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Old 01-02-2012, 02:36 PM
silver creek silver creek is offline
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Default Re: Fly rod line rating, power, and action - an explanation.

Originally Posted by wabi View Post
Not disputing the fact that any particular rod is manufactured to be a specific weight/action/power, just saying if my 5wt fast action rod casting xx feet of 5wt line seems a bit too fast for me, a simple switch to a 6wt line often cures the problem. I know I didn't change the rod taper, but I did alter the way it reacts by changing the load the weight of the line put on it.

Yes, I'm fishing an overlined 5wt fast action rod, but the casting results are so similar to a 5wt medium action rod it will work for me.
My original post was intended to discuss the 3 properties of a fly rod. When the actual dynamics of casting are discussed it gets way more complicated. Because it is complicated we need to be very precise in terminology. I am not "picking" on you; but if you will allow me to use your post, I can use it to expand the discussion.

Allow me to say that I don't think you changed how the the fly rod reacts by changing the "load". The rod is designed to change the amount of flex with different loads. So the rod reacted exactly as it was designed. To say you or I can "alter the way it (the fly rod) reacts", is to imply you or I changed the action of the fly rod.

The fly rod does not know how far we are casting. It is a dumb tool. We place a load and it bends in response to that load.

There are two ways to change the "load" on the fly rod. The first is to change the M (mass) and the other is to change V (velocity). By changing M or V, you are changing what actually causes the fly rod to bend, and that is KE (kinetic energy). KE = 1/2 MVV

The KE formula shows that increasing M does not automatically increase how the rod bends. It is combination of M and V that changes the "load" and V is much more important than M.

Your post equates "load" with mass alone; it is not. The load is KE, and KE is not mass.

However, I do understand that your post assumes that the V is the amount of V needed to cast the increased M of the heavier line the distance you want. By changing the M, you had to also change V to produce the "load" or KE you needed to bend the rod. Where I disagree is that your post implies that changing the mass is the only way to cast the distance you want with a greater load on the fly rod.

The problem is that by misidentifying "load" as line weight, we further confuse what is really happening. In my view, the proper way to consider a fly cast is that both fly line mass and velocity create the "load" which bends the fly rod according to its designed action. Placing increasing loads (by either increasing the line mass cast OR the line velocity) bends the rod more deeply which alters the timing of the cast.

Therefore, to alter timing we can either increase mass or velocity or both, and increasing velocity is more efficient because it is square function of load (KE = 1/2 MVV). It does not take much increase in line velocity to bend the rod because load varies with velocity squared.

As an example, I can shoot line by using the "O" ring method. I can cause the rod to bend deeper by double hauling to increase line velocity. But when I release the cast, I can close the O ring and use the friction of the line against my fingers to bleed off KE and feather the cast so that it falls shorter than the cast would normally go. This is another way of "loading" the rod for a shorter cast. This method of feathering the cast allows a high degree of accuracy in fly placement.

Another factor that is ignored when we slow the timing of a fast action fly rod with a slower action fly rod is that even if timing is similar, the amount of rod bend is not. The bending of a fly rod brings the rod tip closer to the casting hand. The stroke path of the casting hand must compensate for the difference in the amount of rod bend in order to make the fly rod tip travel in a straight line for both the fast and slow action rod. Using the same stroke path of a slow rod for a fast rod leads to an open loop.

So when you say that overloading a fast action rod is similar enough to a medium action rod, you ignore the fact that you are an accomplished caster who unconsciously compensates for the differences in the rod shortening between fast and softer rod action. There are many things that we do unconsciously which we take for granted. They do not translate to less accomplished casters.

I can understand the tendency to say that going up in line weight slow the rod action, but if we instead say that it slows the timing; we more accurately describe what happens. Timing changes, but the rod flex pattern and the stroke path must be matched to the faster action rod and not the slow action rod.

Even more confusing, when discussing load and casting distance, is that load is just one of several factors affecting distance. Distance also varies with the loop configuration, the weight and aerodynamics of the fly, and wind among other factors.


"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

Last edited by silver creek; 06-11-2015 at 08:48 PM.
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