Would someone please explain to me, the term PARABOLIC action? I understand fast, moderate, slow action, not sure what parabolic is???

Thanks in advance.

Most people use it the wrong way. When you hear it, in most cases the person using it means to say that the rod has a very slow action; that it flexes evenly over its whole length even under light loads. This isn't exactly what "parabolic" means, but that's how most fishermen use it when describing action.

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From Dictionary.com
par·a·bol·ic1 /ˌpærəˈbɒlɪk/ Pronunciation Key - Show Spelled Pronunciation[par-uh-bol-ik] Pronunciation Key - Show IPA Pronunciation
–adjective
1. having the form or outline of a parabola.
2. having a longitudinal section in the form of a paraboloid or parabola: a parabolic reflector.
3. of, pertaining to, or resembling a parabola.

pa·rab·o·la /pəˈræbələ/ Pronunciation Key - Show Spelled Pronunciation[puh-rab-uh-luh] Pronunciation Key - Show IPA Pronunciation
–noun Geometry.
a plane curve formed by the intersection of a right circular cone with a plane parallel to a generator of the cone; the set of points in a plane that are equidistant from a fixed line and a fixed point in the same plane or in a parallel plane. Equation: y 2 = 2px or x2 = 2py.



Yea I don't understand it either.!?<>



Edited 1 time(s). Last edit at 05/13/2007 01:39PM by Tim Hurst.

I've never seen a parabolic rod, from Tim's discription it would appear that it would have to have a lighter mid section than tip or butt.

From what I remember from math class... some 50 years ago,,, isn't a parabolic shown as a wave of equal high and low points, kind of a rhythm, almost like a wave in water??

Again, when you hear fishermen use the term, they're not using it in the true definition of the word.

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Tom is correct. A parabolic action is thought of by some as a rod with a very slow action but this is not correct. A parabolic curve is formed by a form of second order quadratic equation and looks like 1/2 of an ellipse. In other words a rod that was parabolic would flex more in the mid section than in the tip and the butt sections. There is also something called a parabolic spiral but that is not what people are referring to when they say a rod is parabolic.
Fred, 50 years is too long to remember. It is not like a wave in water. A wave in water is a sine wave where the amplitude of the wave at any point on the wave is a function of the sine of the angle to that point.

Hello Fred,

This question has been asked and discussed on this forum before. Use the search function and you will find a substantial number of posts on this subject. A good source is a book by Joseph Bates Jr. : "Spinning For Freshwater Game Fish." In this book he gives illustrations of the flexing of a spinning rod with parabolic action. He also describes the action as follows: "...the action of a spinning rod should approximate a parabolic curve--or in other words, that the rod should have parabolic action. The simile is an apt one if it impresses upon our minds that a spinning rod gives maximum relative power if its action is distributed uniformly from tip to butt rather than being too soft or too stiff at either end. "

The diagram can best be described by imagining the locus of points for the equation
X = aY squared and then bisecting this curve and taking only one half of the curve. This will give you a curve that is "parabolic." However, If I understand Emory Harry's discussion on this matter he thinks that this may be more logarithmic. After reading his post I generated a series parabolic curves and found that the curves can also easily be approximated by a logarithmic function. (Thank goodness for MS Excel (or Kalaidagraph) and curve fitting software.

I think for us as rod builders that the math is not necessary and we can visualize a parabolic rod as one with slow action with the action being uniformly distributed the length of the rod. According to what I have read, this was the preferred action for spinning rods when they were first introduced to the United States from Europe. However with the development of fiberglass and graphite as well as modern theory of casting, rods with much faster action (non-uniform distributed action) have become the norm.

One other aspect of those old rods is the use of what we now refer to as Tennessee handles. There is a nice photograph in"Spinning For Freshwater Gamefish" showng four spinning rods designed by Joseph Bates Jr. rods with long handles and two retaining rings for holding the reel. These handles resembled quite closely those described in a recent issue of Rodmaker Magazine on Tennessee Handles. I guess what goes around comes around.

Have fun with this.

Mike Blomme

I'm campaigning for a new term - "semicircular action"

Well, THANKS to Emory and Michael for jarring my mathmatical memory..............50 years IS a long time period.. And you are right,,I was thinking of the sine wave... gosh,,,, I better start fishing before I'm too old to cast a line !!!!!!!!!!!!!!!!!

But I think my question was answered.

And , Tom,, what is the true definition of the word?

BTW this has to do with bamboo fly rods,, if that makes any difference, which I wouldn't think that it would, afterall a blank is a blank.

Thanks guys !

My understanding is that the term orginally was applied to rods by a bamboo builder in a conversation in which someone asked "what if we just put a 2x4 in a vise and bent it"?. Answer: you would get a parabola. And I think that is correct.

