CONGRATULATIONS ! / Oil spill / Casting mechanics .. cont'd

Walter & Group...

CONGRATULATIONS TO ZIGI KOVACS ON PASSING THE MASTER EXAM !

Dear Gordy,

Last week, after a looong and focused preparation I have passed the MCI :-)
I would like to say thanks for you, and the whole group, for your support and enthusiasm. Some of the lately discussed subjects were actually asked at the exam. As I am at the "thank you move", I would also like to thank Philip Maher from Ireland and Paul Arden from Sexyloops for their teaching, instructions, support and generously sharing their knowledge/experience.

I am really-really sorry to read and hear about your oil-pollution disaster.

Best regards from Budapest/Hungary

Zigi
(Zsigmond Kovács)

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Zigi,     You had some first class support and instruction as you worked with Paul and Philip !  Trying to pass the Masters on one's own without expert assistance along the way is almost impossible.

Jim Valle has avidly supported the concept of each Master candidate having a "mentor".  I think he's right on target.

That is the main reason Rick Whorwood and I started this Group 10 years ago.  We began by informing one another and challenging with questions and quizzes each requiring a "short answer" and a "long answer".  Worked so well, we expanded it and now have 263 members with every continent in the World represented.  Actually began on my skiff as we spent hours (while waiting for tarpon to show) as a "two man study group"..... then continued it by email even though I live down in the Florida Keys and Rick lives in Onterio, Canada.

Gordy

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                                                                    OIL SPILL

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Several of you have been calling and writing to ask about our situation in the Florida Keys with respect to the oil spill from the Deep Water Horizon rig in the Gulf of Mexico off New Orleans.

Up to now, the only experience we've had is that during the past 5 days there have been a couple of instances where we got a jet black tarry substance on our fly lines.  Then that has gotten off on our hands as we strip.  This despite what we are told by the media that the oil has not gotten any where near our shores.

This may be from an entirely different source.  However it seems more than coincidence as I reflect back during the 51 years I've been fishing these waters and not had any tar sighted or our fly lines coated in the Gulf waters here.

Gordy

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                                                       CASTING MECHANICS.....  CONT'D

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Walter Simberski comes in with answers to some of our questions :

Hi Gordy,

 

Aitor is absolutely correct. The CA only measures what is happening at the rod butt. More on this in a bit

but first to answer your question -

 

The CA measures the rate of rotation of the rod butt - i.e. angular speed - in degrees per second, along

with the direction of rotation. Together we have angular velocity and this is what is displayed on the CA

charts. The magnitude of angular acceleration is the slope of the graph at any point and we can easily

look at the chart to make a reasonable guess what this value is.

 

Bruce and Noel have come up with the idea of smoothness which is independent of what the current value

of acceleration is but it does tell us how constant the acceleration is, i.e. it doesn't matter what the

magnitude of acceleration is at any point the smoothness ratio can be any value greater than 1.

 

Now back to Aitor's comment(s) - if smoothness is 1 then there is no maximum accleration of the rod

butt. It is constant. There is also no way to determine line acceleration at any instant in time by measuring

only the acceleration of the rod butt.

 

Now for something I haven't brought up before - if the acceleration is constant, and the effective length

of the rod is decreasing during the stroke then the applied torque must also be decreasing during the

stroke in order to maintain constant acceleration...

 

Walter

 

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Walter.....

 

I understand your description of the Casting Analyzer better, now.

 

 Of course, as the effective length of the rod decreases it is perforce due to the increase rod bend.  Now if we have increasing rod bend, wouldn't that be due to INCREASE in torque rather than DECREASE ?

 

Since I don't see that rod bend decreasing until the caster begins the "stop", that leads me to think that we may not have constant acceleration.

 

Gordy

 

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From Aitor Colderon.  My brief comments in his text in italics.   G.  :

Hi Gordy,

Some comments about the concept of acceleration applied to fly casting instruction.

First of all I think that the wording you use to convey the key concepts of casting must be matched to the student caracteristics: some 　beginners will probably grasp better the idea that a casting stroke is an accelerated motion if we avoid the use of the word acceleration; just as the description based on loading move/power snap, talking acceleration can suggest the use of too much force during the cast with the consequent bad results.

Agree.  This speaks to Jerald Lewis's concerns (our last message, today).     G.

However, from the perspective of a casting instructor -and specially in the case of those interested in reaching the highest levels of performance and teaching ability- the understanding of acceleration and its implications in casting is, IMO, essential.

Absolutely !

In my experience a lot of instructors tend to confuse velocity with acceleration. I think that some minutes devoted to the study of this basic concepts are worth the effort. Surfing the web you find a lot of resources that explain this subject in very understandable ways.

