Maximum Rod Bend

[Paul Arden]

Hi Gordy,

That’s a good question! I think we want a very high line speed around the point when the rod tip deviates from the line path’s trajectory for comp distance. So that is pre-RSP on a 170 cast. I believe the haul accelerates after this too but if we save it too late we miss the most important part. At least that’s what I’m thinking now based on results of your analysis of Lasse’s and my casts.

With shorter casts however everything seems much less specific. Many times I’ve filmed my hauling hand only about 2/3rds the way through the haul as the rod passes RSP.

Incidentally I think that completion of the haul or release of the line can initiate loop formation prior to RSP. I see this on backcast 170s and I’m certain it happens on Snakehead shots and probably much more often than we think. That might be worth another topic!

Cheers, Paul

[Bernd Ziesche]

I don't think we can for example match max possible line speed of the line thru the guides and max tip speed to happen at the same time.
Does that make sense to you?

I don't see why you could not do just that since it comes down to a matter of timing between the actions of the two hands.

Even better, I would think that matching the max haul acceleration with the maximum tip speed of the rod tip so you would apply the peak force from the haul over a maximum distance would make sense from a work energy standpoint.

Hi Gordy,
little bit of a missunderstanding here. "Max possible line speed" wasn't meant to be "max line speed" (for a specific cast). In regard of max line speed for a specific cast, I agree with what you said.

That said, elite distance casters seem to reach their max haul acceleration well before the tip is moving at its fastest, so there must be some more complicating factors involved than just applying a force over a distance in terms of achieving the maximum casting distance.

Exactly my point. There are quite differences between max possible line speed (max possible hauling speed) for a high end distance cast and an avg. cast. In an average cast I sure can (and often do) haul precisely down the rod in order to keep friction on the stripping guide as low as possible. That way I do (almost) not move my stripping guide away of my line hand (not almost doubling the speed as theoretical possible). Much more I speed up my line hand here. But in a distance cast I like to bring more speed for the line thru the guides by accelerating my first guide due to rotation. It's exactly here (and here only) where I doubt it to be possible not have the peak in speed of the stripping guide relative to the line hand having stopped way before the (now significant bended) rod has straightened.

Here is an example of the measured speed of the line moving through the first stripping guide compared to the measured angular velocity of one of Bruce Richards casts that was made by Noel Perkins years ago. The line speed was determined by using a Hall effect sensor near the first stripping guide so was a direct measurement of haul speed rather than the derivative of digitized distances from a high speed video. Note that the rod speed shown in that graph is for the angular velocity not tip speed. The maximum tip speed would occur a bit before RSP1 as did the max haul speed.


This is a good example where the max haul speed coincided with the the maximum tip speed, so indeed it is possible to achieve the timing you asked about.

As Paul mentioned Bruce was keeping that cast very much avg. for technical reasons as also shows the haulind speed, too. I remember, that Grunde analyzed casts with significant higher speed numbers. His findings were that max hauling speed was near MCL with the experts. That seems to match with my understanding about the delay between max speed stripping guide and RSP1. So the key is how much does the caster make the speed of the stripping guide support max line speed for the line running thru the guides...
Thanks for your fine and well put thoughts.
Regards
Bernd

[Bernd Ziesche]

That’s a good question! I think we want a very high line speed around the point when the rod tip deviates from the line path’s trajectory for comp distance. So that is pre-RSP on a 170 cast. I believe the haul accelerates after this too but if we save it too late we miss the most important part. At least that’s what I’m thinking now based on results of your analysis of Lasse’s and my casts.

Hi Paul,
170 style or not, in the WC nearly everyone stops at 10 in the delivery shoot. I did check that in many videos as you may remember. I don't think there are too much differencies in where max hauling speed (speed of the line thru the guides) happens. No doubt for the distance experts it happens significant before RSP1 in the delivery shoot. There is significant rod bend involved and thus the rod will need time to straighten post the stripping guide hit peak speed relative to the line hand.

Here is what Grunde said:
"I measured hauling speed many years ago and peak haul speed is usually very close to max rod load (and max rod rotation)."

That to me makes a lot of sense as long as we talk about experts distance casting. I am 100% sure, that he was correct in his findings, and his findings are representative.
I would be very surprised if you can position max hauling speed close to RSP1 for a proper distance cast with the MED5. Think also of the early release thread. There was a proper reason for it to be a great one!
Regards
Bernd

[Graeme H]

Is it possible to accelerate the haul post RSP? Wouldn’t the haul retard the tip? I’m thinking if you continually accelerate the line, say you had especially long arms, wouldn’t the line simply pull all the way through the rod while maintaining a bend in the tip?

