Drysuit Buoyancy ????????????????????

[JeffG]

As a commercial diver I learned to use the dry suit for buoyancy. We don't wear BCDs when diving for work, unless on scuba, which is not done very often.

But, there are some folks here on the board with a lot more scuba and tech experience than myself that will tell you that is wrong and you could have serious buoyancy issues, therefore control buoyancy with the BCD and add air to the suit for comfort.

Your choice.

as a recreational diver, I have learned that it has nothing to do with commercial diving.

Your choice.

 

[Saudi-Diver]

I have recently started Dry suit diving and dive a 5 mm compressed neoprene dry suit with neoprene seals. I was trained to use the suit for buoyancy control but now just seem to use the BCD for buoyancy control and just take the squeeze off the dry suit, it sort of evolved that way for me I don't like having a big bubble of air in my dry suit. I don't seem to need to add much air to my BCD though to achieve neutral buoyancy at depth. My neck seal was a nightmare when I first started diving dry and I had to stretch it over a cake tin for a couple of days so I could actually wear the thing!!! It used to try and tear my ears off every time I put my suit on or off!

 

[Jim Lapenta]

Dry suit for squeeze, BC for buoyancy. One of the other reasons that some books say to use the suit only is that they feel that the average new diver is not intelligent, well trained, or experienced enough to use two forms of buoyancy control. This is really not true and frankly somewhat insulting as well. If you have good buoyancy control to begin with (which you should as a well trained diver), adding a second item related to that task is not big deal. And if you are properly weighted with some people just adding enough air to take the squeeze off may be enough to adjust their buoyancy. If not then you use the bc to fine tune since the bubble is smaller in it and easier to control.

 

[ringmod65]

This is another one of those confounded things that I was taught wrong by PADI and then had to unlearn.

It's a lot easier to learn a skill correctly the first time around than it is to go back and fix an ingrained behavior.

 

[Crush]

I use the BC for buoyancy. The way I see it, it is easier for me to vent from my BC while inverted, swimming downwards (in the event that I have become too positively buoyant) than it is to vent air from the toes of my drysuit. The air in my drysuit is kept to a comfortable minimum. If I feel that air pocket rolling in between my shoulder blades I know that I have really not been paying attention to my situation and it is past-due that I roll slightly left-side up.

 

[TSandM]

There are different reasons to do different things.

The reason new dry suit divers are taught to use the suit for buoyancy is that you MUST put SOME gas in the suit, to be comfortable and remain adequately mobile. So if you put all the gas you need there, you have it all in one place and you only have to remember one way to vent. If you are properly weighted, the amount of gas you have to put in the suit to compensate with a single tank is not excessive.

However, the bubble in the dry suit suffers from several disadvantages. The first one is that air can get a long way from the dump valve, and it takes some time to get it back to where you can vent it. Dry suit dump valves often won't dump as fast as BC inflator hoses can, as well. And finally, the average BC has several place where gas can be dumped, including one that works when you are inverted, whereas once you are feet up in a dry suit, you can't vent anything until you change your position.

I learned the "air in suit" method and used it until Fundies, when I switched to the "relieve squeeze and rest in BC" method, which was MUCH easier. Then I worked with a different instructor who wanted all the gas in the suit again (or much of it) and I discovered how much warmer I was that way, so I switched back. Then I started diving caves where you have to do sections at a severe head-down angle and discovered gas in the suit bit me in the butt in that circumstance, so in caves, I use the 20 foot squeeze again.

In the end, you use different approaches for different situations. Singles, doubles, open water, overheads . . . each may be best managed differently.

 

[Blackwood]

I'm not particularly fond of having my comfort predicated on my buoyancy needs. If I use my suit for buoyancy and we have an issue that leads to gas sharing, I'm likely going to need to run the suit very tight (which is neither comfortable nor conductive to thermal protection).

 

[pjones]

I'd say do what works. For me the BCD is only used on the surface.

Undergarments play a big role in the decision.

Those who wear few undergarments because they are:
a) in relatively warm water
b) have a thick neoprene suit
c) are tolerant of colder temperatures

will probably find that the volume of air required for buoyancy substantially exceeds the volume of air required to alleviate squeeze/loft their undergarments. And many of them prefer to manage that additional air in their BCD.

Those who wear thick undergarments because they are:
a) in relatively cold water
b) have a thin tri-lam suit
c) are afraid of the cold

will probably find that the volume of air required to alleviate squeeze/loft their undergarments is very close to that required for buoyancy control, and their is little benefit in adding any air to their BCD.

Well said sschlesi.
I dive in cooler than tropical water and find that the amount of air required for warmth is pretty much equal to what is required for buoyancy.
Just my two cents.

 

[elan]

I'd say do what works. For me the BCD is only used on the surface.

Undergarments play a big role in the decision.

Those who wear few undergarments because they are:
a) in relatively warm water
b) have a thick neoprene suit
c) are tolerant of colder temperatures

will probably find that the volume of air required for buoyancy substantially exceeds the volume of air required to alleviate squeeze/loft their undergarments. And many of them prefer to manage that additional air in their BCD.

Those who wear thick undergarments because they are:
a) in relatively cold water
b) have a thin tri-lam suit
c) are afraid of the cold

will probably find that the volume of air required to alleviate squeeze/loft their undergarments is very close to that required for buoyancy control, and their is little benefit in adding any air to their BCD.

I have to disagree.
If you have to add more air that your undergarment requires it most likely mean you are overweight.

With the suits that lose little buoyancy like crashed and trilam it does not depend upon when undergarment you use.

Diving with no BCD in a dry suit was an eye opener for me and I figured that you in fact do not need to adjust the buoyancy other then keeping your loft at the working volume.

 

[elan]

I recently purchased a Waterproof crushed (3.5) neopreme drysuit and have had one pool cession with it. Accourding to the PADI Text & My instructor my BCD is only to be used at the surface and not during the dive: buoyancy to be controlled by adding and venting air from the drysuit. The text further states that the only exceptions to this are 1) when using a neopreme drysuit--not crushed, and for technical divers that use a combination of air in the bcd and drysuit. At our world underwater this weekend I talked to a Technical diver and instructor that told me just to add enough air to avoid suit squeeze and to use the BCD for buoyancy ( I have a rear inflation bcd). My guess that it is easier to control a smaller BCD air space. Is is possible that both situations are correct depending on circumstances? Is there a reason that one method is preferred to the other, could someone give me some reasoning. What do other non PADI agencies teach? Also the neck seal seems a bit tight. I tried to stetch it out around a kitchen canister for a week about 1 & 1/2" smaller than my neck. After abouty an hour and 15 minutes I thought that I wasd going to pop. I was told by my instructor not to trim the neck seal because if there is a small nick perpindicular to neck seal it will conmtinue to tear and I will have to replace it. I was further told to stretch and spray the neck with food grade silicone spray. I would really appreciate a good explination from anyone who has the time.

IMHO within rec diving limits when you use about 4lbs of air over a dive if you dive a trilam or crushed neoprene and have average lungs. You do not need to use BCD for buoyancy, all you have to do is just have enough air in your suit for your undergarments to work. When I do shallow shore dives I do not use the BC and just keep my suit inflated enough to undergarment to work well. For those dives I use about 40-50 cuf of air that I can compensate with my lungs easily