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Dry suit buoyancy control

21K views 67 replies 15 participants last post by  Doberman 
#1 ·
Good evening everyone.
It's me again fom sunny Italy. This time with a new question.
In UK I dive with the drysuit and when I did the speciality course in 2006 I was tought that you have to use the BCD only on surface and regulate buoyancy with the drysuit during the dive.
When speaking here with my Italian divers I have been told that this is very unsafe practice d I should use BCD normally like when diving sith a wetsuit.
Has anything changed recently? Is it safe to div using the BCD?
Thanks for your help.
 
#2 ·
You can do either. Using the suit for 100% buoyancy control is the traditional way of doing it where as more people now mainly use the BC and only add enough air to the suit to be comfortable and avoid squeeze. You'll always have some air in the suit, some people just have less air in the suit and the remainder in the BC. The choice is yours.

Make sure you are correctly weighted and this will reduce the amount of air needed for buoyancy control and stop you having a lot of gas that could move around.

p.s.
Don't believe the Italians when it comes to diving practice.
 
#3 ·
It's the norm for most agencies to recommend drysuit for buoyancy, because it's one set of controls to
play with and that makes it both easier to control and less chance of a rapid ascent while learning.

That changes though when more experience kicks in and multiple cylinders start to get used. Now the
lift from a drysuit isn't enough and the BC/wing is used instead.

There is also the issue with air migration in a drysuit where it's not wanted and the dumps not being
able to cope.

In the end it's personal choice, but i'd say the majority of experienced divers I know dive ronseal :)
A drysuit is to keep you dry and a Buoyancy control device is to control your buoyancy.
 
#4 ·
You really use both so deliberately use both.
Put air in the one that will make you more comfortable dump the same way.
Then, on the day when something breaks, you are merely annoyed.
 
#5 ·
This is a frequent one that we get asked during training.

As experience increases you (should) develop a feel for what works best and keeps things simple. Hopefully this is encouraged from day one so that instead of HAVING to learn new ways, you are developing what has already proven to work for you through correct instruction and guidance to tailor your style as opposed to what makes it easiest to teach ! I'm not saying don't try or use different techniques, try them all, but good instruction should teach you to recognise minor air shifts and teach you how to use them to your advantage !

I personally use and teach the suit only technique as have found it to work for me and for the vast majority of those that I teach. I also don't teach ankle weights. An extra pool session if required seems to work much better than accepting a reliance on AWs. Again each to their own, but what works for you. A few thousand trained now, and all good without.... Mastering good air migration, trim and positioning at the EARLIEST stages makes for more comfortable divers.

The argument that needing both BCD/wing and DS for buoyancy is entirely individual, however I carry multiple cylinders during tech training and tech dives and once I refined the cylinder configurations early in, barely need weight in fresh water, and little in salt. The benefit of doing what I teach and teaching what I do. I won't teach anything without going and hammering myself first if I've had even a hint of a layoff.

I think the best thing I ever did was switch my deco cylinders to Ali from steel. I dive either a CCR with Ali bailouts or steel twins with Ali decos. Usually 2-4, but sometimes up to 5/6 of them if its a big dive, and depending on the task ! The buoyancy is negligible once content reduced and easily weighted for with proper buoyancy checks. I've never needed to use my wing as well solely because I've hammered the weighting down.

My golden rule is to do weight checks with everything near empty and with everything near full. I will dive closer to the weighting for all empty of course but good to know exactly what you could use at either end of the spectrum then you know what is spot on, and what is on the edge of being over weighted.

By far and above the biggest nut to crack is people deliberately overweighting. It causes problems. Lots. It's also a poorly informed crutch as the negatives will always outweigh the benefits of overweighting. It's just not necessary...

Hope my 5 cents give you and idea to go off and shed a bit of weight, try DS only and you'll be a lot more comfortable.

Most importantly- I don't know you, don't know your kit, your body type, your physical capabilities etc etc. I'm just saying what works for me. One of the biggest and most beneficial things you can ever do in this sport is find what works for YOU.

Enjoy, and have fun.
 
