Dry suit diving - help

[scubaroyster]

NWGratefulDiver once bubbled...


All well and good if you're using a 7 mm drysuit ... and even then I'll say it depends on how the suit fits, how you're weighted, and how you've distributed your weights for optimal trim. What about folks using other types of drysuit?...

... Bob (Grateful Diver)

I meant that I subscribe to what the others said concerning a shell type dry suit. The only loss in bouyancy with a shell type suit is the reduced volume of air in the suit to maintain the loft in your underwear. As you replace the volume of air in your suit, you trim out your bouyancy.

Not so when diving with a 7mm suit. The extra bouyancy of the 7mm material on the surface requires more weight to decend. The neoprene loses it's bouyancy as you go deeper requiring more air to maintain bouyancy. This causes more air in the dry suit than is necessary for warmth. Those diving the 7mm may want to use the BCD to avoid the excessive air bubble in the suit.

And of course you know I have to stick to standards when teaching dry suit diving by teaching to use the suit for bouyancy. It does make emergency actions a whole lot easier to only have to deal with one item to deflate.

 

[lragsac]

kelpdiver once bubbled...
Looks like I find myself in a minority. If you are properly weighted (and if not, if you add or maintain just enough air in your BC to descend slowly), you should use your DRYSUIT for buoyancy control.

With all due respect, "should" suggests there is only one way, and as you can see from posts here, this is most certainly not the case. I've used both methods. I was initially taught to use my drysuit only for buoyancy, but I now use my wing and only put just enough air in my suit to alleviate squeeze and stay warm. The problem with using your suit for buoyancy is it's a much more unstable amount of air, and when you need to dump it's much harder to keep horizontal trim. More air in the suit means a lot more drag, too.

 

[Snowbear]

... and when I'm properly weighted, with quality thinsulate undies and lightweight polypro under that, I get cold if I try to barely keep the squeeze off the suit and use the wing for bouyancy. I've learned from doing that if I'm needing to use the BC for buoyancy at depth 'cause there's too much air in the suit, I'm overweighted (this is usually 'cause I'm diving a borrowed tank and miscalculated the weight needed). If I'm having to dump ALL the air out of my suit to maintain safety/deco stop depth, I obviously underweighted (what a pain in the @$$!!). As a DM candidate, I've figured out that overweighting by about 2# for OW classes a good way to help me stay warm 'cause hovering for 45 min without moving much and minimal air in the suit just don't cut it!!

 

[kelpdiver]

I'm not saying there's only one way, but I think there's a better way. Please re-read my post. Obviously you use your BC at the surface. And when I say you should use your suit for buoyancy, I did NOT say to fill it chock full of air to get buoyant--that means you're overweighted, and you may need to use your BC until you take the weight off. Ideally, you'd be neutrally buoyant with no air in your BC and yes, just enough air to fluff your underwear to keep warm and avoid squeeze (I even suggested a way to check for that just enough amount). But that means adding air as you descend and vice versa, which is also how you maintain buoyancy, and you can do it all with your drysuit if you're properly weighted. If you add "just enough air" to avoid squeeze and stay warm, at what depth are you talking about? The surface? 33 ft? the bottom? You'll have to keep doing that all the way down, or just enough air will quickly be not enough, and in reverse on the way up, and in small ways as you change depth during your dive. And maintaining that constant volume of air, as pressure changes, means you're maintaining the same buoyancy. That's physics. I mean, if you're not continually adding air to your drysuit as you descend, you either forgot to burp it, or you're getting one heckuva squeeze. And if you're not venting as you ascend, yes you'll have an unstable bubble of air and lots of drag. So how can anyone not be using their drysuit for buoyancy control, whether they know it or not??
I suppose you may need a little air in your BC at the start when your tank is full, that you'd eventually get rid of as your tank empties, but changes in tank buoyancy would occur more slowly than potential changes in depth, so in the meantime, I'd use the drysuit.
IM(not so)HO, and I'll try to refrain from further repititious comments.

 

[MXGratefulDiver]

lragsac once bubbled...


With all due respect, "should" suggests there is only one way, and as you can see from posts here, this is most certainly not the case. I've used both methods. I was initially taught to use my drysuit only for buoyancy, but I now use my wing and only put just enough air in my suit to alleviate squeeze and stay warm. The problem with using your suit for buoyancy is it's a much more unstable amount of air, and when you need to dump it's much harder to keep horizontal trim. More air in the suit means a lot more drag, too.

Again ... depends on the circumstance.

First off ... how much air is needed to alleviate squeeze and stay warm? For some people, that's enough air to maintain buoyancy. Depends on the type of suit, undergarment, and water temperature (unless you're using argon). So this will differ for each person reading this thread.

Then there's gear configuration. While a wing offers definite advantages in terms of stability, not every diver uses one ... in fact, those who do are a distinct minority, even among drysuit divers. And not every alternative offers stability advantages.
If, for example, you're using a jacket-style BCD, it's likely that you'll experience more difficulty maintaining a horizontal position as you increase the amount of air in your BCD ... due to the inherent design of the device. So it's not always a given that using your BCD for inflation provides more stability ... again, it depends on your specific equipment.

Finally, while it is true that adding air to your suit increases your drag ... I think it's misleading to say it "means a lot more drag". In fact, if your suit fits properly and you're properly weighted, the increase in drag will be negligible. If adding more air to your suit increases your drag noticeably, then you have other, more serious issues than the method you've chosen for buoyancy control. Most likely you're overweighted. But it's also possible that you're simply wearing a suit that wasn't built for your body. Proper fit should be the #1 consideration when purchasing a drysuit for just this reason ... regardless of how you choose to control your buoyancy.

