I am wanting to build a sensitive feeling rod for crappie I do not understand if I need a blank with action in the end of the blank or slow action for the most sensitivity.In other words I do not understand x-fast,fast etc. action on a blank Thank you Morris Cross

im not sure about sensitivity but we use fast action for snook because it only bends near the tip of the rod and its good for hooksets and finesing lures...not sure if you need that but if its anything like fishing for snook i would check out a fast or extra fast action rod

Try a lamiglass LSJ700 I built one on this blank and i love it. You can really feel your fish!!!

Extra fast is the most sensitive i believe, according to my rod building books anyway. Look at the St. Croix Legend Elite, its what i use for crappie. Its a 5 foot 9 Ultra Light. Super sensitive, thats why i picked it.

Actually for two rods of equal power as measured using the Common Sense System the one with the slower action, lower action angle, will be the more sensitive.

I guess I've always sensed what you maintain Emory as I prefer slower actions on my three weight fly rods generally fished in smaller streams with lighter fish. I am interested in how that relationship between action and sensitivity is explained however.

Stan Grace
Helena, MT
"Our best is none too good"

Emory,

How are you defining and measuring sensitivity?

A Panfisher with a super ultra fast and light strike tip strike detector would disagree with you based on the ability to sense a tip deflection. I would also think that if the slower action rod was measurably heavier, then your statement might not fit the vibration equations?

I'm glad to see you posted on this though I sent you an e-mail on that other sensitivity thread a while ago. I didn't hear back so I added some comments for consideration on your upcoming article:

[www.rodbuilding.org]


mark

For crappie I would go with a slower action rod as the old paper mouths do not require a hard hookset and the slower rod will be a bit more forgiving while fighting them. This will keep you from ripping the hooks out of their mouths while fighting and hooking. A faster action rod would be more sensitive but you do not require the extreme sensitivity to tell the difference between some gravel on the bottom of a river while drifting worms and the short 2-3 tap nibble of a curious trout. I would sugguest a nice 2 piece 4 or 5 weight moderate/fast action fly rod blank that is 6- 8 ft long. It would give you an extremely sensitive yet forgving rod. Depending if you are fishing standing brush and need the reach and backbone or just open water would determine the weight and how long.

You cannot damp out vibrations quickly enough to prevent them from reaching the fisherman's hand. Damping factor plays almost zero role in rod sensitivity. And, the faster you damp out a vibration, the stronger it will be when it reaches the hand. The more slowly the structure damps it, the weaker it will be when it reaches the hand.

The more the rod moves, the more sensitive it will be. However, even between fast and more moderate action blanks, you'd have to discern whether we're talking about one deflecting more than another, or simply deflecting the same amount in a different area.

...........

Mark,
I did not get your e-mail. Try again at {[email protected]].
I do not quite agree with what you said in the post that you reference above. I understand Fourier Analysis and how an impulse can be converted to a broad spectrum of frequencies and a rod will tend to do this but the mechanical impedance of a rod increases with frequency but then drops dramatically at the resonant frequency of the rod. This means that most of what is felt is at the resonant frequency or much lower. Higher frequency components are highly attenuated. The initial impulse can be felt or the lower frequency components but the higher frequency components will not normally be felt.
As far as how I define sensitivity is concerned, if you will wait for the article I think that you will understand. But basically I define it as what portion of the movement either in the line (mainly longitudinal movement or vibrations)) or the rod (mainly transverse movement or vibrations) get to the fisherman's hand. An ME would call it displacement but you can just think of it as movement. You do not sense anything at your hand other than movement.

I forgot this. The main reason why a slower action rod with a comparable power to a faster action rod will be more sensitive is because the mechanical impedance, you can think of this as the resistance to movement, increases more rapidly with a faster action rod than with a slower action rod. The mechanical impedance is determined by the square root of the mass density times the elasticity but elasticity is a property of the material not the rod. For the rod itself it is the square root of the mass density times the stiffness. And the stiffness of a fast action rod increases more rapidly than the stiffness of a slower action rod. In other words, any movement or vibration at the tip of the rod will be attenuated more before it gets to your hand by a faster action rod than a slower action rod because of the higher mechanical impedance of the faster action rod.