Walter Simbirski has done that very well .....He spent a lot of effort in making physics understandable for us both with messages to this Group and in his article published in the Loop.

I'll try to dig this material out and send as attachments, for many of you were not in the Group at the time.    G.

I don't agree with the concerns about the use of the adjective "constant" to name the kind of rod butt acceleration that it is normally recommended to get a good loop. I can't see any problem with it: its meaning is very clear for those that have a basic understanding of the 　concepts of velocity and acceleration, and apart from that the graphs generated by the Casting Analyzer represent it in a crystal clear way if you dedicate just a little time to study the curves that its software generates.

Yes.  I think we are all understanding it better, despite our banter.    G.

On the other hand those concerns about the meaning of "constant acceleration" seem more surprising to me since that isn't the first time that the term acceleration is used as a basic tool for teaching beginners. I am thinking of Gammel's essential 2 as stated here:

http://www.virtualflycasting.com/essentials.htm

Here we can see that the student must apply to the rod the "proper acceleration".

IMHO "constant" applied to acceleration has a very precise meaning: you must increase the velocity at which you rotate the rod butt in a uniform, progressive way, just as you would do with your car if you wanted to put it in motion without any jerkiness.

I find that "constant acceleration" has a very concrete meaning, and now thanks to the CA we can check to what extent we are getting it. In comparison saying "proper acceleration" is much less meaningful.

Yes.  I don't know if Bruce Richard and Noel Perkins had come up with the concept of "constant" acceleration at the time Bill Gammel wrote that.     G.

Regards,

Aitor=

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From Guy Manning :

Both  AItor and Ally have mentioned that the loop can form somewhere other than rod Straight Point (RSP) where the tip goes into counter flex. The link below will allow people to view an edited verson of Grunde Lovells Supersonic Backcast video. It is kind of rough as it took 2 conversions for me to mark it and another conversion to get it small enough to put it up for download.

 

Here is the link to the video: http://castflys.net/Hidden.aspx  You will need to right click and choose, Save Target/File As?

 

The marks are:

Red = tip path up to RSP

Yellow lines = rod at RSP and MCF (Maximum Counter Flex)

Green = approximate position of line at RSP

Blue = approximate position of line at MCF

 

The blue and green line positions are approximate due to the difficulty of seeing the lines, much of that due to converting file formats. Note that the red dots are not describing a smooth arc. If you just visually smooth the path it is pretty close.

 

Note that even at RSP the line is already beginning to form a loop face (green line) and if the rod were to stop completely at that point the loop would continue to propagate.

 

Pay attention to the 6 right most red dots that are tracing the tip path. Notice how they scribe nearly a straight line. This is our ?straight line path of the rod tip.?  It is obvious that the overall tip path is far from being flat so the SLP is something of a non-entity.  This short ?flat? section is what sets the upper leg in a flat profile. The physical process of forming a flat upper leg depends on that short area of flat or ?straight line path? area.

 

If we understand that waves travel down the line we should be able to grasp that the flat section also travels down the line. Also consider that when a wide loop is created, the line is not moving in a uniform direction but in all directions due to centrifugal forces.  

 

So as the flat section propagates the area of line that has just passed through the flat section is now setup to move in a direction or vector. The new area of line now entering the flat section is being aligned in train with the area just forward of it and adds to the inertia of the flat part of the leg. We now have a flat section twice the length as before. As the flat section moves through the length of the line, the length of line moving along the vector increases. This is why we can take an open back cast yet make a good forward cast with a flat upper leg, and why the loop can be forming prior to RSP.

 

If the tip is sufficiently deflected away from the path of SLP the loop will still be created, but it will travel near the vector that the flat section of line is moving in.  

 

I hope that all made sense.

 

Guy Manning

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From Jerald Lewis :

Gordy,

 

This series of notes on casting mechanics has had some great discussion and very detailed analysis of what happens during the cast.  While I am an electrical engineer and can appreciate (and sometimes understand) the details, I am also very practical.  Being new to the group, I don?t know where we?re headed.  Will there be some kind of summary at the end that brings the discussion back to a practical application?  Or maybe some suggestions on how we can use this to be better teachers and casters.  Does that make sense?

 

Jerald Lewis

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Jerald...

Yes, indeed !  If we fail to relate this directly to our teaching,  we end up being a bunch of theorists accomplishing very little except to enlighten some and confuse others and in some cases bolster our own egos while helping no one.

This time, I think I'll put out another little quiz on how we would handle this complicated information when teaching students at various levels.

Gordy

 

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