OK, a question that has been swirling around my mind as I've been testing various spinning/casting blanks.

To 'predict' two blank's sensitivity assuming that they are the same power and action, I have been focusing primarily on weight. By this, I mean if two blanks are identical in every aspect, except for weight, I'd go with the lighter one and be confident that it would be more sensitive.

(We're not taking into account durability.)

At this point, I could not care less about what material/modulus/method they are made from. I actually don't even ask what modulus the blanks are made from anymore.

Am I correct or am I off somewhere? With two blanks of identical power and action, is it possible that one could find the heavier blank being more sensitive simply because it is of a 'better' material - whatever that means?

Thanks,
Mo

ps: Tom, would love to hear your thoughts. Appreciate your correction on blanks to my Airrus post last week and would love to hear your comments.

In purely simplistic terms, you're on the right track. Now, weight is weight, but weight distribution is something else. And each of these things, and some others, play a respective role in how a blank is going to perform and how sensitive it will be. But out of all the various factors involved in what most rod builders term "sensitivity" the one overriding factor is probably mass density. A lighter, more rigid blank is generally going to be more efficient and more "sensitive" than one that is heavier and softer. For the same stiffness, the one that weighs less should be more efficient and sensitive.

Consider how top woodworkers and turners look at power tools. Heavy, cast iron tools are prized for their ability to deaden or damp vibrations. Lighter and more rigid steel or aluminum tools pass any vibrations on to the user. Sure, less weight is great in a hand tool sometimes, but for large, stationairy machines, more weight or mass is desired in order to reduce or eliminate the vibrations the user has to deal with. So is a softer or more compliant structure.

While vibration is a bad thing with regard to stationairy power tools, it's a good thing as far as fishermen are concerned. So what you want, is something that is light and rigid, rather than heavy and soft.

This discussion may get on an additional track and one that I'll quickly address now. The naked blank is in its most sensitive form when you receive it. Anything you do to it is going to reduce the sensitivity. No, you can't bump up the sensitivity by adding certain types of materials in the handles and seats. You can't build resonant chambers that amplify vibrations. All those things sound good, but they won't fly in the face of reason and science. If you're going to amplify vibrations then you're going to have to introduce and add a system that is designed to do just that. The input we're working with on a fishing rod coupled with the small cavities and chambers often talked about, are not going to amplify anything to the point where you can feel it.

In general terms, and realizing that I'm leaving out some of the other factors that do play a role in all this, I'd say that for the most sensitivity, you want the lightest rod for any given amount of power.


...............

Tom is right... any company selling rods or blanks that claim an air chamber increases sensitivity, or that they do something to amplify sensitivity is hype... you can decrease damping and mass so that you have less loss of sensitivity, but you cannot amplify sensitivity.

A manufacturer might be able to increase velocity of sound propagation, perhaps that is what Lamiglass is trying to do. A builder might be able to increase velocity of sound propagation by using more metal in the finished rod in place of other materials... such as all-metal guides, metal or carbon handles (in the handles, if the metal is heavier than the material you were replacing it with, such as cork, it might make the handle heavier and the rod less sensitive... remember, it's a ratio of sound velocity to mass and damping. It's complicated... there are several variables at work at the same time.)... I even wonder if the metalized thread that is becoming so popular might add some measure of sensitivity if used to wrap guides. These are just my personal theories... I have not done any scientific testing.. but it's interesting, nonetheless.



Edited 3 time(s). Last edit at 04/18/2012 12:34PM by Gary Snyder.

Gary,
Tom is basically correct but the whole issue of sensitivity gets very complicated but it is not the relationship between sound velocity, damping and mass exactly. It is too complicated to try to cover very well here but hopefully the following is not too over simplified and will help a little.
The mechanical impedance of a rod is the square root of the mass density times the elasticity. Both the mass density and the elasticity are determined by the material that the rod is made of. As the mechanical impedance goes up the amplitude of vibrations will go up but the velocity will go down. The amplitude is naturally important but the velocity is much less important in terms of the sensitivity.
Resonant frequency has a much different effect. The rod will try to vibrate at its resonant frequency because there is a property of a rod called Q that dictates that it will take a lot more energy to make the rod vibrate at any frequency other than its resonant frequency. Q and damping are not the same thing but are closely related. The higher the Q the higher the damping factor or the slower the vibrations will damp out. Damping factor is really a measure of how rapidly the energy in the rods vibration will be dissipated, mostly converted to heat. Q is a measure of the rods ability to store energy and over what frequency range.
If the fish bite is a pull or an impulse rather than a frequency that impulse will be converted into a fundamental frequency and a whole series of harmonics of the fundamental by the rod but only the energy in the harmonics very close in frequency to the resonant frequency of the rod be transmitted down the rod.
One more point about velocity. The vibrations and also sound will travel at a little more than 1000 ft. per second in air at sea level. Most rods are going to have resonant frequencies that are roughly 2 to 5 Hz. or cycles per second and this is going to be roughly the frequency of the vibrations that are transmitted down the rod. So even at 5 Hz a cavity in the handle of a rod will have to be about 200 feet long to be resonant at that frequency, at 2Hz the cavity will have to be about 500 feet long. Think about how big the pipe in a pipe organ is to generate low frequency notes of say 50 or 100 Hz.

