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Rod unloading during acceleration

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NM
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Re: Rod unloading during acceleration

#551

Post by NM »

Bernd Ziesche wrote: Wed Jan 10, 2024 8:24 am It looks to me like your rod hand arm already was straight at RSP1, but you rotated your torso and the shoulder came further forward. Thus the rod hand came forward as much as the shoulder did?
The arm is almost straight, but the wrist has not been fully turned over at RSP1.
Bernd Ziesche wrote: Wed Jan 10, 2024 8:24 am Wouldn't you want to use as much distance for acceleration until RSP1 as possible? 🤔
Yes, and that is what we are trying to do, what we feel we do, and why we don’t try to stop the rod. Trying to stop the rod at RSP1 is a recipe for failure and would severely reduce max trod tip speed at line launce. You don’t aim to stop your hand at the point where you release the ball or a javelin when throwing those, do you? So why would you do something different when distance fly casting?
There’s a lot of interesting issues to research further when it comes to the position of MAV and the front-of-shoulder MAV to RSP1 movement. The “stop” is not one of them, it would be interesting to understand better:
  • Why MAV is happening where it is happening and both why it is so early relative to what we try to do, and importantly why it happens so late and with the arm so much in front of the shoulder compared to other throwing sports.
  • What the optimal MAV to RSP1 movement pattern is. Should we push the hand forward and up as most of us do, or just pull it down and release as Henry and some others do?
Bernd Ziesche wrote: Wed Jan 10, 2024 8:24 am Of course such slomos show what in normal speed looks just total perfect and still is brilliant casting.
This cast was from the fall of 2022, so after just a few months of serious practice after my 40 year break from tournament casting (and then only T38) and 20 year break from all fly casting, so not it was far from brilliant.

Bernd Ziesche wrote: Wed Jan 10, 2024 8:24 am Lasse recommended to have the line go early. I agree but are wondering what you hauling longer does to cf. Could be slightly reduced this way.
You cannot from the video see when the line is released and the haul ends. The measurement of the haul is just based on tracing the rod guide and the haul hand and includes the movement of the haul hand after the line has been released. The optimal timing of the line release depends…. It could be that it should have been earlier in this cast, but you can not determine that without looking at what happens to the loop as it unrolls.
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Merlin
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Re: Rod unloading during acceleration

#552

Post by Merlin »

When MAV takes place around the middle of arc (50% accel./50% decel. for the rod butt or handle), and max hauling speed (line speed of line thru the guides) happens here, too - where does the end of the line hand path show up here?
I assume you don't recommend to run out of line hand pull, when the handle was just rotated half the arc!?
Bernd

Haul hand path is not on board, the haul is modeled through the characteristics of the line (linear density) and its haul speed. The end of the haul speed curve was not recorded, so the haul ended quite late (beyond MCF), but at little speed.

Merlin
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Re: Rod unloading during acceleration

#553

Post by gordonjudd »

The best compromise in terms of maximum speed achieved is to keep peak haul velocity rather close to MAV by comparison to RSP. If you look at the four examples mentioned by Nils, they all follow that rule. If you read Ulrick’s study on hauling, the conclusion is the same.
Merlin,
Since the timing of the haul relative to MAV or RSP1 varies so much for different casters I expect the optimum timing window could be quite large.

From a work energy (force applied over a distance) standpoint I would think you would want to apply the added force from the haul to be applied to the line when the tip velocity was around its maximum value. That way the distance the force from the haul was applied to the line would be also be maximized.

The problem with that formulation is how you determine the added force from the haul since the force from the acceleration of the haul also impacts the the bend in the rod.

My reading of Ulrik's study where they measured the timing of the hand separation velocity (rather than the actual haul velocity) seemed to imply that the optimum timing would be just before RSP1 when the tip speed is at its maximum not at MAV when the rotation speed is at its maximum. He notes:
The delayed peak speed of line haul compared to rod rotation suggests a synchronizing of peak speed of the line haul with the peak speed of the rod tip, which would seem optimal to maximize the line speed and thereby distance. This study, however, focused on the coordination of the movements of the rod handle (via a sensor on the butt of the rod) and the line hand. How closely the peak speed of the line haul occurs with the peak speed of the rod tip is something that needs to be addressed in a future study
Practically speaking I suspect that timing the haul so it peaks just after MAV or just before RSP1 is not all that critical to getting the maximum casting distance.

Gordy
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Paul Arden
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Re: Rod unloading during acceleration

#554

Post by Paul Arden »

Hi Gordy, it could also be the difference between a great cast and one not so good. I simply don’t know. But I would love to find out!

