The above graph basically shows the reasoning and is a complex way of saying:
Sage GII.........L[8]=70", L[9]=68.2, L[10]=66, L[11]=65
It predicts that for the Sage GII an 8 wt head will flex it in casting to a lever length of 70", a 9 wt to 68.5, and so on. It also states that the static weight equivalent of casting an 8 wt is 4800 grains, a 9 wt is 5300 grains...and so on. It superimposes two graphs, the real shortened length vrs weight graph......and the line wt specific static weight equivalent vrs shortened length.
QUESTION:
"Is what you’re proposing as simple as weighing a given length of fly line head, possibly plus the leader, and possibly plus a fly, then hanging that weight from the tip of a rod that is horizontally anchored at the handle, then measuring the vertical drop of the rod tip?"
ANSWER
No, nothing that simplistic or invalid. I am proposing that through the force applied to the lever, out at the end of the lever there is a force applied to the line tied to the line/mass causing a constant acceleration. For a given mass the average comfort zone of that force can be defined and set. The question then arises whether that average comfort zon force is different for accelerating lighter and heavier masses...which I think is true. Otherwise I could use just a single Force and have a REALLY simplistic model. But one does testing and defines the comfortable averaged force to accelerate a 210 grain mass, 240 grain mass, a 310 grain mass and so on. If it is the same, eureka! And we have an even more simple model. If there are differences...we then have the Force for each mass. One then presumes that there is a potential weight, with the acceleration of gravity, which acts as a similar Force, if not precisely identical, when hanging on the tip of a horizontal rod. We either accept the mass that creates the most identical static flexion to match our standardized casting flexion or consider some minor adjustments but that weight, specific to the actual casting mass it represents, becomes the testing mass to be hung on horizontal rods to predict casting flexion.
Look at the last graph I put up in the REPLY to the thread. The horizontal axis is in grains. Since I had determined in my static weight x flexion testing that 5900 grains on the Sage GII caused a 50% flexion...and that in my casting photographs with that rod and 300 grains of mass a 50% flexion was at least ballpark...for a ballpark demonstration I then set Force [300] at 5900 grains.(x gravity).
The graph is the lever length vrs hung weight for that rod. There is given lever length of that rod for for every weight x gravity=Force. I could have simply marked the 5900 mark on the bottom line as the equivalent to F[300] but made a separate axis. Then I made up possible figures for F[210], F[240] and so on just to show how this would work.
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