Good Vibrations 2

[DHeseman]

I am a fisherman in a discussion about vibrations with a fellow rod builder. The topic is what grip materials would best transmit a fish "strike" to the hand. Cork and eva foam are the most widely used grip materials. I say that by adding grahite rings in with the cork rings on the grip, it will transmit vibrations better than just cork. Is there a material property that defines how well a materail transmits vibrations? Thanks.

Dirk

 

[IRstuff]

It's not clear that perfect transmission is desirable. The detection of a bite is not unlike any other detection, in that there is a background noise that could be mistakenly interpreted as a bite.

Therefore, you ideally want to filter out the background noise and only retain the signal. Having a high transmission means that you'll have to do the filtering yourself, which is no easy task.

I suspect that the cork may provide sufficient filtering to minimize the false detections. TTFN

 

[DHeseman]

In certain cases, perfect transmission would be a wonderful asset. Actually, I can't think of a situation where it would not be ideal. When a fish strikes, it transmits a very distinguished signal. Also, when fishing lures on the bottom, I like to be able to "feel" what bottom terrain my lure is hitting. I am looking a way to compare how different materials transmit these vibrations.

 

[GregLocock]

At first I was going to ignore this. Then I realised that you are asking a very subtle question.

Your hand is a fairly soft material. A fishing rod is (comparitively) very hard. To get optimum energy coupling between the two you want to use a gradual change in 'hardness' (I'll come back to that in a minute) to minimise the energy that is reflected back from the interface.

OK, the property isn't really hardness, it is the compressive wave speed of the material, given by (Youngs modulus/density)^1/2

So, to a first approximation you need to use a material with a compressive wave speed mid way between that of your hand and the rod. I suspect cork is not a bad choice, tho it may be a bit soft.

You can also adjust the frequency response by making the grip thinner or thicker. The thicker it is the more high frequency it will filter out. Incidentally your hand is sensitive to vibrations up to at least 200 Hz, and I wouldn't mind betting that 500 Hz is more likely.

There's some things here I don't know - compressive wave speed of hands and cork being two of them.



Cheers

Greg Locock