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engine and brakes

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Walter
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Re: engine and brakes

#21

Post by Walter »

Thanks Graeme!

What was the nature of that cast? Was it tethered or untethered? Asking for a friend... :D
"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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Re: engine and brakes

#22

Post by Merlin »

Hi Walter

Yes, this is the “double cast” simulation with the Scandi line. Now to answer one of Paul’s questions here is the case for the reversed Scandi.
Scandi 2.JPG
Scandi 2.JPG (37.53 KiB) Viewed 3689 times
Now the momentum changes for the Scandi in the normal way:
Scandi 3.JPG
Scandi 3.JPG (26.1 KiB) Viewed 3689 times
For the loop, the burst at the beginning corresponds to the fact that the back taper enters the loop to replace running line. Why would those intensities should be equal?
You can see that the momentum of the line is reducing, as can be expected. I think what confuses people is the fact that momentum is a vector first, and that its intensity has two parts:
d(mv) = V dm + m dV

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life
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Merlin
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Re: engine and brakes

#23

Post by Merlin »

Before Paul asks for it, the reversed Scandi case:
Scandi 6.JPG
Scandi 6.JPG (26.05 KiB) Viewed 3683 times
At the beginning, the positive value for the loop corresponds to the effect of the long front head going through the loop, increasing its mass progressively. And the negative burst is of course caused by the back taper crossing the loop.

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life
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Paul Arden
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Re: engine and brakes

#24

Post by Paul Arden »

Thanks Merlin. I don’t pretend to understand the compete work here. It’s interesting - if I understand it correctly - that both lines accelerate. Even the Scandi the right way around that has a narrowing taper? The reversed Scandi is very smooth. Does it have constant taper, Lee?

It would be very interesting to see how a) a DT compares and b) a MED.

Thanks, Paul
It's an exploration; bring a flyrod.

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Lee Cummings
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Re: engine and brakes

#25

Post by Lee Cummings »

50682B54-4490-4D38-B511-5E456C38AD0A.jpeg
This is two sizes shorter than the ones i used in the video.
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Merlin
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Re: engine and brakes

#26

Post by Merlin »

Paul

It is possible to make comparisons but one needs to have a good idea of line dimensions (e.g. diameters, density) and the line carry. And apparently, such information is not always available unless one makes measurements.

Merlin
Fly rods are like women, they won't play if they're maltreated
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Paul Arden
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Re: engine and brakes

#27

Post by Paul Arden »

Absolutely agree Merlin. Often the drawings of tapers are quite different to how they really are. That’s actually understandable since small taper adjustments can only really be measured and not seen.

Cheers, Paul
It's an exploration; bring a flyrod.

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Graeme H
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Re: engine and brakes

#28

Post by Graeme H »

Walter wrote: Sun Jun 30, 2019 6:30 am Thanks Graeme!

What was the nature of that cast? Was it tethered or untethered? Asking for a friend... :D
No worries Walter. Let your friend know that it was mostly tethered. I lowered the rod tip as the cast rolled out. I think that had stopped by the time the 1m point was into the loop though.

The little bounce you see in the track on the left is the line sliding forward.

The big drop in the plotted values of velocity are the rapid decelerations as marks pass through the loop. The lower step on each graph shows you the speed of the line after the loop had passed. If it's positive, the rod leg is moving forward.

Cheers,
Graeme
FFi CCI
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Walter
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Re: engine and brakes

#29

Post by Walter »

Thanks again Graeme,

It’s refreshing to get some actual real world data presented without bias.

One more question - you’ve probably said this before but, are the plots the X component of velocity only or are they raw speed? It would be interesting to to see separate X and Y components plotted for your 1 and 4 meter points.

I’ll reserve actual comment of what I think I see happening until I have a better idea of the the data presented.

Walter
"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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Graeme H
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Re: engine and brakes

#30

Post by Graeme H »

Hi Walter,

In this plot, it's Velocity magnitude. I'll change the data being plotted when I get home to show both Vx and Vy for each point shown there.

I think you'd also enjoy looking at the same graphs for the Dolphin Nose casts. Some cool stuff going on in the fly leg leading into the loop. Vince and I are working through some options around that.

Cheers,
Graeme
FFi CCI
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