I know that several years back one of blank manufacturers were putting tungsten in their blanks. Because tungsten transmits vibration 125 times faster then fiberglass. They were some of the most sensitive blanks I had ever used. Unfortunately I sent my last one to the bottom of a lake about 8 years ago

Steve,
Actually the faster that a vibration travels up a blank the lower that the amplitude of the vibrations will be.

I see, Emory. It's much more complicated than I thought.

I am surprised how low a rods' resonate frequency is... 2 - 5 hz.... yes, I can see there would be no way to practically amplify a frequency that low... you would need a horn the size of a house probably. Talking about resonate frequency, I would think that higher would be better... I would think it would be more efficient.

I wonder also if a higher Q factor would make for a more sensitive rod... again, wouldn't it be more efficient?

Sound/vibration/sensitivity and rod blanks seem to have a lot of similarities to electrical curcuits... I would think they could be modeled as such in many ways... in fact, it's my understanding that carbon fiber is a decent conductor... probably not as good as copper, but I believe it can reasonably pass an electric current. I wish there was an easy way to measure rod and blank sensitivity... too bad we can't just test them with an Ohm meter or something, LOL... seems they are too complex, and would require a lot more testing and more sophisticated equipment.

Do you think that metalized rod wrapping thread used to wrap guides might do anything to a rod's sensitivity? You may find this hard to believe, but some inexpensive consumer RCA cables for home theater and stereos utilize metal impregnated thread as conductors rather than solid or mulit-stranded solid copper. If it's good enough electrically, maybe it might have some potential?

I have considered using non-ceramic metal guides, such as Recoils, to keep the finished rod lighter, but just can't bring myself to put them on a rod... I've done extensive testing with monofilament and found that lines start wearing quicker than many people probably realize... they start to wear down as soon as we start to fish and they begin to come into contact with anything hard short of ceramic guides. I once did a crude test on one of those SS304 guides... ran some mono back and forth across it about 15 times... it melted the line flat. the same test on a Fuji Hardloy guide had no visible effect on the line.

I know the metal guides are becoming popular, but I feel the need to stick with Fuji titanium concept guides at best to protect the line and shave weight.





Edited 1 time(s). Last edit at 08/13/2006 01:30AM by Gary Snyder.

Emory:
Which one of these definitions of the word amplitude are you applying to this subject .

am·pli·tude [ámplə td]
(plural am·pli·tudes)
n
1. largeness: a largeness in size, volume, or extent
2. breadth: a breadth of range
3. abundance: an amount that is more than required
4. physics distance from mean point: the furthest distance that a vibrating or oscillating system such as a pendulum travels from a mean or zero point
5. electronic engineering signal’s maximum value: the maximum value of an alternating signal
6. mathematics angle of vector representing complex number: the angle between a vector representing a complex number and the positive real axis


[Mid-16th century. Via French , from Latin
Encarta ® World English Dictionary © & (P) 1998-2004 Microsoft Corporation. All rights reserved.


Also , Why would a faster traveling vibration cause “lower that the amplitude of the vibrations”?
I am under the impression the faster a vibration the higher the frequency. But that suggests nothing of lower amplitude (your definition)

Gary and Steve,
Yes, the resonant frequency of rods is relatively low. You can get an indication of this by just locking down the butt of a rod, deflecting the tip and then releasing the tip. The oscillations in the rod that result are at the rods resonant frequency. With many rods it is slow enough that you can count the oscillations by eye for a period using a stop watch and measure it. many rods though will be too fast to count by eye and other techniques must be used to measure it. Everything shows up in the resonant frequency, the rods length, power, action , construction material. Generally higher is better in terms of sensitivity when comparing two very similar rods but if the rods have significantly different properties like length or power than a direct comparison of resonant frequency does not tell you much.

You can use electrical variables to model a rod rather than mechanical variables if you prefer because for each mechanical variable there is an electrical equivalent. Here are some of the key variables.
F ( force)=V(voltage)
X(position)=Q(charge)
k(spring constant)=1/C(reciprocal of capacitance)
v(velocity)=I(current)
b(damping factor)=R(resistance)
a(acceleration)=di/dt(rate of change of current)
m(mass)=L(inductance)
I can give you a lot of the math if you would like for example the formula for resonant frequency but I think that you will find that a rod blank is surprisingly complex. The fact that it is tapered(basically a cone) and the wall thickness varies makes the math a lot more complex than the math for say a beam or a tube

Why amplitude and velocity are directly related? Here is a web site that you can go to that will explain it much better than I can [physics.usask.ca/~hirose/ep225/anim] There are some good animations here that demonstrate the relationship and also some of the math.

I think that metalized thread will have an insignificant effect on sensitivity.

