Physics of vibration and motion

[froggerbass]

This may have been addressed previously but I could not find it. Looking for some explaination and interpretation regarding the physics of some of the more common vibration/ motion creation surfaces such as jitterbug lips, scroungers, chatterbait blades, and back joints on multi jointed swimbaits. Also, on the jitterbug lip, if you made a back section of a swimbait the shape of a jitterbug lip, would the action be similar or would there be too much deflection of the flow. 

 

Thank you and Merry Christmas!

[Anglinarcher]

The answer is 'it depends'.  Lots and lots of variables involved.

I seriously doubt any single simulation program could deal with all of the variables involved so it sometimes comes down to trial and error.

In my experience, if the front of the bait is thin, there would be sufficient water flow, but it would alternate to each side (hydrodynamic flutter).  There would still be alternating flow,  but much larger periods, with fatter bait fronts.

I hope this helps some, but this is a pretty tough question to answer.

[mark poulson]

Do a search for vortex here.  Vodkaman Dave has some good thoughts, based on his own testing and engineering experience.

[hazmail]

Froggerbass

Yep, like Mark says, Dave will tell you (lip surfaces)  it's all  related to vortices, he's all over this stuff.

Pete

[Vodkaman]

As stated above, it is all about vortices, more specifically the Kármán vortex street. If you go to YouTube and search for 'flat plate vortex street' you will find plenty of examples. These vids are fine for explaining what happens with a front lipped lure, but for rear lipped lures it is not the whole story.

Jointed lipless lures are also driven by vortices created around the nose of the bait. So, you have an alternating vortex flow which then interacts with the rear lip. You cannot consider the vortices as independent, the water flow is a complete or closed system were the vortices work together. If the lip width is tuned to match the nose vortices then a more powerful action could be developed (theory).

 

Here is a video of a round and square lip side-by-side. The different lips should have a slightly different oscillation speed, but you will see that the lures swim in perfect sync as the vortices interact.

 

 

[DingerBaits]

Great video! Thanks for sharing that!

 

[Anglinarcher]

Dave, I/we sure miss your tank and videos.  

[Vodkaman]

Anglinarcher - many thanks. I still haven't set up my workshop and so there will be no more videos for a while. I was doing a lot of fishing, 2x 3 hour competitions per day, but they would only let me use a specific bait, tapioca jelly flavoured to your own choice. I was doing well too, with a daily success rate higher than 50%.

I have a job now and so the rest of my activities are on hold.

Dave

[mark poulson]

Dave,

Is "twerk" the engineering term for the motion of a jointed rat's tail section?

[Vodkaman]

1 hour ago, mark poulson said:

Dave,

Is "twerk" the engineering term for the motion of a jointed rat's tail section?

I do believe it is mate, a rapid up and down motion.

Dave

[froggerbass]

Spectacular info. Thank you!