Drysuit or BC for boyancy control?

[seeker242]

The truth of the matter
First of all, there are not two schools of thought.

People on the innerwebs seem to have this idea that PADI says that you should always use the suit.

That's probably because of what it says in the AOW manual under the dry suit chapter. It says "Use a BCD for surface flotation and backup buoyancy control. Underwater, use your dry suit to control buoyancy"

 

[rhwestfall]

ww4u (what works for you), but I prefer to use the suit for warmth, and the wing for buoyancy. My DS is custom cut to fit me, so no "big bad bubble", bit I prefer the ability to dump my wing easier than my suit.

YMMV

 

[Diver0001]

That's probably because of what it says in the AOW manual under the dry suit chapter. It says "Use a BCD for surface flotation and backup buoyancy control. Underwater, use your dry suit to control buoyancy"

Well... I guess if the AOW book you have is recent then the materials are obviously inconsistent. It wouldn't be the first time. They don't update all of their materials at the same time. I guess this verifies what I was saying before about the history, though. Clearly this recommendation is out there.

Either way, the reality on that ground is that you can't teach someone to dive in a drysuit and expect them to trim only on the suit. It's unrealistic, especially as you go deeper and particularly if the suit is made from certain types neoprene. It's unrealistic to expect it in every circumstance in a trilam suit too... PADI knows this, they recognise this and the specialty book handles it as I described above. Since I work from Dutch translations, I assume the English books describe it the same way.

So I stand by what I wrote in the second post. There are no two schools of thought. Only the reality that at least some (if not all) of the air will be in the suit and that the bubble shouldn't be bigger than the diver finds comfortable.

Should the diver be able to trim only with the suit. Absolutely. Moreover, it's a performance requirement.

Should this be the ONLY thing they can do? Of course not. That would be absurd.

R..

 

[wetb4igetinthewater]

The drysuit course (the book) says what I said above aside from the history lesson.

There is a performance requirement in the drysuit course that requires the student to achieve neutral buoyancy using only the suit. This is completely logical seeing as how they are learning how to control the suit. That is not the same as recommending that they dive like that at all times in every circumstance.

You can compare this to the performance requirement in the Open water course that lets the student hover and control their buoyancy only with breathing. This is not the same as requiring the student to control their buoyancy at all times under all circumstances with ONLY their breathing. It's teaching a step in the skill set, not setting a rule in stone.

R..

I'm going to go back and review (as I don't have the manual in front of me), but my memory says that PADI for recreational diving recommends using the dry suit for buoyancy, not the BCD. In tec, PADI recommends using the BCD for buoyancy and the dry suit for squeeze. SSI (I have the manual and took a course before becoming a DM) and NAUI (asked an instructor) both recommend using the dry suit for squeeze only.

I'm pretty sure my memory is right, but I'll go back tonight and look at the manual.

I've always told my students that they have to meet the performance requirements for certification. I give them the option of repeating the hover skill using their BCD for buoyancy and their dry suit for squeeze. Every single one, without exception, prefers the latter method.

 

[wetb4igetinthewater]

Yes, I give that specialty regularly.

Have you read the book?

R..

Page 156 in the Adventures in Diving (version 2.10), Dry Suit Diving, section "Dry Suit Buoyancy Control Underwater" is pretty clear about using the dry suit completely for buoyancy, except for emergency. I'll have to check the course manual separately.

 

[OMANDIVER]

I'm going to go back and review (as I don't have the manual in front of me), but my memory says that PADI for recreational diving recommends using the dry suit for buoyancy, not the BCD. In tec, PADI recommends using the BCD for buoyancy and the dry suit for squeeze. SSI (I have the manual and took a course before becoming a DM) and NAUI (asked an instructor) both recommend using the dry suit for squeeze only.

I'm pretty sure my memory is right, but I'll go back tonight and look at the manual.

I've always told my students that they have to meet the performance requirements for certification. I give them the option of repeating the hover skill using their BCD for buoyancy and their dry suit for squeeze. Every single one, without exception, prefers the latter method.

You are correct. So there are clearly two schools of thought...if not more...indeed everyone who has ever worn a drysuit has an opinion.

 

[w3dge]

Why does the discussion have to descend into which agency says what? The question was 'why are there two schools of thought'. There clearly are two schools of thought, and what agency a or b teaches doesn't really matter.

So why do some people prefer to use the suit for squeeze only, and others prefer to use it for full buoyancy compensation?

 

[Diver0001]

Why does the discussion have to descend into which agency says what? The question was 'why are there two schools of thought'. There clearly are two schools of thought, and what agency a or b teaches doesn't really matter.

So why do some people prefer to use the suit for squeeze only, and others prefer to use it for full buoyancy compensation?

So, I will repeat where I started with this. There are not two schools of thought. There is only the reality that no matter what you do, you will have air in your suit. If the bubble gets too big to be comfortable, which can happen with certain suits, especially as you go deeper, then you need to use the BCD. Nobody on the planet -- regardless of agency -- is going to teach you anything else, because it would be completely absurd to tell someone that they need to put all of the air in the suit even when they do not find it comfortable.

The PADI drysuit specialty book and some of the technical specialties address it along these lines although in the side-bar to this discussion a number of people have pointed out that the materials are not consistent. As I pointed out in the second post there are historical reasons that can help you understand why this recommendation existed at all, but those reasons are no longer relevant to modern divers.

The materials get updated slowly and the swarm-think on the innerwebs even more slowly. As you can see on this thread, even some IDC's are confused about what exactly needs to be taught, even though it's crystal clear once you actually start teaching people to dive dry that there is only one possible "school of thought", namely what I said above.

As for why some people prefer more squeeze, I would submit that for more or less the same reason that some people tie their shoelaces tighter than others.

R..

 

[chrisch]

Why does the discussion have to descend into which agency says what? The question was 'why are there two schools of thought'. There clearly are two schools of thought, and what agency a or b teaches doesn't really matter.

So why do some people prefer to use the suit for squeeze only, and others prefer to use it for full buoyancy compensation?

Because people like to argue about agencies. Diver0001 has given the background information to the situation. In practice a neoprene suit will frequently give enough lift to avoid the BC, but a membrane suit is much more problematic. Too much gas in a suit can lead to feet first ascents and is a bad idea. Keeping the lift in the BC keeps it in the upper part of the body and so is by far the best way to do it.

 

[clownfishsydney]

I have a neoprene suit. I use the suit for buoyancy about above 35 m, below that, I use suit and then BCD as suit cannot provide enough lift. Works well, but all this will depend on your suit.