Diving Safely Without A BC

[2airishuman]

Current teaching from PADI is that it is unsafe to dive without a BC. I assume other agencies teachings are similar.

Some divers nonetheless dive without a BC, at least some of the time, either because they are vintage equipment enthusiasts or for reasons of simplicity and streamlining.

Under what circumstances, if any, do you believe it is safe without a BC? What skills or knowledge do divers need before undertaking this style of diving?

 

[tbone1004]

not sucking?

It is all a balancing act. If you are diving a balanced rig, and your lungs are able to compensate appropriately for the tanks being used, it is a non-issue.
Tank size: Anything smaller than an AL80 is fine. LP72's, AL63's, LP50's etc etc etc. Your lungs can compensate for the amount of air in these tanks with little issue. It is roughly 6lbs, or 3l of lung volume. Normal tidal volume is typically 0.5l, or 1lb, but expanding it to a couple of pounds is not that difficult. Average humans have roughly 6l of lung capacity, with a vital capacity of somewhere around 3l. You'll be fighting it a little bit at the beginning of the dive with a larger tank, but you can adjust that a little bit with weighting. It is not a-typical to be a little underweighted when diving like this and use a suit like a 3mm to give you a few pounds to help out in the beginning of the dive and cut the dive a little earlier than normal on gas or to stay down a bit deeper to let the suit compression help you out.

Exposure protection: this is the important one. You can't use thick wetsuits and dive deep. This is the secondary function of a BCD, and as long as you are diving in a thin ish wetsuit 3mm or shorty, or no exposure protection, it is not that bad to work with.

 

[MaxBottomtime]

Gallery of California Backpack Divers : 1999-2001

 

[ronscuba]

My lungs might be able to compensate for various tank buoyancy, but I want to breathe normal when diving. This would be my concern about diving w/o a BCD.

Does anyone know a rough estimate of how much we breathe in/out in a relaxed state ?

If average lung capacity is 6 liters, we don't typically breath from 0 to 6. When diving, I breathe normal and relaxed, not full deep in/out. I imagine it is somewhere on the low side like 1-1.5.

 

[MXGratefulDiver]

Under what circumstances, if any, do you believe it is safe without a BC? What skills or knowledge do divers need before undertaking this style of diving?

... monkey diving ...

... you need to be able to drive a scooter with your toes ...

... Bob (Grateful Diver)

 

[Hawkwood]

Current teaching from PADI is that it is unsafe to dive without a BC...

I have missed that in my instruction materials and in the student materials.

Could you please point out where that is so that I can be aware of that?

 

[2airishuman]

It is in the safe diver pledge that students are supposed to sign. You know, the one where you promise not dive without a buddy, and promise not to loan your gear to people who aren't certified divers.

 

[2airishuman]

I looked. It is titled the "PADI Standard Safe Diving Practices Statement of Understanding." In rev 5/09, v. 2.0, paragraph 3 lists required equipment:

• Bc with power inflator
  
• SPG
• Alternate air source
• Dive computer or tables.

 

[Hawkwood]

Yup, that's were it is.

Still, I do not recall in any teaching materials being required tell students it is unsafe to dive without a BCD.

 

[Storker]

Current teaching is that it's unsafe to drive without a seatbelt. Some drivers nonetheless drive without a seatbelt, at least some of the time, either because they are vintage car enthusiasts or for reasons of simplicity.

Under what circumstances, if any, do you believe it is safe without a seatbelt?