Reg Braithwaite
Contributor
From another thread:
Summary: It is not necessary to be overweighted. This seems correct for my recreational setup: For warm water I am diving a 3mm wet suit, AL80, steel BP, and need only 2lbs. of weight to be neutral with an empty wing at 10'.
I will have to play with my dry suit and see how things work out for my just-purchased HP-130s. Maybe I can keep the steel BP, maybe I need even more weight to compensate for the undergarments' buoyancy.
All that being said, what about choosing a wing capacity? Although things can balance out nicely in the normal case, in my n00biditrudinous mind I am thinking you need a wing with enough lift to handle the worst case. For a wet suit, that is full compression at depth. For a dry suit, would that be a suit flood at depth with all tanks full of air? I am assuming that the undergarments will lose some of their buoyancy if flooded, and you would need to add enough air into the wing to make up for the suit flood.
Is this right? Or is the loss of buoyancy negligible when the suit floods?
Start with the *Minimum Buoyancy* of your dry suit.
What is the minimum buoyancy of your suit? It is the amount of ballast you need to get neutral if you were wearing only your undergarment and drysuit, in neck deep water with an open exhaust valve.
Let's say you test your suit and find that it takes 24 lbs to get neutral with only your undergarment and drysuit on.
What is the goal for your total weighting? To have your total ballast equal to the minimum buoyancy of your suit (+ 1-2 lbs) with empty tanks.
Why? If you need to hold a shallow stop while you breathe down your backgas to zero you need enough ballast to offset the buoyancy of your suit. Pretty simple.
If your "rig" i.e. back plate +harness + empty tanks + bands and manifold + regs + can light provides more than ~26 lbs. (24 +2) then you need to change components, lighter plates, lighter tanks etc. until it does.
If your rig provides less than 26 lbs you need to add ballast, or you will not be able to hold a shallow stop with empty tanks. Different plates, and or adding ballast to the rig or using a belt.
Now if your rig provides ballast equal to the minimum buoyancy of your suit +2 lbs with empty tanks how negative will you be when you have full tanks?
The weight of your back gas + 2 lbs.
Do you ever **need** to more negative? No. If not why select components that increase the problems a diver will face if they suffer a buoyancy failure?
Carrying more ballast than is required to hold a shallow stop with empty bottles offers no advantage, and increases the risks for the diver.
Over weighted + a larger wing is simply ignorance in action.
Summary: It is not necessary to be overweighted. This seems correct for my recreational setup: For warm water I am diving a 3mm wet suit, AL80, steel BP, and need only 2lbs. of weight to be neutral with an empty wing at 10'.
I will have to play with my dry suit and see how things work out for my just-purchased HP-130s. Maybe I can keep the steel BP, maybe I need even more weight to compensate for the undergarments' buoyancy.
All that being said, what about choosing a wing capacity? Although things can balance out nicely in the normal case, in my n00biditrudinous mind I am thinking you need a wing with enough lift to handle the worst case. For a wet suit, that is full compression at depth. For a dry suit, would that be a suit flood at depth with all tanks full of air? I am assuming that the undergarments will lose some of their buoyancy if flooded, and you would need to add enough air into the wing to make up for the suit flood.
Is this right? Or is the loss of buoyancy negligible when the suit floods?