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Walter & Group...
[GH] Many instructors use the terms, "CONVEX" and "CONCAVE" to describes things such as the path of a rod tip during the cast .... or to help describe the geometry of a fly line taper.
This is crystal clear to some students and a source of confusion for others. I have observed that many who take the CCI exams fail to get the correct answer to any question which uses those terms.
Let's discuss the issue in the light of two messages I received while I was away.
I'll give you my take on this, then ask that some of you help with descriptions or definitions of these terms which have worked well for you as you teach.
Gordy
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>From Tim Kempton:
Good Morning Gordy
May I introduce myself.
I recently completed my CCI with Peter Hayes and Roy Wybrow in Tasmania. Thank you for including me in your discussion group. I travel a lot, but I do receive your emails.
I have become a fly fishing tragic, and find learning and practising very relaxing. I have played lots of competitive sports, and am intrigued by the science and art of fly casting.
I teach at our Mallard and Claret Fly Fishing club in Brisbane Australia, and also teach school students and teenagers. They are unafraid to ask the hard questions.
I have attached a query about convex vs concave rod tip path that was raised as a simple question, and became a major point of conversation. I am writing to ask your help in the clarifying the definitions. I have not distributed this because I did not want to create an unnecessary distraction unless the points raised are valid.
I have been following the comments about definitions with interest, especially the definition of CASTING STROKE. I will give my thoughts later.
I agree with all those requesting clear definitions. It makes our tasks as teachers difficult without clear, unambiguous definitions.
Kind regards
Dr Tim Kempton
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More from Tim Kempton:
Dear Gordy
Just following up on this.
My student is a university physics lecturer and is persistent
My thought is that the only way I can explain the logic is to imagine the angler is inside a lens. That way the rod tip, or hand will scribe a convex arc (bulging out) and a concave arc (bulging in) as you see in a lens.
Any thoughts would be useful please..this guy is driving me nuts
Kind regards
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Tim,
No distraction at all .... and relevant to our discussion of definitions.
As I'm certain you are aware, it is especially important when teaching young students to use simple, easily understood terms which relate to everyday things or events in their lives. No fancy mathematical or scientific descriptions.
I try to avoid the terms CONVEX and CONCAVE, for students below secondary grade levels.
For these young fly casting students, I'll use terms to describe a convex path of the rod tip such as:
- "Draw a rainbow in the sky with your rod tip".
- "Make your rod tip move over the top of an Eskimo's igloo".
- "Your rod tip climbs over the top of the mountain".
It's a little harder to get the concept of CONCAVE across:-
- "Your rod tip dipped way down and then up".
- "The tip moved like the shape of a saucer".
- "This time it moved along an upside down rainbow".
Words alone may not do the trick.... so I use my hand and index finger to to pantomime the various paths. I'll sometimes to it with my rod tip. In classroom, I draw simple diagrams.
Students with higher level of education may want more than the ultra simple explanations. If so, still avoiding mathematical descriptions, I do use the terms CONVEX and CONCAVE. I'll use statements such as these if there is any confusion:
CONVEX: "The shape of the outside of a soup bowl".
"Dome shaped".
"Shaped like a hill".
"Curved outward".
"Shaped like a bump".
"Bulging".
"The outline of the outside of an arch".
CONCAVE: "Shaped like the inside of a bowl".
"Shaped like an upright saucer".
"Curved inward."
"Shaped like a dent."
"Shaped like the inside of a cave".
"Shaped like the inside of an arch".
With respect to the rod tip path when casting, we imagine a vertical or nearly vertical rod plane; then relate the curved path of the tip to the ground or water. If we didn't do that, then one might draw the curved line representing that path and say, "Well, we have a curved line one side of which is convex and the other concave" !
When casting with a horizontal rod plane, I'd relate the curve to the caster, or an imaginary vertical plane.
We might look at it this way:
If the path dips toward the point of reference (the ground, water, or caster) it is CONCAVE.
If the path bulges away from the point of reference, it is CONVEX.
For those who have a burning interest to go a lot deeper:-
Gordy
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>From JF:
Hello Gordy,
Since you seem to know everything J, I thought I would ask you about 2 things i noticed reading Bruce Richards’s book – Modern fly lines.
1- On compound tapers. At page 78-79-80 he talks about concave and convex compound tapers.
The first one he addresses is concave (tapers quickly and then more smoothly) and then he refers to the first drawing.
He then talks about convex and refers to the second one.
Question: Are the drawings good? Shouldn’t they be switched (1st drawing presently represents convex (p79) and second concave (p80)?)
2- Chapter 4, New line rating system
He proposes a new rating system for heavier wt lines and suggests weighting the first 50’ instead of the first 30’ likes for smaller wt lines.
Now that book was written in 1994. Is this suggestion what evolved as what we now use today to measure two-handed rod lines? We do weight the first 50’ for these two-handed systems correct (spey, skagit and scandi)?
Thank you for your time, it’s really appreciated.
The challenge of becoming MCI which seemed so far and impossible recently has suddenly become a lot more accessible thanks to the Group and the reading suggestions found on the FFF website preparation part for the MCI.
I practice a lot with the rod and that is going well I find, but I was really lacking the more empiric and theoretical part mainly everything not linked to casting.
This is really helping a lot!
Thanks again
JF
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JF:
First of all.... I do NOT know everything ! I'm learning just as you are. The main value in these Study Group discussions is that we have access to many experts whose combined knowledge is greater than that of any one of us. That they help us learn, is a beautiful thing!
In discussing things like CONVEX and COMPOUND, it is hard to beat pictures and / or drawings.
Unfortunately, some of those books came on the market with the drawing labels reversed !!!
This was corrected early on, so most of the books had the correct labeling for those drawings. I lent my original copy and it was never returned, else I'd show you the drawings and the reversed captions. I did provide the corrected drawings from my present copy in an attachment. *
The proposed line rating system was not actually used, though I do think it has merit, and many agreed.
* MODERN FLY LINES, by Bruce Richards, 1994, Odysseus Editions, Inc., Lefty's Little Library of Fly Fishing, pp. 79, 80.
Gordy
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Attachment:
Convex : Concave compound tapers.pdf
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