Mark, I am building crappie rods in a spinning blank setup, but I am using 2wt fly rods, one in a 7'6" St Croix, medium action, and 2 in the forecast line, 6'6" 2wt fly rods, and building them in spinning blanks also. All three blanks are 2 piece. I was given an article out of an In-Fisherman magazine, and using this type of setup, you can use 1/100th oz jigs and heavier, they will cast well and are excellent in sensisitivity to bites. I can't recall the article date nor the author, but he seems to have the expertise, as he has been crappie fishing for many years with many different setups. The extra lenght is also great when you are fishing in pockets in cover. I can't wait to try them out. I also have built on the SCV 5'9" and they work well for perch, crappie and bluegill. The fly rod blanks are about a third the cost of the SCV so they really won't be expensive to put together.

Emory,

There are a couple of general concerns about what you are saying here. When you talk about resonant frequency and mechanical impedance…. those concepts apply more generally to a system which is continuously driven. I would submit that what typically happens in the case of a fishing rod is that the rod receives a stress pulse which is more transient in nature and the complex waveforms go into free decay.

I’d have to know more about your experiment though if you are grabbing the tip and driving to equilibrium at a fixed frequency and amplitude, what your saying fits a better description. Again though, I don’t think that a fixed frequency and amplitude experiment mimics the fishing situation as well as a transient tapping mode would. Picture a crankbait bumping over a rocky bottom….


But set that aside for a moment and consider some similarities between the equations that govern a driven vs. a transient system. Like systems in free oscillation, the response of mechanical impedance in a driven system has both an inertia term as well as a damping term. The inertia is dependent on the mass and shape of the sample and there is also a modulus term in as well. My main point then……There could be a pitfall in this case if you compare the amplitude of vibrations in rods of different actions just based on comparable power alone in that you’re ignoring the mass term. It is very possible to have two rods with different actions that are similar power, but the slow one could substantially outweigh the other. The heavier blank, would act much like the case of a mass damper which of course can attenuate the amplitude of transmitted vibrations. So in either the case of free or driven vibrations, the general dependencies are very similar. Let’s assume that the damping is low and also is the same in all rods, so drop that term for the moment. Now your problem becomes exceedingly simple and as I’ve mentioned in the past the amplitude of the vibrations are largely dependent on the inertia of the system….no surprise.

Then of course it’s very interesting to see what the various line types transmit (through water) and what the hand can detect, especially in the frequency domain.

mark

Tom,

With regard to what you said about damping, I really don't understand at all what you're saying. It sounds like you're trying to make some kind of qualitative description of damping, but you've got it backwards. The greater the damping, the weaker, or lower in amplitude each successive cycle of the oscillation becomes. The damping from internal friction represents the exponential decay, or loss of the elastic energy with each cycle.

Two common ways to damp oscillations are by a large mass of low damping material...a mass damper, or even much lesser amounts of high damping material. Materials with high damping factors can very effectively damp vibration, particularly high to moderate frequencies over distances of millimeters. Lower frequencies penetrate much deeper into structures. A few years back Orvis published some interesting work in this area of damping vibrations and decreasing settling time in fishing rods by applied thin coatings. I think they may have even gotten a patent on at least one of the concepts. I'll see if I can find a reference.

mark

Here’s a pretty decent reference on damping as it is described as the loss or dissipation of mechanical energy. Damping doesn't cause a compression of the signal, but rather an exponential decay in each successive cycle of the oscillation at a given frequency.

[www.mfg.mtu.edu]


Here are links to a couple of the Orvis patents. In these cases they were able to demonstrate the damping of unwanted vibrations through the application of a layer of damping polymer inside the tip section and also though a thin layer of damping material placed between the rod blank and the grip.

If the links don't work you can search them up by these numbers: 6,360,475 and 6,092,324.


[patft.uspto.gov]


[patft.uspto.gov]

mark