Loop formation issues 8

Walter & Group...

[GH] Ally Gowans sends his attachment explaining line launch in terms of Newton's laws of physics. I have included it with this message.

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>From Craig Buckbee. ( I added the highlighting):

Gordy,

I response to Guy Manning's comment : "Wouldn’t line launch begin the moment the rod starts forward?"

IMHO (and I do mean that) :

When I move the rod forward I am pulling line, pulling it into position to be launched.

In my teaching I often use "The Loop is Born" but after reading "Loop Bud " - an absolutely brilliant visual from David Diaz ! - I've now a new term.

Craig

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>From Soon Lee. (I added Jim Hund's question to his text.):

Hi Gordy,

Regarding Jim Hund's question:

"This discussion brings out just how quickly the end of the stroke occurs and how many things happen during the split of seconds between the stop of the rod butt and RSP 3. I have a question (probably a dumb one) related to your response to the post of Bob Dionne. Your response mentions the term "line launch." In my mind "line launch" occurs when the line (in the formation of a loop) over takes the rod tip. Is "line launch" different from loop formation at RSP1? If so how and when does it occur?"

I do not think the "physics" of the interval between point of line launch and RSP-1 is settled as yet. Currently it is claimed that line can only overtake rod tip, and therefore loop can only form, after RSP-1. It sounds reasonable, and video studies with late-model rods seem to support that. But what if a cast is made with a suitably slow, low modulus rod, yet with rod tip speed identical at point of line launch: may the line not visibly overtake rod tip even before RSP-1?

Anyhow when exactly loop may be stated to form is a wooly question. Visibly it is formed when rod tip halts at maximum counterflex. The precise instant loop begins to form we will leave to physicists and investigators.

In a similar vein, visibly, line launches when rod tip deviates from its SLP. The precise instant when line overtakes rod tip we will also leave to physicists and investigators.

What we need meanwhile, before the physics of the cast is fully researched, is a simpler approach when we are teaching students. For that purpose I have been advocating that casting stroke be defined to end when line launches, rather than when loop forms. For one thing this determination makes SLP an entirely understandable objective.

In no way am I saying I am right, and others wrong. But thanks for listening.

Soon.

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[GH] Soon,

You raise some valid points.

One of the things which makes the discussion of line launch uncomfortable for many, is the fact that it is becoming more and more obvious that this is a variable depending upon many factors. Added to this is the fact that we don't have hard data based on experiments and measurements to show exactly when it occurs with respect to each variable or combination of variables in relation to SLP or the start of loop formation.

This is why I have taken the position that it probably occurs, during most casts, at a short but variable time prior to loop formation.

Kind of like the Higgs Boson. Scientists have had the dickens of a time trying to identify it, whilst in theory, it exists.

Going back to the Middle Ages, we can actually see the point of launch of a rock starting to leave the basket at the end of a catapult. That "launch point" would be the point at which the catapult no longer propels the rock.

Perhaps some brilliant physicist could design an experiment which would show the point of line launch relative to each variable (line length, rod flexibility, forces applied, line design, etc., etc), where the moving rod tip no longer actively "pulls" the line.

A challenge for a budding physics Ph.D. candidate?.... Maybe.

Would this actually help us cast ? I doubt it would.

Would it help us teach fly casting ? Probably not.

Would it give us a better physical understanding of fly casting for research and development into the future? I think so.

Gordy

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[GH] For those of you who are interested, I urge you do do as I did and take a couple of pieces of rope out on the ground (or snow) and try the simple experiments Ally outlined.

Tomorrow, before I go on a trip for a few days, I'll send the findings both Ally and I made.

Gordy

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