Faber HP100 Bouyancy - way off??

[WetSEAL]

If it is a 12.9 l tank you know the water displacement of that volume

What is the volume of water that will be displaced by a tank with an interior capacity of 12.9 L? Obviously the displaced volume would be larger due to tank wall thickness, etc.. I'm sure there is a lookup table somewhere but I am not sure

 

[BRT]

What is the volume of water that will be displaced by a tank with an interior capacity of 12.9 L? Obviously the displaced volume would be larger due to tank wall thickness, etc.. I'm sure there is a lookup table somewhere but I am not sure

Read what I said
"If it is a 12.9 l tank you know the water displacement of that volume and if you know the weight you can calculate the volume of steel in the tank. Adding the two together gives you total water displacement which gives you the ability to calculate how much flotation the tank has. Subtracting that from the weight tells you how much it will float or sink."
The interior volume is 12.9 liters of water. The weight of the steel in the tank lets you calculate the volume of the steel. Add the two volumes together and you have the volume of the entire tank.

 

[rjack321]

Empty weight is the mass of steel, divide by the density and you have the volume of steel. Depends slightly on the chosen value for the density of steel. But here's a range.
Density of Steel - The Physics Factbook

You can do the same calculation with the valve and brass.
Metals and Alloys - Densities

 

[Kevrumbo]

Air has a pressure of 14.6959 psi at 1 ATM.
Tank inner volume is 100 cuft / 3442 psi x 14.6959 = 0.43 cuft
Steel has a density of 490 lbs/cuft
The volume of the tank metal is 33 lbs / 490 = 0.067 cuft
The density of salt water is 64 lbs/cuft
Total weight in water: (0.43 + 0.067 ) x 64 = 31.636 lbs
Air has a density of 0.07647 lbs/cuft.
The air in a full tank weighs 0.07647 x 100 cuft = 7.65 lbs
Tank buoyancy when empty: 31.636 - 33 = -1.4 lbs
Tank buoyancy when full: 31.636 - 33 - 7.65 = -9 lbs

From:
Scuba tank size and buoyancy calculator

 

[sh0ck1999]

ahhh so much math, just take a couple pound of lead off whats the big deal. you want an ungodly heavy tank go find a faber 3180 i had a 120 i sold not to long ago. boy full was -16lbs boy empty was -8lbs. old hiesers are even worse i think they are more lead than steel

 

[guruboy]

Scuba tank size and buoyancy calculator