Gordon & Group...
[GH] Paul Arden answers Dan McCrimmon's question :
[DM] "What is the "tension" in the loop that Paul describes? Could it be centrifugal force that maintains the loop shape (tension)? Or more correctly, dissipation of energy, via centrifugal force?"
Dan
[PA] No it's the momentum change that creates the tension. I had an physics paper on this somewhere in my hard drive. I'll try to get another copy.
Cheers, Paul
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[GH] Paul, I agree. However, it isn't tension unless that momentum of the traveling loop is resisted by the "tether" or friction between the rod leg of the loop and the rod tip (tension varies according to whether the line is being shot or not) as I see it.)
I'd love to see that paper.
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[GH] From Dusty Sprague :
Gordy....
" [GH] One problem lies in our not as yet having full agreement on exactly when that point (line launch) appears during the casting stroke." "
[DS] `I must have missed all the views on this during the discussions...i.e., when the line is launched during the casting stroke. It seems to me the line would launch the instant the rod tip begins its deceleration, or very shortly thereafter, as the oncoming line overtakes the slowing rod tip. The process of stopping.....hand, rod butt and tip certainly occur later, in my view........what is your view on this ?
Sorry for the digression...
Thanks,
Dusty
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[GH] Dusty ,
Probably so.
The exact point that the rod tip begins its deceleration, however, is not something I know how to actually see and measure in terms of where it appears during the casting stroke. One can get much closer to it, I suppose, on the computer readouts from the Casting Analyzer.
If I understand Ally, he says something to the effect that you can back into it by following the line back after the actual launch and he feels that knowing the point of launch is not important whereas knowing its direction is because it is that which is material to the outcome.
One point which I had considered a "given" is RSP ..... until even this was challenged by those who pointed out that with powerful distance casts only the tip section is "straight" while there exists an "S" curve in the remainder of the rod !
In case you missed it or, in any event to refresh our collective memories, I've included two of Ally's overlay depictions.( See attached) The first shows the line launch direction. The second, the approximate point of launch.
When we fire a rifle, we launch a bullet. Was the point of launch at ignition ? Or was it at the muzzle ? More importantly, DOES IT MATTER ?
The launch direction sure does !
Gordy
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[GH] From Michael Heritage :
I really don't understand the concept of line launch, it infers we can throw the line off the rod tip in any direction we choose, which is obviously not the case. The angle the line travels is dictated by casting plane (trajectory) and the portion of the tip path that complies with SLP. Whatever happened to loop formation?
Mike
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[GH] Mike... Throwing around these terms may be a bit confusing to many. I've been wrestling with some of these terms for some time after gaining some input several years ago while teaching fly casting to an employee of the NASA space program. I introduced the term "launch angle" to this Group shortly after that as I thought it was not much of a stretch to compare what we do to the launching of a projectile. (Not so much for a rocket since that is self energized.)
The one term which was new to me was "Line launch direction" introduced to us by Ally Gowans.
Here is my simplified "take" (Bear with me as I strive to learn as you do) :
Launch : To send forth, catapult, or release. (Free from additional input of the caster's rod motion.)
Launch angle : Synonym for CASTING PLANE and TRAJECTORY. (The angle between the direction which will be taken by the traveling loop and the horizon or artificial horizon.)
Line launch direction : The direction in which the line was launched just prior to RSP. (Seems that this would determine the direction of the newly forming fly leg of the loop as it overtakes the rod tip.)
My understanding of Ally's discourse is that the launch actually occurs somewhere just prior to RSP (Rod Straight Position) or the point of early loop formation where the line starts to overtake the rod tip.
I used to think that one couldn't launch a loop until it had actually formed. The present discussion takes me to the concept that the launch direction has been determined a fraction of a second prior to that. To me that only makes sense if we think of the line being launched prior to loop formation and that it is this which determines the direction of the loop once formed.
Of course, there is a limit or "range" to the directions in which a line (or loop) can be launched. That was suggested by Ally's question # 10.)
10.)
