rod bending and it's benefits - during casting

[Bernd]

Hi everyone,
it was often said we need to bend the rod to be able to gain the right amount of tip speed over a longer distance (=less force) while keeping the tip path as straight as possible.
If we would cast with a rigid rod and need high tip speed it gets difficult to achieve an almost straight tip path during acceleration while using a relatively wide arc.
But with the small arc it's inpossible to achieve high tip speed. And it's even more difficult to still being smooth in acceleration. Also the small arc means higher force being necessary.

But how is this related to the length of line we are using?

I think the longer the line outside the tip is, the more line speed and the more direction we need.
So for the long line it helps to use a relatively wide arc to match the line speed and still keep tip path nearly straight due to having a good amount of bend in the rod.
For medium length of line I don't think we need much speed. With most rods I think we could gain enough speed on a relatively small arc while matching an almost straight tip path while having only small bend in the rod.
On a short line I think we don't need any bend and can cast pretty nice with using a small arc to keep the tip path almost straight. To have no CF here would make it even look better.

Finally I see three reasons why we need bendy rods:
1. It really helps to cast longer lines (smoothly gaining high tip speed on an almost straight tip path).
2. It allows to almost use ones typical favourite arc on the short line, too while not ending up with a too convex tip path.
3. It helps to have less force acting at our wrist.
Specially in the beginning of rotation.

Can you technical experts agree with this?

What other benefits do you see?
Thanks
Bernd

[Merlin]

Hi Bernd

I would say a global "yes", these are some examples and if this fits your observation then we can use that as a guideline to interpret a more theoritical approach. I hope I can be able to upload the work I done on the topic, and you will see the general trends between load and performance characteristics.

Merlin

[Bernd]

Hi Merlin,
thanks for answering. I really would like to see your conclusions of your work here! Looking forward to you posting it!!!

For quite a while I had something in mind which I didn't really understand.
I think it was Gordy who marked the effect of cf to loop size (when using relatively small to average arc sizes) being around 80% compared to 20% effect based on typical tip path during acceleration.
This made me think casting with a really stiff rod should always be pretty cool in order to form tight loops as long as we can create enough speed on a small to average arc size and still being smooth in acceleration.
And from all testings I'd say it is. Overhead casting this is.

But when testing rod line combinations on roll casting issues - especially the static issue this was significantly different for me always.
On short to medium length of line it felt much more comfortable (effective) to me to use a very soft rod.
I always thought this helps to achieve a straighter tip path.
And I am sure it does cause am using a realtively wide arc here. So I asked myself why I was using such a wide arc if I was just casting/rolling a relatively short line.

Was there more speed needed to lift the line of the water (compared to an overhead cast)?
Or did I just use something like my favourite arc, not realizing I could have used a smaller one, too?

Finally I thing I understand what the difference is.
When casting overhead my line is (almost) perfect straight when starting to accelerate my tip. So after very short distance of accel. all the line will have the same speed. Enough momentum will be created to cast the whole line.

When rolling the line this is different. Additional distance of acceleration will move more and more length of line = more and more momentum will be created (not only by increasing the speed level). This is what I feel to be way more easy I think when using the wide arc on these type of casts. And the soft rod matches much better for the wider arc. Using the stiff rod doesn't make it here until I add "a smart movement" of my rod hand in order to create an almost straight tip path while using the wider arc.

Does it make sense to say on D-loop casts every inch of lengthening the distance of acceleration will increase the momentum not only by the speed up of the tip but also by lengthening the line to be moved here?

If I am right here, I understand this to be the main reason why I like to have pretty stiff rods for overhead (even short) casts but prefer soft rods for short to medium length D-loop casts.

Thanks
Bernd

p.s.: I know, tons of weired stuff in my mind! :kungfo:

[gordonjudd]

I think it was Gordy who marked the effect of cf to loop size (when using relatively small to average arc sizes) being around 80% compared to 20% effect based on typical tip path during acceleration.

Bernd,
More specifically it is the relative y-distance the tip goes through from RSP1 to MCF as compared to the y distance it has from MRF to RSP1. That distance will depend on the direction the tip velocity has since I don't think you can eliminate the overshoot of the tip travel after RSP1 unless you are using Alejandro's broomstick rod.

Based on the "effective" mo mass of the rod and the mass of line being cast the counterflex will depend on how much of the KE in the rotating rod remains in the moving mass of the rod at RSP1. Higher velocities will have higher RSP1 moving mass energies in the rod as well, and thus tend to produce higher counterflex magnitudes.

Damping with the hand will impact the total overshoot, but I don't think you can eliminate it. However, you can change the direction the tip is moving with the timing of the stop.

Alejandro's video shows that an earlier stop will result in the tip moving in a more horizontal path from RSP1 to MCF as shown below. In that cast he timed his stop so that angle of rod butt at RSP1 was around 42 degrees from the horizontal. That resulted in the tip traveling more in horizontal direction as it went through counterflex.


In the case with a wider loop the rod was angled at 28 degrees at RSP1. Thus the tip path from RSP1 to MCF was more vertical, and produced a wider loop. It appears the distance the tip traveled from RSP1 to MCF in the first cast was somewhat shorter than the distance in the second, but I think the direction of its movement was a bigger influence on the resulting loop size.


