# Extra buoyance

Discussion in 'Sailboats' started by BertKu, Jul 8, 2016.

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### BarrySenior Member

The submerged weight only would have to be subtracted as we are discussing a flooded compartment with balls of some type in it?
Ie if you used a HDPE ball, which floats by itself, then the ball provides some bouyancy

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### BarrySenior Member

Gonzo and Mr E have this figured out correctly.
If you put one ball tightly into one box, then the displacement of the ball is about 50%.

But the second layer of balls will be offset and fall into the voids created by the balls below and the number is around 63%

Believe it or not you can google this.

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### TANSLSenior Member

Barry, what I say is that in an infinite volume the percentaje is not 63%, believe you or not and whatever google says. In an infinite volume, the sphere volume is infinite and the cube volume is also infinite, so the ratio is not 0.63, is undefined.
If you put one ball tightly into one box (a cube), then the volume of the ball is about 53% (see my figure in post #29). 63% will only be achieved in a very specific case, with more than one spheres, depending on the size of the spheres. The same total volume can be "filled" with a sphere, with two, three, .... and in each case the percentage will a certain value. I can not say in which case that value will be equal to 63%, but it could be calculated.
About weight and flotation : It is clear that the weight of all that you have on board must be included in the total displacement, but do not know what sense has the deduct of "flotation" (I do not know what is). One colud say balls volume (not weight) to be deducted from the amount you want to have as reserve of buoyancy (even that is not colrrect). That was the meaning of my correction.

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### TeddyDiverGollywobbler

BR Teddy

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### BarrySenior Member

The only situation where the percentage is 53% is when each ball is say linearly aligned along the x, y,z axis. AND you exactly stated that this percentage is 53%
But the second layer of balls will fall into the voids between any 4 ball combination and increase the number of balls that you can get into a box, etc

I believe that we are discussing floatation balls in the back of a boat that has sprung a leak. If the spheres are made of of a heavy weight material say 5 pounds and each sphere displaces 5 pounds of water, then you will not get a buoyant effect from the spheres.
And this is what I think Gonz meant. I added that if the ball material was in fact buoyant by its own density, you could add this incremental increase to the amount air that each sphere displaces.
Ie the AIR VOLUME inside the sphere displaces 10 pounds of water.
If the material that the sphere has neutral buoyancy, then this material say displaces 5 pounds of water, but it weighs 5 pounds, the sphere provides 10 pounds of lift. (by the water that the air displaces.

If the material is denser or lighter than the density of the water, it will either help floatation or not

Certainly, when there is not water in the compartment, the weight of the balls add to the weight of the boat

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### TANSLSenior Member

Barry, in fact the percentage is not 53% but 52.36%. Only occurs this case with one cube and one (not more) sphere inscribed in it. In other cases the percentage will be different.
What I say in relation to Gonzo's comment is that if by flotation (I do not know what that is) we understand a volume that serves as a reserve of buoyancy, you can not deduct any weight. Weight and volume have not the same units of measurement, are different physical properties and, although it may be normal confusing, I think it is a major mistake.
Whatever the weight of the balls, their volume will be the reserve of buoyancy because that volume may not be occupied by water. The weight of the balls will increase the initial draft of the ship, but nothing more.

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### gonzoSenior Member

TANSL: if as you say, you don't know what flotation is, perhaps you should not enter this discussion. Buoyancy and flotation are similar and conversationally interchangeable. If you say the the weight of the balls, and consequently their density have no bearing in their buoyancy, that is absolutely and totally wrong. Buoyancy only can exist when the density of the object is less than the density of the medium.

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### TANSLSenior Member

@Gonzo, in my opinion "flotation" (whatever it is) is not the same as reserve of buoyancy, that's why of my answers.
You're confusing the buoyancy of a ball, how it floats, with the reserve of buoyancy it entails. Review your concepts because they are two totally different things. Another way to see things, to see if you understand: the density of the ball, his weight, has nothing to do with the volume of water it will prevent to enter the boat.
Paraphrasing a great friend of mine, "if you do not understand that, you should not participate in this discussion".
We could talk about negative buoyancy, what do you think?

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### BertKuSenior Member

I agree with you TANSL.
Guys, guys, guys, All your calculations about percentage buoyance you can throw out of the window, as I will place the balls in Ziploc bags. The bags are not exposed to sun and thus deterioration is practical zero. The weight from foam and the weight of the balls are nearly the same. If I hit a leak, it will probably be a crack. If I have a big hole, the plastic bags are still covered by some foam. (very little I hope to use) Now suddenly the complete buoyance has gone up from 53, 49 63 74 etc. to far over 80% The rest I will fill up with foam. Thus only the 20% foam can start soaking water up what was the case with my boat and explained so nicely by SteveW in a previous thread. It took me a half year to dry my foam in my hull out. I have sealed and closed the leaks, but like to avoid such situation with my extension. You have given me some great thoughts to chew it over. Thank you all.

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### BobBillSenior Member

Pool Noodles?

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### BertKuSenior Member

I am interested. What are pool noodles? Where are they made from and are they "soak poof" i.e. does not absorb water. Bert

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### mydauphinSenior Member

Not enough info to give proper advice. What type of boat, size, mission. etc...?
Foam has good and bad. It also holds water, moisture, and can increase corrosion, some are fire hazards, and all put out some kind of gas. On my boat, I put everything to the propane torch for a few seconds, if it catches on fire, it is not on my boat except toilet paper, etc... which I keep in careful compartments. The foam in a can actually passes my fire test. But if I was to fill a compartment with it I would out in a garbage within the compartment so that I could remove it.

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### BobBillSenior Member

I apologize, I forgot the audience comes from diverse regions and also did not want to step on anyone's toes who advised perfectly functional bags, balls, milk jugs, etc.

"Pool Noodles" are varied forms of light foam lengths, for use in floating around swimming. Closed cell foam, easily cut, bent and so on. Some are 4 inches in diameter and solid, some have a lengthwise hole. I used the large diameter solid version, color was whatever was low cost.

Sits in dark, relatively dry area in hull, as did the old material.

I replace the typical hard, open cell foam with the softer noodles (first two pics - white stuff) as cheap, nearly indestructible, long lasting, quiet flotation...if I have pics of the old white stuff, will show.

In the one pic, bits of the deteriorating styro foam used by the maker can be seen. Was two interlocking blocks of styrofoam inside plastic bag, which had been punctured and the foam had become waterlogged, stinky, etc.

I bought the noodles through Amazon, on sale, for little cost.

Trouble was, each was sent individually from same supplier...so I had lots of cardboard cutting and recycling, 20 boxes 4 feet long and a foot square, when they could have sent them smushed in two or three boxes. These were the 5-foot long, solid, 4-inch diameter variety as you see.

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### mydauphinSenior Member

I guess another advantage to filling your boat with noodles that if it is sinking, you can lay a trail of noodles so it makes easier for the Coast Guard to find you. Though you may get fined for littering.

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### BobBillSenior Member

I like the way you think...

Forgot to mention one salient point. I believe the noodles I used have a 350 lb capacity or 25 stone each!

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