Sinking BCD

[Clive]

I have been told by someone that his partner was having difficulty maintaining buoyancy during training in the pool and when the instructor told her to change her BCD and cylinder the BCD "although fully inflated started to sink under the weight of the steel 70 cu ft cylinder and regs alone". I have checked the spec for the BCD and it has 18lbs lift and I know another female diver who uses the same model with no problem.

This just doesn't sound credible to me, but before I go off half cocked and say so may I ask for the benefit of experience on this forum? Is it reasonable to believe this statement? Any possible explanations?

 

[jbisjim]

It is possible the BCD did not have enough lift for the tank and the weight and diver.

BCDs have different lift. by manufacture and or bladder size

 

[Don Burke]

I have been told by someone that his partner was having difficulty maintaining buoyancy during training in the pool and when the instructor told her to change her BCD and cylinder the BCD "although fully inflated started to sink under the weight of the steel 70 cu ft cylinder and regs alone". I have checked the spec for the BCD and it has 18lbs lift and I know another female diver who uses the same model with no problem.

This just doesn't sound credible to me, but before I go off half cocked and say so may I ask for the benefit of experience on this forum? Is it reasonable to believe this statement? Any possible explanations?

I would go for weight integrated as my first suspect with heavy stuff in the BC pockets as a second suspect. It is also possible that there was a bunch of stuff on the console.

If the cylinder restricted the BC bladder, there would not be 18 pounds of lift. Coming up with 14 pounds (a guess) or so negative from the cylinder and regs would be difficult, so I would want to see this thing sink before I believed the story as told.

I would ask the other diver (the one with no problems) for some details about the BC.

 

[eod]

I have seen a similar situation. Diving dry with a TP2 and venture wing with weight pockets (many kg of lead in them). The venture couldn't lift the rig when she took it off. It wasn't by much, but it sank. After that she got a rec wing instead.

About the situation you mention. It sounds very strange that the reg and bottle is too heavy for the BCD, specially when it is sufficient lift for another person. Sounds like some weights were put into the BCD.

 

[android]

That's easily believable. An E7-65 is -6.5lbs full and a reg with console could be another 2 or 3 lbs That's almost half the lift capacity before you throw in integrated weights. 8-10lbs for a beginning woman in a wetsuit would be average, so now you've sunk the BCD once you remove it from the diver.

The other diver could be using an AL tank which would make quite a difference in this situation.

 

[Clive]

Thanks for those ideas. I had thought it must be weights left in the pockets, it is a integrated weight design. The tale I was being told though was "fully inflated and with cylinder and regs only", ie no weights.

 

[pasley]

When diving from a friends boat, we inflated (but not to the max) my BC, weight intergrated with 20 pounds of lead and AL80 tank, and tossed it into the water to don there. It floated, briefly, before sinking out of sight. Fortunatly, we had it on a line. My BC which floats me just fine with my 7mm wetsuit on, does not float itslef. Go figure.

 

[liberato]

Same here, but that is with a full load of cold water integrated weights. Not a problem unless you try to do an in water donning like pasley (would love to have seen your expression!). I think the presence of the weights got lost in the relaying of the story or it wasn't really fully inflated.

 

[ScubaTexas]

Did the BC have any (substantial amount) water in the bladder? If so, that would restrict the lift capacity.

 

[Virgil]

I have been told by someone that his partner was having difficulty maintaining buoyancy during training in the pool....

Is it possible that, whilst having buoyancy problems, they kept trying to vent air but with no air in the BC just kept letting in water which could exacerbate any weighting problems?