SMB as backup lift source.

[doctormike]

So with near empty tanks in shallow water, id be pretty close at around -6 or -7 lbs buoyant. Is that good enough? I guess if my wing(s) ever failed I could just start purging air if I kept sinking.

Dunno, can you swim up 6 lbs? I think that if you are going to be a tech diver, you probably could do that.

People talk about that idea of dumping gas to help with buoyancy in an emergency. Gotta say, that would be about the last thing I would ever do.

Yes, theoretically it would make you more buoyant, but I would try every other source of buoyancy before resorting to that. If you intentionally free flow a reg and can't get it stopped, it will drain a tank pretty quickly. So yeah, you could quickly close that post, but it's always good to have your gas. Ditch anything heavy that you are carrying, use one of your two SMBs (you have two, right?). Use a double bladder wing. Or get a dry suit. And balance your rig. No reason you can't put something together that you can swim up.

 

[PfcAJ]

So with near empty tanks in shallow water, id be pretty close at around -6 or -7 lbs buoyant. Is that good enough? I guess if my wing(s) ever failed I could just start purging air if I kept sinking.

Obvious troll is obvious.

 

[MaxBottomtime]

So many posts about solutions to a problem that shouldn't exist. Don't dive steel doubles with a wetsuit. Period. Get a couple of aluminum tanks and double them up until you get a drysuit.

 

[CaveSloth]

So... double bladder wing.... yes.

2 smbs? Ok can do.

Will definitely test trying to swim up etc... thanks.

 

[MaxBottomtime]

 

[Ayisha]

So... double bladder wing.... yes.

2 smbs? Ok can do...

Or instead find an instructor from an agency that will teach you the importance of diving a balanced rig and how to achieve it as a start.

 

[rsingler]

Since this is the Basic Forum, @Ayisha or @doctormike or @Ryan Mcshane , can we take a minute to define "balanced rig", please?
Or if that's too contentious, how about, "In the event of a buoyancy failure (wing failure, drysuit flood), a balanced rig will allow you to _____, because it _______."

 

[Ayisha]

Since this is the Basic Forum, @Ayisha or @doctormike or @Ryan Mcshane , can we take a minute to define "balanced rig", please?
Or if that's too contentious, how about, "In the event of a buoyancy failure (wing failure, drysuit flood), a balanced rig will allow you to _____, because it _______."

Balanced Rig: "At the start of the dive, to be able to surface from depth/the deepest point with a full tank and a wing failure. At the end of the dive, to hold a 10 foot stop and make a controlled ascent with an almost empty tank".

 

[rsingler]

At the end of the dive, to hold a 10 foot stop and make a controlled ascent with an almost empty tank"

Just to clarify...with a wing failure?

 

[Ayisha]

...At the end of the dive, to hold a 10 foot stop and make a controlled ascent with an almost empty tank".

Just to clarify...with a wing failure?

No, a wing failure at the beginning of the dive (the heaviest point). The nearly empty tank at the end of a dive (the lightest point). So in other words, you are prepared for the 2 extremes you encounter on every dive. If you can't swim up your rig from depth with a wing failure, then it's not a balanced rig.

To answer your question specifically, it wouldn't matter if you had a wing failure at the end of a dive with a balanced rig, since your tank is less negative and the BCD should be nearly empty at the last/safety stop anyway if you're correctly weighted.

The easiest time to get your weighting correct is at the end of a dive. With a nearly empty tank at 10 feet, your BCD should be empty and you should be able to make a controlled ascent to the surface. If there's gas in your BCD at 10 feet at the end of the dive, you're overweighted. You can remove 2 lbs each time until it's just right. If you can't hold a 10 foot stop with a nearly empty tank and empty wing or can't control your ascent to the surface, then you're underweighted. You can add 2 lbs till you get it just right.