#6 ·
As experience increases you (should) develop a feel for what works best and keeps things simple. Hopefully this is encouraged from day one so that instead of HAVING to learn new ways, you are developing what has already proven to work for you through correct instruction and guidance to tailor your style as opposed to what makes it easiest to teach ! I'm not saying don't try or use different techniques, try them all, but good instruction should teach you to recognise minor air shifts and teach you how to use them to your advantage !

All nice and fluffy in an ideal world, but the reality is that many agencies mandate a single method and Instructors don't get the choice.
 
#8 ·
Has anything changed recently?
Not really.

Is it safe to div using the BCD?
Yes. After all, that's what it's there for and it's even described as a Buoyancy Control Device.

I recognise that some teach using the dry suit only and there are (some) compelling reasons (already stated) for that yet there are also compelling reasons for using both, ie only putting enough air into the dry suit to keep you comfortable with the rest going into your BCD/Wing. Ultimately it's up to you how you do it, there is no wrong or right way. In reality if you use just enough air in your dry suit it is only an issue on ascent as your gas volume increases at lesser depths but your vent button should always take care of that anyway. If not, check to see what's (usually) blocking it, you'll probably find that the culprit is your undersuit bunching up and blocking the vent as a result. That's a common enough problem until you realise what's happening, usually when you start to involuntarily ascend too quickly.

Mind, that can happen with a dry suit whatever methodology you might prefer and if it starts to heppen to you, vent some air from the sleeve of the dry suit to get you back to equilibrium rather than, probably ineffectually, mess about with your vent button. Getting a bit of water down the sleeve of your dry suit is, in my book anyway, a whole lot better than possibly getting bent or suffering a pneumothorax.
 
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#9 ·
When learning it's easier to learn with just one source of boutyance, and seeing as you need to add air to a suit to ease the squeeze then "most" agencies seem to teach use the suit.
Having said that once the course is passed then it would appear that most divers then go on to use just enough air in the suit to manage the squeeze, and then use the BCD for actual bouyancy control.

TBH as long as you are in control I don't think it matters much provided you aren't massively overweighted.
If you use the suit then you are just managing one lot of air, if you use the BCD the air is all on your back making it easier to trim out/manage.
It's entirely up to what you find easiest.
 
#10 ·
Dry suits are made to keep divers dry, not to control their buoyancy. For that we have BCDs and wings.

Due to the way, dry suits work, it's inevitable that they also influence buoyancy and, in certain cases, the amount of air to keep the suit comfortable is enough also to maintain the diver neutral. When diving with a single I don't need to add extra air to my wing.
But if that is not the case, the extra lift should come from the BCD/wing. They were designed for it, they keep the air manageable in a controlled space (no large amounts of air moving around inside the suit, rushing to the arms or, worse, the legs from where it's not possible to dump it, filling the boots and making fining uncomfortable, etc), they allow for faster release of air than the suit valves and they don't suddenly cause changes in buoyancy either from air loss (for instance the neck seal not holding the pressure of a large amount of air and letting it out) or due to air displacement (diver moves slightly to inverted to take a look in some crevice and all the air moves up to the feet by over a meter).

It is certainly another thing to control, but it's not that hard (suits with well positioned valves help a lot) and shouldn't be a reason not to use the BCD/wing.
 
#11 ·
I always use my suit for buoyancy and usually dive with twin 12s with optionally one or two stages (Ali 7s or 80s) and always with an DSLR camera and two strobes.
I have on occasion added a little to my wing but as Scubagypo says once you really nail down buoyancy and weighting this is hardly necessary.

At the end of the day it's a personal preference thing and anyone that says otherwise is being a bit too rigid in their views.

I find it particularly irritating when people trot out the mantra BCD = buoyancy control device therefore a drysuit isn't a buoyancy control device.
These people (who usually use a wing) seem to forget that a wing is for flying and not buoyancy control!
 
#12 ·
I find it particularly irritating when people trot out the mantra BCD = buoyancy control device therefore a drysuit isn't a buoyancy control device.
These people (who usually use a wing) seem to forget that a wing is for flying and not buoyancy control!
Less of a mantra and more just a simple fact based on the primary function.

The BCD is designed for that one purpose, it's not like you'll get warmer using it :)
The drysuit on the other hand might be perfectly acceptable as a buoyancy aid, but that's it's secondary, not primary function.
 