A lot of the statements I've seen in this thread are only partly true, and only under a specialized set of circumstances. They most likely represent the best choice for the person making them ... but they shouldn't really be presented as a universally best solution for everyone. It's really not that simple.

It's far better to understand what aspects of your gear affect your buoyancy control, stability, and hydrodynamic efficiency ... and apply that knowledge to your specific situation. There are trade-offs either way ... and only the individual can decide which trade-offs they want to live with.

... Bob (Grateful Diver)

 

[padiscubapro]

There definately isn't one answer consider the following variables:

Shell suit vs neoprene
single aluminum vs doubles al vs double steels
hand held light vs canister light ect..

each of these adds another point of contention to the equation..

Someone diving a neoprene suit generally has light undergarments and at shallow depts is very bouyant, at shallow depths very little gas is needed to aleviate squeeze and still be warm, go deeper now you need extra gas to stay warm since you are losing insulation..

now take it a stp further a tek diver using doubles (steel) canister light and whatever else is needed for the dive, this diver is more than a little negative, the amount of gas needed to offset this weight can be dangerous at depth and usually has the diver moving a gas bubble around their suit.. I can usually spot someone who likes to use their suit for buoyancy since they usually resort to something like ancle weights and/or gators...

The biggest problem I run into when trying to train tek divers is to get them to relearn how to use a drysuit because suit only buoyancy is inadequate.. These divers also can't remove their righs and replace them underwater if necessary since they are so buoyant without their gear..

someone with a single al 80 need very little gas to offset their gear and its pretty easy to do suit only..

For a new diver manipulating multiple air spaces may be difficult but with practice its a piece of cake.. when changes are made one must adapt and learn.. I remember the first free ascent I tried in my drysuit and my rebreather.. I now had 3 airspaces to control... lets just say it wasn't pretty... now I don't even think about it... its natural...

 

[Bonnet Ray]

Thanks for all the replies. I have decided that on Sunday I will try using just enough air to stop the squeeze and use my bc for bouyance.

The following week I am going to go to our local quarry for another practice/try out before we start the course on the next sunday.

My hubby has just booked us a week on a liveaboard in the red sea for the week after we finish the rescue course, so I am all smiles at the moment

 

[scubaroyster]

NWGratefulDiver once bubbled...


...If, for example, you're using a jacket-style BCD, it's likely that you'll experience more difficulty maintaining a horizontal position as you increase the amount of air in your BCD ... due to the inherent design of the device. ...
... Bob (Grateful Diver)

I wonder why some of you keep professing that a jacket style BCD is not stable. They are very stable and I'm able to hover in just about any position I care to. Horizontal, upright, upside down, horizontal on my side, and horizontal on my back. And yes I can remove and replace the unit while maintaining a horizontal hover. Now, I be using a Scubapro Classic with integrated weights, but come on guys. Agree, easier to stay horizontal with a back inflate or BP/Wings while wearing gobs of gear that's not easy to balance. For most of dry suit divers, wearing gobs of gear is not the issue, it's getting properly weighted so you don't need an unecessary amount of air to be neutral.

I have a Seaquest Pro QD that's also very stable in any position, so at least these two "jacket style" "poodle jackets" work pretty good. And 61 lbs of lift to boot!

 

[Phish-phood]

I think it is pretty clear from the thread that there is no right way of doing this. What works for some doesn't for others and it is a matter of experimenting and finding out what works for you. In my case it's my drysuit.

I think the only thing that everyone can take is that they should know how to use both drysuit and BC/wing because if one fails you do not want to waste dive time trying to figure out how much air in your other bouyancy source is enough for bouyancy. BC inflators can stick, drysuit inflators can stick, cuff dumps can be blocked by undersuits, shoulder dumps can stick etc. Not knowing your kit inside out and all your options available is one of the main reasons for accidents, uncontrolled ascents/descents etc

Although I use my drysuit for bouyancy control I know that if for some reason the inflator sticks open all I have to do is disconnect the drysuit hose and use my BC. Same does for if the cuff dump gets blocked by my undersuit (has happened) I am not losing dive time because I am comfortable using my BC as a bouyancy control method aswell

 

[MXGratefulDiver]

scubaroyster once bubbled...


I wonder why some of you keep professing that a jacket style BCD is not stable. They are very stable and I'm able to hover in just about any position I care to. Horizontal, upright, upside down, horizontal on my side, and horizontal on my back. And yes I can remove and replace the unit while maintaining a horizontal hover. Now, I be using a Scubapro Classic with integrated weights, but come on guys. Agree, easier to stay horizontal with a back inflate or BP/Wings while wearing gobs of gear that's not easy to balance. For most of dry suit divers, wearing gobs of gear is not the issue, it's getting properly weighted so you don't need an unecessary amount of air to be neutral.

I have a Seaquest Pro QD that's also very stable in any position, so at least these two "jacket style" "poodle jackets" work pretty good. And 61 lbs of lift to boot!

Perhaps you misunderstand what I wrote. I said it's more difficult ... not that it can't be done. It is true that a wing is more inherently stable at a horizontal position than a jacket. However, with practice, the jacket wearer is perfectly able to maneuver just as you say. I did not intend to imply otherwise ... I know too many good divers in jacket-style BCDs, including the one I'm married to (she wears a SeaQuest Diva LX).

I have consistently been a proponent of the philosophy that diving isn't about gear, but about practice and judgement. That does not negate the fact that some gear performs certain tasks better than others. So when a diver chooses a particular piece of gear they must learn the subtle differences in diving style that are required to use it properly. It is always a matter of trade-offs and preferences as to what any individual diver finds works best for them.

Hope this clarifies my position ...

... Bob (Grateful Diver)