[SPAM] Acceleration-Jim-#5

Walter & Group....

Jim....

I agree.  (I included a couple of the back messages.  I'll repeat that all should scroll down and read Shane's 3rd paragraph.)

Gordy

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Gordy & Group,

Lag of the rod tip is Really Interesting… therefore…

 

The deeper the rod is loaded, the more extreme the recovery acceleration of the rod tip. Something to think about when trying to make a distance cast.

In my experience if I can get a caster to focus on loading the rod deeply rather than quickly, the distance comes easier, lays out straighter and turns the leader over. Better line control!

Something to think about!

 

Jim

 

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From: Gordon Hill [mailto:masterstudy@xxxxxxxxxxx]
Sent: Tuesday, June 13, 2006 6:32 PM
To: Jim Valle
Subject: More on Acceleration

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Shane....

 

Yes....this is exactly what I was talking about.   It's the progressive acceleration of the rod TIP not that of the rod butt that I was considering.

 

Remember the limitations of the casting analyzer.....it only measures angular change of the rod butt.  I certainly agree that this is probably linear, but you have answered the question of what happens to the tip of a flexible fly rod.  All should read your 3rd paragraph on Einstein's Gedankin experiment.  This is what I feel is happening with respect to the tip motion of the fly rod !

 

Gordy

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-----Original Message-----
From: Morrison, Shane C. [mailto:shane@xxxxxxxxx]
Sent: Tuesday, June 13, 2006 5:37 PM
To: Gordon Hill
Subject: RE: More on acceleration

This is an very important discussion and not simple. Here are might thoughts. I was just at the instructors workshop in Mt Home, Arkansas, and Bruce Richards talked about the casting analyzer. It was clear from this that an expert caster achieves the best results with a linear acceleration of the rod butt (rotational acceleration).  This is what we mean by smooth application of power -- linear acceleration of the rod. This is unlike a less adept caster that tends to have a non-linear application of power (speed) during the stroke, often overcompensating at the end of the cast or an erratic application of power through the cast. The casting analyzer gives

us good experimental evidence of what is happening at the rod butt. But what is happening at the rod tip? 

 

Of course assuming the rod tip is traveling in a straight line (through balanced arc length and power application), the rod is converting angular acceleration to linear acceleration of the rod tip. In essence this is a mechanical amplifier, amplifying the rotational movement of the hand, rod butt, and rod to linear velocity of the the rod tip and fly line.

 

Here is a Gedanken Experiment (as Einstein called thought-based scenarios) If the rod did not flex at all (a broomstick) the rod tip would accelerate (angular) at the same rate as the rod butt. (Ignore translational movement of the rod butt.) But we know the rod is a flexible lever and bends as the rod is accelerated (we must accelerate to bend the rod). When the rod bends from linear acceleration of the rod butt, the rod tip necessarily lags behind a straight rod position due to inertia. If we accelerate continually and smoothly, it will continue to lag more, deepening the bend, until the rod butt is rapidly decelerated (at the stop).  Therefore the rod tip starts moving at a slower speed and is accelerating slower than the rod butt. Although accelerating, it continues to travel slower than the rod butt and accelerates slightly slower until it the rod butt stops.  At this point the rod unflexes continuing to accelerate (quite rapidly at the end) to the RSP. The acceleration is over the same arc length (ignoring counterflex), but over a slightly longer period of time (~0.1 s). Therefore, I think the rod tip is starting out a slower rate of acceleration early and ending at a higher rate of acceleration and moving very rapidly (higher velocity) at the end (ultimately we are after line speed, right.) According to Bruce and Nolan's results, the loading of the rod approximately doubles the velocity over a straight non-flexing stick. I think this is an increasing rate (non-linear) of acceleration (straight line) of the rod tip, despite the linear rotational acceleration of the hand. But it may still look very smooth.

 

Does this make sense? I think it is insightful, but not as certain as quantitative data. I'm not 100% sure, so there may be a flaw. Does this contradict Troy's findings. I think this is an area where we really need some experimental results to confirm whether the rod tip is accelerating linearly or non-linearly. Are there other experimental data on this? I haven't read all the papers Bruce and Nolan have written.

 

Shane