Cylinder type and proper weighting (SPLIT FROM 'Pull Dumps - Lose them')

[CuzzA]

LMAO. Ya. I find no fault in what yer saying. The thing is, it's pretty much that temperature year round below 70' up here. Well, maybe 39° but still....

Did I mention the wind was howling, and it was sleeting or something as well? Here's evidence and a nice beach shot.

View attachment 453285 View attachment 453286

Awesome. I'd love to ice dive maybe one time. Pictures always make it look so cool and then I'm reminded I'm a Florida guy and 50 degrees outside may as well be Antarctica. Haha.

 

[BRT]

steel tanks don't have bouyancy, at least mine don't. if something is buoyant it will float to the surface. a steel tank will not float to the surface, the amount of air thats in the tank will only affect the speed that it will sink.

Your lack of understanding is astounding.

 

[Celt]

Your lack of understanding is astounding.

maybe your not making yourself clear

 

[Stoo]

Awesome. I'd love to ice dive maybe one time. Pictures always make it look so cool and then I'm reminded I'm a Florida guy and 50 degrees outside may as well be Antarctica. Haha.

Traditional ice-diving (saw a hole, tenders, lines etc) is something every diver should endure at least once. If nothing else, it'll end any complaints you have about Florida in March. I haven't done that for years, and generally just keep diving around and under lose ice.

These days, my idea of ice diving is a tall glass, a lump of ice and a generous slosh of rum in it.

 

[BRT]

maybe your not making yourself clear

I think this is a waste of time but OK, once more. A rock has buoyancy. Try diving with 10 lb of rock for weight when you need 10 lb of lead. It won't work because even though rock sinks it has more buoyancy than lead. A steel 100 weighs about 8 lb less when empty than when full. It displaces the same amount of water when empty or full so it has less buoyancy when full, even if it sinks when empty. For you to be neutral in the water, neither sinking or floating up you will have to change your weighting 8 lb between a full tank and an empty one. You do that by carrying enough lead to hold you down with an empty tank, OK, split hairs, an almost empty tank and you offset that extra weight by putting air in your BCD when the tank is full. I understand that you can also keep more air in your lungs instead of air in the BCD, or you can swim up slightly when the tank is full, or you can breath at the bottom of your lungs when the tank is nearly empty, or swim down when the tank is nearly empty. Something has to offset the weight of the air that you breath during the dive. As you get bigger and bigger tanks I.E. 130 cubic foot tanks (10+lb of air) this difference becomes very apparent and hard to offset by breath control or swimming slightly up or down.

 

[Umuntu]

Deleted

 

[Steelyeyes]

Just a personal example for my most recent post:

When I taught OW classes in a warm pool using a 3mm shorty and an aluminum tank, I regularly demonstrated that I was correctly weighted and able to dive with no weights whatsoever.

The day I dived in Puget Sound using a dry suit and my warmest, fluffiest undergarment and a steel tank, I did not think there was enough lead in Seattle to sink me.

No kidding.

 

[Celt]

Y

Well, it is now pretty clear that you are not going to understand this. I am responding for the benefit of others who might still be confused.

1. Buoyancy is the relationship between an object's weight and its volume. If it weighs the same as that volume of water, it is neutrally buoyant. If it weighs more than that volume of water, it has negative buoyancy. If it weighs less than that volume of water, it is positively buoyant. A steel-hulled ocean liner floats because its total weight is less than the volume of water it occupies. A steel tank sinks because it weighs more than the volume of water it occupies. All objects have buoyancy--it is just a matter of how much. This is Archimedes Principle.
2. This chart shows the buoyancy characteristics of different scuba tanks. It lists the degree to which the different tanks are positively or negatively buoyant, both when empty or full. In every case, aluminum or steel, that difference is based solely upon the amount of air in the full tank. The full tank is heavier than an empty tank, but it still occupies the same volume, so it is more negatively buoyant.
3. According to Archimedes Principle (see #1), the buoyancy of a diver is determined by the total weight of the diver and all the gear combined. During the dive, the diver's volume will not change, except for the adjustments made to the BCD and the compression of the thermal protection, but the diver will lose weight because of the loss of air in the tank. It is the loss of air in the tank that causes the change in buoyancy, and as the chart in #2 shows, that is true for all tanks, aluminum or steel.
4. It does not matter whether the tank being used will sink or float on its own, whether full or empty. What matters for the diver is the weight and volume of the diver plus all gear, including the tank. If the weight of that total package is not enough, the diver will be positively buoyant and must add weight without creating a significant increase in volume. That is usually done by adding lead.
5. Because it is the weight of the total package that counts, all factors have an impact, and no one factor is alone responsible for the buoyancy. A diver using a single aluminum tank with a 3mm suit and standard BCD in fresh water will need very little weight--perhaps none. That same diver using a single steel tank in salt water and wearing a dry suit will need a significant amount of lead to do the dive.

you need to look at the chart you posted every single one of the steel tanks have a negative bouyancy Empty. density is what affects bouyancy, aluminium has a density of 2560 lb/ft3 steel is 7850 lb/ft3

 

[boulderjohn]

No kidding.

Obvious to some; an inexplicable paradox to others.

 

[Dan]

Y

you need to look at the chart you posted every single one of the steel tanks have a negative bouyancy Empty. density is what affects bouyancy, aluminium has a density of 2560 lb/ft3 steel is 7850 lb/ft3

I think you have the unit of measurement of density mixed up. Those numbers are for kg/L or g/mL, not lb/ft3. You need to multiply them by 62.4 to convert the numbers into lb/ft3. Density of water = 1 kg/L = 62.4 lb/ft3.

And go back & study: Archimedes' principle - Wikipedia