drysuit as BC

[geraldp]

I was following a thread over in the Accidents and Incidents forum ("panic"), and read a post that you should never use your drysuit as a BC. This confused me, as I was taught in my SSI Drysuit class that you should NOT use your BC for bouyancy control when you're diving in a drysuit. You should use your drysuit for bouyancy control when at depth, and use your BC when at the surface. It also stressed that you should always use a lift bag if you're going to lift anything.

So are there other theories about this? What does DIR recomend?

Thanks,

Jerry

 

[Boogie711]

DIR says use your drysuit to stay dry, use your bouyancy compensator to compensate for bouyancy.

Unfortunately, the world is full of people who've been taught otherwise by agencies who think divers are too stupid to be able to handle two inflator mechanisms. The only reason they teach you that, Gerald, is to minimize taskloading. Personally, I think if a diver can't handle both a drysuit and a BC, then they shouldn't dive.

Incidentally, this topic has been discussed ad nauseum. Do a search on "dynamic instability."

 

[Hallmac]

Well Not all SSI instructors teach the drysuit for bouyancy method. In my class we will discuss it, practice it once and then move on to only adding enough air to stop squeeze and use the bc as a bc not a tank pack. I teach both, recommend one over the other and let you make the choice as to what works best for you!

Hallmac

 

[sharkmasterbc]

Using ur drysuit for buoyency to about 30 ft (if you are properly weighted in a single tank) should be fine...it also eliminates the squeeze....after that use the thing that is actually called a buoyency compensator....after all thats what it is for isn't it ?
Then just little bursts of air in your suit to get rid of squeeze and BC for buoyency control, the amount of air you need to put in your suit is ridiculous if you use it exclusivly for buoyency.
I understand why agency's teach drysuit only when learning to help take away some of the task loading but once you are comfortable and trim in the water you should progress to using both....if you keep a horizontal position in the water...you can keep your suit valve all the way open and just simply roll a bit to let the access air out on ascent, besides when you go to use your bc deflator the arm goes up and the air comes out of your suit...pretty elementary don't you think.
For newbies in neoprene suits I have seen people use the suit only to about 60 ft without having an excess amount of air in it....but after you progress to the next level and get into a trilam or bag suit the bc will definetly help you with your trim and position in the water.
If diving doubles which are neg at the start of the dive there is no way you can use only a suit for buoyency...if you are in Al80's then you should be about 10 lbs neg at the beginning of the dive, because you have "of course" weighted yourself neutral with empty tanks right ??? I'd like to see someone put enough air in a drysuit to become neutral at the beg of a dive with doubles....the michelin man comes to mind !!!

 

[DA Aquamaster]

This whole qestion isn't really a big issue iunless you are badly overweighted or carrying stage bottles, etc or are using doubles where there is about twice the bouyancy change in the tanks throughout the dive.

If you a single tank diver and are properly weighted the air needed to overcome the squeeze in the suit will be sufficient for you to maintain neutral bouyancy. At the beginning of the dive you will be 4-5 pounds heavy but that does not require an excessive amount of air in the suit.

You do not want an excessicve amount of air in the suit as the air can shift and cause trim problems and in extreme cases can make it difficult for the dump valve to dump fast enough to keep up with the expansion of all that air in the suit resulting in an uncontrolled ascent.

However, some people take minimizing this risk to the extreme and reduce the air in the suit way too much. This just makes the suit colder and in extreme cases can make the dump valve less reliable due to interference with the underwear squeezed against the valve and due to a general lack of air in right place in the suit. This will make the suit much wetter as water will enter the dump valve while you are attempting to dump and the inability to efficiently dump what air you have in the suit can actually cause signficant bouyancy control problems.

In my opinion there really is no right or wrong answer. What will work best for a given diver depends on their configuration on a given day. I like the idea of instructors teaching both aproaches as well as identifying the potential pitfalls of each and identifying the situations where one may be preferable to the other.

Of course then I am also a big fan of divers having enough common sense and knowledge to be able to make intellegent choices about these types of issues. Its a lot better than doing something blindly just because someone, even an instructor, said to do it that way.

 

[roakey]

You should dive shrink wrapped in your drysuit. Any buoyancy control comes from the BC.

Roak

 

[bcsean]

I actually came out of a dive recently and noticed little red lines running up and down my arms. Guess my drysuit got a little tight.

Valve is always wide open, BC for buoyancy. I was taught both methods, but found it hard to stay trim as a new diver with lots of air in drysuit. I actually adopted the method of no air in drysuit by practicality.

 

[Rick Murchison]

If diving a shell suit...
If properly weighted...
If the proper amount of gas is in your dry suit for proper loft of your insulating underwear...
Then
Keeping the dry suit properly inflated to retain loft of your insulation will keep your buoyancy very near neutral anyway, and the BC will see minimal use, other than to replace lost volume as you descend (steel tanks that required gas in the BC for neutral at the surface), and to dump some as you use gas.
Some people have misinterpreted this as "using the dry suit for buoyancy control" - which it isn't... it just works out that very little in the way of BC use is required (steel tanks excepted).
Rick

 

[Boogie711]

If diving a shell suit...
If properly weighted...
If the proper amount of gas is in your dry suit for proper loft of your insulating underwear...
Then
Keeping the dry suit properly inflated to retain loft of your insulation will keep your buoyancy very near neutral anyway, and the BC will see minimal use, other than to replace lost volume as you descend (steel tanks that required gas in the BC for neutral at the surface), and to dump some as you use gas.
Some people have misinterpreted this as "using the dry suit for buoyancy control" - which it isn't... it just works out that very little in the way of BC use is required (steel tanks excepted).
Rick

Rick - you assume one needs loft of your insulation in order to maintain warmth. That may be true for something like a weezle, but many varieties of DS insulation (Diving Concepts, Bare, the DUI stuff) can be crushed to all heck and lose only minimal insulating value.

 

[VTernovski]

you're not alone. Unfortunatelly this how my PADI instuctor also thought the Drysuit class. The bottom line is that this is wrong, and you to get a better understanding why, read Dynamic Instability artcile.

I was following a thread over in the Accidents and Incidents forum ("panic"), and read a post that you should never use your drysuit as a BC. This confused me, as I was taught in my SSI Drysuit class that you should NOT use your BC for bouyancy control when you're diving in a drysuit. You should use your drysuit for bouyancy control when at depth, and use your BC when at the surface. It also stressed that you should always use a lift bag if you're going to lift anything.

So are there other theories about this? What does DIR recomend?

Thanks,

Jerry