Q and Damping factor are neither good nor bad it depends. They do relate directly to resonant frequency. I will try to find a web site that will explain this as well. I am afraid that it will take me too long to explain it very well it here. But the higher the Q the better the ability of the rod to store energy and the higher the amplitude of the vibrations but over a narrower frequency range. Damping factor is the ability of the rod to damp out or dissipate the oscillations.

I hope this gets at most of your questions. If it does not come back at me and I will give it another try or try to find some reference material on the web that will help.




Edited 3 time(s). Last edit at 08/13/2006 10:14PM by Emory Harry.

I have no idea where that jumping icon came from. That line should read:
X is position and is equvalent to Q which is charge.

I should also probably explain the di/dt if you have forgotten or are unfamiliar with calculus symbols. di/dt is just the rate of change, in this case of current, or the first derivitive of current.



Edited 2 time(s). Last edit at 08/13/2006 11:01AM by Emory Harry.

Edit - "first derivitive of current (please add) with respect to time" - now please! be exact and complete when such important issues are at hand!

Tom - Now THAT icon is totally "kewel" and properly placed!

"Clyde Gator" and consorts have prepared a joint statement in reply to this thread. It will be passed to the editor of the Friday Funnies for approval before posting.



Edited 1 time(s). Last edit at 08/13/2006 01:11PM by Bill Stevens.

Bill,
You are absolutely correct that di/dt is the first derivative of current with respect to time. Sorry for the omission but I would have thought that the words rate of change of current would have made that obvious to you.
I did not realize that you found all of this so trivial and humorous. That being the case why didn't you jump in and answer Gary's, Steve's and Mo's questions.

Wow, thanks for all the read. I need to pull my engineering texts back out....:)

OK, to ask a simpler question: I place physical weight as the #1 characteristic of import when I evaluate two blanks of identical power/action. Is this appropriate or inappropriate when I'm trying to build rods that are as responsive/crisp/quick recovering/sensitive as possible. (This is assuming that both blanks are durable enough when used with care and not abused.)

Thanks for all the responses,
Mo

Emory;
I'm still waiting for you to answer my question?

Emory - Your ability to reasonably connect the sciences, i.e., both math and physics, to the world of fishing rods totally astounds one who has a little more than basic understanding of elemental lower power derivatives. As long as you keep it to the lower order and do not head off into momentum and inertial higher power derivatives we will continue to read with pleasure and interest while responding with good natured kibitzing! I only have the ability to fire the cannon and have no clue as to how to make the gun powder! The icon blew me away - I don't even know how to make one of the little yellow smiley faces or I would offer it for you at this point!

Bill,
Yes, I think that sometimes you fire the cannon and then have no idea where the bullet is going.
I do not have a clue where that icon came from. It just showed up and I could not edit it out.

Steve,
I thought that I answered it but I can see that I did not. Amplitude as you point out can mean a number of things but in the case of the vibrations traveling up a rod it is how much the rod actually moves. the more motion the higher the amplitude. What you sense when a fish bites is the movement of the rod. Did you look at the web site that I gave you. It uses a wave traveling up a string, if I remember correctly but the principle is exactly the same. The big difference is with a rod, because of the changing diameter and wall thickness, the amplitude is constantly changing.

Mo,
Yes, you are basically correct. Those factors will be closely related to the weight, all other things being equal. A better indicator for comparing the responsiveness, crispness, recovery time and sensitivity is the resonant frequency because everything shows up in the resonant frequency but it can be a bit more difficult to measure.

Emory;
Yes I did look at the site and all of the animations. What I did not was an explanation of my question.
Why would a faster traveling vibration cause “lower that the amplitude of the vibrations”? [your quote]


Or any thing that contradicts my impression
“I am under the impression the faster a vibration the higher the frequency. But that suggests nothing of lower amplitude “
Are you saying that if something ( a rod blank in this case) because it has a higher frequency would necessitate it have less movement (amplitude)?
And if so what are you basing that on?

I also saw nothing that would suggest adding tungsten steel fibers would do any thing to slow down wave transmission or lesson sensitivity.
To the contrary
Tungsten being much harder then fiberglass or graphite on the other hand should increase vibration just because of it’s hardness,. Which I can testify to based on the practical experience of using those blanks for over 10 ten years.







Edited 1 time(s). Last edit at 08/13/2006 05:09PM by Steve Gardner.

Unless I'm misunderstanding resonant frequency, it seems that resonant frequency would be very easy to measure. Just pick up one of those cheap gizmos that radio control airplane enthusiasts use to measure rpm of their prob and point it at the tip of a rod with the butt end firmly held against a heavy bench. Pull the tip and release and see how many oscillations the tip goes through per unit of time.

However, I just take two rods I'm comparing and 'plonk' them at the tip and see which one oscillates faster. I'd bet that the lighter blank of equal power/action will inevitably have higher oscillation.

Am I missing something?

Mo

Emory: I am no rocket scientist but I believe the Origin of the Leaping Monkey is somewhere in North Carolina!

The "smiley" was automatically generated by a particular keystroke that you typed in that spot!!

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!