What's My Problem ?

[MattS]

Is it regarded as bad diving practice to use your BC/Wing to control buoyancy when diving with a drysuit, rather than the drysuit itself?

It is bad diving practice to not be in control of your buoyancy. How you maintain buoyancy control is completely up to you. Using the suit is not wrong. Using the wing/stab is not wrong. Having a rapid is!

When teaching people to use dry suits it is usually easier for them to just use the suit. 7mm neoprene suits are the obvious exception as they need so much lead to sink that the suit is not capable of holding the volume of gas required to become nuetral. For many people using membranes with single 12s, maintaining nuetral buoyancy on the suit alone is the most comfortable way to dive. The more negative you are at the start of the dive more likely it is that you will want to use the wing.

A couple of tips for people moving from cuff dumps to auto dumps. First, slow down your ascent so the dump has time to vent. Second, placing hands on opposite shoulders and squeezing is often quicker and morte effective than using the press/purge on the valve itself.

[nigelH]

Originally Posted by Violent Ken

Is it regarded as bad diving practice to use your BC/Wing to control buoyancy when diving with a drysuit, rather than the drysuit itself?

In some circles yes, however I paid good money for a Buoyancy Control Device and I'm getting my money's worth out of it.

I set the auto dump to wide open, add gas to the suit when I feel it close up a bit and dive the wing. Once I hit the surface aprés dive I close the dump right up and put gas in the suit to make it comfortable or the waves massage the gas out again waiting for my turn for a pickup. It is argued that you only use three kilogrammes of gas on a dive with a 12/232 and you can manage that on the suit but why bother? The BCD will dump much faster if you want a sudden *down a bit* adjustment. Also don't be tempted to close the dump valve up a bit and ascend. You have just converted the system to run at a constant over-pressure and it will fight you all the way. Wide open and use the BCD and you discover why we call them auto-dumps. It just works.

If you ever have to CBL somebody the first thing to do is screw their valve wide open or you are on a hiding to nothing.

[Mark Chase]

I have had a dry suit dump fail and send me to the surface and now i dive the wing. It has three optons to dump air none of which involve flooding the suit. A dry suit has usualy only got one.

That said with my single tank rig getting the squeze off the suit is more than enough for boyancy control so I dont need to use the wing. With heavy rigs like twinset and stages I have minamal amount of air to stop the suit pinching and the rest in the wing


ATB

Mark Chase

[MattS]

It is argued that you only use three kilograms of gas on a dive with a 12/232 and you can manage that on the suit but why bother? The BCD will dump much faster if you want a sudden *down a bit* adjustment.

Average vital capacity is about 4Ltrs (4Kg) with average resting tidal volume a mere 500ml. So if you can learn to use your vital capacity on demand (diaphragm breathing) you do not need the BCD and you will not find a faster method of losing and gaining buoyancy. You will also find it easier to descend from the surface with less weight. Additionally your breathing rate will drop along with stress levels and CO2 levels. So there are some good reasons to learn to breathe properly and once you can do that you don't need to _control_ buoyancy with a dry suit or stab. The C in BCD used to stand for Compensator and some of us believe that Buoyancy Control Device is a misnomer!

Also don't be tempted to close the dump valve up a bit and ascend. You have just converted the system to run at a constant over-pressure and it will fight you all the way. Wide open and use the BCD and you discover why we call them auto-dumps. It just works.

It is a constant volume valve right. So if you close it a little to maintain a nuetral volume in the suit, providing you do not ascend so fast that the valve can not dump the gas as fast as it is expanding, you should remain nuetral. I am misunderstanding something here?

[Hoppy]

Originally Posted by Violent Ken

Is it regarded as bad diving practice to use your BC/Wing to control buoyancy when diving with a drysuit, rather than the drysuit itself?

Having been taught to use the suit and not the BCD, I would say that the answer is best given within the following questions.

What is the purpose of a dry suit. A. To keep you dry.

What is the purpose of a BCD. A. To control your bouyancy.

To be serious for a moment, I was taught to use the suit. This however, gives me a problem with handling the air bubble within the suit. Especially if you are trimmed properly, this seemed to exacerbate (sp) the problem for me. Increasing the likelyhood of a feetfirst Polaris style exit. Very embarrasing as well as dangerous.

I moved to using the wing for what it was designed for and suit air just enough to remove the squeeze. IMHO it's a lot easier to manage now.

My tuppence worth, FWIW.

Hoppy

[Andy M]

Originally Posted by pat

Started to accend without shotline got to 12 meters and took off on rapid accent - repeated pressing of dump valve on shoulder had no effect - Pretty scary & dented my confidence - any info greatly appreciated

Pat, most common problem with divers in new drysuits is too much weight. If theres too much weight on your belt, you'll have more air to control in the suit.

A membrane suit, with a single 12L cylinder, means at most you have 3-4kg of buoyant air to deal with. Not a lot, which means you can dive the suit. If youre diving twin 12s or something, you'll need to put a bit in the wing to keep the air bubble manageable, but I dont bother.

I'd definately speak to instructors in your club and see if any of them will take you on a few drysuit familiarisation dive. I do this with our new drysuit divers, and we practice the various recovery methods from inverted, air in the legs, too much weight, uncontrolled ascent, jammed inflator, jammed dump etc. all sorts of useful skills to pick up. You just need someone to take you through it all in 3-6m of water. Its an excellent confidence building exercise. Happy to do with you sometime if you can get to guildenburgh.

Regards

Andy

[nigelH]

Originally Posted by MattS

It is a constant volume valve right. So if you close it a little to maintain a nuetral volume in the suit, providing you do not ascend so fast that the valve can not dump the gas as fast as it is expanding, you should remain nuetral. I am misunderstanding something here?

It's a spring pushing on a constant area so it's a constant over-pressure system. The suit won't dump until it overcomes the spring so firstly the gas fills all the spare places in the suit. Great if you have an Adonis-the-dive-god figure hugging suit with no spare but I'm blobby in all the wrong places and the suit roughly conforms. What took the squeeze off at 40m can probably go another 30% in size or more before it needs to push to get out but if the valve is wide open it just slops up to my shoulders and suddenly finds it's in open water and not my problem any more.

It would be constant volume in an elastic suit where a constant overpressure would strech the suit a predictable amount but who dives one of them these days?

[MattS]

It would be constant volume in an elastic suit where a constant overpressure would strech the suit a predictable amount but who dives one of them these days?

Your talking compressed neoprene aren you? Another good reason real divers wear rubber then :-)

P.S. Never been accussed of being an Adonis before.

[Mr T.]

*bump*

[nikos]

Originally Posted by Mark Chase

I have had a dry suit dump fail and send me to the surface and now i dive the wing. It has three optons to dump air none of which involve flooding the suit. A dry suit has usualy only got one.

I recall that my dry suit instructor mentioned that if all else fails on the "dumping" front stick a finger down the neck or a wrist seal and air will vanish...... (mind you water comes in but what the heck...)

Equally it is foolhardy to rely on just a dry suit for maintenance of positive buoyancy on the surface for the very reason that seals can blow....