want to help people - I like this no doubt, but this has for me no influence on the topic ("The practical side of considering loops as waves").

You seem to want a special wave for a loop, so you go for it.

Again, I don't consider the loop as a wave. I know that Gatti/Perkins have called the loop a "non-linear wave" but I don't agree. Spolek has written that the loop "travels down the line like a wave". But it's not a wave - sure there are some similarities (e.g. tension plays a certain role) but other properties simply do not match and we have pointed out that in this and other threads.

I think for teaching it makes sense to use physics only sparsely and if you have really thoroughly understood all principles, otherwise the risk is high to teach pseudo-scientific bullshit (like Carl's whiplash stuff). When I have helped people with their casting (sure I'm not a instructor), I've always used simple, abstract guidelines like the SLP and never physics.

Thanks,
Torsten

[Paul Arden]

Hi Graeme,

I have of course done this before and I’ve just done it again.

I would say it’s when the amplitude becomes significantly greater than the tip travel. Sometimes it’s difficult to find the exact point when one thing ends and another begins. For example when does Drag become the Casting Stroke? However we know it’s there because at the other extreme if you hit a long carry too soon you can collapse the cast. So at that point you can see it’s not behaving as a transverse wave.

Cheers, Paul

[Graeme H]

Why such theatrical comments Graeme, you don't want to write in the physics sub-forum, but even you first posting contains a lot of physics terms.

I was quite happy discussing this in the physics forum in a thread about this very thing, until you started another thread specifically excluding discussion of waves in loop propagation.

[Graeme H]

Hi Graeme,

I have of course done this before and I’ve just done it again.

I would say it’s when the amplitude becomes significantly greater than the tip travel. Sometimes it’s difficult to find the exact point when one thing ends and another begins.

Okay, so for you the difference between a transverse wave and a loop was its amplitude.

Cheers,
Graeme

[Paul Arden]

No I don’t think that the difference is only Amplitude! That’s just me casting on the roof

I don’t think “Transverse Wave” fits. For example you can make a fly cast without gravity. We can slide the line along the floor into a loop, we can cast the loop in all planes irrespective of gravity and I’m quite sure we can cast in Space (someone needs to go up in Virgin Galactic to check this). It all works just fine!

The transverse wave approach however doesn’t work without gravity acting on the line. It doesn’t propagate transversely on the floor for example. So the fly cast is only a transverse wave when subject to gravity? For me that’s just gravity pulling the loop down, no transverse wave required.

“Wave” I would actually be fine with, but “Transverse Wave” only applies under very strict criteria and certainly not every cast.

Cheers, Paul

[Dirk le Roux]

Propagation of a “transverse wave” in a flyline is determined by gravity.

No, it's not. Partly, maybe.

[Paul Arden]

Sorry I probably didn’t make that clear. Thats not what I think, Dirk. I was restating Graeme’s argument. I don’t think that the fly cast propagates transversely. I think the loop propagates in the direction the force was applied to the line, and the reason it falls to ground is because of gravity.

Cheers, Paul