Redundant Bouyancy - Dual Bladder v. Lift Bag v. Dry Suit

[tbone1004]

you "should" always be able to kick your gear to the surface, which goes in the "balanced" rig category. Worst case you drop a weight belt if you have one, but doubles are rarely more than 25lbs ish negative, which should relatively easily be kickable to the surface with fins on. That being said, I use a drysuit as a "backup" and if I'm in the ocean I have an SMB and a min 50lb lift bag on me at all times so that works, but I have never not been able to kick my gear to the surface. SMB would be my go to for ocean diving as I could hang from the line and chill out on deco. In a cave, drysuit and bounce out moon style. Or since I dive sidemount, drop one cylinder, clip the other to my scooter D-ring and kick out that way in a real emergency, come back and get the other bottle later. Practiced this in the quarry a few times and it's interesting, but it works

 

[PfcAJ]

Dropping half your gas seems highly suspect as a way to manage loss of buoyancy in a cave...

 

[randy88k5]

My TDI AN/DP instructor insisted that the students use a dual bladder wing if a drysuit was not being used and the diver was using steel tanks. He would exempt the redundancy with aluminum tanks on a case-by-case basis. Part of the class was ascending on a lift bag and holding your stops without the use of the wing.

 

[Tortuga68]

I use an AP Valves Buddy. 1.4m long, 20cm wide - self-sealing. I approximated this at 20kg/44lbs (20 litres) lift when full

Yeah I believe they're about 40# as you said - for some reason I always think they're 30#

doubles are rarely more than 25lbs ish negative

Depends what tanks you're using

 

[DevonDiver]

Dropping half your gas seems highly suspect as a way to manage loss of buoyancy in a cave...

Not really.

It depends when you lose buoyancy.

On the way in... little/no deco accumulated. Remove stages, abort and exit on back-gas..

On the way out... backgas minimal - ali cylinders buoyant. Deco stages being consumed - ali cylinders gaining buoyancy. No need to dump stage/s.

Of course - that assumes you've got your rig balanced right...

 

[ajduplessis]

All three methods will provide you with additional lift if used in a proper way (read well trained/experienced). All three have pros and cons and need to be carefully thought through based on the diving requirements and conditions.

Gaining diving experience coupled with solid and open minded research will help you a lot. I dive with a drysuit and carry lift bags, however they are useless to me if I don't know how to use them as redundent buoyancy devices. I am not a big fan of dual bladder systems and rather spend money on a drysuit that also adds additional value.

Diving is all about reducing risk and what you feel comfortable with. Do your homework and you will soon come to a solution that will work for you without adding additional workload when the pooh hits the fan.

 

[PfcAJ]

You should reread the above post. we're not discussing stages.

Not really.

It depends when you lose buoyancy.

On the way in... little/no deco accumulated. Remove stages, abort and exit on back-gas..

On the way out... backgas minimal - ali cylinders buoyant. Deco stages being consumed - ali cylinders gaining buoyancy. No need to dump stage/s.

Of course - that assumes you've got your rig balanced right...

 

[Scott L]

My TDI AN/DP instructor insisted that the students use a dual bladder wing if a drysuit was not being used and the diver was using steel tanks. He would exempt the redundancy with aluminum tanks on a case-by-case basis. Part of the class was ascending on a lift bag and holding your stops without the use of the wing.

Deployed on the surface or hanging on for the ride while expelling gas?

 

[waterpirate]

How about an intro to tech class one weekend? That will give you some face time with an instructor, maybe gain yourself a mentor, maybe dive some borrowed kit, and meet some people who can answer these questions for you locally.

One of the biggest mistakes in gear purchaseing is buying what you think you need. Invariably it will not fit what the instructor you choose wants to see, unless you have met him ahead time for some one on one prior to gear purchase.
Eric

 

[Scott L]

How about an intro to tech class one weekend? That will give you some face time with an instructor, maybe gain yourself a mentor, maybe dive some borrowed kit, and meet some people who can answer these questions for you locally.

One of the biggest mistakes in gear purchaseing is buying what you think you need. Invariably it will not fit what the instructor you choose wants to see, unless you have met him ahead time for some one on one prior to gear purchase.
Eric

Unless of course, one acquires Halcyon.