Is the cast itself a transverse wave?

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Is the cast itself a transverse wave?

Post Number:#71  Postby Graeme H » Fri Jan 12, 2018 10:27 am

James, are you saying the wave shape is now problem? If it's not a sine wave, it's not a transverse wave? That can't be your objection or you'd never believe a mend is a transverse wave.

If wave shape is not a problem, try the bottom function for another shape so that the fly leg elements all have the same velocity. It's still not quite right as shown because in a cast, gravity will be acting on the fly leg, and in a cast, the triangle would not be any where near as "equilateral" as this shows.

Image

The pure sine function can never approximate how we move the rod tip in a cast. If someone presented to me with that sine wave loop shape, I'd tell them they need to stop later and keep accelerating their rod tip for as long as possible. The sine wave begins decelerating as soon as "midnight" is reached. We go later than that.

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Is the cast itself a transverse wave?

Post Number:#72  Postby Paul Arden » Fri Jan 12, 2018 11:10 am

Why do you think that the "loop wave" if you want to consider it that, Graeme, is transverse? Surely the loop and the wave are in-plane?

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Is the cast itself a transverse wave?

Post Number:#73  Postby Graeme H » Fri Jan 12, 2018 12:07 pm

Actually, I don't call it that Paul. It was Gordy (I think) who called it a "loop wave" way back. But I know what you mean. It's the loop.

I don't understand your question though Paul. The loop is a crest of a transverse wave. Almost by definition, the displacement of a transverse wave is planar and the loop occupies that plane.

Can you rephrase the question please?

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Is the cast itself a transverse wave?

Post Number:#74  Postby Paul Arden » Fri Jan 12, 2018 12:58 pm

The definition of Transverse Wave is:

transverse wave
nounPHYSICS
a wave in which the medium vibrates at right angles to the direction of its propagation.

In the case of a fly cast the wave (if that's how you consider it - and I believe you can - but it's complicated) travels in the same direction as it propagates. So I don't see how it's "transverse"?

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Is the cast itself a transverse wave?

Post Number:#75  Postby Graeme H » Fri Jan 12, 2018 1:27 pm

Ah, I see where you're coming from.

That's what this thread is about. Back to page one for you! :D

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Is the cast itself a transverse wave?

Post Number:#76  Postby Graeme H » Fri Jan 12, 2018 1:31 pm

More seriously though, it has been my contention throughout this thread that the loop is one side of a very wide transverse wave.

The reason a lot of people think it's complicated is because they think the loop itself is the whole wave, not the displacement component of a transverse wave that is propagating in a completely unexpected and counterintuitive direction (i.e. vertically).

Have another look at this video and look at the picture below to see what I'm talking about.

Image

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Is the cast itself a transverse wave?

Post Number:#77  Postby Paul Arden » Fri Jan 12, 2018 1:39 pm

I still don't see why it's transverse. It's been argued that it's a wave in an untethered line but from those discussions it appears that the physics are more complex. (To the extent that I don't know anyone who's actually gone there?)

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Is the cast itself a transverse wave?

Post Number:#78  Postby Graeme H » Fri Jan 12, 2018 1:55 pm

Okay, well let's look at the definition you posted (which is correct)

transverse wave
nounPHYSICS
a wave in which the medium vibrates at right angles to the direction of its propagation.


In this photo, the wave crests (the points to the left and right of me) are moving downwards. That direction is the direction of wave propagation.

The crests themselves consist of the fly line (the medium) at the end of it's sideways movement, after which time they move back to the other side. That is, they are moving at right angles to the direction of propagation. Those points (crests) are loops (viewed from the side here).

Image

In the video, I maintain the exact same motion of the rod tip, but I gradually make the stroke longer and slower. You can still see the wave moving down and the line moving side to side, even as the last stroke is made. When I stop everything, the line continues to move to the side and eventually comes to rest well to my left. The thing we call a loop is the crest continuing to my left.

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Is the cast itself a transverse wave?

Post Number:#79  Postby Paul Arden » Fri Jan 12, 2018 2:12 pm

But how does that apply to an Overhead Cast? Wavelength being the height of the loop and the direction of propagation being?

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Is the cast itself a transverse wave?

Post Number:#80  Postby Merlin » Fri Jan 12, 2018 3:09 pm

Mark
About a year ago Aitor gave me an equation for travel velocity of the farnarkolipse being half the difference between the velocity of the fly leg minus the velocity of the rod leg. This explains to me the obvious difference between hauling and not hauling, shooting and not shooting and indeed at least some of the effects of pullback (negative V for the rod leg).

Half the difference of leg speeds is the speed of particles along the line (representative of the rotation speed of a half circle loop, make the leg speeds equal and your loop is frozen). The travelling speed is half of the sum of leg speeds. If you haul you improve both speeds (rotation, travelling). If you pullback you improve rotation but you reduce travelling speed, this is why it should be used as an adjustment.

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