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Rod frequency static or dynamic?

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Paul Arden
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Post by Paul Arden »

Hi Merlin,

We're taking two different timings, the pull-back I'm referring to occurs pre-RSP. http://www.sexyloops.com/movies/pullback.avi

Cheers, Paul
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gordonjudd
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Post by gordonjudd »

I believe you can affect the rod straightening velocity if you can effectively reduce rod length.

Eugene,

You are also changing the lever arm in that case, so even though the time to unload is shorter, so is the distance the tip moves. Even if you could do it, it would more than likely be a near wash on the line speed.

That is Merlin's point about the effect of the second mode. With a load the node for the second mode is about 90% of the rod length. Thus the distance a lever 10% as long as the fundamental mode's length is not going to have much of an effect on the net line speed. Its phase is also likely to be out of phase with the fundamental mode (that was the case in Tom's experiment) so it probably won't have much of an effect in increasing the net line speed.

Gordy
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Merlin
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Post by Merlin »

Paul,

I took that example because the dynamics are the same for the line. If you (think) you pull back before RSP, the result is that the tip gives a backward speed to the bottom leg, hence a forward speed to the upper leg. The time needed by the rod to respond to the pull back will make that happen after RSP.

Merlin
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Paul Arden
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Post by Paul Arden »

Hi Merlin,

This has been a debate for many years on this board and previous boards when I was adamant that pull-back didn't work. However it's quite clear now that when I pull-back it happens pre-RSP and invokes and S-shape in the rod. It definitely results in higher line speed and quicker loop propagation, I know that and can see it. I posed the question here as to why it works last summer, and I had three different answers, 1) increased tension in the loop to rod tip 2) second mode frequency invoked in the rod and 3) more total force applied during the Casting Stroke.

If you (think) you pull back before RSP

I know I pull-back before RSP. I can pull back after RSP, but I don't call that pull-back. For me that's some sort of mend. The high speed video linked to this clearly shows the butt being pulled back pre-RSP, as I use to tighten the loops, throw overpowered casts etc and I've seen many times with accomplished casters on long carries and even for accuracy (I pull back for accuracy). The rod feels different, it unloads differently and I teach this for tight looped roll casts.

I think the question here is does a S-shape second mode frequency result in a higher tip speed? It certainly results in greater counterflex and CF2.

Cheers, Paul
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mac brown
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Post by mac brown »

What if the pull back acts as a direct nitrous to line speed because it acted on rod leg tension and has nothing to do with the rod? Similar to a forward snap (removing mass)?

That has to be significant using pull back (I think it is also the reason one can carry a long hands cast with no rod by focusing more on increasing tension for the rod leg of the loop). :D

That opens up a whole other can of worms though.
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Paul Arden
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Post by Paul Arden »

Hi Mac,

increased CF2 would create a Snap effect. Alejandro sent me some high speed videos recently of an S-shape on the 170. The weird thing is I don't feel that I'm pulling back on the 170.

Many years ago when I first met Mel Krieger - in the UK - and watched one of his demos, part of his demo was to take a rod without line and throw it around the audience, asking them to flick the rod as you would in the shop. I'm sure now that that was pull-back. I still regularly use that demo to tighten a Switch or even overhead cast.

Cheers, Paul
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gordonjudd
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Post by gordonjudd »

What if the pull back acts as a direct nitrous to line speed because it acted on rod leg tension and has nothing to do with the rod?

Mac,
Good intuition.

From what I get from the whip wave paper that is same effect you get by acceleration the hand back as you form the loop in a whip.

There is no rod in that case, but there is certainly increased F=ma from the backward acceleration of the hand. I think that has a lot to do with the acceleration of the line hand in the haul as well.

I think Tom put his finger on a related effect here as well. Again, nothing to do with exciting a 2nd mode in the unloading of the rod.

Gordy
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Merlin
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Post by Merlin »

Hi Paul,

OK, you start your pull back before RSP with a crisp motion of the wrist that makes the second mode pop up.

Effect of the second mode: I assume an immaculate sense of timing and you get the second mode speed in synch with the fist mode. Given the short lever arm due to the node in the tip, the extra speed is a handfull of percent of the first mode speed.

But your pull back, given the lag in response from the rod which takes place after RSP, gives also a backward momentum to the bottom leg of the loop, and accelerates its motion. To me this has the largest effect on the line, by comparison to the hypothetic increase in line launch speed.

Merlin
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