SMB as backup lift source.

[-JD-]

Dual bladder wings are not an immediate solution.
Having both inflators connected would make it very difficult or determine which one would be auto inflating, so only one is hooked up at a time.

If that one fails, there’s no way you’ll be able to identify and inflate the other one to arrest your descent in a reasonable time frame. You’re still a lawn dart.

There’s no way you can arrest a rapid descent caused by heavy steel doubles by orally inflating. Everything is working against you. Ears screaming. Gas compressing in the wing as you descend. Putting enough gas in the wing orally since its starting empty. Ain’t happening.

With light tanks, you could kick your clippers to stop your descent.

With a drysuit you can press the button to stop the descent.

Just to play devil's advocate ...

If you have a BC & DS, if both inflators are hooked up, then you are in essentially the same situation. As far as I know, pretty much everbody diving dry also has their BC hooked up.

I'm having a really hard time figuring out how any of these buoyancy sources are fundamentally different, except that a DS probably has a higher chance of "failure" (flood) than a bladder all things considered.

 

[PfcAJ]

Just to play devil's advocate ...

If you have a BC & DS, if both inflators are hooked up, then you are in essentially the same situation. As far as I know, pretty much everbody diving dry also has their BC hooked up.

I'm having a really hard time figuring out how any of these buoyancy sources are fundamentally different, except that a DS probably has a higher chance of "failure" (flood) than a bladder all things considered.

You can feel a drysuit inflating. It’s way different than a wing inflating. In either case, the immediate action is the same - tilt head up and vent the suit and wing.

Two wings hooked up? Now you’re playing a guessing game for which it is.

 

[doctormike]

There’s no way you can arrest a rapid descent caused by heavy steel doubles by orally inflating. Everything is working against you. Ears screaming. Gas compressing in the wing as you descend. Putting enough gas in the wing orally since its starting empty. Ain’t happening.

With light tanks, you could kick your clippers to stop your descent.

With a drysuit you can press the button to stop the descent.

Again, I still don't understand your point. Who said anything about a rapid descent caused by heavy steel doubles?

The question was about redundant buoyancy for a wet suit diver. I agree that you shouldn't dive an unbalanced rig. So why is a double bladder wing a problem, but an SMB for redundant buoyancy not a problem (as was taught to me in my TDI AN/DP class, which was done in a wetsuit)?

 

[AJ]

There is no reason to hook up the second inflator to a gas source. You just have it in case your primary bladder fails. Then you would inflate it by mouth.

And if you are concerned about sudden descent with a wing failure, how would a single bladder wing make that less of a problem?

In case of an sudden descent you'll be very busy. So whatever solution you choose, it has to be ready the moment disaster strikes. Therefore I do not consider SMB's and non attached double bladders as a real solution. Attaching both bladders can cause problems (does not have to be if you know your gear), but is to me the only way to solve this problem within this config. The whole porblem is caused by a non balanced rig and the proposed solutions only fix the symptoms. Imo they do not provide a real solution, which is: buy the right stuff or don't do the dive!

 

[doctormike]

You can feel a drysuit inflating. It’s way different than a wing inflating. In either case, the immediate action is the same - tilt head up and vent the suit and wing.

Two wings hooked up? Now you’re playing a guessing game for which it is.

In case of an sudden descent you'll be very busy. So whatever solution you choose, it has to be ready the moment disaster strikes. Therefore I do not consider SMB's and non attached double bladders as a real solution. Attaching both bladders can cause problems (does not have to be if you know your gear), but is to me the only way to solve this problem within this config. The whole porblem is caused by a non balanced rig and the proposed solutions only fix the symptoms. Imo they do not provide a real solution, which is: buy the right stuff or don't do the dive!

I agree with both of you. The oral inflate is for a hard bottom, that's the only time I ever used a double bladder wing.

But the bottom line is that you shouldn't be in a situation where you need redundant buoyancy. That's the most important take home message of this thread. You should be able to swim your rig up without relying on your BC. And you should do what you need to do to achieve that configuration, by choosing appropriate tanks and exposure suit.

HOWEVER, the OP is taking a tech class where redundant buoyancy techniques must be demonstrated. Which was the same when I did my OC tech training. So whatever you think about balanced rigs, in this situation the OP still needs to demonstrate the use of redundant buoyancy. Which might be used with an unbalanced rig, hopefully not in blue water over a 3000' bottom.

In THAT case, getting back to the OPs question, a double bladder wing is a better solution than an SMB. Which doesn't mean that you don't also need two SMBs.

That's all I'm saying.

 

[-JD-]

You can feel a drysuit inflating. It’s way different than a wing inflating. In either case, the immediate action is the same - tilt head up and vent the suit and wing.

Two wings hooked up? Now you’re playing a guessing game for which it is.

So, check me here for a dual bladder rig ...

Tilt head up, raise both hoses and dump. Once you get neutral, assuming a FAST or FULL RUNAWAY inflator leak (and only in that case would it be a crisis issue) one should be notably venting away. Release the dump on the good hose and unplug the bad inflator's hose.

 

[PfcAJ]

Again, I still don't understand your point. Who said anything about a rapid descent caused by heavy steel doubles?

The question was about redundant buoyancy for a wet suit diver. I agree that you shouldn't dive an unbalanced rig. So why is a double bladder wing a problem, but an SMB for redundant buoyancy not a problem (as was taught to me in my TDI AN/DP class, which was done in a wetsuit)?

If you’re diving a balanced rig, you don’t even need redundant buoyancy because you can easily swim against the weight of the gas in the tanks.

Ergo, you don’t need a dual bladder wing.

If you don’t need it, why take it?

 

[KevinNM]

Do the rest of you agree with this?
I think it's important we start from common ground.
And more important, now that we've defined the buoyancy criteria, "balanced rig" means NO weight can be ditched, correct?

No, a balanced rig means you can swim yourself and your tanks/BCD up and maintain a safety stop. It doesn't mean you have to take everything with you. Swimming up from the bottom with a failed BCD is kind of an emergency. You can drop whatever you need to drop to accomplish this, whether that is $50 worth of weights or your $12,000 camera. But have a tested plan before you need it. And if you don't like the implications of dumping gear then you should change your setup to avoid it.

 

[Ayisha]

Can you REALLY wear ditchable weight?

Yes. Ballast includes ditchable and non-ditchable weight. You have to be aware of what is ditchable. A can light or camera are ditchable. You may not want to drop them, but you can.

"Double wings are an invitation to a disaster" - GUE

Sure wish they would further explain that...

They do explain all of this much further - in a GUE Fundamentals course.

None of this discussion replaces the knowledge and skills you would learn in an appropriate course.

 

[PfcAJ]

So, check me here for a dual bladder rig ...

Tilt head up, raise both hoses and dump. Once you get neutral, assuming a FAST or FULL RUNAWAY inflator leak (and only in that case would it be a crisis issue) one should be notably venting away. Release the dump on the good hose and unplug the bad inflator's hose.

I suppose that would be a reasonable immediate action if you insist on diving an overweighted rig with a dual bladder wing with both hooked up.