Ducpilot
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I give up….
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An aluminium Luxfer AL80 weights 31.38 lbs, a steel Faber HP80 weighs only 28.3 lbs, and actually holds 2.4 cft more air. Meaning the steel tank is actually 3 lbs lighter out of the water. However, since it is more dense, the empty steel is 1.74 lbs negative buoyant while the empty AL80 is 4.1 lbs positive buoyant. So the steel tank is 5.84 lb more negatively buoyant in water.Well there is obviously a material density difference between steel and aluminum. But the steel tank weighs about 12-13 lbs more. So buoyant force is equal to mass of water displaced. If the tanks are roughly equal dimensions the it largely comes down to weight of the tank.
You’ve made the classic mistake of comparing the full capacity of cylinders. It’s the mass and water displacement that determines whether a cylinder is buoyant or not when empty.An aluminium Luxfer AL80 weights 31.38 lbs, a steel Faber HP80 weighs only 28.3 lbs, and actually holds 2.4 cft more air. Meaning the steel tank is actually 3 lbs lighter out of the water. However, since it is more dense, the empty steel is 1.74 lbs negative buoyant while the empty AL80 is 4.1 lbs positive buoyant. So the steel tank is 5.84 lb more negatively buoyant in water.
I have no idea where you got the idea that steel tanks weigh 12-13 lbs more. Were you comparing a steel 120 to an AL80?
You have make the classic mistake of not looking at the actual numbers, using water displacement rather than capacity, you are even more wrong:You’ve made the classic mistake of comparing the full capacity of cylinders. It’s the mass and water displacement that determines whether a cylinder is buoyant or not when empty.
I’ve used 12Lt cylinders, all at 232bar, with tare weights ranging from 8kg to 17kg.
I don’t think that exists, unfortunately (which is obviously your point). Maybe some carbon fibre monstrosity? However, there are 12x200 tanks at 12.4 kg, which ought to be about neutral at the end of the dive. Sidemount specials.I would love to have some of your 8kg empty 12Lt 232 bar tanks! Where can I get such an awesome thing?