BC or Drysuit for Buoyancy

[thor]

I have read in some of the manuals and have also been instructed that the drysuit should be used for buoyancy and that the BC should only be used on the surface.

However, I have also read in some tech manuals that the drysuit should only be inflated enough to insulate and avoid squeeze, but that the BC should be used for buoyancy due to the weight of gear (doubles, backplate, etc.), and that the drysuit would be overinflated if used for buoyancy under most tech conditions.

Which is correct?
Discuss

[skdvr]

Which ever you like better. I personally use my Wing more that my DS, but both come into play obviously. If I am starting to get a little cold then I use my DS more. As long as you are not severly over weighted then the air bubble in the DS should be very manageable. Try both and see what you like....

Phil

[CWSWine]

I have talk to my Padi instructor about getting dry suit certified and he said that Padi now teaches to use the DS for buoyancy not the BC. He also believes that using the DS for buoyancy is good skill to learn but also teaches buoyancy control with BCD. After the class the choice is yours but he prefers the BCD over the DS.

[MSilvia]

Understand both schools of thought, and do what's best for you. As I understand it, the DS buoyancy school of thought feels that there is less potential for task loading when divers are taught to use their drysuit for buoyancy control. Since you can't assume that divers in a PADI dry suit specialty class are comfortable enough to manage multiple (artificial) air spaces, it's safer for everyone if they teach to the lowest common denominator... in other words, they teach what's easier to learn, not what works better if you take the time to practice doing it correctly.

The other school of thought holds that a BC is for buoyancy control, and a drysuit is for exposure protection (except in emergencies). You maintain a constant gas volume in the suit in order to maintain loft in the undergarment, and use the BC to adjust buoyancy as needed. It allows divers better trim and buoyancy control (as there is a smaller and more consistant dynamic airspace), but does require the diver to manage multiple air cells, which can be challenging at first.

[thor]

Upon ascent, what is the best way to vent air if you are using the BC for buoyancy, while also venting from the DS.

I was using a drysuit for the first time and had difficulties holding the inflator hose to vent air and trying to make a "chicken wing" to vent the DS, at the same time. Any suggestions?

[jj1987]

It's also a lot easier to vent air from a front zip drysuit if you're horizontal than a back zip, due to exhaust valve placement.

[MSilvia]

Originally Posted by thor

I was using a drysuit for the first time and had difficulties holding the inflator hose to vent air and trying to make a "chicken wing" to vent the DS, at the same time. Any suggestions?

The first 12 dives I made in my drysuit were pretty difficult for me, so I think it can take a little getting used to. In general though, I'd say slow your ascent... if you're ascending too quickly to manage your buoyancy, you're ascending too quickly. Other than that, I'd recommend getting as much gas out of the suit as you can at the beginning of the ascent.

[skdvr]

I guess for me it really depends on how much air is in my DS but normally on my ascent I will grab thedump from my BC and vent a little, then the next vent comes from by DS by rolling just a touch to my right, then back to the BC to dump. I just alternate back and forth. Like MSilva said, you need to take it SLOW, espically your first few dives. After a little while it will become like second nature. I truely do not even think about it when I do it now. It just sort of happens. If I feel that the bubble in my DS is getting a bit to big then I may vent from there a few times without dumping from the wing, it all just comes down to feel.

Phil

[SkuaSeptember]

I fall into the DS for control category and here is the reasoning. At any given depth you require a certain specific volume of air to maintain neutral buoyancy. It does not matter if that air is in your BC, a lift bag that you hold onto or in your DS. If you are properly weighted at the surface - the lofting is just comfortable, the BC is empty and a full breath will float you while a full exhale will let you descend, then this is the balance that you want to keep throughout your dive. Hence no need to play with the BC. If you are wearing a shell suit, the only air space that will compress when you descend is in the lofting of your under garments. Keep the loft consistent and you will maintain neutral buoyancy. If you are wearing a crushed neoprene suit the compression of the material should be negligible to slight. If you are wearing a suit made of a more traditional neoprene, I would think that more of a case could be made for using your BC for control in conjunction with the DS.
As for the ascent, the general practice is to dive with the dump valve at the full open setting. Then all you need to do is keep your left bicep up slightly as you make a slow ascent. If you still feel excessivley bouyant all you need do is raise and then sharply lower your left elbow - easily done even if both your hands are occupied.
In the end, either method will get the job done, go with what works best for you.

[Heavy D]

Originally Posted by jj1987

It's also a lot easier to vent air from a front zip drysuit if you're horizontal than a back zip, due to exhaust valve placement.

Where are you getting that information from? Nearly all suits regardless of zipper configuration have the dump valve on the left sleeve. The only difference the zipper really makes is getting in and out of the suit.

FWIW, I prefer to use the wing for buoyancy and only put enough air in the drysuit to maintain loft. It's just easier to vent the wing IMO.