Questions about Dual bladder wings

I started my Padi Tech 40 class and the instructor told me i need to purchase a dual bladder wing. So I purchased the wing and another istructor told me I didn't need a dual bladder because if there was a tear in the wing it probably would tear both bladders because they are on top of one another. And PADI is the only agency that uses dual bladders. I listened to my instructor but I am just curious about what I heard. It's really makes sense what he told me. I am diving in a wet suit year round here.

this is an ongoing heated debate. both sides make valid arguments. However, a redundant wing can't hurt you if dive with the secondary inflator disconnected. On the other hand, if you have an OPV fail, a bladder delaminates, or your corrugated hose somehow comes loose (yes, I have seen every one of these failures on dives, both recreational and technical) and you don't have access to a redundant BCD, your deco is going to be interesting. Yea you can use a lift bag, but it's a PITA compared to just switching to your backup. Seems like a no-brainer to me.

I like a large (~40lbs lift) closed-circuit SMB and/or a drysuit for dives where buoyancy redundancy is necessary (heavy steel doubles rig and/or deco stops on ascent). Double bladder wings provide the same redundancy but also add an extra set of hoses, valves, and inflators to confuse an already over-crowded area/get tangled/fail.

The whole 'well, an extra bladder is much easier to use on deco' point focuses on the wrong issue. Yes, in a world where nothing goes wrong (aside from the main wing), the redundant wing will be an easier backup to use than a SMB or drysuit. However, things do go wrong and the SMB/drysuit provide adequate redundancy without the increased chance of attracting Mr. Murphy.

If your Tec/Rec instructor insists on your using sub-optimal equipment on serious dives, I'd call it a sign to find another instructor. If the Tec/Rec requirements demand all instructors force you to use that equipment, I'd call it a sign to find a different agency.

You really cannot go wrong with an additional bladder. Notice that others say SMB and or Drysuit. You don't wear a drysuit on the Rock (Okinawa) so that takes you to SMB only. There are not additional hoses! If you have a drysuit then you have two LP inflator hoses and if something goes wrong you remove the hose from the defective item and place it on the additional bladder. If diving wet then you keep it attached to the additional bladder. You can listen to the "if something put a hole in one bladder then it would more than likely put a hole in the additional bladder," if you like. But what about a stuck open exhaust valve, broken LPI etc? Look at Cave Divers Forum where Sandy had to crawl out of a cave because he did not have a dry suit nor a double bladder. Anyone care to try a SMB in a cave?

Redundant buoyancy is a PADI requirement for Tec 45 and higher. If you use a Tec 40 rig (single cylinder) it is not mandatory. I believe if you take Tec 40 with back mount doubles, it is a requirement based on this statement in the Instructor Guide: "If you opt for double cylinders, you should wear the standardized technical rig, not the Tec 40 kit."

A drysuit can also be used to meet the redundant buoyancy requirement. Other organizations specifically ban the use of redundant bladder BCD's.

Brian

Double bladder for me.
I dive ONLY in tropical water so I don't need a dry suit. A reduntancy bladder is what I need as a back-up.

Dr. Lecter:

The whole 'well, an extra bladder is much easier to use on deco' point focuses on the wrong issue. Yes, in a world where nothing goes wrong (aside from the main wing), the redundant wing will be an easier backup to use than a SMB or drysuit. However, things do go wrong and the SMB/drysuit provide adequate redundancy without the increased chance of attracting Mr. Murpy.

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what exactly do you foresee going wrong with a properly rigged dual bladder wing?

kierentec:

what exactly do you foresee going wrong with a properly rigged dual bladder wing?

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It can self inflate if left hooked up and if you've ever experienced a runaway inflator the 3 extra seconds it takes to even figure out which one is a huge issue. If its not hooked up then you have to find the extra whip and attach it when you need it most. If you are doing serious dives even in the tropics, the dry suit as redundancy is quite popular since you won't get cold with compression and have redundant buoyancy at any necessary time.

you dive it disconnected with the LP hose bungeed to the inflator. haven't seen one magically self-connect, and takes seconds to connect and be back on track. no downside, as I have yet to see one connect itself on a dive.

yes, a drysuit is a great form of redundant buoyancy, if you also need it for thermal protection. otherwise, you're adding several failure points on top of the dump and LP inflator. I've seen way more dives called due to blown DS seals than failed backup inflators. In an environment where the air temp is 90+, and the water temp is 86 all the way to the bottom, a drysuit can be horribly uncomfortable.

the argument can go on for days, the important thing is you need to have some sort of a plan in the event of BC loss. whether it's a balanced rig that you can swim up, drysuit, lift bag, or truly redundant wing, it needs to be appropriate for the environment you are diving in and you need to be proficient in its use.

yes, PADI has a standard for everything, and they do require either a drysuit or dual bladder wing for redundant bouyancy.

rjack321:

It can self inflate if left hooked up and if you've ever experienced a runaway inflator the 3 extra seconds it takes to even figure out which one is a huge issue. If its not hooked up then you have to find the extra whip and attach it when you need it most. If you are doing serious dives even in the tropics, the dry suit as redundancy is quite popular since you won't get cold with compression and have redundant buoyancy at any necessary time.

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Anyone ever had a runaway inflator? 600 plus dives and I have not! Care to tell everyone what your drysuit's lift capacity is. You can't because they don't list the lift capacity because it is not ment to be used as a BC. Easier to hook up a hose than to deploy a lift bag.