Walter & Group....
From Aitor Colderon.... My comments in his text in italics. G. :
Hi Gordy,
IMO the effective rod length is the length of that cord you mentioned but measured at any instant during the cast.
OK... but then you have redefined the term "effective rod length" from the original definition proposed by Vincent Marinaro who is given credit for the concept (1976). G.
The leverage of the rod is in play during the whole casting stroke so the effective lenght of that lever has an impact during the whole stroke also. Consequently if that effective lenght varies along the stroke we must take that fact into account, and not only consider the effective lenght at maximum bend.
Agree .... except for the use of the term "effective rod length". G.
The problem is that this bend in the rod is affected not only by the linear and angular acceleration of our casting stroke but by the angle between rod an line as well. The smaller that angle the shorter the portion of the rod that gets flexed and the bigger the flex in that particular portion.
Agree fully. G.
This angle is very important; for instance, if we consider rod load from the standpoint of the potential energy stored in the rod we can have the same spring energy with different rod bends. Regarding the ideal straight line path of the rod tip we get it due to the varying bend of the rod, and we get that different bend profiles even when we apply constant acceleration thanks to the variation of the rod/line angle.
Yes. A compendium of variables. G.
Regarding the previous link:
http://www.revver.com/video/314935/paradigm-long-cast-1/Here we can see a cast that IMO (although it would be better to draw some lines to check it accurately) doesn't show a decreasing effective rod lenght but an increasing one, even if the caster is accelerating.
Agree .... (except for your use of the word, "effective". A matter of whether or not we wish to stick to the original definition. )
Thanks for resending that link. I had no trouble opening it this time. G.
Regards,
Aitor COTERON :^))
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Ally Gowens answers my comments in red italics. My comments, today, in UPPER CASE/GREEN. G. :
Ally... To me, it nonetheless
still fits the simplified concept that loop formation happens when the line
begins to overtake the rod tip.
I don?t think that this is a simplified concept, it is fact.
If we relate it to rod bend, it is
somewhere very close to the Rod Straight Position #
1.
You may have noticed that I typed ?line? instead of line in my last message. In other than short casts the vast majority of line segments (we can think of a line as a number of short segments of equal mass or when pulling in line with a straight line as one mass) have inertia according to the maximum velocity reached and therefore they will tend to travel in that direction. That is why the line travels forwards as intended instead of following the rod tip when the rod tip velocity in the line?s direction is less than that of the line (tip ceases to effectively pull the line) (line overtakes the rod tip if you like).
AGREE. THEN THE ROD TIP MUST DEPART AT LEAST A BIT FROM THE PATH OF THE OVERTAKING LINE SEGMENT. G.
Ultimately in the case of the back cast in question the rod tip velocity was at right angles to the line due to the location of RSP whilst the line travelled several feet above that location practically in line with the maximum velocity (straight line movement) of the rod tip. Only a small amount of line that could not escape the tip movement due to proximity was forced to follow it however all of the energy in that portion would not have been lost to the line as some of it would have been transferred round the loop according to the law of conservation of momentum.
MAKES
SENSE. G.
If loop formation always occurred at or close to RSP the fly line would continually hit the rod because the direction of the tip and the line would be similar. The loop certainly forms before RSP and in many cases a relatively long distance before as shown in the video. It?s possibly more correct to think of the line going off at a tangent and you will see a fairly good example of this in those 170 degree casts. Lefty may not be physics guy but his observations are generally spot on ? if you want to make a really tight loop try to hit the rod tip with the line. Now you have loop formation close to RSP but you have to stop sooner than you might normally. Usually of course we rotate further to prevent this collision.
THEN YOU ARE RELATING THE POINT OF LOOP FORMATION TO THE ROD TIP PATH AND PERFORCE TO THE SIZE OF THE LOOP. YOU MAY BE RIGHT ABOUT THAT ! G.
As I go over in my mind the studies
already done on this including my own and the information we have received in
our messages, I wonder if it may sometimes be prior to actual RSP 1
and sometimes after, depending upon the cast and the characteristics of the fly
rod.
For very short casts (say up to
4 x rod length) the tip will exert much more influence on the line?s direction
and I suspect that is where the information that you mention emanates from.
Therefore it is probably a sufficiently accurate estimate for short casts but
not as a general rule. As we have previously discussed the disposition of the
line prior to commencement of a cast also has an effect on direction of the cast
and therefore also on the point of loop formation (launch point).
I suspect that many consider
that loop formation occurs when they see it. Unfortunately it starts before then
and the difference can be significant. Fortunately the line direction (fly leg
direction) is a fairly clear indicator of where the loop formed, especially if
the loop is parallel.
I don?t mind if someone can prove me wrong on all of this, it?s a long time since I studied physics, maths and engineering but not as long ago as I started fly fishing.
FRANKLY, I THINK YOU ARE MAKING GOOD SENSE.
SHORT ANSWERS :
1.) NO ONE HAS ACTUALLY PROVEN EXACTLY WHEN LOOP FORMATION BEGINS RELATIVE TO ROD BEND.
CAVEAT : THIS MAY BE A CHANGING RELATIONSHIP DUE TO A MULTIPLICITY OF FACTORS. IT MAY BE A BIT DIFFERENT WITH EACH CAST AND EACH DIFFERENT ROD.
2.) WE DO AGREE THAT LOOP FORMATION BEGINS WHEN THE FLY LINE STARTS TO OVERTAKE THE ROD TIP.
GORDY
Ally
Gowans