[SPAM] Acceleration # 4

Thanks for that input.

I just went outside - here in Mexico - and made two different "styles of casts".

One was where I moved my hand/reel throughout the stroke.

Then I left my hand stationary and only rotated my wrist open/closed.- like winding up a spring.

Both "styles cast the line".

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Yes. 1.) Now try to cast with no angular (rotational) change at all....just linear motion in the direction of the target.

2.) Compare that with the distance you can achieve as you did it using rotation alone.

3.) THEN compare with the distance made using both.

1.) Using linear motion (casting stroke with no rotation/angular change) you really can't get much distance.

2.) With rotation (angular change) alone, you'll get better distance, but you won't be satisfied with this.

3.) With BOTH rotation and linear motion, you have employed a casting stroke and a casting arc. This will give you the best distance.

The word, "linear" has more than one meaning. In the case of acceleration, it can be used to mean, "in a straight line direction". It can also mean a straight line graph of the rate of acceleration which remains a constant, ie. (the rate does not change.)

Confusion over the role of acceleration and the descriptions of it is often based upon lack of understanding as to what is being accelerated. As Shane pointed out, the accelerated movement of the HAND should be smooth and constant.(ie., "linear") The acceleration of the ROD TIP is a very different matter. Its acceleration, while not erratic, is progressive due to the flexibility of the fly rod. Its acceleration is at a much slower rate as the cast starts and becomes much greater as the tip approaches RSP. This, I see, as a progressively changing rate of acceleration. I used the term, "accelerated acceleration" for that......a term to which some folks object. It is, "linear" only in that it may well be in a straight line direction.....but NOT, "linear" in the sense that it is constant or unchanging acceleration.

This is very will explained, I think, in Shane's 3rd paragraph, starting with a description of Einsteins intuitive ("Gedanken") experiment. This should be read by ALL as it gets to the guts of the matter. (See, below)

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 Noel'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 Noel Perkins have written.

Shane