What if... [loss of buoyancy question]

[Freewillow]

Somewhere in other threads, the solution - at least one of it - was described as using a closed smb in order to put in place an alternative boyancy device. But my guess is that this solution is a bit too sophisticated for the op. If not, please let me know and I will search for the discussion.

 

[Diving Dubai]

In my earlier days of diving (less than 100 dives) I did have a BCD failure underwater. Mine was the inflator getting stuck and filling my wing. Where the similarities arise, to prevent an uncontrolled ascent I was purging my wing from the butt dump, while disconnecting my inflator hose.

In this instance I dumped all my air - it was a reaction and I didn't want the ascent. I ended up swimming my rig (steel 15l with 180 bar as it was early in the dive) to the surface (3mm suit)

I am sure that at the time I wouldn't been able to inflate my DSMB - too much task loading.

 

[Freewillow]

Well done, DD

Not so frequent to think about taking off the inflator house while relativelly inexperienced!. For my part this is the most frequent and dangereous situation that can happen to a BCD. Therefore I change my valve every 2 years - cost 1 USD - .

 

[Diving Dubai]

Uncontrolled Ascents, descents and OOA, are, IMO the 3 worst scenarios needing immediate attention. With OOA obviously you need another source, with the ascent and descent you need to arrest both first, as your immediate action. Only then can you come up with a plan. In an emergency your brain is focused.

If for instance I pulled a top dump off, I'd go head down to allow air to be trapped and to slow or stop the descent. This buys me time to come up with a solution to get to the surface. Maybe it's a DSMB or lift bag, maybe its a buddy. These actions take time (both to think about and to carry out). If people were to reach for their DSMB as a first action, then they'd probably be making a dent in the sand before they arrested the descent.

 

[Storker]

If people were to reach for their DSMB as a first action, then they'd probably be making a dent in the sand before they arrested the descent.

Which isn't necessarily particularly dangerous if there's a hard bottom below you at rec depths, but it can be downright nasty on a wall dive...

 

[Killerflyingbugs]

How much weight are people using that you rocket to bottom with out a bcd? I don't understand how you can be too heavy to swim to the surface with a rec rig.

 

[Freewillow]

My guess would be that 90% of the "low average" divers are clearly overweighted . It is enough to look at most amateur videos where most divers swim like sea horses .

 

[Neilwood]

My guess would be that 90% of the "low average" divers are clearly overweighted . It is enough to look at most amateur videos where most divers swim like sea horses .

Either they are trying to offset the overweighting by finning as you suggest (normally bicycling as well) or you find the occasional one with decent trim but with the BCD nearly fully inflated at depth.

The BCD should only have a minimum amount of air in it to offset suit compression & weight of gas (which should no where near fill it).

 

[archer1960]

How much weight are people using that you rocket to bottom with out a bcd? I don't understand how you can be too heavy to swim to the surface with a rec rig.

Probably not all that rare in cold-water areas. I dive with a full 7mm suit, etc, and a HP117 tank. It takes 20 lb of lead to keep me down when I'm shallow at the end of the dive, so if I'm deep at the beginning of the dive, I'm probably 20lb negative, even though I'm not over-weighted. I'm pretty sure I can swim that up (though I haven't actually tried to yet), but it's not going to be easy.

 

[rx7diver]

Hello guys,

I was wondering what if your jacket brakes while you are under water? what you are supposed to do then? if it doesn't pump up anymore? you just remove your weights and try to go slowly up?

Thanks!

Alessandro Calello,

I recently (about a year ago) initiated a discussion with my little group of university divers that addresses this:

ME: Your BC suddenly, catastrophically fails, instantaneously losing all its air (losing all its lift), while you are lazily finning along, enjoying your recreational scuba dive at your planned 80 fsw (say) target operating depth (TOD). (Think of the corrugated BC inflater hose suddenly breaking apart where it meets your BC.) Assume you're wearing a full, high-quality, 0.25 in or 6 mm Farmer John/Jane wetsuit. What do you do? (Hint: There's NO single best answer, I don't think.)

ME: I was imagining diving a sheer wall on Grand Cayman Island, which drops precipitously several hundred feet. Or diving an upright, level shipwreck whose superstructure tops out at a depth of 80 fsw or so. Et cetera. And, for whatever reason (including, possibly, a failed seam), your BC suddenly loses all lift and all capacity to regain any of its lift.

ME: I don't have a definitive answer (is there one!?), but I think the germ can be found in [another member of our group]'s statement, "I dive with ... very little air in my BC at depth"—essentially, minimize the *effects* of a sudden, complete loss of your BC's buoyancy. A BC *compensates* for the buoyancy swing of your tank as its air is depleted. And a BC *compensates* for the loss of buoyancy of your wetsuit (which becomes more negatively buoyant as you descend and ambient pressure increases). A thinner wetsuit made of higher quality foam neoprene (containing a lot of really small bubbles) will have a much smaller buoyancy swing. And a cylinder which has a smaller capacity will have a smaller buoyancy swing. So, simply diving with these two types of items, instead of something else, AND BEING CORRECTLY WEIGHTED will mean you need to put less air in your BC at depth, which consequently means that a sudden, complete loss of your BC's buoyancy will be simply more of an inconvenience, and less of a life-threatening event. (So, for example, wearing a 3/8 in Farmer John/Jane constructed from lower quality neoprene while using a 100 cu ft cylinder is almost certainly NOT a good idea!) What do you think?

ME: [To another member of our group], by way of example, the buoyancy swing of my OMS LP 125 is about 10 lbs (if it starts out filled *only* to its rated service pressure). And the buoyancy swing of my old-school steel 72 is about half that. Both of these tanks are approx neutral in salt water when empty. So, at depth at the beginning of a dive with a (nearly) full tank means I will have to have more air in my BC (to make the BC ~5 lbs more positively buoyant) if I'm diving the OMS 125 than if I'm diving the 72. Okay. Then suddenly becoming *10 lbs* more negatively buoyant (because of a sudden, catastrophic, complete loss of my BC's lift) if wearing my OMS 125, is much more of an issue than suddenly becoming only *5 lbs* more negatively buoyant if wearing my 72. Make sense?

Safe Diving,

rx7diver