DAN advocating using drysuit for buoyancy control while diving

[tbone1004]

Just got my DAN Safety Stop in and am very baffled by this comment

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[TD]1. Buoyancy – Use your suit for primary buoyancy control rather than your BCD. Use your BCD for surface support or if your suit buoyancy fails[/TD]
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Does this bother anyone else? The suits form a bubble that is difficult to control, difficult to vent quickly, etc etc. I get they are appealing to the new recreational divers and the general though is let them control one bubble instead of two, but come on, don't make that your #1 drysuit tip. Enough air in the suit as necessary for thermal comfort, the rest should be taken up in the wing....

Uggh, just frustrating when stuff like this comes out.

 

[kwinter]

Been doing it that way for years. Difficult to control the bubble? Ridiculous. Moving gas around in the suit helps control trim while that's impossible with a wing or BCD.


iPhone. iTypo. iApologize.

 

[MXGratefulDiver]

Seems this is another one of those topics that's been flogged pretty well around here. PADI teaches suit for primary buoyancy, and I suspect that DAN is just following their lead.

I've had drysuits from a half-dozen or so companies, and the manufacturers are about evenly split in terms of which method they recommend. NAUI says only put enough air in the suit to remove squeeze, and use the BCD for primary buoyancy control. That's my preference as well. But I recommend to my students that they try it both ways and go with the one that's most comfortable to them ... if you're properly weighted there won't be enough of a difference to matter (unless you're carrying multiple tanks and it's just at the beginning of the dive).

... Bob (Grateful Diver)

 

[Dhboner]

I use a hybrid of the two philosophies I add air to the suit at the beginning of the dive to loft my undergarment and get warm. If needed, I add air to the wing after that for buoyancy however if the dive goes long and I need to warm up I will vent my wing completely and add more air to the suit for warmth.

 

[Akimbo]

I don’t have a problem with either technique. Using the suit as a BC was common practice before BCs and when drysuit dump valves were manual. It also depends on how much gas you are packing. The weight change on a single 80 is much less consequential than on a diver packing 200-300 Ft³.

Using the suit for small changes in gas weight over the dive is probably easier for a properly weighted diver than using a BC. Minor back-pressure adjustments to the suit’s automatic dump valve handles it.

 

[boulderjohn]

This has been discussed numerous times. Almost all agencies advocate this for basic OW recreational dry suit use. The book Dry Suit Diving: A Guide to Diving Dry, by Barsky, Long, and Stinton, also advocates it. (The authors are founders of DUI and Viking dry suits.)

The current PADI dry suit course differentiates between different kinds of suits and diving. For example, tech divers who are of necessity overweighted at the beginning of a dive will need to use both the dry suit and the wing for buoyancy.

With the last recreational dry suit student I taught, we zeroed in his weight so well that he found no need to put any air in his wing. Once he had the proper amount of air in the suit at depth, he was neutrally buoyant. All he had to do was roughly maintain that proper amount of air to maintain that good buoyancy control. I just did a pool session with him a couple of hours ago. He is now starting technical instruction, and he was wearing double steel 85s with his dry suit. That's a different situation, and he had to use both the wing and the dry suit to maintain his buoyancy because of the extra weight.

A properly weighted, single tank diver should not have a need for much air (if any) in the wing. If you have a properly inflated suit and still have enough air in the wing to be using that as your primary buoyancy control, then I would suggest you might be overweighted.

 

[tbone1004]

Dhboner, that's the method I use if it's cold water, enough air to get comfortable, then wing for the rest, often times that may be more than is actually needed but I'm comfy and the unfortunate effect of that is having less air in the suit at the end of the dive than you do at the beginning of the dive, which is the opposite of what I want in cold water. In warm water it is always just enough to offset the squeeze and wing for the rest.

My issue is really in advocating using it for primary buoyancy. BC's do two things, they offset the weight of the gas you are breathing during the dive, and they offset any change in buoyancy from the exposure suit. Even though an al80 is only about 6lbs of air when it is full, and is inconsequential for the recreational diver, what happens when that diver goes to an E8-130 and all of a sudden has 10+lbs of air he is offsetting or to doubles and then has to learn a new method for controlling buoyancy.

Ken, I use the suit to control trim all the time, being able to pack air in your feet is one of the wonders of drysuits, but I am bloody miserable if I have too much air in my legs and have to move around. I'm not saying you should only put enough air in to offset the squeeze, that is practical for warm ish dives, but once you're below 60f or so you need more air in their for thermal protection. Put enough in until your comfortable and take up the slack with the wing. I disagree with the statement, but for a non-training agency to be giving training advice is my issue. If they had stated, "put as much air in the suit as you need to stay comfortable" that would have been fine, but with the ever progressing amount of high volume steel bottles in the recreational market, 6lbs in al80 or LP72 is a lot different than 11lbs in a 130.

 

[Redshift]

I think there is a problem with terminology here.
In my opinion, dry suits should not be used for buoyancy control. Of course that, as they require air inside to be comfortable and to insulate, they will affect buoyancy. And it is usual that for recreational divers, the amount of air inside a suit so that it's comfortable is also very close to the amount of air needed for buoyancy. But this is a secondary effect, it shouldn't be said the suit is being used for buoyancy, the suit is what it is.
Using the suit for buoyancy means to go over what is needed for comfort and insulation, specifically to offset our weight in the water. That's using the suit not for its main purpose and in a suboptimal way that can cause other problems.
The contrary can be done though, when the BCD is already empty and the diver is still light, removing air from the suit becomes a means to control buoyancy, but it's preferable to be properly weighted and not have to be squeezed

 

[kr2y5]

As I personally found out not long ago, it really makes a lot of sense to have a redundant source of negative buoyancy... and some even argue it is warmer this way... so, I am definitely putting more air into my drysuit than just to avoid the squeeze.

 

[JohnN]

A properly weighted, single tank diver should not have a need for much air (if any) in the wing. If you have a properly inflated suit and still have enough air in the wing to be using that as your primary buoyancy control, then I would suggest you might be overweighted.

I dive with an HP120 and see almost a 9 lb swing from full to 'on-the-boat' That is a lot of air in a suit, no thank you.