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Analysing loop propagation

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Graeme H
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Re: Analysing loop propagation

#71

Post by Graeme H » Mon Sep 28, 2020 7:39 am

To which my answer is: Yes, watch this video ...



Imagine what would happen if the floor was above my head.
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Paul Arden
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Re: Analysing loop propagation

#72

Post by Paul Arden » Mon Sep 28, 2020 7:53 am

I don’t have to imagine anything :D I have a tile floor and a bead chain! I can’t go from one big loop to many small loops, so there is no transverse wave propagation unless there is tension on the line perpendicular to the tip path, either tethered or from gravity. If there was transverse wave propagation I would be able to go from one to many on the floor. That simply doesn’t happen - I must admit I tried it just to be sure :D

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Graeme H
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Re: Analysing loop propagation

#73

Post by Graeme H » Mon Sep 28, 2020 8:48 am

So take the floor away from the equation ...
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Re: Analysing loop propagation

#74

Post by Paul Arden » Mon Sep 28, 2020 9:32 am

I am fully aware that a transverse wave will propagate through a string suspended under the weight of gravity! That’s the part I was taking out of the equation :D
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Graeme H
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Re: Analysing loop propagation

#75

Post by Graeme H » Mon Sep 28, 2020 10:26 am

Why were you taking it out of the equation? Are you heading to the space station soon? :D
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Re: Analysing loop propagation

#76

Post by Paul Arden » Mon Sep 28, 2020 4:02 pm

Are you saying that the flycast is only a transverse wave when affected by gravity?
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Re: Analysing loop propagation

#77

Post by Paul Arden » Mon Sep 28, 2020 5:09 pm

Just so we are discussing the same things.
8B7B5C3D-D372-4B56-99F4-2C6D7FBBEFDF.jpeg
8B7B5C3D-D372-4B56-99F4-2C6D7FBBEFDF.jpeg (57.66 KiB) Viewed 231 times
For you the height of the loop is half the wave length I assume. What is the amplitude? Back and forward casts combined, or just one of them?

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Graeme H
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Re: Analysing loop propagation

#78

Post by Graeme H » Mon Sep 28, 2020 10:59 pm

Paul Arden wrote:
Mon Sep 28, 2020 4:02 pm
Are you saying that the flycast is only a transverse wave when affected by gravity?
No. I'm saying it's a transverse wave.
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Re: Analysing loop propagation

#79

Post by Graeme H » Mon Sep 28, 2020 11:16 pm

Paul Arden wrote:
Mon Sep 28, 2020 5:09 pm
Just so we are discussing the same things.
8B7B5C3D-D372-4B56-99F4-2C6D7FBBEFDF.jpeg
For you the height of the loop is half the wave length I assume. What is the amplitude? Back and forward casts combined, or just one of them?

Cheers, Paul
This is where things get complicated because our string is not long enough to get the complete picture. Give me a 50 metre tall tower and a 100 m long level line and I can get closer to it for you.

Frequency (1/period) can be measured easily and from that we'd need to calculate wavelength. Wave speed (c) can be calculated from the descent rate of an object under the influence of earth's gravity and the period.

Amplitude can't be measured because it is dependant on the input from the caster/rod. Give it a bigger hit and the amplitude increases. Since we almost never use the perfect amount of power (where the loop only just reaches the fly), amplitude only has a minimum value, not an actual value unless we underpower the cast.

To answer your question, the minimum amplitude is how far the loop travels from my feet, either forward or backward.

Image


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Graeme
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Re: Analysing loop propagation

#80

Post by Paul Arden » Tue Sep 29, 2020 8:25 am

I suppose another difference when fly casting is that the 1/2 wave length decreases in size as the loop unrolls, usually disappearing to zero? Whereas with tethered string one would expect the transverse wave to propagate at 90 degrees away from tip path, with a maintained constant wave length?
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