Weight-integrated BCD with trim pockets and positive buoyancy?

[archer1960]

...

The take home message is NOT how strong of a swimmer you are, but rather how you can ditch enough ballast so you can make it to the surface with out too much trouble. I had a whole thread a while ago on a BC failure and how i handled it with a thick wetsuit on in 80 ft.

No doubt, dumping weight is FAR preferable to exerting yourself that much. When I'm in my 7mm suit, I carry 16lb in my BC's ditchable pockets and 6 on the tank band to get my trim right. Dropping that 16 lb would make things a whole lot easier...

 

[george_austin]

So I just picked an aqualung axiom BCD. It was the one I trained in and it was good so I got one. It has 2 releasable weight integrated pockets and 2 trim pockets near the tank band, of non-releasable weight. But I didn't use either because I just had a weight belt at the time. I plan on using them now and I was reading the manual and it has this warning about the trim pockets.



My question is theoretically what exactly is going to create the positive buoyancy if your BC is completely deflated and you drop the releasable weight? Especially if you are wearing a full tank like an AL80, which is negatively buoyant? Is it just the buoyancy of your body? The buoyancy of the deflated BC? It seems different people have different body buoyancy characteristics depending on their weight, body fat %, muscle mass, etc. With some being naturally N buoyant and some naturally P buoyant. I haven't tested this weight configuration out in the water yet but I'm planning to. I'm just theoretically curious as to where the buoyancy is going to come from according to the above warning? Especially if you happen to be naturally negatively buoyant body type? Two other factors that come to mind would be salt water and shorty or full wetsuit. Although, I don't know how much of an effect they would have.

you, the diver, achieve positive buoyancy by swimming to the surface - yes, with a completely deflated BC -

---------- Post added September 16th, 2015 at 10:02 PM ----------

You will never be so negative ( if you know what you're doing ) that you cannot swim up yourself. OTOH - I see new divers quite often doing benthic dives with a fully inflated BC. Yep, crawling across the bottom in a cloud of silt with 40 lbs of lead on and a puffed out, BC filled with air. On training dives - a dive casualty just waiting to happen