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## Counterflex, energy loss and absorbation

Moderator: Torsten

Merlin
Posts: 1470
Joined: Wed Jan 09, 2013 8:12 pm
Location: France

### Re: Counterflex, energy loss and absorbation

Hi Gordy

I am sending you a paper explaining the principle of calculation and another one with an example (a cane rod). It is necessary to take the rotation into account otherwise you have mo butt = 0 and mo mid = 0. This is what makes the experimental measurement of mo butt and mo mid extremely difficult from an experiment (to be imagined at this time). The MOI I use is the one taken at the grip of the handle (not taking into account the reel seat), nothing new here. It is measurable in different ways (Grunde's method or the pendumul one which you have experimented). In the same paper you will find the explanation for speed evaluation: I use a small deflection curve. I tested a first mode deflection and the difference is marginal.

There is the explanation of the basics of the methodology in the document "The physics of the overhead fly cast" which is somewhere on the forum. In that case I use a "spring & marble" model to derive the equations, since they are much simpler. For technicians the "equivalent mass" of a simple spring is well known, it is one third of the mass of the spring. Now if the spring is moved forward, it is wrong to use the equivalent mass of the spring to describe its kinetic energy, you must use the total mass of the spring. This contradiction can be resolved with the two other equivalent masses. Amazingly, they also are 1/3 of the mass of the spring in that particular case. So when one calculates the kinetic energy of the spring which is bending because of the inertia of the marble, the total mass of the spring is taken on board and you have total mass = 1/3 +1/3 +1/3, the same type of equation which I wrote for a fly rod, considering the MOI this time.

SDM is visible on a video from Server Sadik, as he casts a rod with a transparent cup (and a strange line to load the rod). One can see the rotation of the butt practically stopping briefly at RSP, before rotating again. The "mass transfer" is what causes the tip to kick back at the beginning of the cast if you use too much power. Those phenomenon do exist

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life

Paul Arden
Posts: 13811
Joined: Thu Jan 03, 2013 11:20 am