non-flexible vs. flexible fly rod

[Walter]

Actually a true broomstick may not be possible but a near broomstick is easy. Just remove the tip section from most 4 piece rods. The remaining 3 pieces will be pretty close to a broomstick for bend. Matching the swing weight would be a bit more difficult but could be done by adding some weight to the tip of the bendier rod.

Making efficiency measurements would be harder but there is the "Lasse Casting Machine" used to compare two rods given identical casting strokes. This could at least give us an idea of which one casts farthest when using identical casting strokes.

After saying all that this is one case where modeling might be easier. (especially if someone else is doing the modeling)

[Merlin]

Yes Walter, this is another possible option, we can design a very very stiff fly rod but in that case the mass will change which has large consequencies on the energy input, and twists the comparison.

I guess Bernd wants to compare flexibility to rigidity first, and not blend altogether like in reality. Let's wait for his comments.

Merlin

[Walter]

Merlin,

Did you read my whole first paragraph? Swing weight = moment of inertia. This would be more important than mass.

[LaMouche]

The identical casting strokes get me a little worried, because it seems everyone assumes that you'll take a casting stroke suiting the flexible rod and reproduce it on the broomstick. My guess is that if we do the reverse, the flexible may well produce a tailing loop. My point being: I believe you may compare energy transfer at the first RSP with ceteris paribus clauses, but I don't see how it would translate reliably wrt. loop shapes or distance.

... or maybe I fail to understand the whole argument

[Merlin]

Yes Walter, I did. I used the word mass to align with Bernd´s initial post.

Merlin

[Merlin]

LaMouche,

There is no perfect comparison possible. Introducing the line in the comparison is very complicate. It would be simpler to start by maximum tip speed, making the blunt assumption that the caster is smart enough to produce similar loops in both cases.

Merlin

[Lee Cummings]

I'm certain I remember that grundes high speed videos showed that the maximum tip speed was achieved sooner with the "broom fit" overlay.

Lee

[Merlin]

Yes Lee, this is the time when the rotation speed is maximum. For the flexible rod, the maximum tip speed occurs very close to RSP, which corresponds to a later time.

I can't tell where Bernd is at the moment but in the meantime I made some virtual tests with my (representative) casting model. For a normal fishing cast, the efficiency of a flexible rod with some 30 feet of line is around 67%. Casting the same with a stiffness 100 times higher gives 50% (same swing weight Walter). If I consider the same energy input (a different casting arc), this does nor vary very much: 48% only.

In fact this issue has been already adressed in the forum, so the results are similar without surprise. The flexible rod is significantly more efficient, even if we consider the uncertainties. This comparison is limited to considerations about the line flight and loop shape, I leave that to people smarter than me in this area.

Merlin

[Bernd Ziesche]

In fact Bernd, when you said "to make it simple", you just made it awfully complex. Forget that and come back to our center of interest. I suggest we imagine it is possible to make a broomstick of equivalent mass to the flexible rod, although there is no material to make it happen. If you agree, then we can progress step by step and see how the picture goes on.

Hi Merlin and everyone else,
thanks a lot for all your help!
Yes, I now understand that "massless" was a bad idea to start with .
Ok, so let's compare two rods in the same length and offering the same mass and mass distribution while rod a) is none flexible and rod b) is flexible (like an avg. fly rod).
My question is, if transfering energy to the line would not be most efficient with a) the none flexible rod?

Walter already threw in the tip path to be optimized for the flexible rod. Yes, I agree for specific circumstances (as Walter perfectly described them). No, I disagree (as I know Walter agrees ) for how I would cast these two rods.
Of course I would adjust my rod hand movement to each rod.

What I want to know is, if the none flexible rod would not be more efficient in transfering energy to the fly line since there would be no loss by flexing and unflexing the rod itself.
In reality I know that the none flexible rod would be much more heavy, especially in te tip section. But still it is impressive that I could cast 33m (5wt. line) with Alejandros broomstick - even without any training at all. Imagine this rod to be as light as a flexible avg. fly rod and I could rotate it much faster! That should make for an looong cast for sure. And I have a feeling that this would be a tool offering me high efficiency in transfering energy to the cast. To be honest, I think I would outcast myself compared to the flexible (avg.) fly rod.

I am not after a comprison for one and the same arc. One arc can only match rod a) or rod b) better.
It would be like choosing a dead small arc and then the flexible rod would create a tailing while the none flexible one would produce an efficient cast.

I fully understand the advantages of the flexible rod. But I don't yet understand why bending and unbending this rod would not mean a transfer of energy on costs to the output into the fly line?
Thanks
Bernd

[Bernd Ziesche]

I guess Bernd wants to compare flexibility to rigidity first, and not blend altogether like in reality. Let's wait for his comments.

Exactly!