Redundant Bouancy

[Glaucus]

Paddler,
You would be wise to heed RedHead's advice and not think about clipping a lift bag or SMB to your now defunct bouyancy compensator. Doing so would not only increase your ascent, but it would also increase your chances for a stay in your local hyperbearic chamber. Here is my freely shared opinion on why it's not a good idea: the magic eight ball of task loading says that all signs point to no.

Your bc breaks and you think you'll need help ascending so you clip off a lift bag. Now you have to find a way to get air into it. Most likely you'll use your primary in some way because you realize squeezing off your secondary could cause a free flow. Once the air hits the bag, you're on your way up. If the bag doesn't jerk you into an awkward position, then maybe you will have a chance to try and pull the dump valve in a near feeble attempt to control your ascent rate as you simultaneously jam your reg back in your oral cavity. Now you only have to decide if you're going to watch bubbles to montior your rate or if you're going to swing your computer to your saucer wide eyes and use that. Now do all that in a one smooth motion with just a seasoning of panic and I'll give you my old bowling trophy - sure, I'll snap off the bowling ball and rubber band a small tank on his back. Now count the number of tasks and if that number is higher than two, I sure wouldn't be doing it.

Can a bc failure occur? Absolutely. Is it likely? Not really. At some point you are going to have to trust your gear. And don't panic! If you're breathing, your situation is only urgent and not emergent. You're a solo diver. You're good at what you do. You know how to weight yourself properly. Stay calm! Try swimming up. Ditch weight as a very last resort. And if you feel the need to use a smb or lift bag, clip it to a reel, deploy it, and use the line as an ascent assistance device kick-pull-kick-pull-kick-pull-kick-pull-kick...

Acquatically yours,

 

[cdtgray]

I understand that the use of a lift bag for redundant bouyancy certainly has it's critics, there are a few points to consider.

BC failure is not a likely occurance as long as you take some general preventative maintanence steps with your gear. When it does happen though, it is an emergency situation.

While it is ideal to have your gear configured in a manner to allow you to swim it up in the event of a BC failure, being able to do so is not always a reality due to a variety of factors.

Employing a lift bag is not difficult once you have practiced, it allows for just as controlled ascents as with a BC and it does so with far fewer possible points of failure than any BC.

Clippling a lift bag to yourself can put you at a different than normal position, but not so much so as to prevent you from being able to easily add/remove air and make a controlled ascent.

I do completely object to the notion of sending my lift bag to the surface attached to a spool/reel in a negative bouyancy situation. If I am negatively bouyant my goal is to become neutral. I dont want to send the source of that neutral bouyancy to the surface at the end of a thin piece of nylon line. I want it with me.

I again restate the recommendation for an open-ended lift bag with a good pull dump. This gives the additional option of simply inverting the bag and rapidly dumping the air if you run into trouble.

 

[Nemrod]

Wow, y'all really need all that to dive in a little ol' quarry? N

 

[Charlie99]

BC failure is not a likely occurance as long as you take some general preventative maintanence steps with your gear. When it does happen though, it is an emergency situation.

It is an emergency situation only if you are so negatively buoyant that you have trouble maintaining depth. That will happen only if you are grossly overweighted, or if you have a very thick wetsuit (multiple layers of 7mm for example).

I did have an incident where, sometime between when I setup my gear on a boat and when I jumped in, somebody or something had caught on my corrugated hose and pulled it hard enough to break the pull dump wire. It lodged under the dump valve, making it so that the BCD wouldn't hold air.

I discovered this shortly after jumping in to do a 130' wall dive with an AL80 and a 5mm full wetsuit.

While not being able to get neutral was a nuisance, it was by no means an emergency, and I chose to go ahead and do the dive. I did find it a lot easier up above 60' where the suit expanded enough to reduce the negative buoyancy, but it was still a controlled situation even at 130'.

You can easily simulate a failure by emptying the BCD bladder or wing at depth at the beginning of a dive when your tank is heaviest, and find out whether for you it is an emergency or simply a minor nuisance.

