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The point of tapers in fly lines and leaders

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Will
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Re: The point of tapers in fly lines and leaders

#31

Post by Will »

Graeme H wrote: Mon Jun 17, 2019 11:15 pm The "at the same time" bit is where the issue is. It doesn't happen at the same time in one cast. If we pull back on the rod leg, we can momentarily increase the speed of the taper and leader going away from us. If we push forward on the rod tip (reducing tension in the rod leg) we can let the energy wipe off the taper.

However, this only works properly if the cast was not overpowered in the first place. An overpowered cast will still kick a bit, but not as much as if there were no taper on the front.
Hi Graeme

This doesn't really help me I'm afraid. I understand that input from the caster can change the speed of turnover. I understand that pullback can speed up turnover, and that reducing rod leg tension can kill a cast. But I'm not asking about caster input. I'm asking about the behaviour of fly line tapers.

I think Lee's videos confirm that a thick-to-thin line accelerates the loop faster than thin-to-thick (so much for air-drag!). Which is great! :yeahhh:

The interesting thing for me now is what happens at the end of the cast, as the tip of the fly line turns over. You said that acceleration and dissipation of energy don't happen at the same time. So when does dissipation happen? At point of turnover? How is it dissipated?

I'm guessing that with no taper/no leader, some of the dissipation is seen in a wave going back down the line? But how does it work with a taper and a leader?

This is important to me in understanding the function of a front taper on a fly line, and the way a tapered leader works to deliver a fly.

Still struggling...

Cheers

Will

PS - I was interested to see how little difference there is in final delivery between the two lines in Lee's video. i'd expected the reversed line to kick way more than it did.
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Graeme H
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Re: The point of tapers in fly lines and leaders

#32

Post by Graeme H »

G'day Will,

I wish you were sitting with me and we could discuss face to face rather than with the delay of a question mis-read and mis-answered. I've got an answer but I'll need to make another diagram ....

The answer is in the direction of travel of the mark on the line and how it will continue to keep moving that direction unless something stops it going that way (Newtons 1st Law.)

Be right back ...
Graeme :)
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Will
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Re: The point of tapers in fly lines and leaders

#33

Post by Will »

:cool: Cool!
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Re: The point of tapers in fly lines and leaders

#34

Post by Graeme H »

Okay, did some more tracking of points on the line to explain what is happening. Remember, Newton's 1st Law ("N1") says that "A body will continue in a steady state of motion unless acted upon by a force."

Screen Shot 2019-06-18 at 6.13.28 pm.png

In this diagram, I've tracked more of the marks on the line to show each point of the line follows a very similar path through space. At first, it's traveling right nearly horizontally, but as it reaches the loop, it gets deflected from its path by the tension in the rod leg. That's N1 working as expected.

At the top edge of the loop, line is traveling in the direction of the yellow arrow. It would keep going that way after the loop had passed if it were not for the pull of the line near the red dots in the direction of the red arrow balancing out the pull of the line from the rod tip from the left of the picture.

The yellow dots have mass. They want to keep moving in the direction of the yellow arrow. If the line ended at the yellow dots and there was nothing to pull those dots to the right, they would keep heading downwards unimpeded. That's N1 in action again: A point in the line would keep going down if it were given the chance and the line would kick down violently as you've seen in Lee's video.

The wave travelling back along the rod leg seen in Lee's videos is the result of that violent downwards kick of the line. It's also why that joining section in my videos makes a wave.

Screen Shot 2019-06-18 at 6.18.26 pm.png

Let's pretend this is an extreme close-up and we are seeing only the front taper. In the taper, each dot has less mass than the one to the left of it. Pretend the dot on the left has a mass of 10 units, the next has 8 units and so on. The last one has a mass of only 1 unit, so it has only 10% of the mass of the first dot and a similar velocity. It's probably slowed a bit, but that's up to the caster (as discussed earlier). With 10% of the mass, the kinetic energy* of the triangle dots is <10% of the first point's KE.

The triangle dot has less mass "trying" to head down", so it takes less mass in the leader to stop it from doing so.

Energy was dissipated in the taper because the mass of each dot was less than the one preceding it into the loop.

The other side of the coin is that tension in the rod leg drops as the taper enters the loop. With each dot having less mass, each dot pulls on the rod leg less. You'll see the rod leg sag dramatically as the loop reaches the taper's lightest line. Newton's 3rd Law is in play there: For every action there is an equal and opposite reaction. As the pulling force of the dots in the taper reduce, the tension in the rod leg also reduces and it sags.

In Lee's video, the reversed head has an increasing amount of mass entering the loop for most of the cast and the rod leg stays taught until the very last moment.

The head in the correct direction has less mass entering the loop throughout most of the cast and the rod leg sags progressively. It has a lot less kick at the end though, because the line's energy was gradually lost throughout the cast.

I hope I got the gist of the questions this time. :D

Cheers,
Graeme


* KE = 0.5 x Mass x Velocity^2
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Graeme H
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Re: The point of tapers in fly lines and leaders

#35

Post by Graeme H »

And here's the video of that same loop:



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Re: The point of tapers in fly lines and leaders

#36

Post by Paul Arden »

What are the numbers there, Graeme? It appears that the loop has accelerated in your diagram.

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Re: The point of tapers in fly lines and leaders

#37

Post by Paul Arden »

I asked Winrich if he could crack a level whip using a whip wave, but he responded that he was not aware of anyone making such a weird whip.
Thanks Gordy. When I watch the video of the lady casting the loops look remarkably similar to fly loops. When I watch Lee throwing the reversed head there is an obvious acceleration towards the end. I wonder if I can make a reversible bullwhip? I’m not sure what sort of shops sell them. I think sex shops are illegal in Malaysia, so it will have to be a cowboy shop. :pirate:

Cheers, Paul
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Graeme H
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Re: The point of tapers in fly lines and leaders

#38

Post by Graeme H »

Paul Arden wrote: Tue Jun 18, 2019 12:18 pm What are the numbers there, Graeme? It appears that the loop has accelerated in your diagram.

Cheers, Paul
The numbers are just to simplify the concept Paul. They are not real mass values but are discussed in the text of the answer.

And yes, in that cast, the taper does indeed accelerate. The line has a totally unrealistic leader and "fly" tied to it: ~6' of 30 or 40 pound monofilament on an 8wt line. I was not making the video for this purpose but had it in stock so I used it. A fishing leader and appropriate sized fly would have been a better choice to illustrate this discussion, but at least this shows the importance of leader design in delivering a fly as required.

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Graeme
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Re: The point of tapers in fly lines and leaders

#39

Post by gordonjudd »

Remember, Newton's 1st Law ("N1") says that "A body will continue in a steady state of motion unless acted upon by a force."
Graeme,
How do Newton's laws apply to a variable moving mass situation such as we have with a fly line?

Here is an article on the abuse of Newton's 2nd law being applied to variable mass problems that you might find interesting to study.
http://www.aei.tuke.sk/papers/2012/2/10 ... C3%ADk.pdf

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Re: The point of tapers in fly lines and leaders

#40

Post by gordonjudd »

I think Lee's videos confirm that a thick-to-thin line accelerates the loop faster than thin-to-thick (so much for air-drag!). Which is great!
Will,
That is true in the first part of the roll out, but the reverse is true at the end when the thick part of the line starts going around the loop.

I am wondering if the lines were longer if the loop with the reversed head would overtake the thick-to-thin head.

There must be a reason that many of the lines designed to get the maximum distance in an overhead cast such as the MED 5 have a thin to thick belly section2.
Image

Gordy
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