Could try the Archimides principle if you have a large enough bathtub...

Gestalt said...

put the board in a pool and load it up with weights until it sits flush with the top of the water.

weight = volume

Is that always true? Dunno coz its been years since I've done any physics or maths like that. What I'm thinking is some materials are more buoyant than others and have different densities. I could be completely wrong about this.

I would have thought Windxtasy's thought of Archimides principle would be the go.

Anyway what sort of board is it? There could be someone here that knows the board and its stats.

An object displaces the water volume of its weight
1000ml = 1000g = 1000cm cube

Mobydisc said...

<<<<

Is that always true? Dunno coz its been years since I've done any physics or maths like that. What I'm thinking is some materials are more buoyant than others and have different densities. >>>>>>>>

Yep, doesn't matter what the density or buoyancy is, if it's just completlly submerged, but still floating, it's weight is the same as the volume of liquid it's displacing.
If that's pure water, it's 1kg per litre.
Sea water is a bit heavier, it's been stated here before on similar threads, by exactly how much, but ancient sieve for brains memory forgets.

So you have to weigh everything that's sinking the board, including the board's own weight, to get it's volume.

Seawater is taken to be 1.025 kg / L, in actual fact this too varies with water temp and is correct in water of 4degC, (ie I'll never sail in that density)
So a 100 L board in seawater will float the same as a 102.5 L board in fresh water.

Oh yeah and don't forget, if your weights go under water, you're also measuring the submerged part of their volume.

Cheers thanks for everyones input .