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Conservation of Momentum

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gordonjudd
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Conservation of Momentum

#51

Post by gordonjudd » Fri Jun 07, 2013 6:11 am

Maybe you should try some of Grunde's bluntness lessons.
Walter,
Since you asked for it, to be blunt, your claim that :
So I can get the fly leg to accelerate using conservation of momentum but only under limited conditions.
is B.S.

As Grunde noted there is no conservation of momentum going on to accelerate the fly leg. In fact, it is just the opposite. There must be a change in momentum (F=dP/dt ) to produce the accelerating force that helps to offset the deceleration effects of drag.

Gordy

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Lasse Karlsson
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Conservation of Momentum

#52

Post by Lasse Karlsson » Fri Jun 07, 2013 6:44 am

Gordy, I used 4x tippet for the eksperiment, about 10 feet of it.

I'll be happy to redo it with a lighter line, gonna chop up a 3 weight, redo both that and the mpr line in a headwind and again as in the two clips without Wind.

To be honest, I don't think it will make a difference.

Cheers
Lasse
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http://www.karlssonflyfishing.com

***Bring Mark back!!!!!! ***

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guest
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Conservation of Momentum

#53

Post by guest » Fri Jun 07, 2013 7:55 am

Lasse Karlsson wrote:Gordy, I used 4x tippet for the eksperiment, about 10 feet of it.

I'll be happy to redo it with a lighter line, gonna chop up a 3 weight, redo both that and the mpr line in a headwind and again as in the two clips without Wind.

To be honest, I don't think it will make a difference.

Cheers
Lasse
Nor do I.

At such low tensions as seen in a fly line, the wave equation is not applicable as it is dependant upon the subject being configured as an ideal string. The Gatti-Bono/Perkins papers do show that after counterflex, the tension in the line reduces quickly, which suggests that little tension is required to propagate the loop. For me, the experiments show that if the mass of the rod leg is sufficiently large compared to the moving mass it can create sufficient tension in the loop to cause it to propagate.

regards

Vince
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Walter
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Conservation of Momentum

#54

Post by Walter » Fri Jun 07, 2013 8:15 am

gordonjudd wrote:
Maybe you should try some of Grunde's bluntness lessons.
Walter,
Since you asked for it, to be limitednt, your claim that :
I can get the fly leg to accelerate using conservation of momentum but only under limited conditions.
is B.S.

As Grunde noted there is no conservation of momentum going on to accelerate the fly leg. In fact, it is just the opposite. There must be a change in momentum (F=dP/dt ) to produce the accelerating force that helps to offset the deceleration effects of drag.

Gordy
Gordy,

This is why you are still on the slow learner's program after all these years. I explained quite clearly what some of the limited situations were. You consistently choose to ignore that part and focus on misconstruing what I have said for whatever purpose or perhaps you really aren't getting it. Just relax and try reading all of the information with a view towards understanding. You will get it if you really try.
"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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gordonjudd
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Conservation of Momentum

#55

Post by gordonjudd » Fri Jun 07, 2013 2:13 pm

I'll be happy to redo it with a lighter line, gonna chop up a 3 weight, redo both that and the mpr line in a headwind and again as in the two clips without Wind.
Lasse,
More data is always good to help understand what impacts what. We obviously have two different results in doing what appears to be the same experiment. More data will help to sort out why.

What is a mpr line?

If you can tie a short piece of tippet to a sinking head that would be interesting as well. The linear mass density of the line is a big driver in wave propagation, so I would expect that a much heavier line could have a big effect.

Thanks,
Gordy

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Lasse Karlsson
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Conservation of Momentum

#56

Post by Lasse Karlsson » Fri Jun 07, 2013 2:41 pm

Hi Gordy

MPR stands for Micro practise rod, it's The thick yarn line that comes with Tim Rajeff 's practice tool. The one I'm handcasting in the clip.

What weight sinking line would you like? Got from leadcore down to a 4weight sinker.

Cheers
Lasse
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Walter
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Conservation of Momentum

#57

Post by Walter » Fri Jun 07, 2013 3:26 pm

gordonjudd wrote:The linear mass density of the line is a big driver in wave propagation, so I would expect that a much heavier line could have a big effect.
Gordy - FYI, the loop is not a wave.
"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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Merlin
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Conservation of Momentum

#58

Post by Merlin » Sat Jun 08, 2013 8:23 am

CoM is not the tool to understand how the fly leg speed changes. The convenient way is to write that the variation in kinetic energy of the moving part of the line (neglecting the influence of the gravity) equals the work of drag forces on line and fly.

With a simple model you get a relationship between the variation in speed as a function of the variation in length (of the fly leg). Depending on the signs in the equation, either the speed increases, or levels, or decreases. In other words there is a limit diameter of the line which corresponds to that limit (no variation in speed).

Main parameters are loop height, line density and line size (width). For a given loop height, increasing line density reduces that limit diameter and for a given density the limit diameter increases with loop height. This is why a larger line number is favorable in terms of loop propagation, and why thin lines do not accelerate (e.g. #3) in most conditions. This is also why a denser line develops faster (sinking vs floating).

Merlin
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gordonjudd
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Conservation of Momentum

#59

Post by gordonjudd » Sat Jun 08, 2013 3:30 pm

What weight sinking line would you like? Got from leadcore down to a 4weight sinker.
Lasse,
I hope you can try a 3 wt (or less) into a slight headwind first. That will be close to what I was doing when I took my video.

Going in the other direction, as Merlin noted, the key parameters are diameter and linear mass density. I would expect a piece of lead core would have the minimum diameter/linear mass density ratio.

Merlin do you have a feel for the impact of the conservation of angular momentum on this? Hendry showed that is why the loop would be expected to narrow as a sink tip line starts going around the loop as shown below.
Image

I am wondering if that could help the line to keep going around the loop and thus shorten the fly leg even though no force was being applied to the end of the rod leg as happens when you let go of the line in the experiment that Lasse and I have conducted with such different results.

Gordy

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gordonjudd
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Conservation of Momentum

#60

Post by gordonjudd » Sat Jun 08, 2013 3:47 pm

The one I'm handcasting in the clip.
Lasse,
As we have discussed before the problem with that clip is that there is a force on the rod leg coming from the line on the ground at the end of that clip where the loop start to propagate again.

Before that rod leg touchdown happens it appears to me the yarn is turning into spaghetti as shown below:
Image

Cast that yarn with a regular rod so you can let it go from a higher initial y position, shoot it from the side (90 degrees) and I expect you will see it will still be spaghetti just before the rod leg hits the ground.

My intuition could be wrong (as is often the case) however, so doing that would be another piece of useful data as the drag on the yarn should be pretty high.

Gordy

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