Negatively buoyant divers vs. ditchable weights

[Dack]

This is NOT a discussion about ditchable weights or not. This is a question about what to do about ditchable weights if you don't run any weights.


For whatever reason you plus your rig are negatively buoyant, and therefore you don't need to run any weights. Maybe you're diving in warm fresh water, so no exposure suit needed. Maybe you're diving doubles. Maybe you're 0% body fat and you'd sink even in the Dead Sea.

Whatever the reason, there's no extra weight you can jettison from your rig. Maybe it's by a little or maybe its by a lot, but at the surface you will sink without an inflated BC.


So there seems to be a conflict between divers who are negatively buoyant, and ditchable weights. I've never heard this discussed before. Does that mean these divers be carrying floats? It sounds absurd, but I don't know another solution.


Personally I am a sinker with a standard BC + single steel tank in fresh water. So far I've only dived cold waters so it's not an issue. Yet...

- Dack

 

[boulderjohn]

Does that mean these divers be carrying floats? It sounds absurd, but I don't know another solution.

That is, in a nutshell, the solution many divers have when their rigs are negative enough to be a concern.

For some, it means diving with a dry suit, which supplies redundant buoyancy in case of a bladder failure in the wing.

For some, it means using a wing with dual bladders.

For some, it means carrying a lift bag or SMB that can be inflated in case of a wing failure.

And some don't worry about it if they are not too negative.

 

[aquaregia]

Personally I am a sinker with a standard BC + single steel tank in fresh water.

I think the why is important. You could use an aluminium tank and score 4-6lbs of positive buoyancy.

 

[Bubbletrubble]

If you are negatively buoyant at the surface, need to remain at the surface, your BCD/wing won't hold air, and you have no ditchable weight, you have to:

• Ditch something else from your rig (negatively buoyant camera gear, canister light, etc.),
• Inflate something that you carry/wear with you (your lungs?, drysuit, SMB, lift bag, etc.),
• Kick to remain on the surface,
• Hang onto some physical object that allows you to remain at the surface (ladder, rock, anchor line, float, etc.) or
• Ditch your rig.

If your buddy is nearby (and he should be), then he can also support you at the surface with his buoyancy device(s). Another possibility is the buddy can help ditch some weight on your rig which is not usually readily ditchable (weights in pockets on tank cambands).

If you are properly weighted (not over-weighted), then it makes it a lot easier to deal with this situation. At the surface, you really should never be more negatively buoyant than the weight of your gas.

 

[aquaregia]

If you are negatively buoyant at the surface, need to remain at the surface, your BCD/wing won't hold air, and you have no ditchable weight, you have to:

• Ditch something else from your rig (negatively buoyant camera gear, canister light, etc.),
• Inflate something that you carry/wear with you (your lungs?, drysuit, SMB, lift bag, etc.),
• Kick to remain on the surface, or
• Ditch your rig.

Depending on your gas levels, you could get a few pounds by purging the tank down. A pair of 80s could get you 10lbs.

 

[Bubbletrubble]

Depending on your gas levels, you could get a few pounds by purging the tank down. A pair of 80s could get you 10lbs.

Yup. You're absolutely correct.

 

[Jim Lapenta]

Another reason that non swimmers should not be diving. If you can't tread water or swim to stay afloat you need to be in a life jacket and maybe some of those water wings for kids. Not on scuba.

 

[rjack321]

Personally I am a sinker with a standard BC + single steel tank in fresh water. So far I've only dived cold waters so it's not an issue. Yet...

How many really really warm water lakes are you planning on diving with a steel tank?

 

[Dack]

Another reason that non swimmers should not be diving. If you can't tread water or swim to stay afloat you need to be in a life jacket and maybe some of those water wings for kids. Not on scuba.

What does non-swimmers have to do with it? If you're unconscious or exhausted knowing how to swim doesn't help. Ditching weights does.

And personally, I'm not planning to dive any warm lakes...but I like to think about such things.

- Dack

 

[DivemasterDennis]

Good discussion question. First of all, your BC can inflate manually at the surface,unless it is leaking or broken, so that is option one. If the BC is not functional then the back up plan is a safety sausage. I carry one on all open water dives- you know, the long bright tube that rescuers can see if you are adrift at sea. They are compact but will offer plenty of lift for anyone in your situation that doesn't want to jettison valuable gear. Another option is to dive an aluminum tank that will be positive when under about 1000 psi. Fianlly, consider some amount of buoyant protective gear- like a 3 mil vest, to be less negative.
DivemasterDennis