#15 ·
Using a suit for buoyancy control is something you need to learn, just like you learnt to use a BCD. Then you have control of both and it isn't going to be a problem to you.
On a single, where full to empty the tank on your back only changes weight by three kilos you can just about do it all on the suit but three litres of air above what it takes to make things comfortable does tend to rush about a bit so I bang some in the BCD. On twins with over 6kgs full to empty I don't believe anybody does it. Look at 6 litres of milk in the fridge and imagine that slopping about in your suit looking for the highest point to rush too. They just underweight themselves and kid everybody that they could hold a stop down to empty.
 
#16 ·
personally, I use both for buoyancy. I vary which one is primary depending one the dive and how I feel like doing it that day. Most of the time my drysuit is inflated just to take the squeeze off and other times I am like a balloon in order to keep warm. Like others have already posted, it is good to be able to use either without much thought.
 
#36 ·
Simple test.

Get a student in a drysuit, do the squats and release as much air as you can, then jump in and do a buoyancy check.
Now do the same thing, but this time do the squats with a weightbelt on.

What do you reckon the chances are of the buoyancy being the same :)
 
#46 ·
I admit I'm with Woz on this one. I've never found that a tight weight belt stopped the gas in my suit rushing from end to end with annoying alacrity.
It is a gas and gasses don't seem to mess about when it comes to going through holes.
 
#47 ·
Change your body/size/shape, type of suit and thinsulate etc. and a whole list of other variables and yes it can happen.
Air will migrate yes, but that doesn't mean it will migrate fast enough when you really need it to.

Need to stop thinking about what we would do and try and put ourselves in the mind of a new diver with enough on their
plate trying to deal with a new experience of how much gas to put in the suit, when still having trouble remembering what
they've been told in the pool about the BC a week before.
 
#61 ·
Totally disagree. Dry suits are there to provide a comfortable environment AND a buoyancy source. BCDs and wings are additional buoyancy sources.

A wet suit is not a buoyancy control device....a dry suit can be. Thousands of divers find that to be the case, are you saying we are all wrong?
 
#62 ·
As a newbie diver with 30 odd dives and in a dry suit that does not fit perfectly I find this thread confusing. Should I use my BC or suit for buoyancy? Does a weight belt really cause air migration problems? I cant see it myself.

I personally use a bit of both for buoyancy am I wrong?

For us newer divers is there a readable post for correct use of a dry suit I can read?

Oh and if you "professional experienced" divers cant agree what hope for us newbies?
 
#63 ·
Iain,

You highlight a very good point in how people that have been diving a while can't agree and then argue about advice for newcomers to the sport which does nothing but confuse you. I'd advise you to do it how you were taught (although I hope that is not to use a bit of both) and once you're absolutely certain you have that nailed then start experimenting with other ideas in shallow water to fine tune your technique.

I don't think that learning this stuff on the internet is the right way to do it. Go to a decent instructor and get some advice; if you're not happy with the instructor then find another.

Hope that helps.
 
#65 ·
I was taught to use suit for buoyancy and BC for "surface" and my phrase "I personally use a bit of both for buoyancy am I wrong?" did not come out as I intended, I should have said I use the BC for accent/descent and the suit for underwater for squeeze etc.

After a bit of experimentation I seem to be going the way of using the BC only and suit for squeeze, whether that's right or not I don't know but seems to work for me.
 
#66 ·
Shouldn't have to apologize for choosing a particular way, just as long as that choice is by comparison and
not cause it's the only way that you've been taught.

In your case you've settled on what you prefer, but could in a jam revert back to the other method, which is
about the best of both.
 
#68 ·
I started diving by using my BCD for buoyancy and my suit for comfort. On dive #50 I did my sidemount course and the instructor told us to use the suit so I gave it a try... What a difference! I personally found it much easier and never bothered with the wing again. I only use the wing when I am on the surface!
My suit can comfortably support 2 steels and 2 Alis. I haven't tried a 3rd Ali yet, but I can always use the wing for that bit extra if needed. :teeth:

If you are currently using both and it woks fine, stick to it. I tried the suit-only way on my dive #50 and I found it much easier. I was still a noobie and my buoyancy needed improving and that method helped...
 
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