Cheers, Paul
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Re: Rod unloading during acceleration

#555

Post by NM »

Paul Arden wrote: Wed Jan 10, 2024 3:46 pm Hi Gordy, it could also be the difference between a great cast and one not so good. I simply don’t know. But I would love to find out!

Cheers, Paul
Me to.
Gordy in an email exchange (Paul and Daniel was copied) suggested that I started the haul too early in that old ST27 cast that we have been looking at. I have subsequently been experimenting with delaying the start of the haul, which may or may not cause max haul speed to happen later, and my experience to date suggest that Gordy may have been right. It’s a bit hard to judge because a number of other things may change as a result of the later haul start, including with the shoulder rotation and final rod turnover.

The hand path and time between MAV and RSP1 may also have an impact on when it is optimal for max haul speed to take place. It is interesting that max haul speed for Henry, in the clips I shared earlier, was at RSP1. He may well have had max rod tip speed in the direction of the cast at RSP1 and not earlier. It is not obvious that that is always the case with a different hand path and more active wrist turnover (or wrist flailing).
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Re: Rod unloading during acceleration

#556

Post by Paul Arden »

Hi Nils,

I went the other way and came to the conclusion that on a 170 the optimal time to peak haul is around about when the rod tip starts to deviate downwards. This was also after a conversation with Gordy and Daniel. Or in other words, not leading up to RSP, but instead earlier than this. Admittedly that’s because they told me that was what I was doing :laugh:

It’s amazing how much we don’t know.

Cheers, Paul
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Re: Rod unloading during acceleration

#557

Post by NM »

Paul Arden wrote: Wed Jan 10, 2024 4:18 pm Hi Nils,

I went the other way and came to the conclusion that on a 170 the optimal time to peak haul is around about when the rod tip starts to deviate downwards. This was also after a conversation with Gordy and Daniel. Or in other words, not leading up to RSP, but instead earlier than this. Admittedly that’s because they told me that was what I was doing :laugh:

It’s amazing how much we don’t know.

Cheers, Paul
and that may well be at max speed of the rod tip in the direction of the cast.

Yes there is a lot that we still do not know, and likely guite a bit that we think we know that is wrong. I guess that is part of what makes this exploration fun.
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Re: Rod unloading during acceleration

#558

Post by gordonjudd »

You don’t aim to stop your hand at the point where you release the ball or a javelin when throwing those, do you? So why would you do something different when distance fly casting?
Nils,

Because we are constrained by using an intermediary flexible spring to apply the optimum force (and distance) to the line in fly casting while there is a direct connection to the object being thrown in other throwing sports. The loaded frequency constraints imposed by the long rod make for an apples to oranges comparison of the mechanics of fly casting to other sports.

I suspect the mechanics involved with throwing a long dart with an atlatl would be much different than the physics of javelin throwing as well.

Gordy
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Paul Arden
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Re: Rod unloading during acceleration

#559

Post by Paul Arden »

Yes there is a lot that we still do not know, and likely guite a bit that we think we know that is wrong. I guess that is part of what makes this exploration fun.
Absolutely!

I have thrown an atlatl, Gordy. I have a crazy friend in the US who is a fly fishing pastor. He introduced me to the atlatl in Montana and we had some fun with it! If I remember it correctly (and we are going back 20 years now!) he likened it to the 170.

But I do nowadays think that the point of deviation away from the trajectory path is what we are playing with and not RSP. Lasse’s video of the point of the loop translating back to the end of the haul on the backcast 170, and not RSP which happened later, started this chain of thought. Your analysis of my distance cast in KL, Gordy, made me think of this some more.

I think that the haul helps control or delay that deviation as well. As a result of some of Grunde’s analysis.

And so I question the significance of RSP and rod angles on a full blown distance cast. We are talking fractions of a second involved. Which is probably what keeps us absorbed in the field.

A lot of unknowns for me. Which is good!

Cheers, Paul
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Bernd Ziesche
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Re: Rod unloading during acceleration

#560

Post by Bernd Ziesche »

NM wrote: Wed Jan 10, 2024 3:14 pm You don’t aim to stop your hand at the point where you release the ball or a javelin when throwing those, do you? So why would you do something different when distance fly casting?
A ball, a javeline, a stone, a dart and all these are free to move as soon as they left our touch.
We don't touch the fly line, but the handle of the rod. With positioning the rod movement we adjust loop shape and trajectory. Also the loop will still be attached to the rood via shooting line. There are differences though.
I never saw a fly caster do this post letting go:


But I saw keeping a ca. 10am position of the rod for a moment many times.

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Bernd
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