One for the physicians

Northantslad

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Watching a programme the other day and an angler using a trimmed pop up to imitate a dog biscuit, yep no problem there, works well.

On trying to alter presentation to get a take, which he did, he advised that he had just trimmed it down further to make it sit lower in the water.

So..
Is it the displacement principle coming into play here and it would then sit lower in the surface film?
I wondered if lighter perhaps, then it would perhaps sit higher up and be more susceptible to the surface film counteracting any displacement principle?
Or would it indeed sit lower, as with being a pop up, trimming it has taken away some of its further buoyant material?

Would it actually have sat lower or higher, or little change and why?
 

brian carragher

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I'm not a doctor ;) but my understanding of physics would be changing the size of the biscuit makes no difference to how it sits in the water, the density of the biscuit can't be changed so it's all relative to the water/biscuit density as to how a bait behaves
The only way to alter density ratios is to either add or subtract buoyancy
Well that's how I see it, hopefully there'll be a few responses
 

squimp

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A hook has a fixed weight (mass) that will counteract a fixed amount of buoyancy.

so IF (for example) a 1cm cube of foam holds up a size 6 hook; if you gradually shave bits off the foam it will bit by bit sit lower in the water and eventually start to slowly sink. The mass of the hook has remained constant but the buoyancy of the foam has been gradually reduced.

A while back carp anglers were obsessed with ‘critically balanced’ pop ups and that was achieved either by shaving bits off the popup (less buoyancy) or sticking a bit of lead wire into the popup and trimming the lead wire to have the reverse effect.

Fly anglers do a similar thing; we tie the same fly dressing on different weight hooks - it changes how the fly sits on the surface (dry flies) or how fast it sinks (wet flies).
 

spanky

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A hook has a fixed weight (mass) that will counteract a fixed amount of buoyancy.

so IF (for example) a 1cm cube of foam holds up a size 6 hook; if you gradually shave bits off the foam it will bit by bit sit lower in the water and eventually start to slowly sink. The mass of the hook has remained constant but the buoyancy of the foam has been gradually reduced.

A while back carp anglers were obsessed with ‘critically balanced’ pop ups and that was achieved either by shaving bits off the popup (less buoyancy) or sticking a bit of lead wire into the popup and trimming the lead wire to have the reverse effect.

Fly anglers do a similar thing; we tie the same fly dressing on different weight hooks - it changes how the fly sits on the surface (dry flies) or how fast it sinks (wet flies).
What he said.

You might also need to consider that by changing the shape could also change the surface area which might change the way it sits in the water and also if the finished surface of the original bait was more water-resistant than the inner structure that you've just exposed, this could disproportionately change the buoyancy.

But, ultimately it's the buoyancy of the bait vs weight of the hook that will effect how it sits in the water.
 

Dave

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By pop-up I'm assuming you mean a buoyant bait anchored to the bottom?

The same principle that wafters (and other brand names use) critically balanced against hook weight so that they lift off the bottom, and move, with the minimum of effort. A fish comes along and when it sucks in the bait the resistance is minimal and the wafter or boilie gets sucked in easily compared to sucking in a heavier or more buoyant bait that would offer more resistance.
 

squimp

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By pop-up I'm assuming you mean a buoyant bait anchored to the bottom?

The same principle that wafters (and other brand names use) critically balanced against hook weight so that they lift off the bottom, and move, with the minimum of effort. A fish comes along and when it sucks in the bait the resistance is minimal and the wafter or boilie gets sucked in easily compared to sucking in a heavier or more buoyant bait that would offer more resistance.
Sometimes ‘minimal resistance’ is counter-productive. Watch some (eg Korda) underwater footage of feeding fish and you will soon work out why.
The current trend in carpfishing is back towards over-weighted pop-ups.

Issues like hook and bait separation are critical and Understanding what the hook actually does when it is in the fish’s mouth.

As an example I actually put weight on my hook link with bottom baits. And it isn’t just to stop the link looping up off the bottom.
 
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