In distance casting the longer tip path results in lower angle at RSP1 and tends to produce a bigger initial loop size. Fortunately the loop will tend to morph into a more narrow loop and get better aerodynamic drag characteristics, but I don't know why that is the case.

Gordy

[Bernd]

Fortunately the loop will tend to morph into a more narrow loop and get better aerodynamic drag characteristics, but I don't know why that is the case.

Gordy

Hi Gordy,
thanks for the explanation.

Doesn't the loop morphing (in the way you described it here) happen cause the fly-leg is pretty long, straight and due to it's high speed has lots of momentum and will simply pull the rod-leg straight (directed to the loop front)?
This is what I think happens when using very thin shooting lines? Perfect to throw tightest loops.


The rod Alejandro was using here was pretty short. Using a longer rod will mean a bigger effect of the tip path from MRF to RSP1 on loop size?
I remember your analyses of the two casts of (I think) Matthias showed:
Small arc = huge percentage happen due to cf & wide arc = more percentage happen due to tip path before RSP1.

Since you came up with that I have tested a lot of tackle focusing on these relationships. My conclusion so far would be. CF has huge (mostly biggest) effect on loop size always.

Greets
Bernd

[gordonjudd]

The rod Alejandro was using here was pretty short. Using a longer rod will mean a bigger effect of the tip path from MRF to RSP1 on loop size?

Bernd,
Not necessarily. The magnitude of the counterflex will also be bigger for a longer rod, so the ratio would probably be in the same ball park as long as the rod butt angle at RSP1 was the same.

Small arc = huge percentage happen due to cf & wide arc = more percentage happen due to tip path before RSP1.

I don't know if that was my concept, and I do not see why that would necessarily be the case. From an energy standpoint (and using the same rod in both casts) I would think the small arc would probably have less KE in the moving mass of the rod and thus have less counterflex than the large arc.

It would also be expected to result with a larger (i.e., more vertical) rod angle at RSP1 and thus have a more horizontal path from RSP1 to MCF. Both of those effects would tend to produce a smaller loop size for the smaller arc.

I don't know how much difference there would be in the relative tip path ratios, but I think the timing of the stop would probably be a bigger effect than the arc length. You could try making some casts to see.

Doesn't the loop morphing (in the way you described it here) happen cause the fly-leg is pretty long, straight and due to it's high speed has lots of momentum and will simply pull the rod-leg straight (directed to the loop front)?

It is the change in momentum that produces the tension in the rod-leg and that is nominally equal to T=(Vfly/2).^2*rho. That says the rod leg line tension for a sinking line (that has a larger linear mass density, rho) would be larger than the tension in a floating line assuming the fly velocity was the same for both lines. Yet the loop morph effect in a sinking line is smaller that it is in a floating line. That argues that tension is not the only thing involved with changing the loop shape.

I wish I knew what caused the loop to morph into the rising loop shape. Your guess is as good as mine when it comes to that (and others as well) topic.

Gordy

[Bernd]

Hi Gordy,
have you seen this video:
http://vimeo.com/36248999
Should visualize some of the points here?
Greets
Bernd

[Bernd]

Small arc = huge percentage happen due to cf & wide arc = more percentage happen due to tip path before RSP1.

I don't know if that was my concept, and I do not see why that would necessarily be the case.

Hi Gordy,
http://www.sexyloops.co.uk/cgi-bin....98;st=0
Post 2 & 4 is where I got this idea from.
Of course these numbers arevaluable. So we probably can't call it a concept.
But I think these two casts show what happens to most casters using similuar arc sizes. So I think the numbers you visualized in that thread are pretty fine for a lot of casts, not all.
I have checked these numbers on quite a lot of videos. I don't have such a cool programm like you have but I have a frame by frame player (thanks Aitor ) and a board marker to mark the position of the tip on my screen. That way I can make a fair estimation.
From all I have seen I think your numbers were pretty good and representive.
Thanks
Bernd

[gordonjudd]

Small arc = huge percentage happen due to cf & wide arc = more percentage happen due to tip path before RSP1.

Bernd,
I was thinking in terms of conventional accuracy casts using different arcs, not the difference in the initial loop size and shape between an accuracy cast and the huge loops you get with the 170 style. The butt angle change in Matias' cast with the Paradigm rod was around 90 degrees, and that had a much flatter y path from MRF to RSP1 (the white path) as shown below.



As a result you can see the y difference in the red path from RSP1 to MCF was much larger, and thus it dominated the size of the loop that was produced in that cast.

If you were thinking that the large arc was associated with the 170 style and the small arc was for a conventional accuracy cast then I think your comment would be true since the y variation in the large curved tip path used in the 170 style is much larger than the y movement related to counterflex.

Gordy

[Bernd]

Thanks Gordy,
that was exactly what I had in mind and now I see you were thinking about changes in the more smaller arc sizes. Very helpful to understand these relations much better due to your help with all these perfect visualizing. Many thanks!Best
Bernd