Using a Drysuit for Buoyancy Control

[MikeS]

I’m a new drysuit diver and still a relatively new diver for that matter. On another thread I saw the issue of drysuit buoyancy control come up again and thought I would start a new thread to discuss it and share what I’ve learned while learning to “ride the bubble.”

Issue

For clarification, the issue is whether to use the drysuit for buoyancy and maintain the bladder solely for backup or to add just enough air to the drysuit to eliminate squeeze and use the bladder for buoyancy control.

The PADI Philosophy

I took the PADI drysuit training. As explained to me, the PADI philosophy is that using the drysuit for buoyancy reduces task loading since only the drysuit rather than the drysuit and bladder have to be adjusted for buoyancy after a depth change. If this is not the PADI philosophy, someone please let us know. Based on drysuit learning experience I think that there is some merit to this under certain circumstances but sometimes the reverse is true.

Based on my admittedly limited experience there are three situations that require adding or dumping air to change buoyancy; descending, minor changes based on terrain, and ascending. It’s best to look at the three independently because the task loading is different in all three cases.

Descending

When it comes to descending, based on experience, there would be less task loading adding air to a single device and because of potential squeeze this would have to be the drysuit. However, task loading isn’t a big concern on descent. As long as you add enough air to one or the other to stay off the bottom, life is good.

Ascent

Again, there would be less task loading dumping air from a single device. Task loading is certainly more of an issue on ascent as controlling the rate of ascent is important. What I’ve found is that if I properly set my dump valve and keep the proper orientation, slightly head up, I can ignore the drysuit, as it dumps air on it’s own, and use the bladder to control buoyancy and hence rate of ascent.

Changing Depth

At first glance, it would appear that there is less task loading with a single buoyancy source, but I have found this not to be the case in practice. In fact, I have observed that task loading would be dramatically increased by only using the drysuit for buoyancy. Once again ascending is more complicated than descending. When descending as long as you add enough air to either to stay off the bottom, life is good.

Most drysuit problems are encountered when you ascent slightly, for example swimming up to the deck of a sunken boat. In a typical scenario, you start to swim up, your buoyancy increases, you start to swim slightly down to hold position but still need to dump air, and dang if the drysuit dump doesn’t require that your oriented head up to work. So you have to go head up which means you stop fining down and start to rise; maybe you can dump fast enough to stop and maybe not.

In contrast, in the same situation using the bladder for buoyancy, you start to swim up, your buoyancy increases, you start to swim slightly down to hold position but still need to dump air, you reach back and use the rear dump to return to neutral buoyancy.

I’m sure that this will be a moot point with experience. I’m already finding that I subconsciously raise my shoulder to automatically dump air from the suit and dump air from the bladder so that I never loose buoyancy, but this is a learning process that is going to take time.

As always and comments and/or suggestions are appreciated.

Mike

 

[MikeFerrara]

First off, most agencies teach the use of the suit for bc not just PADI. That's how I was tought and it worked just fine for a couple hundred dives. Then I climbed into a set of double LP steel tanks and learning took place.

I don't think it's as clear cut as some would have you believe.

 

[metridium]

I too learned the PADI approach...but I got better. (c.f. Monty Python).



BTW, keep in mind that drysuits do not dump as fast as BCs, nor do BCs trap air far from the dump valves.

 

[annie]

I went drysuit diving last weekend for the first time in years and couldn't decide whether to use BC or suit and tried both during the dive. During the descent it's best to use the suit for this as you have to control squeeze too anyway.

I tried using the BC but it felt strange not being able to feel it through the suit. But everytime I tried to control buoyancy using the suit I overdid it and had to add air to stop the squeeze. Maybe that's a practice thing but I'm happy keeping anti squeeze air in the suit and using the BC for fine adjustments.

 

[Dryglove]

I was also taught to use the drysuit for buoyancy in my class. I did that for a while then started reading about using my bc for buoyancy. I much prefer to use my bc for controlling my buoyancy and the best part is that i just recently had my exhaust valve relocated on my forearm so as i raise my arm to dump air from my bc i am also venting the expanding air from my drysuit so there is no extra task loading.

 

[Scottri]

I teach drysuit use and have never advocated using the drysuit for bouyancy control. I think its a bad idea. That is what the BC is for. You add air to the suit to deal with the squeeze. The bladder in a BC is much better suited for bouyancy control. Why else wear it? For the surface? Hell you can inflate your drysuit to look like the pillsbury dough boy on the surface. Drysuits are a more advanced piece of gear. It requires you dump two devices, so what. You shouldn't have that much air in it anyway. And if you deflate valve is on the left upper arm it should self vent somewhat when you deflate your BC anyway. I've never been "task loaded" dumping my drysuit and bc. It's an aquired skill like diving itself. It takes practice. It is much easier dealiing with a runaway ascent with a BC than with a drysuit.


Scott

 

[skynscuba]

At the start of the dive, I usually put a bit of air in the BC to stop my descent. By the time the tank is empty, I wouldn't be able to stay down with air in the BC, unless my drysuit were too squeezed for comfort (including cold). So, I typically make sure the BC is empty as I head up toward the safety stop.

skyNscuba

 

[ColdH20diving]

I don't dive overweighted so the amount of air needed to eliminate the squeeze pretty much corrects my buoyancy. When working with students I follow PADI protocal for the obvious reasons. I can see both sides of the issue, but feel the task over load argument would certainly apply to new dry suit divers.

 

[SDAnderson]

Even though most of us have on occasion used the handle of a screwdriver to pound away at something, nobody argues that you don't need a hammer in the toolbox.

A drysuit is designed to keep you dry and, with the proper insulation, warm. The bouyancy issues that arise with a drysuit are an unintended side effect that can work for you but can also work against you. A bouyancy control device is designed to...control your bouyancy...and is better at the job.

My .02 worth.

Steven

 

[Uncle Pug]

We saw a student just finishing his private PADI OW course and he was wearing a drysuit.

He explained that the drysuit course had been included in the OW class and went on to explain that this particular instructor teaches his students to add gas to the suit to take off the squeeze and to add gas to the BC for... of all things... buoyancy control.

I guess it depends a lot on the instructor.