Before doing things like clipping off a lift bag to your BC and using its dump valve to try and maintain neutral buoyancy, my suggestion is to first do the simple, straightforward thing and fin around at a 45 degree angle like a newbie diver.

 

[Nemrod]

Not sure you should really need one BC much less two. Cannot you just swim back to the surface.

Why am I so happy, I don't need no stink'n BC, redundancy or much else. Free yourself, dump the gear, you don't need it. All that stuff is like riding a bike with training wheels. N

 

[TheRedHead]

You get a lot of suit compression in that shorty, Nemrod.

I think the OP's thinking about these things is a very positive sign. Redundant buoyancy is a concern of those diving doubles or those in very thick wetsuits and steel tanks.

 

[captain]

I have dived many time with a 3/8" full suit and steel 72 with no BC. It can be done very easily. All the newer equiptment makes things a little easier but it is not impossible to do without them.

 

[DeepBound]

I have a similar setup, I have a thick wetsuit, a HP100 tank and a 6#STA plus 6# of ditchable weight. I've found that with the wing deflated, even ascending from 60ft on fin power is very hard.

My backup plan until I get a drysuit for real redundant buoyancy is.. don't go below 60ft when solo, and also I know that if I ditch the 6# the swim up will be a lot easier. I might be buoyant at the top, but so what, fin down for the safety stop, it's better than being stuck on the bottom.

I also carry a strong SMB so that I can fill that and *pull myself up the line*. Typical #24 line can carry more weight than your lift bag is probably rated for. I'd never clip it off to myself. Combined arm-pull power plus finning power will make the SMB much more useful than a big expanding bag of air racing you to the top. What a nightmare scenario.

That being said, drysuit is where I'm looking to go, for the proper fix to these problems! No, I won't use the drysuit for buoyancy *normally* but in an emergency, it can be used for buoyancy.

Nemrod, I envy you with your shorty diving in those warm waters Come up to Canada in January some time for an ice dive heee

I think I'm hitting a problem with the wet suit...

Right now I have a SS backplate and use a Steel 119. I dive 8# of lead. I tried 6#'s, but it gets a bit tricky at the safety stop when tank pressue drops. All together 14# of weight.

I'm going to have a hard time diving wet, aren't I? I believe I see where you are going.

So there really is no piece of actual gear that would really compensate for redundant bouancy. It is just techniques? What I mean by actual gear as an example would be diving doubles with an isolation manifold and two regs, two computers, two masks, two compases, so on so forth.

 

[grazie42]

Paddler:
I think you may be a bit overweighted. I dive 5,5mil +7mil and use 6lbs (I am still a bit heavy). I don´t know if you are or not but doing a proper weightcheck is a good way to find out. You may not even have a problem.

As for buying gear, once you get the hang of a drysuit, you´ll love it for a bunch of other reasons (besides added redundancy), get one ASAP (and make sure you get one that fits)...

 

[Diver Dennis]

It is an emergency situation only if you are so negatively buoyant that you have trouble maintaining depth. That will happen only if you are grossly overweighted, or if you have a very thick wetsuit (multiple layers of 7mm for example).

I did have an incident where, sometime between when I setup my gear on a boat and when I jumped in, somebody or something had caught on my corrugated hose and pulled it hard enough to break the pull dump wire. It lodged under the dump valve, making it so that the BCD wouldn't hold air.

I discovered this shortly after jumping in to do a 130' wall dive with an AL80 and a 5mm full wetsuit.

While not being able to get neutral was a nuisance, it was by no means an emergency, and I chose to go ahead and do the dive. I did find it a lot easier up above 60' where the suit expanded enough to reduce the negative buoyancy, but it was still a controlled situation even at 130'.

You can easily simulate a failure by emptying the BCD bladder or wing at depth at the beginning of a dive when your tank is heaviest, and find out whether for you it is an emergency or simply a minor nuisance.

Before doing things like clipping off a lift bag to your BC and using its dump valve to try and maintain neutral buoyancy, my suggestion is to first do the simple, straightforward thing and fin around at a 45 degree angle like a newbie diver.

Good post Charlie, I agree. You would have to have a lot of weight on you not to be able to fin up slowly. Why not dump the weight if it's a problem?