But what we have to realize is that the "bendy" part of the parabla would be at the butt, and the tip would be relatively straight, if you built a rod that esentially had no taper. So the term hung on to describe the "action" of this builders bamboo rods, sort of like all rod marketing terms, with no real exact meaning. But the implication is that a lot of the bend is near the handle.

Now we tend to think of the "parabola" a tapered rod makes with most of the bend at the tip. But the origin of the term would describe a rod bend pattern that has the tip perfectly straight and most of the bend of the parabola at the butt (upside down). And that would describe a very slow action rod. So the "Young's parabolic" rods do not bend in a parabola because they are tapered, but they are slim at the butt and do bend a long ways down as opposed to a rod like the T & T and othe rods that have a "swelled butt" to make the action a faster, crisper taper that flexes mostly at the tip.

Michael,
I think that you are cheating. If you bisect a parabolic curve it is no longer parabolic. I am not sure what it should be called but one half of a parabolic curve could describe almost any action, fast, slow or whatever depending upon the curve.
A bisected conical section is a parabolic curve though.
Bob,
A semicircular action would be closer but it would not be parabolic either. A semicular action would have uniform deflection throughout its length while a parabolic action would have more deflection in the center of the rod.

Fred,

I think others here have covered it as well or better than I can. And I think that Bill's explanation is pretty close to exactly why that term came into being among rod building and fishing lingo. At least, I've heard the same story and have seen the term used very often in writings about bamboo fly rods.

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Good Morning Emory,

I agree with you that taking only parts of a function such as the positive values of Y in the equation listed in my first post would not be accepted in terms of pure mathematics as a parabola . In that sense I "cheated". However, in the fields of chemistry, engineering, and physics we are often confronted with cases where not all solutions to a function give "real" values. Since in those fields we are often trying to find values of physical properties (force, energy, volume, length, density, etc,) we can only use solutions, which give "real" values. In this sense I chose only positive values of Y (the amplitude when a specific force is applied).

I quoted from Joseph Bates and he does use the term "approximates a parabolic curve" to describe what he calls the ideal action of a spinning rod. He also distinguishes the action of a spinning rod from either a casting rod or a fly rod. In his example he also applies the flexing force at the butt of the rod and then describes the flexing action along the length of the rod as a result of that force. I also admit that it is very dangerous to use only one source when discussing any topic as complex as the flexing action of a fishing rod. I use Joseph Bates, because at the time I started building spinning rods (1958-1960) this was the only source I had from the libraries that were available to me. The rapid telecommunications industry did not exist and the Internet did not yet exist as even as a gleam in someone's eye. However, from what I've read, spinning rods of that day were assumed to have this slow "parabolic" action. From the 1960s on the deelopment of different resins and the easy way that tapers could be changed led to the rapid change in the actions of fishing rods. As rodbuilders we are all aware that the actionof a fishing rod depends many factors other than just the deflection modulus of the material used in the manufacture of the blank.

I sometimes wonder if language and mathematics fails us in trying to describe the flexing of a rod by saying it follows some purely mathematical function. I would think empirical functions would be of much greater use to us. As rodbuilders we simply can ignore the more abstract mathematics and apply the CCS methods to determine the relative power and the action angle to give us an idea of how fast or slow a particular rod blank is. If we can then add in the resonant frequency that Emory is trying to help us understand, we should be able to describe the characteristics of our rods better.

Mike Blomme

I'm a little late on this, but can give you an idea what bamboo rodmakers mean when they use the term. A parabolic action really has little to do with the shape of a parabola. It refers to a specific type rod action. Generally the action is thought of as having a flexible tip section, a relatively stiff mid section, and a flexible butt section. In practice, the rod has two distinct flex points; one in the tip and one in the butt. Rods with a "parabolic" action are a little tricky to cast until you get the feel of them because of the distinct flex points.

Where did the term "parabolic" come from? My guess is that it came from the graph of "parabolic" rod's "stress curve." Bamboo rodmakers credit Everett Garrison and Hoagy Carmichael with popularizing the graphs of stress curves. Bamboo rods can be roughly modeled by graphing their tapers as the deflection of a cantilever beam. If one graphs the stresses on a "Parabolic" rod using Garrison's mathematical model, the graph looks a little bit like a parabola.

For more information, consult "The Master's Guide...." by Garrison and Carmichael.

Hope this points you in a good direction,
Harry Boyd
maker@canerods.com

Harry Boyd

thanks for chiming in with your expertise harry. i'm new to bamboo and so shouldn't have added my understanding of it from a bamboo perspective, which differs from everything most stated so far here. but what you wrote is exactly what i've gathered from reading about bamboo. i think i have a semi-parabolic blank to wrap, a PHY driggs river and i'm looking forward to learning the action.

eric
fresno, ca.