Shorter vs Longer rods sensitivity

[fissure_man]

How are you incorporating acceleration into the model?  Do we need more equations!?  ? lol

 

I don't think that considering a 'bite' as an acceleration instead of a displacement changes the assumption that the resistant force developed in the rod at that transient moment depends on its stiffness and how far it's been flexed. In other words, it still doesn't make the resistant force a constant.  

 

If a dynamic analysis is needed, I'm all ears. When it comes to transmitting a wave, I'm guessing that length doesn't tend to help

 

Quote

Sensitivity to weight at the end of your rod is just weight.

 

To be fair, everything I'm talking about is sensitivity to tip deflection or line movement (causing tip deflection). Hanging a weight from your rod is a known and constant force; what you feel is independent of the rods characteristics other than length - not what I'm after. 

[Deephaven]

Do you feel the tip deflection as it is happening or after it is fully deflected?  Does it stay fully deflected?  

 

I would ask the question in return.  How do you have tip deflection without acceleration?

[jbsoonerfan]

Boy, I just thought the guys in the IPT vs gear ratio threads were trying to show everyone how smart they are, you guys are really showing out for the crowd.

[Armtx77]

 

On 3/15/2021 at 10:08 AM, Catt said:

The most sensitive worm rod I've ever owned was a 5' 6" medium heavy fast Shimano Crucial.

 

The down side was I fish a lot of 12-18' of water, setting hook better be done with authority.

I bought two Diawa Tatula rods, late in the season last year. One was 6'3, the other 6'6" and I immediately started getting better hook ups. 

 

I am one of those guys, that has never met a hook set I didn't try to break their head open with. On of the club pros told me I should try shorter rods because of this habit and he is was right. I hook more fish.

 

My only issue was that both have a bit of broom stick feel to them, for being Medium/Fast rods. When I pick up the Falcon Low Rider, it feels like a buggy whip.

[islandbass]

10 hours ago, Teal said:

Yall had to break out the calculus and trig...booo

There’s still a few days of winter. Let them enjoy the reminder of the winter blues, lol. I was. 
@Deephaven and @fissure_man

thanks for the physics discussion. I Haven’t seen such math in probably over 20 some years but just following along brought much of it back quickly. I love the beauty of F=ma. ?

[fissure_man]

9 hours ago, Deephaven said:

Do you feel the tip deflection as it is happening or after it is fully deflected?  

 

Both. The premise is that the angler detects the change in M_A that results from the bite. In a static sense, maximum change in M_A occurs at the maximum tip deflection, so we analyze that case. We're looking at the end point but it's a gradual process. To use the same equations for the interim state, an assumption would need to be made that the deflection is happening slow enough that the resulting tip force at any stage can still be estimated based on deflection and the stiffness properties + length of the rod (i.e. ignoring any considerations of dynamic or inertial effects). Depending on the scenario (rate of change, damping properties of the rod, etc), this may or may not be valid for the interim state. However, plugging in F=ma to the static equations doesn’t solve this complication, and, IMO it doesn’t make sense.

 

9 hours ago, Deephaven said:

Does it stay fully deflected?  

 

It might, or might not, depending on the situation. I don’t think it matters to the discussion.

 

9 hours ago, Deephaven said:

How do you have tip deflection without acceleration?

 

Well, it depends on what you mean.  The rod can be in a flexed state with no acceleration occurring – that’s the ‘static equilibrium’ these equations solve for. The internal forces don’t go away because acceleration = 0, it just means that the net force on the system is zero. The rod (supported by the angler) exerts an upward force equal to the downward force of the bite, and nothing is accelerating. Same as if you press your hands together – you're applying force, but zero acceleration occurs because you’re pushing equally hard in opposing directions.

 

On the other hand, for the rod to transition from an unflexed to flexed state, some motion (including acceleration) has occurred. Conceptually, when the line starts to move, the tip moves as well until the resulting force from rod flexure is equal to the force applied by the ‘bite.’  At that point, again, forces are in balance and acceleration is zero.

[NHBull]

10 hours ago, jbsoonerfan said:

Boy, I just thought the guys in the IPT vs gear ratio threads were trying to show everyone how smart they are, you guys are really showing out for the crowd.

I read all the post and looked up a few of the formulas and am amazed that all the wicked smart ( Boston voice) post don’t answer the op’s question ?. To the OP, keep pointer finger under the line.  That said, I will reach out to the Wicked Smart anglers when I need need to help my grandkids with there arithmetic homework ?

[Deephaven]

1 hour ago, fissure_man said:

Well, it depends on what you mean.  The rod can be in a flexed state with no acceleration occurring – that’s the ‘static equilibrium’ these equations solve for. The internal forces don’t go away because acceleration = 0, it just means that the net force on the system is zero. The rod (supported by the angler) exerts an upward force equal to the downward force of the bite, and nothing is accelerating. Same as if you press your hands together – you're applying force, but zero acceleration occurs because you’re pushing equally hard in opposing directions.

My question was more straightforward than the rest of our discussion.  If the premise is that the angler feels the fish due to tip deflection then that deflection has to occur.  As it deflects it is then felt, this is a motion which is driven by a force and therefore is most easily described by acceleration.  As with the rest, the approximation has to be that the static is assumed to be ignored because without change there is nothing to feel.  

1 hour ago, NHBull said:

I read all the post and looked up a few of the formulas and am amazed that all the wicked smart ( Boston voice) post don’t answer the op’s question ?. 

It was answered, albeit not in a way that provides any clarity.  Functionally speaking longer is more sensitive with all things equal, but never being equal rod make up is just as important.  

[fissure_man]

If the “doink” (scientific term) of the bite in terms of line movement was charted out on a displacement vs. time chart, you could take a couple derivatives and plot out the acceleration.  But to determine the resulting force at the rod tip, you still need to take into account physical characteristics of rod, either dynamically or in a static calculation. Intuitively, wouldn't you agree that the same “doink” on an UL/slow rod results in a different force at the tip (F_B) than on a HVY/fast rod? It's like hitting a punching bag vs. a brick wall. That's why it doesn’t make sense to consider F_B as a constant when comparing rods. In general this is why, IMO, the flexible beam analogy is more valid than the rigid lever.

 

37 minutes ago, Deephaven said:

As with the rest, the approximation has to be that the static is assumed to be ignored because without change there is nothing to feel.  

 

Not really sure what you mean here, but using a static calculation doesn’t mean nothing changes, we're just considering forces at a given point in time. Ultimately we’re comparing one state to another (“bite” vs. “no bite”). 

[Boomstick]

From simple physics, the shorter rod should be more sensitive as there is simply less material to go from the tip to your hands. Do you actually notice? Especially if it's a 7' vs a 7'5"? Probably not.

[Deephaven]

23 minutes ago, fissure_man said:

If the “doink” (scientific term) of the bite in terms of line movement was charted out on a displacement vs. time chart, you could take a couple derivatives and plot out the acceleration.  But to determine the resulting force at the rod tip, you still need to take into account physical characteristics of rod, either dynamically or in a static calculation.

Ah, I am referring to the force causing the reaction on the rod.  The doink in this case is one of three things (great simplified of course): the fish accelerating the bait from a velocity of 0 to something, the fish changing the motion the angler is imparting into another direction, or the fish stopping the motion.  This fish applies an acceleration or deacceleration to the bait.  What happens next depends on the length of the lever and it's material make up along with the line characteristics.  The fishes force on the bait is what causes the change of motion in the tip that we then end up feeling.