North Australian FISH FINDER TM forums

We've sorted out the vibration characteristics of a hardbody lure (we think).

But is there a point where the length of the body "downstream" of the vortices from the bib interfere with the vibrations being generated?

There sure is.

The original "chimney, wharf, bridge and pole" doctor was a guy in Europe in the 1890s. His job was to design "fixes" to prevent structures from collapsing from the effect of excessive vibration (some from water flow and some from airflow).

The fix he designed for fixing chimneys is easy to see, is still used today and also applies to water.

He added a fin to the outside of the chimney to separate the chimney surface from the vibrations. Reduce the effect of the wind-induced vibrations.

Here 'tis for chimneys:


How it works:
Look what’s happened to the vibration. Its been moved back from chimney AND reduced in magnitude. Chimney doesn't fall down. You've all seen these spiral strakes.

So, what’s this got to do with lures?

Well, notice anything in the vibration image above? Compare it with an ordinary hardbody lure.

Anything on a lure that looks like a vibration reducing fin?

Yep, sure is. The lure’s body. It looks and acts just like the vibration reducing chimney fin from the1890s to prevent collapse. It IS a fin and it interferes with/reduces the stream of vortices coming from the base of the bib. It doesn't change the vibration rate 'cos that's set by the bib which is "upstream" of the body.

But it does reduce the magnitude/strength of the vibration.

Can we reduce the length of the lure body to reduce the interference? Make the vibration stronger? Yes, we can but only so far. To have no interference, the answer is to have no lure body. But how does that work?

It does 'cos we already use 2 other types of lures like that. With one type we've shifted the bib generator downstream of the body so that there is no interfering body "downstream". The other has the body and the bib all rolled into 1.

Trial and error seems to favour a compromise hardbody lure with a body length below 100mm. Getting smaller and not as strong as a full-sized body but pretty effective.

Useful to be able to generate max vibration? Very.

Why is the ability to generate full strength vibrations useful?

Hardbody lures and hard bite tactics

We’ve all come across these hard bite times particularly when barra fishing in winter. Trying to attract the attention of a barramundi seems like a hopeless and disappointing task.

You need to have “everything” going for you to achieve success. Much good advice has appeared on these pages (and others).

Lighter leader, suspending lures to keep your offering in the strike zone longer, smaller lures, differing retrieve rates have all been recommended.

Only one of these recommendations has achieved any modicum of success for me and that’s smaller lures. In the Fitzroy floodplain lagoons in winter, it worked. In the river it also succeeded. Not every time but it worked.

So I spent many hours trying to figure out why.

One of the more successful winter/hard bite lures I used was one of Rob Gaden’s/Halco/RMG masterpieces (Poltergeist). A lure designed for murray cod. Its worked in the NT (Daly and Roper rivers) and also in Fitzroy R Qld for barra.

Some of you should have noticed that a junior B52 and shorter versions of bomber lures do OK in winter as well.

You would all have seen the well-known one called a Poltergeist 80mm with a swimming depth of 5m. Bit deep for our floodplain lagoons which (even when full) don’t exceed 3 metres.

Yeppen lagoon (Rocky’s original water supply) is an exception with a “hole” of 11m which it still has.

Well, Rob designed a smaller shallower lure called a Poltergeist 50 mm which is what was successful as a smaller lure in the shallow lagoons.



Rob Gaden’s poltergeist in 2 sizes. Note that both lures are under 90mm in length. Why is that of significance?

Those of you who were paying attention when I was talking about “uncle” Vincence Strouhal, would have found how he reduced the wind-induced vibration to stop chimneys from falling down.

He added a fin to the side of the chimney to reduce the vibration. Here's the result.



Look what’s happened to the vibration. Its been moved back from chimney AND reduced in magnitude.

So, what’s this got to do with lures?

Well, notice anything in the image above? Compare it with an ordinary hardbody lure. Anything on a lure that looks like a vibration reducing fin?

How about the lure’s body? Yep, it looks and acts just like “uncle” Vincence’s chimney fin from the1880s to reduce vibrations.

To achieve the ideal situation of having zero effect on vibration, a hardbody lure then can’t have a body "downstream" of the bib to interfere with the trailing vibration-induced vortex stream.

But a lure can’t work with only a bib but no body.

Sure it can. Two other types of lures that we use already do but we’re talking about hardbody lures here.

So, increasing vibration strength with a reduction in lure body length is a compromise.

Now look at the “fin” on a hardbody lure. The body of the lure after the vibration generator (the bib).

An ideal comprise is a lure body of 90 – 100mm. That size body doesn’t change the vibration rate but it sure changes the magnitude of the vibration itself.

The only thing preventing our Poltergeist (only 80mm) from being ideal in lagoons despite it being an ideal length is its 5m swimming depth. With only 3m depth the Poltergeist 50 is manageable.

THAT’S why it worked for me. Smaller lure and not as strong but I’ve caught barra up to 85cm on ‘em. The full size 80mm poltergeist is built like a brick toilet so strength isn't an issue.

Think about any hardbody lures that you might use (100+mm in length). They’ll have reduced vibration magnitude compared to a 80mm version of the same lure.

Both versions of the Poltergeist will stir up the barra due to larger magnitude vibration attracting more attention in winter than longer lures. Other brands have similar lure size differences as well.

Note the difference between a Jackall squirrel 78 x 3m and a Jackall Super - Squirrel 115mm x 3m. Same vibration rate (same bib) but the squirrel is 78mm (32mm shorter) and well under the “rule of thumb” 100mm length.

So the magnitude of vibration is a no contest. Squirrel 78 every time. But retrieve very slowly to keep vibration rate down around the 600 beats per minute mark. Speeding up a retrieval rate does zip for the vibration strength. Just increases the vibration rate.

What are the two other lure types that operate with no interfering body?

Soft plastics (esp swinbaits) and soft/hard vibes.