Archimedes Dunk Test

[mark poulson]

35 minutes ago, gliders said:

Bob p, that's a method I use a lot on fry feeding trout and other predators over here, we call it fishing on the drop and I make patterns designed purely to be taken on the slow descent when predators crash into fry shoals and then pick off the stunned victims. 

 

That's exactly how a Duo Realis Spinbait 80 falls on a semi-slack line.  It's slightly tail down, and wobbles side to side as it falls.

[gliders]

Had a look mark, interesting looking lure. These type of spin baits not really used over here, have toyed with some experimenting with spin props..

[Speckledtroutfish]

Does the test work with brackish or ocean water? Will the salt skew the results?

[mark poulson]

On 10/16/2017 at 5:09 PM, gliders said:

Had a look mark, interesting looking lure. These type of spin baits not really used over here, have toyed with some experimenting with spin props..

I bet they'd work on both trout and salmon.  Those fish eat other fish, bigtime.

[Vodkaman]

Speckledtroutfish - you would have to apply an adjustment factor. Sea water has a density of 1.025. As for brackish water, the density is likely to be variable depending on the tide.

You can establish the water density with a brewers hydrometer, easily available and not expensive. If you can establish the water density, I can create something for you, perhaps a spreadsheet that will make it easy.

Dave

Edited February 16, 2020 by Vodkaman

[gliders]

On 2/16/2020 at 4:46 PM, mark poulson said:

I bet they'd work on both trout and salmon.  Those fish eat other fish, bigtime.

Hey Mark,sure they would, our Atlantic salmon stop feeding long before they run our rivers. I did build a few prototypes for pike, maybe get back to them in a few months, I bought a hundred stainless props plus cups !

[mark poulson]

On 2/20/2020 at 3:21 PM, gliders said:

Hey Mark,sure they would, our Atlantic salmon stop feeding long before they run our rivers. I did build a few prototypes for pike, maybe get back to them in a few months, I bought a hundred stainless props plus cups !

Gliders, salmon are some really strong fish.  

I caught a 30" plus male salmon here on the CA Delta, on a wiggle wart, and he twisted the rear hook hanger 90 degrees!

[Hillbilly voodoo]

10 hours ago, mark poulson said:

Gliders, salmon are some really strong fish.  

I caught a 30" plus male salmon here on the CA Delta, on a wiggle wart, and he twisted the rear hook hanger 90 degrees!

yup big springs/chinook are good at wrecking lures and burning gears out of reels 

You may already do this and I know it still can bind at times. A swivel or bead chain is how I limited the abuse on my salmon plugs and spoons. Big springs destroy hook hangers and split rings if they bind them up and roll

Not really an issue with other salmon species 

[DGagner]

I love this topic. I taught it to 7th graders for a few years.

The metric system is cool in that it has standardizations you just can't do easily in the standard system.

When talking about water:

1 gram = 1cm3 = 1 ml

Water has a density of 1 gram per cubic centimeter. So a 1 cm cube block of water would mass at 1 gram. You can do a lot with this.

There are two ways to make something float more. Make it bigger for it's weight, or make it lighter for it's size.

Take a 50,000 ton block of steel. It sinks. Shape it into a battleship and it floats. It has nothing to do with the air in it. It's the size. The same block of steel, when made larger will float more in water. It's size has to get larger than it's weight (to put it roughly).

If you have a lure that has a mass of 10 grams, and is 10 cm3 in volume, it won't float or sink in water. It will stay at the level it is put at.

If you have a lure that has a mass of 10 grams and is 11 cm3 in volume, it will float in water. And sink if the numbers are reversed.

Oil has a density less than 1 gram per cm3. So the same lure will sink in it. And of course oil, which seems denser because it appears  thicker than water is actually lighter, oil floats on water.

This principle causes submarines to work, weather to happen, plate tectonics to occur, computer chips to be made... and a myriad of other things. Things in this universe can be explained by some basic principles you can count on one hand. Density is one of them.

Thanks for your indulgence. I retired awhile back but I still have the ability to get long winded in the sciences at the drop of a hat. Ask my kids.

 

 

[eastman03]

Seriously, blows my mind. haha  It seems so obvious when you think about it.  But I've never really given this topic much thought.  I've never really tried to make a neutrally buoyant lure. Great topic!

[Sailybait]

Hi All,

 

Thank you very much for all the information above. Extremely helpful!

I was wondering if anyone would be able to assist me. I wanted to make a resin bait with the same density as paulownia which has a Specific gravity of 0.285. My question is, what percentage by weight of microballoons  do I need to add to the resin to achieve this density. I am using smooth cast 300

 

I understand with this ratio that the mixture will be extremely thick with this level of micros but I have an idea I’d like to test to get it to work. 
 

Any help will be greatly appreciated.

 

Thanks in advance

[Vodkaman]

The lightest density that I ever achieved was 0.67g/cm³ and the texture was that of English mustard and had to be injected. So, I would say that your paulownia plan is impossible.

Dave