Air confuses me

[pauldw]

So three plus decades ago I took OW, and my perception then was that the thing to do was to overweight so there'd be no question about whether the wetsuit would keep me from descending, and then the BC was like an elevator with an up button and a down button. Getting back into diving recently, I perceived that it is good to be neutrally bouyant through very careful weighting, and to pretty much not use the BC except for at the surface. OK, especially with a wet suit. But now I'm getting used to my dry suit, and taking a class on that, and what I'm learning is to be empty of air in the dry suit and the BC on the surface when it's time to descend, to exhale to descend, and then to add air to the dry suit to keep it from squeezing. I'd like some additional views on this process, though, to supplement what I'm learning in class. It seems like my suit is already quite snug when I'm floating in the water at the surface. Going down, the only way to keep it from preventing posterity and whatnot is to add air. But then even a little air (not enough to prevent squeeze) brings me back up. What am I not doing right?

 

[grf88]

You also need enough air to loft your underwear which will vary according to the type of underwear and the temperature you are diving in. You probably need to add at least 4 lbs and probably more from where you currently are and in cold water even more. Don't forget to also allow for the weight of the gas you consume. Make sure you have enough as you don't want to get shrink-wrapped.

 

[BRT]

Air is warmth in a dry suit. And it takes lead to sink air. By the time my tank is low on air I want to have no air in my BCD and still have enough air in my suit to stay warm. At that point in the dive I am usually getting cold and letting out my insulation is not something I want to do. On the other hand I could carefully exhaust as much air as possible out of my suit and dive with less lead, and be cold.

 

[pauldw]

So when I’m burping my dry suit on the shore, that doesn’t mean to try to evacuate 100% of the air and perhaps doing it again in the water...I want to be somewhat puffy floating at the surface, and add weight to be neutral at that unquantifiable level of puffiness, correct? I think what confused me is we did just the pool session already, with no insulation to puff for. I’ll talk to my instructor before the dives, but am checking here for all perspectives.

 

[Zef]

you need enough weight to be neutral/slightly negative at your safety stop with however much air you need in your suit for you to be comfortable (warm).

If you weight check without air in the suit then you will not have enough weight towards the end of the dive and will be positively buoyant and have a hell of time trying to stay down.

-Z

 

[JackD342]

Use of BCD or of drysuit as primary means of buoyancy control depends on the type of suit, and the type of diving.
Seems everyone comes out of the PADI course believing they should only use the BCD at the surface, when PADI actually recommends you use the suit for comfort and the BCD for buoyancy when diving a neoprene suit, or a shell suit on tec dives, and use the suit for primary buoyancy when diving a shell suit on recreational dives. Not gonna get into the "defined" differences here.

 

[Doby45]

Also while you are hanging out upright at the surface there is nothing much you can do about the squeeze below. You will find that what bit of air you do have in your suit is up at your shoulders and your feet, legs and waist are squeezed a bit. When you get into a proper diving position the "squeeze" in general will be better and will not take much more than a simple puff to relieve. I can get down about 30ft before I really feel like I need to add a puff to relieve the squeeze.

 

[BRT]

Also while you are hanging out upright at the surface there is nothing much you can do about the squeeze below. You will find that what bit of air you do have in your suit is up at your shoulders and your feet, legs and waist are squeezed a bit. When you get into a proper diving position the "squeeze" in general will be better and will not take much more than a simple puff to relieve. I can get down about 30ft before I really feel like I need to add a puff to relieve the squeeze.

That is a lot further than I want to go without adding air.

 

[Doby45]

That is a lot further than I want to go without adding air.

Everything is personal. That was no "rule" it was simply me stating that I can get to about 30' before I need to add me a puff. It is also totally depend on the dive profile. If your dive is only going to 30' then you probably want to add air at a different rate. But, when my target depth is much deeper than that and I am busy with other items, such as running a reel, a stage bottle and a scooter. I can wait just a bit on the suit inflation.

 

[BRT]

Everything is personal. That was no "rule" it was simply me stating that I can get to about 30' before I need to add me a puff. It is also totally depend on the dive profile. If your dive is only going to 30' then you probably want to add air at a different rate. But, when my target depth is much deeper than that and I am busy with other items, such as running a reel, a stage bottle and a scooter. I can wait just a bit on the suit inflation.

I get it. I feel squeezed about 15' and start dropping faster than I want to.