- Rod Design by Deflection -

Is there such a method as designing a rod taper by deflection? It will be fantastic if there was.

To tell the truth, it actually exists. Let me introduce it.

At first, it is needed to assume the conditions how the rod deflects. For instance, do you assume such an image that the rod is deflecting by the lead weight hanged over the tip top? Or, the image where the rod is moved in a certain speed with any length of fly line? You may need to understand the assumed image of the subject rod's deflection.

Now we assume here that the rod is held vertically and moved horizontally in the speed of 4G (4 times of gravity acceleration) acceleration with a certain line length to fish out of the top guide. Under this assumption, we draw a rod deflection as an expectation that the rod would bend like this. Of-course, as it is impossible to draw such a deflection by free hand, we use a tool to do it. The panel shown below is the tool, called as "Deflection Designer".

The graph at left is the "rod deflection" we aim. The right graph is called as "Action Genome". It means the genome which is embedded in the rod. Haven't you ever seen this genome? Yes, it is very likely to Mr. Garrison's stress curve. After reading this entire article, you may begin to understand what Mr. Garrison's stress curve implies. The Action Genome is measured by the degrees of bend angle of the rod. Further, the difference between Mr. Garrison's design model and Max's design model, is whether the calculation is made based on the statically deforamated rod (not moved) or the dynamically deformated rod (moving). Max's dynamic calculation includes the time duration when the rod is moved from time to time. This is called as dynamic calculation for a dynamic rod model. There is another type of calculation as dynamic calculation for a static rod model. This means like this, even if the rod is not moved, as hanging a weight over the tip top, the rod will deflect changing its shape from time to time.

The Action Genome has the understandable definition and can explain the relationship with the rod deflection clearly. Let's see.

The x axis of the Action Genome graph populates one inch sections of the action part of the rod. The action part is the part which is the length from the point where your hand grips to the tip top, also called as Action Length. The Action Genome is the graph which plots the bend angle of each 1 inch section over the action length.

The Deflection graph is connecting each 1 inch section of the rod with the value of the Action Genome graph. Yes!, the rod deflection is drawn by manipulating the action genome. The rod deflection graph moves automatically by changing the shape of the action genome line. There are several control buttons which can change the shape of the action genome line.

There is the genome bank in the tool, to and from which user can invoke/save the designed action genome. It is also possible to input a specific bend angle number to the corresponding rod point. To increase/decrease the tip top tangent angle (the entire bend angle), there is a button to shift up/down the entire genome line. A button to keep the both end to a specified value and move up and down the rod point value within the range. A button to smooth out the line within a specified range. You can draw any shape of action genome for the rod. The rod deflection graph moves as soon as you change the genome. On the picture above, a very parabolic rod is drawn now. That is the one of Para 17 of Paul Young.

The tool can also manipulate the hardness/softness of the rod. The Expected Rod Angle field at upper center part, if specified with the smaller number, the rod becomes the harder, and vice versa. TipTop Tangent Angle has a tight relation to the action genome. As the bend angle of each 1 inch section means the bend angle against the previous 1 inch section, the accumulation of the bend angle of all the 1 inch sections becomes the value of Tip Top Tangent Angle.

In summary, by specifying Rod Angle, then specifying Tip Top Tangent Angle, you can have a general characteristic of the rod deflection. After that, if you manipulate the distribution of the number of Tip Top Tangent Angle over the action length, you can have several patterns of rod action, by the shape of action genome, such as parabolic, progressive, semi parabolic, even bend, tip action, body action, etc..

I hope you already have realized that you can create/generate any kind of rod action by this tool. From nothing, you can invent your own rod taper from the action genome.

But how to acquire the rod's dimensions? It is a kind of the s.e.c.r.e.t..

DynaRod program has the secret logic of converting the rod deflection to the dimension number of the rod. The DynaRod logic performs a similar calculation to the one used at NASA to trace the flight of their space shuttle. Very complex and very time consuming calculation is needed. But it is limited to the extents which an ordinary personal computer can perform.

Let's get back to the assumptions of the rod deflection which we referred to at the beginning. When you use DynaRod, you can apply such assumptions to this rod deflection, and get the result of the rod taper which actually actions like the designed deflection (or like the designed genome). If you apply an heavior fly line or an faster acceleration assumption to the same deflection, the results would become a softer rod taper comparatively than an ordinary assumption, and vice versa. Since the deflection is drawn expecting that the rod should deflect under the applied assumption, this design objective is more understandable than using a stress curve as an objective. (DynaRod also packages design model by Stress Curve.)

If we apply such an assumption to this rod deflection that the rod is held horizontally, the rod hangs a lead weight of some amount at the tip top, the rod is moved up in the acceleration of 1G (that means a statically deformated rod), we can get the resulted rod dimensions for the bate fishing rod used on the boat on the sea. The applied assumption can be in such wide variety as changing bamboo specie (Tonkin, Japanese bamboos, Chinese bamboo, softer bamboo, harder bamboo, according to the user's table entry), cross section (round, quad, penta, hex, octa), Solid or Hollow (fluted or dammed, and how much hollowed), the length of fly line to fish, the line wt. number, pieces of the rod, type of ferrule (NS, bamboo, upon user defined table, etc.), fish is on, etc.. Even carbon graphite or grass fiber could be applied as the material of the rod if you can specify the data in the bamboo attribute table by means of MOE and the weight per cubic inches.

Any rod could be designed like lure rod, spinning rod, bate rod, surf casting rod, spey rod as well as of-course our single hand fly fishing rod.

Max Satoh
June 9, 2007

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