This sort of stuff keeps me awake at night.

Thanks,
Paul

The bend in the rod is due to force, so you'd need to be continuously accelerating the rate of pull AND do so with an additional rate due to the loss of line mass outside the tip. I think the acceleration required by the end of the line (say with only 10cm outside the tip) would be impossible to achieve. A fun thought experiment though.

Cheers,
Graeme

[Paul Arden]

Hi Graeme,

If my arm was as long as the line I could potentially pull it all the way through the rings without a loop forming. Although I suppose that would depend on if the mine was travelling quicker than the haul, which it normally would be... no that doesn’t help

I remember being very surprised seeing videos of my hauling (sometimes) to MCF in the days when we thought (and taught) that the haul finished at MCL.

I would like to see more studies of how the haul affects/retards rod bend/unbending.

Cheers, Paul

[Merlin]

Hi Paul

Below you can find the rod elastic energy history along the timing of the haul. Peak elastic energy is obtained when the haul is made early, PHV occurring 25 ms before MAV.

To avoid a tailing issue it is recommended to have PHV something like 50 ms after MAV. This corresponds to something close to MCL timing (see below the black circle) for PHV. The respective timings of MCL and RSP by reference to MAV are illustrated as a function of the delay between PHV and MAV. Zero in abscissa corresponds to PHV timing = MAV timing.

haul timing panorama.JPG (29.23 KiB) Viewed 2226 times

For teaching, it is then highly recommended not to refer to maximum rod loading since it corresponds to a tail in the fly leg (dip in tip trajectory). MCL is hard to capture but it should be the goal for PHV.

Merlin

[Paul Arden]

Thanks Merlin. That’s much earlier than I thought in the past. I think we always assumed that RSP was most important moment in Flycasting but, at least with hauled casts, the key moment seems to occur at and immediate after MCL. (If I understand this correctly).

It brings me back to the early release discussions with Lasse. We used to argue that finishing the haul pre-RSP causes a tail but I think this only applies in certain circumstances. I’m fully aware that in my Snakehead shots (and some distance casts) I am releasing far earlier than RSP. (I must video a Snakehead shot with a zebra line. I shall definitely mark one up for a video next week).

I think a fair bit of what we’ve been teaching up to even very recently about the nature and timing of the haul is flawed. I’ve always thought that we accelerate the haul right up to haul stop, but I can see particularly on the forward cast this may not be the case.

It has some interesting effects on how we then think about the Casting Stroke when we release pre RSP.

Thanks, Paul

[Lasse Karlsson]

It has some interesting effects on how we then think about the Casting Stroke when we release pre RSP.

Thanks, Paul

It sure does the release timing video clip was done 9 years ago

Cheers
Lasse

[gordonjudd]

Below you can find the rod elastic energy history along the timing of the haul.

Merlin,
How are you calculating the elastic energy in the rod? Is it based on the perpendicular tip deflection and the spring constant of the rod (i.e. k1*x.^2/2 + k3*x.^4/4) or on the curved shape of the rod along with its variable stiffness characteristics?

Does the maximum elastic energy correspond with the maximum perpendicular tip deflection and thus it is a bit less at MCL?

Since the perpendicular tip deflection and cord length require digitizing a number of points from a high speed video would it make sense to base the relative timings on MAV rather than MCL since MAV can be measured with a mems sensor and haul speeds could be directly measured by putting a mems sensor at the first stripping guide and on the haul hand?

The instrumentation that Ulrik Röijezon used in his study of haul timing makes sense to me, although I am sure reducing all of that mems data was still a formidable task.



His curve shows that the max haul velocity (based on the separation speed of the hands) was around 75 ms after MAV when false casting and a shorter 60 ms difference on the delivery cast.

Gordy

[gordonjudd]

Here is what Grunde said:
"I measured hauling speed many years ago and peak haul speed is usually very close to max rod load (and max rod rotation)."

Bernd,

If Grunde was referring to the study of haul timing that he participated in with Ulrik Röijezon, then it appears that "very close" involved a nominal delay of 60-70 ms between MAV and the peak haul velocity (PHV) for most of the expert casters involved in that study.

If max rod load is taken as the max perpendicular tip deflection then it occurred about 15ms after MAV in the cast made with a Paradigm rod. It could well be a even bigger difference in a distance cast.

As noted above I think from a measurement standpoint it makes sense to look at haul timings relative to values that can be measured directly with MEMS sensors rather than the massive digitizing task (for me anyway) it takes to reduce video data. That would lead to choosing MAV as the preferred reference value not MCL or max rod deflection.

Gordy