Rebreather BCD question

[g1138]

I was skimming through the Robert Stewart accident/incident posting and am not familiar with rebreathers configs.

Is it not standard practice to have a separate buoyancy bladder? Do some users configure to rely on the loop alone for buoyancy with no redundancy?

There were some speculation about Robert Stewart flooding his loop and sinking from the weight. So excluding more speculation to his incident, I just wanted to know if some rebreathers choose to configure this way.

 

[tstormdiver]

Although I will not say it cannot happen, personally, I cannot see any advantage to using the loop for buoyancy. Especially with eCCR's with Oxygen being continually pumped in & Oxygen being metabolized, it would wreak havoc on buoyancy control. I keep optimal loop volume in mine. Just enough to breathe comfortably, but not much else. Keeps the buoyancy swings to a minimum. As for flooding the system.... yes, it does tend to make the unit very negative. It can make my Prism2 nearly 16# negative if the canister is fully flooded.

 

[rjack321]

Is it not standard practice to have a separate buoyancy bladder? Do some users configure to rely on the loop alone for buoyancy with no redundancy?

There were some speculation about Robert Stewart flooding his loop and sinking from the weight. So excluding more speculation to his incident, I just wanted to know if some rebreathers choose to configure this way.

All CCRs use a buoyancy device. Some oxygen rebreathers don't have a separate wing per se but that is not what this incident or one's like it is about.

The loop is kind of like having a 2nd drysuit. Your primary buoyancy control is your wing, that's what its made to do. secondary control is through a combination of the drysuit (if any) and the loop. You can use one or the other or neither. While some people do dive using a drysuit for all of their buoyancy control nobody does that on a CCR.

If you flood the loop you get really heavy whether it was involved in buoyancy control during the dive or not.

 

[sea_ledford]

The unit he was diving is particularly negative as well. It's all stainless steel and air. Remove the air and just about every part of it is negatively buoyant. I was seriously considering a Revo for a long time, but the negative weight inherent in the system is one of the main things that swayed me away from it.

If a flooded Prism gets to be -16 lbs and is mostly plastic, I would guess a Revo would be double that at least.

-Chris

 

[rjack321]

The unit he was diving is particularly negative as well. It's all stainless steel and air. Remove the air and just about every part of it is negatively buoyant. I was seriously considering a Revo for a long time, but the negative weight inherent in the system is one of the main things that swayed me away from it.

If a flooded Prism gets to be -16 lbs and is mostly plastic, I would guess a Revo would be double that at least.

-Chris

You know if he was diving a stainless or titanium version?

 

[sea_ledford]

You know if he was diving a stainless or titanium version?

I don't. I actually forgot about the titanium option. For the standard size the weight difference is about 5 lbs (43 lbs vs 38 lbs) without tanks or sorb.

-Chris

 

[g1138]

Thanks everyone, that's great clarification.