steve_r0binson
Guest
I just wondered if I get a dry suit and a BCD could I use just the BCD for boyancy and the dry suit just for keeping dry and warm? Or do they both come into the equation?
Do I have to use dry suite for boyancy
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No, you don't have to use your drysuit for buoyancy. I use my BCD for buoyancy and just add enough gas in the suit to eliminate squeeze (I keep the dump all the way open). They do both come into the equation since the drysuit is a large airspace that will need to have gas added to it at depth (to eliminate squeeze) and vented from it on ascent (to prevent a runaway ascent - just like your bcd). Luckily for us, drysuit dumps are automatic and you only need to position the dump high to dump the necessary gas (i.e. raising your left arm/shoulder with a conventional shoulder dump).
I use mine in the same manner as O-ring.
To preface - one must do what is comfortable without compromise to safety OF COURSE.
According to PADI:
"Use your BCD for extra bouyancy at the surface - not your dry suit. Extra air in your dry suit restricts movement, puts pressure on your neck and makes you uncomfortable"
"When you're ready to descend VENT YOUR BCD and exhale. At this point stop using your BCD for buoyancy control and use primarily your dry suit (of course lung volume for fine tuning)"
Using your dry suit for buoyancy control has several benefits:
1. Simplification - one buoyancy control system to deal with throughout the dive.
2. Minimizes dry suit squeeze.
3. Keeps you warmer because throughout the dive the focus is on adding and removing air from the suit.
According to PADI:
"Use your BCD for extra bouyancy at the surface - not your dry suit. Extra air in your dry suit restricts movement, puts pressure on your neck and makes you uncomfortable"
"When you're ready to descend VENT YOUR BCD and exhale. At this point stop using your BCD for buoyancy control and use primarily your dry suit (of course lung volume for fine tuning)"
Using your dry suit for buoyancy control has several benefits:
1. Simplification - one buoyancy control system to deal with throughout the dive.
2. Minimizes dry suit squeeze.
3. Keeps you warmer because throughout the dive the focus is on adding and removing air from the suit.
Arnaud
Contributor
I'll second that. I don't have a huge experience with dry suits, yet. But it seems to me much easier to handle one buoyancy device at a time rather than 2.
Similarly, I just don't understand how you can inflate your dry suit just once and then forget about it if your depth is changing. At some point, the pressure will create a squeeze. And if the depth is not changing, well, you're not supposed to adjust your buyancy anyway...
I can only see two reasons why you would have to use your BC underwater, and none of them are good. Either your dry suit is too small and it won't hold enough air to allow for proper buoyancy or the weight is not appropriate.
Maybe, it's another story if you go below 130 ft, but that's deeper than I want to go...
Similarly, I just don't understand how you can inflate your dry suit just once and then forget about it if your depth is changing. At some point, the pressure will create a squeeze. And if the depth is not changing, well, you're not supposed to adjust your buyancy anyway...
I can only see two reasons why you would have to use your BC underwater, and none of them are good. Either your dry suit is too small and it won't hold enough air to allow for proper buoyancy or the weight is not appropriate.
Maybe, it's another story if you go below 130 ft, but that's deeper than I want to go...
ERP
Guest
You can do either, the primary arguments seem to be.
Your BCD is designed as a buoyancy control device, its a small pocket instead of a big human shaped bag, so it gives you more control.
on the converse
Using your suit you only have to vent the suit on ascent, arguably reducing task loading.
My Instructor (PADI) doesn't teach the drysuit course because he doesn't agree with using the drysuit for of buoyancy control.
Your BCD is designed as a buoyancy control device, its a small pocket instead of a big human shaped bag, so it gives you more control.
on the converse
Using your suit you only have to vent the suit on ascent, arguably reducing task loading.
My Instructor (PADI) doesn't teach the drysuit course because he doesn't agree with using the drysuit for of buoyancy control.
...is wrong.
But true to form they teach to the lowest common denominator... the inexperienced diver who purchases an ill-fitting bag to use in conjunction with a horribly designed BCD that was really only meant to function as a surface PFD.
Most drysuits I see on folks don't fit... they are horrible bags with so much extra material to fold and pucker that of course there is great potential for not only squeeze but air trapping on ascent as well.
Most BCDs that I see are huge bags of *ballistic* (what does that mean?!) nylon, straps, buckles and shiny metal rings. These monstrosities could be used as PFDs even without adding air due to their intrinsic flotation.... however charged with air underwater they bloat even further and become impediments to forward progress.
Not that any of this matters to the targeted market.... rototillers.
Now none of this answers your question Steve... but I had to preface my answer with the above.
