Weighting question

[J-Vo]

I did not know ditching stage bottles was a thing. Are there real life examples where this has happened?

I would have no hesitation ditching an empty deco/stage bottle if my life depended on it. I regularly drop them when I finished with them, when I know I come back and pick them up later.

 

[Imla]

Also remember that a "standard" bottle isn't a standard bottle...
Bottles of different materials have different properties. Some are inherently positive. Some are more negative. This is for eksample why diving 300Bar steels as doubles, with steel stages in a wetsuit is an idea no-one would attempt... (i hope)
This is also the reason why most staged bottles are aluminium even if in some parts of the world, doubles are made of steel. Like people have stated above, when you are done with the gas, shoot an smb, and let the bottle go.
Other things to remember is that gas weight is not standard. More or less Helium will influence buoyancy.
By carefully choosing the gas on bottles, some of the starting gas weight problems can be overcome. Rebreatherdivers doing deep wreck/cave dives can offset the gasweight of their decogasses by adding helium. So whil a gas of 50% Oxygen for a standard T1 dive is perfectly nice. Adding 30% Helium will make an Alu80 Perfectly neutral whilst filled to the brim.

 

[The Chairman]

I did not know ditching stage bottles was a thing. Are there real life examples where this has happened?

Yes. There are even "real dead" examples of where they didn't.

Most tech divers use steel tanks for their back gas. They are quite heavy, and their weight usually accounts for 4 to 6 additional aluminum tanks you might be carrying. I can't remember the last time I saw a steel tank as a stage or bailout bottle. I tried it once and had to ditch them. It was shallow, so retrieval was easy.

Aluminum tanks sink when full, but don't really add a lot of buoyancy when empty. I've never seen a mostly empty AL tank float to the surface. Ever. Are they out there? Dunno. I just haven't seen them. In reality, the real issue is having adequate buoyancy at the beginning of the dive. This might change if you dive al as your back gas.

I would have no hesitation ditching an empty deco/stage bottle if my life depended on it.

We don't know that. That's our plan on the surface, but emergencies screw up your cognitive process with panic. Our ability to redefine our current emergency while the caca is hitting the fan is immense and consequently poor decisions are made, often by the very same people who think they are immune to panic. There are various stages of panic and the first, most common, and seldom noticed is perceptual narrowing. Now add depth as a contributing factor as it blunts your thinking even more, sometimes leaving you with the mental equivalency of a cow, and even minor issues become insurmountable. Again, the people who think they are immune from narcosis because they never feel it are the worst offenders. IOW, dive in a manner that precludes emergencies, except which ice cream flavor you want after the dive is through.

Also, if you dive heavy, please use redundant buoyancy systems. Double bladder BCs or drysuits can be a life saver. And please #2, don't try to go with the least amount of buoyancy you might need on that BC. It's always better to dive neutral, but it's not always possible.