Redundant Bouyancy

[SparticleBrane]

I have never understood the argument that "if one wing failed, the other will probably fail too".

I'd like to hear some scenarios that actually have happened not some "once upon a time" fairytale about potential failures...

-s

From MossMan Scuba: (emphasis mine)

The use of a double bladder has also been an issue of contention. Personally I would rather be properly weighted before I go down under pressure. If I am not extremely negative on the surface I should be able to swim myself up from the bottom once I have discarded a minimal amount of weight. Whether I am diving in cold or warm water I do not count on any flotation device to ensure my ascent to the surface. I observe the double bladder as a crutch for undisciplined divers. If you do not buy my theory about proper balancing of the system and you are a cold water diver then remember you also have a drysuit to assist you to the surface in the event your single bladder fails. In reality the redundant bladder is prone to the same mechanical injury as the primary and more often than not if the primary is punctured the secondary will suffer the same demise in one single motion.

I observed this on a recent trip. The diver relied on the two bladder system and instead of insuring the integrity of his system before he went into the water he chose complacency due to his trust in his back ups. The diver began his descent and when he went to add gas to his primary bladder he discovered the malfunction. Not a problem right? Wrong! He went to the back up and sure enough he discovered the same malfunction on his redundant bladder. The diver was somewhat off the downline and did not have a balanced system so he was extremely negative in the water. He went all the way to the deck of the wreck 200 Ô down, equalizing dead air space frantically along the way. The diver was experienced enough to gain his composure and dragged himself over to the upline and pulled himself up to the surface. He did not even have any weight to drop, as it was all inherent to his diving harness. Upon investigation on the surface we found a puncture hole through the same area in his bladders which had been sustained in transportation to the dive site. The double bladder also increases drag in the water, which makes it difficult to swim. You may not notice this while leisurely strolling the dam site or cruising a pristine wall, but when the chips are down and you are in a blowing current trying to swim back to the upline you will notice it is a definite CO2 builder.

Today's wings from most manufacturers seem to be pretty tough. Something has enough force to poke a hole through the outer protective layer and the first bladder, chances are it's going to go through the second one too. Personally I'd rather take better care of my gear and use a balanced rig (and a drysuit as redundant buoyancy) than use a dual-bladder wing.

 

[Ghost69]

Sparticle,

I am a cold water diver and I always use a dry suit with a single bladder 60lb wing when diving in cold water with steel double 95’s.

My only question was if the diver was going to a warm water location such as the Florida Keys, Bonaire, or Cozumel during the summer months which set up would you choose if using a set of double steel 95’s or greater:

• dry suit and a single bladder wing
• wet suit and stack two single bladder wings
• wet suit and a dual bladder wing

Instead of doing my trimix course in the Great Lakes I was going to try and finish it somewhere nice and warm in the Caribbean. Not sure how comfortable wearing a dry suit would be in Cozumel in July so I was considering opting for the wet suit route.

 

[Ghost69]

Sparticle,

"Personally I would rather be properly weighted before I go down under pressure. If I am not extremely negative on the surface I should be able to swim myself up from the bottom once I have discarded a minimal amount of weight. Whether I am diving in cold or warm water I do not count on any flotation device to ensure my ascent to the surface. I observe the double bladder as a crutch for undisciplined divers."

Could you elaborate? What type of gear configuration are you wearing when you refer to this. Just curious and perhaps I could pick up a pointer. Other than my stage bottles I have nothing else I can dump weight wise. I typically dive steel 95's, one aluminum 80 oxygen, and a 40 aluminum EANx 36% or 50% depending.
Just with the steel 95's I am pretty negative.

 

[Ghost69]

This is all that I am trying to get a consensus on.

Question for everyone. I am a cold water diver who dives the Great Lakes and my set up has always been a single bladder 60lb wing while using my drysuit as my redundant buoyancy (please note I do carry a 50lb lift bag, I just do not rely on it for bouyancy). This is pretty much all that I dive in cold water.

I may have the opportunity to do some warm water tec diving in July 2008 in Key Largo which I have not done before. All experience has been cold water thus far with drysuit and single bladder wing.

My question is which option is best. And please feel free to list pros and cons of all three choices with safety being of utmost concern.

1. dive a dry suit with a single bladder wing (got to be hot in July in the keys going dry)
2. dive a wet suit and stack a 60lb single bladder wing with a 45lb single bladder wing
3. dive a wet suit with a 60lb dual bladder wing (Apeks WTX 60)

 

[Thalassamania]

I'm thinking worst case scenario. You are in a wetsuit, and double steels(AL80s would be best possible positive bouyancy characteristics). You dive down on a wreck and a wire punctures your BC going in the door for a short swim through/penetration. (As said, this is thinking outside the box). You abort, and for some reason get blown off the wreck. So a) you are still full of gas and a little heavy and b) you are in a scenario where you are away from your team member(s) (I have the team mentality and not a buddy that is going blindly follow you off the wreck, so you're on your own). You have to come up, do your deco/stops on the lift bag and now you're heavy and drifting in heavy waves. The dive boat most likely saw your bag (provided you popped your bag in a reasonable amount of time, as taught) and now you gotta stay afloat for awhile while the boat waits for the rest of the divers to do their deco and come onboard before they follow the current to come get you.

Other than taking the double bladder advice, I like "do it easy"'s advice, get out of the rig (which IANTD actually teaches), clip it to the ring at the bottom of my bag and float in the wetsuit. I will most likely still either do the double bladder or stick with my drysuit (TLS350). If these options were not available at the time, I want to know my options.

Thanks again,

Daryl

You're at the surface so your suit is back to normal buoyancy. Your "excess" weight is the gas in your tank which you could get rid of with your purge button. You could also ditch any weights (with a 7mil suit and twin steels you'll likely have some lead).

If you really feel that you need redundant buoyancy, get a Fenzy and wear it also.

 

[Ghost69]

Don't you have to get back to the surface first? And won't one still be negative in a 7mm? I am still negative in a dry suit with steel 95s and I do not have any extra weight, plenty negative as is.

 

[Thalassamania]

Don't you have to get back to the surface first? And won't one still be negative in a 7mm?

There was an assumption that he was back at the surface.

I am still negative in a dry suit with steel 95s and I do not have any extra weight, plenty negative as is.

If I were negative with near empty tanks, I'd rethink my setup and add some non-compressible buoyancy.

 

[DutchDown]

This has certainly been an interesting thread! But at the end of the day, I still don't understand why some folks are so vehemently opposed to a redundant wing. Seems to me that redundancy is good. The potential for a runaway inflator can be solved by planning to inflate the redundant bladder orally if necessary. That seems to be a simpler solution than unrolling a lift bag or smb, attaching it to a reel, then inflating it. It could be that both bladders might be punctured at the same time. It could also be that one remains intact. It is equally true that your drysuit could be punctured or torn in the same incident. Certainly a drysuit has more surface area to be punctured, along with fragile neck and wrist seals. We rely heavily on redundancy in diving: extra mask, backup lights, two second stages, etc. Why is a redundant bladder so offensive? I have both a single bladder wing and a double bladder wing. I use one or the other depending on the dive, just as I dive single or double tanks or a wetsuit or drysuit. That's the way I like to dive.

Best regards,
Phil

 

[Ghost69]

What would you add for some non-compressible buoyancy? Reason I am asking is I am negative with steel 95's (near empt). Are you talking about adding a wing or something else?

 

[Thalassamania]

I've used any number of items in different situations ranging from small spherical net floats to specially cast syntactic foam.