Drysuit or BCD which to use for BC

[Tigerman]

Let me know how you fair cave diving while using your dry suit as your buoyancy compensator. If your feet are the highest point, the air will go to that highest point. Are you actually trying to argue that? Damn people on the internet will stop at nothing......

You can be horisontal without having a constant incline from your chest to your feet, think a bit about it and im sure you can figure out how..
The downside is if you go head down (which is no more horizontal than head up is)

 

[Dad31]

I am with tgsmith,,, bc for buoyancy.. It also make things a bit more stable when using dubs.. Like having the bubble in a confined space..

 

[ianr33]

There's good reason. Maybe PADI doesn't want divers getting confused in an emergency with which buoyancy source needs to be dumped.

Thats something I have never understood.

A wing dumps much faster than a drysuit. If I start ascending too quickly I go slightly head up and roll to the right a little as I dump my wing. That puts the drysuit shoulder dump as high as possible so that automatically starts dumping as well. I cant remember the last time I manually dumped air from my drysuit.

 

[TSandM]

I think the best answer is, "I use whichever is appropriate for the circumstance."

New divers are taught to use the suit, because PADI thinks that managing air in the BC and dry suit at the same time is too much task loading. It's the way I was taught, and the way I tried to dive at the beginning, and it resulted in several ballistic ascents. Diving a dry suit with a lot of air in it requires a fine sense of changes in the suit, an ability to anticipate buoyancy changes, and pretty good control of your position in the water -- and brand new divers have none of those things.

When I took Fundies, I went to the "20 foot squeeze", using the wing for buoyancy and only putting enough air in the suit to retain mobility. I wasn't as warm, but I had BUOYANCY CONTROL! The wing is much easier to dump rapidly, and can be dumped in any position, unlike the suit. This went on for a couple of years, although I did gradually increase the amount of air in the suit, as I got better at anticipating changes.

Then I took a Helitrox class this spring from a well-known technical instructor, who wanted us to use the suit as primary buoyancy control. It felt very strange and led to a bit of wobbly buoyancy control at first, but what I have found is that it is MUCH easier to use the suit for buoyancy control if you are going to be doing something that requires your hands (eg. running a reel). All I have to do to vent my suit is raise my elbow, whereas I have to find a free hand somewhere to vent my wing. However, in some circumstances (such as some cave sections, where you have to swim almost straight head-down) minimizing gas in the suit is preferable.

Now, if you are diving with a lot of gear and starting the dive considerably negative (as technical divers can do), you will not be ABLE to use the suit for your only buoyancy compensation, as the amount of air you would have to put in it would be unmanageable. But by that point in your career, managing two air spaces should be pretty trivial.

So I think I would say that my experiences suggest to me that new dry suit divers should be encouraged to keep as little air in the suit as they can, consistent with maintaining a degree of comfort and mobility, and use the BC as primary buoyancy control. They are used to it, and it's easier to get out of a bad situation that way. As you gain facility with the suit, you can try using more and more gas in it. You will be warmer and more mobile, and with a well-constructed suit, may find that it's actually easier. In the process, you'll identify a point beyond which you don't want to go with air in the suit. If you reach this point while doing single-tank diving, you are probably overweighted.

 

[dave4868]

Let me know how you fair cave diving while using your dry suit as your buoyancy compensator. If your feet are the highest point, the air will go to that highest point. Are you actually trying to argue that? Damn people on the internet will stop at nothing......

For most of my diving, I usually wear large amounts of insulation, requiring 38 to 54 lbs of lead, and I use only my drysuit for buoyancy.

Even with that huge amount of air in my suit, I have no problems with air shifting, even when totally head downward.

With that same suit, wearing light insulation requiring less than 28 lbs of lead to offset, significant air shifting will often disrupt my trim.

How can that be?

It's because the amount and speed of air shifting depends on how closely the drysuit fits over the insulation.

So, when I dive with light insulation, (like I might in a 72-degree cave), to reduce trim problems, I use very little air in the drysuit and rely on the bcd for primary buoyancy control.

In real cold water, I much prefer using only the drysuit for buoyancy control, not just because it's simpler, but mostly because it's so much warmer!

Maybe the real issue for people who have trim problems due to drysuit air shifting is the fit of their drysuits!

Dave C

 

[Standingbear56]

How about this: Weight yourself so that when your suit is comfortably inflated, you are neutral. If you are carrying too much weight to do this, then inflate the suit to the comfortable level, and use your BCD for the rest. Either way, the suit is part of your buoyancy, which is why you need to learn how to use it as such, whether it is being used for 100% of your buoyancy control, or only a portion of it.
Take care & Happy Holidays,
George

 

[ssidiv3r]

I didn't select either poll choices because I was taught to use both; the BCD on the surface (to avoid straining the neck seal) and the suit while at depth (obviously to help combat suit-squeeze)

 

[Web Monkey]

If you're weighted properly, adding enough air to keep the insulation from being compressed will be just about exactly how much air you need to be neutral, so you won't need the BC, and won't need to make a choice.

Terry

 

[ssidiv3r]

True, proper weighting is essential. Even then it's still a very good idea to use the BC on the surface when trying to maintain positive buoyancy

 

[vioch]

Here is some explanation why most divers feel uncomfortable maintaining buoyancy with a drysuit
BAUE Dynamic Instability FAQ