Buoyancy = specific gravity of water - the specific gravity of the object being floated (or sunk, in which case the answer is - ).

Sg

PS: the specific gravity of water (distilled) is 1 gram per cubic centimeter (equivalent to its mass) at sea level.

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Buoyancy = specific gravity of water - the specific gravity of the object being floated (or sunk, in which case the answer is - ).

Sg

PS: the specific gravity of water (distilled) is 1 gram per cubic centimeter (equivalent to its mass) at sea level.

Also, when determing displacement and flotation is used it needs to be accounted for in your calculations like this: 2lb foam (2 pounds per cubic foot) would be deducted from the cubic foot of water being displaced. 62.40 - 2 = 60.20.

Here are some examples of specific gravity for different materials:

Aluminum 2.60

Bronze 8.00

Concrete 2.25

Fiberglass 1.5 to 1.8

Douglas-fir .50

Gasoline .72

Glass 2.50

Cast Iron 7.00

Lead 11.00

Mahogany .60

Human 1.10

White Oak .80

Oil .83

Sitka Spruce .42

Steel 7.80

Teak .83

Buoyancy is equal to the weight of the water displaced by the vessel. Period.

For example, steel has a high SG, and therefore, should sink. However, we can make steel float, if we can form it into a shape (like, say, a steel-hulled boat) that

Okay, let's say you have a pontoon made of balloon material, and one made of basketball material....same size. Would one float a 200lb person better than the other??????

Of course, the additional answer is, if both materials have the strength to remain intact under the stresses. For example, if the balloon material is too thin to withstand the stresses, then the balloon would break - this eliminates the displacement, and eliminates the buoyancy. If the balloon material is strong enough, the buoyancy provided would be the same.

If you use the chart I provided you can see that if you designed a drift boat hull and built one of fiberglass and one of aluminum the fiberglass boat would ride higher in the water.

So, again I will say, specific gravity has nothing to do with buoyancy :ray1:

OK, you're right. I was thinking of the combined specific gravity of a hull made of any material plus the very low specific gravity of the air contained within. If the hull were filled with another material, like your fiberglass in fiberglass example, the specific gravity of the material matters, but it matters in the same way as the displacement of the water by the hull. You said it better. And a lot more succinctly.

Sg

So, basically what you're saying is that if I add 5% to say 15% helium to my air mixture on the pontoon, then that will change the specific gravity of the way that my toon floats by increasing the buoyancy, & lessening the displacement factor?

Yes/No?

Yes/No?

There are a lot of factors mixed into your question. First, if you add Helium to your toon, the mass (or weight) will be decreased, so the density will be decreased, and that is the key. Forget Specific Gravity - Specific Gravity has nothing to do with it; your toon will simply be less dense. For an object of a fixed volume (like your toon in this example), the less it weighs, the less density it has, and the higher it floats.

As to the lessening the displacement factor ... your toon will sink into the water until it displaces an amount of water equal to it's weight. The more your toons weighs, the more water it will displace. At some point, it will either sink or float, depending on how heavy it is. Remember, we are talking about an object of a fixed volume - your toon. So, when we talk about weight, we are also talking about density. There is a far better explanation here:

I hope this helps ...