Redundant Bouyancy - Dual Bladder v. Lift Bag v. Dry Suit
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DevonDiver
N/A
You mentioned 'dropping gas'. That wasn't very explanatory.
The 'thread' is about configuration of 'tec gear'.. in the 'technical diving' forum. Consideration of a buoyancy strategy and appropriate redundancy for technical diving should incorporate the use of stages. The OP didn't specify what type of 'tec diving' he wanted to configure his gear for - because he probably doesn't know - but I didn't assume cave would be the focus. For general 'tec' - stages are a given, for cave they aren't.
If you were talking about a dive with no stages, then my comments can still apply. For a properly weighted diver in balanced kit, with no stages, it's even more straightforward.
Wetsuit + Ali Doubles + Ali Backplate = maintains ditchable weight to off-set cylinder buoyancy as gas is consumed.
Buoyancy failure on Entry (negative doubles) - ditch weight & exit.
Buoyancy failure on Exit (neutral - positive doubles) - exit.
Assuming rule of thirds is used, and again - the rig is well considered and balanced - then the diver would only be marginally negative for the entry (1st third). Approximately neutral for the exit (2nd third) and marginally positive for the contingency (3rd third). They would carry weight to off-set the potential buoyancy of near-empty cylinders. That weight could be ditched for an exit if the wing failed.
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even without stages if you are managing gas properly, on the way in it's better to drop one of your main bottles and exit, and you just drop the bottle with the lowest amount of gas in it. Unless it happens right as you hit thirds you will be nowhere close to draining that tank by the time you get out. If you're planning on doing deco on backgas it may get a little squirrely but that's why if I'm doing any deco I just bring a stage anyway. An extra AL80 never hurt anyone
PfcAJ
Contributor
You still didn't read it, did you?
Sax, I think a better answer is just to dive a drysuit if you're using steel tanks and not futz with dropping half(ish) of your gas, which could make a situation worse. Practice in a quarry is one thing, but doing it on a real cave dive is something else.
DevonDiver
N/A
Which post are you referring to? LOL I did obviously miss something?!
I contribute with at least half of my attention on addressing/furthering the OP's question - so that's where I am coming from with this.
I don't think that 'strategies for side-mount diving on scooter in cave' is really applicable to the OP's question about 'duel bladder vs lift bag vs dry suit'.
The issue of dropping gas (whether a stage, a side-mount, or even to dump gas from the doubles) is kinda more relevant - as it fits with the concept of 'balanced rig' - which should be something the OP considers as he sets up a basic tec rig for the first time.
I contribute with at least half of my attention on addressing/furthering the OP's question - so that's where I am coming from with this.
I don't think that 'strategies for side-mount diving on scooter in cave' is really applicable to the OP's question about 'duel bladder vs lift bag vs dry suit'.
The issue of dropping gas (whether a stage, a side-mount, or even to dump gas from the doubles) is kinda more relevant - as it fits with the concept of 'balanced rig' - which should be something the OP considers as he sets up a basic tec rig for the first time.
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oh, I dive dry, fear not. I'm just saying, worst case scenario it's an option. Especially on the beginning of the dive when you are really heavy.
Thanks for all the good info guys. I plan on taking a intro course but its hard to do when you've been sitting in a desert country for a year! I'm just wanting to get opinions early on that way I at least have an idea of what to discuss. My main goal for getting into tec is so I can dive deeper, longer and with a clearer head. I love to dive but I hate only having a 20 min dive bc i'm limited by NDL, single tank and planning for extra gas in that single tank for emergencies for myself or my buddy.
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drysuit will be your usual go to for redundant buoyancy. This is obviously a rather rare occurrence. While not necessarily ideal, a drysuit is easier to control than a lift bag and less irritating than a dual bladder wing which just gets in the way. The HOG drysuits are only about $1400 custom cut and they are fantastic suits. I would not buy a dual bladder wing. I only see one or two per year. They all seem to be in ocean dives too with non tech divers. I can't think of any that I know that have one. A couple lift bags are good to have, but you won't find them in the caves unless you're diving with a scooter.
How does a redundant bladder wing get in the way, it's tucked away inside the wing cover. Drysuits are great if you dive cold water or long exposures, but why invest $1400+ if you dive warm water, just in case the "rare occurence" happens... a drysuit 'gets in the way' (has to be managed) every dive even if you don't need it for thermal protection
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