s shaped rod - How does it happen?

[Bernd]

sometimes, if there are two much vibrations, I do not use the wrist but only the arm rotation to avoid them. No theory behind, just practice.

Hi Merlin,
this is (I think) what I had in mind, too. When casting pretty relaxed, not using wrist rotation and using an abrupt stop, but not extremely abrupt, the cast (straight oeverhead cast) feels pretty effective to me. And this is what brings in effective distance for me, too (not talking about max possible distance in a high end distance cast here).

If for example I add pull back to the rod-leg, it means I need energy to do this and even though I may speed up unrolling for a special purpose here, it will mostly cost me distance.
Of course if this speed up of unrolling will make my leader straighten instead of collapsing it can add distance also.
But then (in most situations) there was something wrong in the cast without pull-back as I understand it.

So after all for a simple straight over head cast I think casting with using the rod as a (flexible) lever where some of the energy will be stored in the rod and transfered into tip speed after reaching max load by it's first natural frequency is the best way to aim for.

Trying to somehow find a way to hit the 2nd or 3d mode of frequency for a simple straight overhead cast seems to be a dead end in my understanding.

Of course there are situations like this one here:
http://vimeo.com/21349829
Where the s shape helps me to make the tip flip back like hell in order to speed up unrolling and make a wave travelling the line backwards.

A quiet similar effect might happen when Jerry Siem uses pull-back in his bc to speed up unrolling for feeling an increased line tension. I know that feeling pretty well, too and it works for me, too. But again this is for extra tension not distance in the bc.

Hope all this still makes some sense.
Greets
Bernd

[gordonjudd]

Merlin,
How do you see the transmission of energy in the flexure wave we appear to see going up the rod being converted into flexure wave energy in the line? I think it is that kind of transmission Alejandro has mentioned in his rod wave observation, and what Ian is referring to here:

The way I have been thinking about counterflex of rod is aligned with thoughts of energy transmission. (similar to design of radio transmission antennas... you want as close to 100% transmission of energy and minimum reflected energy..).)

There is energy stored in the bent rod, as it unloads the energy is transferred to the loop (wave form).

My out on a limb theory is that thrust assists in letting the energy flow into the loop in a controlled fashion , such that there is very little left to cause the rod to bounce..

Just based on the reflections you get in electromagnetic waves at different impedance boundaries I would think the mechanical impedance of the tip of the rod would be much much different than the mechanical impedance of the line. Consequently, there would be little or no wave energy transmission through the rod / line impedance discontinuity as discussed here.

I can understand applying force over a distance to the line with the rod to increase the line velocity, but do not see how wave energy transmission could be involved in that process.

There is nothing magic about the fact that you generate higher order modes in the rod, but I don't see that their higher oscillating frequencies are going to do much of anything to increase the line speed. Haun even goes so far to say that:

If the frequency of vibration matches a higher order mode of natural frequency of the rod, energy will be dissipated by the rod and not transferred to the line.

Gordy

[Merlin]

Hi Gordy

Well a good question. Sometimes I figure out fly rods as whips that can transmit energy from butt to tip. Imagine a fishing tackle as a continuum and us “throwing” a wave in the system that would start from the butt and reach the line smoothly up to the fly. For the time being, I just see a “mechanical wave” coming from the angle between the rod and the line, and no single wave thrown intentionally. But I also question myself about the shaping of the loop: is it the proof of a “wave transmission”?

We all dream of a cast without counter flex and a nice sharp loop getting out of the tip in perfect synch. Unfortunately, all cast records do show a counter flex. Some confusion can come from cushioning solutions to kill the counter flex, like following through the cast, and let us think we succeeded in throwing a wave.

The problem is that I never got an evidence of that. For the time being, models have always been able to capture even a drastic increase in rotation speed, increasing abruptly rod deflection. But the suspicion remains. Our models are in fact unable to get the complexity of wave transmission issues (by the way I have to check what is in the link “here”, I think there are some mistakes and a confusion between longitudinal and flexural waves). My guess is that the comments from Alejandro and Ian may be valid for an analogy with longitudinal waves, but flexural waves seem to be one order of magnitude more complex.

On one hand, I’m always searching for the “wave issue” and I started some serious investigation on that point with academics, and on the other hand I pragmatically see that the current model shortcuts are good enough to describe what is happening.

Dr Hauns’ comment is again right for me, although I think that too much emphasis is given to the amount of energy loss through higher modes. This energy would have been spoiled anyway by counter flex, I think. However, tip vibrations are not pleasant to get during casting, so one aim of the designer is to get the customer rid of them, even if they ignore the problem.

Interesting and challenging thread, you know.

Merlin