With a proper backplate/wing and properly fitted drysuit you only add enough gas to the suit on descent to eliminate excessive squeeze but still allow the water pressure to cause the suit to hug your body. This minimal gas is added in very small amounts every ~20 feet or so and vented as soon as possible and as much as possible on the ascent. Excursions up and down +- 10 feet should not require suit gas adjustment.
The extra weight carried to offset the gas that will be used out of the tank for breathing needs to be compensated for at the beginning of the dive. This is the role of the buoyancy compensating wing. Gas is added to the wing (BCD) at depth and as the dive progresses and gas is used from the tank and the tank itself starts to gain buoyancy then gas is released from the wing (BCD.) On ascent any remaining gas in the wing (BCD) will be vented as appropriate.
If you are properly weighted*
then when you reach the end of your dive there should not be much gas in either your suit or your wing (BCD) to vent on ascent.
Hence... proper weighting is the most important issue.
*neutral at 10' (0~15' is another debate) with no gas in the wing (BCD) an as much gas out of the suit as will go... and with only 500PSI (0~700PSI is another debate) in the tank.
But true to form they teach to the lowest common denominator... the inexperienced diver who purchases an ill-fitting bag to use in conjunction with a horribly designed BCD that was really only meant to function as a surface PFD.
Most drysuits I see on folks don't fit... they are horrible bags with so much extra material to fold and pucker that of course there is great potential for not only squeeze but air trapping on ascent as well.
Most BCDs that I see are huge bags of *ballistic* (what does that mean?!) nylon, straps, buckles and shiny metal rings. These monstrosities could be used as PFDs even without adding air due to their intrinsic flotation.... however charged with air underwater they bloat even further and become impediments to forward progress.
Not that any of this matters to the targeted market.... rototillers.
Now none of this answers your question Steve... but I had to preface my answer with the above.
With a proper backplate/wing and properly fitted drysuit you only add enough gas to the suit on descent to eliminate excessive squeeze but still allow the water pressure to cause the suit to hug your body. This minimal gas is added in very small amounts every ~20 feet or so and vented as soon as possible and as much as possible on the ascent. Excursions up and down +- 10 feet should not require suit gas adjustment.
The extra weight carried to offset the gas that will be used out of the tank for breathing needs to be compensated for at the beginning of the dive. This is the role of the buoyancy compensating wing. Gas is added to the wing (BCD) at depth and as the dive progresses and gas is used from the tank and the tank itself starts to gain buoyancy then gas is released from the wing (BCD.) On ascent any remaining gas in the wing (BCD) will be vented as appropriate.
If you are properly weighted*
then when you reach the end of your dive there should not be much gas in either your suit or your wing (BCD) to vent on ascent.
Hence... proper weighting is the most important issue.
*neutral at 10' (0~15' is another debate) with no gas in the wing (BCD) an as much gas out of the suit as will go... and with only 500PSI (0~700PSI is another debate) in the tank.
Arnaud
Contributor
Uncle Pug, as most, I'm not familiar with wings. Are you saying that wings, with a dry suit are only used to offset the increased buyancy of the tank?
I absolutley agree with Pug. I didn't take the drysuit class specifically because I didn't want to learn to dive in a big buoyant shopping bag. I got in some shallow water and taught myself how to deal with a stuck inflator.
It's really rather easy to control both a drysuit and BC at the same time. As you descend, you just bump air into the drysuit to keep it from squeezing hard, then use your BC as normal. As you ascend, dump your BC and drysuit. No big deal. The "hug" effect is really kinda nice and comforting.. the shopping bag effect is really disconcerting. If you do it right your drysuit will have more or less the same buoyancy throughout the dive.. It's not a problem at all.
It's easier to dive, it feels more natural, and you don't have a blob of air shifting around you. You have on a suit that fits, and a BC to hold all that air.
It's really rather easy to control both a drysuit and BC at the same time. As you descend, you just bump air into the drysuit to keep it from squeezing hard, then use your BC as normal. As you ascend, dump your BC and drysuit. No big deal. The "hug" effect is really kinda nice and comforting.. the shopping bag effect is really disconcerting. If you do it right your drysuit will have more or less the same buoyancy throughout the dive.. It's not a problem at all.
It's easier to dive, it feels more natural, and you don't have a blob of air shifting around you. You have on a suit that fits, and a BC to hold all that air.
Keeping in mind that we are in the basic scuba section and only addressing recreational diving....
The wing... during the dive has the function of buoyancy compensation... offsets the weight of the gas in the tank.
A properly designed wing will wrap up along the sides of the tank and present minimal area to create drag.
The wing on the surface is used to provide buoyancy for the diver and his rig. Ideally the wing should be sized to be able to float the rig when it is removed at the surface. If this were not a service requirement then the wing could be very small indeed.
So why would one need a 100# wing?
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