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I don't get it. Assume I'm stupid and spell that out a little for me, please.Remember, Al and steel tanks trim oppositely. On steel tanks you're moving weight. On AL tanks you're moving the bubble in the butt of the tank, so you're actually moving buoyancy, not weight.
True if the AL tank is mostly empty, not when it is full. That is part of the problem....it changes around 2000psi, and become noticable at maybe 1500, and can be nasty at 1000-500psi psi left.Steel are negatively bouyant, aluminum are positive. Consider the cylinder band as a fulcrum and the tank as a lever arm. Steel pulls the long end down, aluminum pulls the long end up.
Steel are negatively bouyant, aluminum are positive. Consider the cylinder band as a fulcrum and the tank as a lever arm. Steel pulls the long end down, aluminum pulls the long end up.
True if the AL tank is mostly empty, not when it is full. That is part of the problem....it changes around 2000psi, and become noticable at maybe 1500, and can be nasty at 1000-500psi psi left.
Because even if they both changed by the same amount over the course of the dive, the steel cylinder started out MORE negatively buoyant than the aluminum cylinder. Here are some specs for you to look over. Note that in these examples, the steel 80 starts out -8.05 lbs negative when full, while the aluminum 80 starts out -1.5 lbs negative.Mine has two tank bands, so I'm magically trim!
Here comes my stupidity showing again, but I've never grasped this. A tank weighs what it weighs. Maybe it's heavy steel, but then there's less lead on the weight belt. If two tanks have the same amount of air in them (and I know steel probably has more, but that just makes things even more confusing) then the air in each of the tanks weighs the same, so when it's gone the tanks should each weigh the same amount less. If the divers breath the same amount from each tank. So how does one tank (steel) go from making a diver negatively buoyant to making a diver neutral, and the other (aluminum) goes to making a diver positive, if they're each losing the same weight of air?