The truth of Stress Curve No.2

Here, let's see another difference of the rod design method between Mr. Garrison and Max Satoh.

In Mr. Garrison's mathematics, what is the meaning of "multiply 4 to the weight of all the rod parts"?
The meaning of "4 times of weight" can be described in such a manner as if we were in the space.  Weight=mass x gravity acceleration at 1m above the surface of the earch. 

On the other hand, when we move a rod in a certain acceleration, the force which the rod receives is calculated by the formula, Force = mass x acceleration.

In DynaRod, as all the calculation are done from the space oriented view point, all the rod parts weight are converted into the mass value.  Then the meaning of "4 times of weight" becomes; the entire rod, that is, fly line, top guide, snake guides, stripping guide, bamboo sections, ferrules are moved together in 4 times of gravity acceleration.  In other words, it assumes the rod is moving as shown in the graph below from right to left.

The vertical rod is moved horizontally.  This casting style is called as "Translated Rod" casting.  You hold the rod vertically and push your hand forward.  The skillful tournament caster must use this style. 

Mr. Garrison and his math. calculates the rod taper in this assumption. 

Then the rod deflects like below. (simulated by DynaRod). This deflection is the shape of the first resonated vibration. This resonation can load fly line weight to the extents of maximum. Then the maximum force can be stored on the rod. In general, the caster can feel that the rod is fully loaded.

On the other hand, we may not do this kind of casting in our actual fishing, do you?   Perhaps, we may throw our fly by the following casting.  As the rod is turned around the grip as a center, it is called as "Rotated Rod" casting.

This deflection is the shape of the second resonated vibration.   You can make this deflection by flipping your rod up and down, or right and left.  (referring to the left most curve on the above graph).  The load on the rod becomes less in comparison to the "Transfered Rod" case.  It is easy to feel the load on the rod by actually flipping the rod in both  ways respectively.   Or think about like this, in the "Rotated Rod" casting, the tip top is travelling more distance and the grip part moves less distance, in the same time duration.   It is obvious which part of the rod receives more acceleration.  It is sure that the tip front receives more force of inertia.  We can say that this casting style is the one which throw the entire line load by the front half of the rod.

Well, let's see the stress curves of the above cases respectively.

Mr. Garrison's case, the case of "Translated Rod" shows the stress curve of the next graph.  We can know that almost equal stress value is distributed over the rod. (blue line).

On the other hand, "Rotated Rod" casting shows the following stress curve.   The stress of the tip front goes high and that of grip front stays low.    The interesting thing is that both are the stress curve of the same rod.

Now let's come back to the main issue of this article.

Do those who design rod taper by Mr. Garrison's method, know that you are assuming the "Translated Rod" casting?   If not, when you draw such a stress curve as descibed in the "Master Guide", left up, right down, it is very probable to have a rod taper which butt section is very hard.  Though I guess the rod can be used....

When you are ordered to make a good tip action rod which is used in actual fishing field, do you see the resulted rod taper by multiplying 4 over the entire rod parts, I mean by "Translated Rod" assumption?    I guess that the skilled rod designer who knows well about the above differences, can design a good rod taper by trial and error.  But it is also probable that the good tip action rod might have a little harder butt section than the "to be" taper.

DynaRod can prevent the misled design caused by the misunderstanding.

Designing a rod deflection as the target, and applying the assumption of   "casting style" to it, DynaRod made it possible to design the rod practically.   Of-course, after understanding the above effects well, the design method by stress curve can be usable as it is also packaged within.

Interesting?  I think there must exist more useful rod taper than the one which we produce now.

Max Satoh
June 11, 2007