Hi Ron,
I agree with this … BUT that is not the question that I am asking. I want to know what the optimal bend is for one specific set of circumstances.
If we made a robot that copied your best movements on your longest distance cast and swapped out different rods, we would eventually find one that threw further than what you were currently using. So in theory, there would be an optimal rod bend for robojoeblogs, and the taper would be more tippy orientated i would imagine. In reality, the optimal window would change, as no one has ever or will ever throw the same loop twice. We aren't robots, and the optimum bend you speak of would always change, as we are human. Also, when we haul we apply much less force to the rod for the same line speed, so this would significantly reduce the bend, it's a very complicated question that seems easy to answer. It's not that important until we go to the absolute extremes of stiffness, for distance casting you dont want much bend because the rod has to unbend, and that counterflex is pulling the line off-target and reducing line shoot. To reduce counterflex we either use a stiffer rod, use thrust, or just haul much faster whilst taking out the force input on the rod hand, it's not only the rod that contributes to line speed.
See below;
Consequently there is no optimum rod bend, it depends on the caster, and the most powerful caster should be able to make a broomstick work. In fact I do not think that there are many casters able to cast a 1.5 Hz loaded rod with a large weight. I am curious to know the (linear) stiffness of a ST27 or T38 rod. I guess such rods are tuned below 1.5 Hz. There is a lower limit at about 1 Hz loaded, which corresponds approximately to a normal rod casting more than 60 feet of line outside the tip.
Even if the industry developed a standard — and I think it should, it would only indicate how much force it would take to bend the rod a certain amount. Then all the other factors — namely the casters strength, speed, and style; the line type and weight; and finally the atmospheric conditions would come into play.
To me it’s crazy that we, as fly fishermen and fly casters, can’t pick up a fly rod, read the flex rating, and know how that rod will perform. With this objective rating system the caster could, through experience and experimentation, choose the rod that he thinks will work the best for the conditions and what he is trying to do.
A good caster will make anything work, i suppose it depends on what level you are talking. General angler or an elite distance caster? There never was and never will be a standard for rods i'm afraid, the number on the rod is always someone's opinion, and most of the marketing blurb talks about rod load as being the reason casting works, and it's not.
All rods are progressive in action, but a rod that is very tippy to start off with is probably the best for extreme distance, i know rods with soft butt sections are quite bad, and i have had experienced just that with a well known brand. It was so bad that i took it back and got something else.
So to answer your question, yes, there would be an optimal bend, if the caster didn't change and was a robot (theoretical) in reality we just bang different lines through rods to see what happens, you can use the common cents system to see what type of taper it has, though.
What casting level is this aimed at? In a practical sense, the answer is relatively easy. You do a certain amount of casts with different rods to see which one you throw the furthest with, under the same conditions that you have already mentioned. This is how i picked my current new rod, the only reason i changed is because the rod butt kept slipping off my arm with the cradle grip, and i wanted one rod for all the British events in the afternoon.
Maybe later on i'll find a stiffer rod that gives me slightly more, but i doubt it. I'm about the same with a 690 and a 990. The 990 does give me some more distance, sometimes. Not all the time, so i need to practice more, and this is the key. I use the 690 all the time for fishing, and this is the one that throws the furthest for me, in fact it gave me a new #5 PB of 139'.
Difficult question, there isn't an optimal bend in the real world i'm afraid, not a practical one anyway.
All the best
