New Wing - Buoyancy change

[Oezkan]

Hi Divers!

I was always diving with hiring gear and just got my First own bcd. Its a wing (Cressi Commander) and I know the Buoyancy and trim is different with a jacket style bcd and despite that I'm not sure if it's the commander, if it's a faulty bcd or if it's normal but:

I got a perfect Buoyancy and trim position in the water in horizontal position. But as soon as I change my position (looking to the side, like one shoulder shows to the ground or even worse super much when I do head down feet up position) my Buoyancy changes without deflating or kicking. I start to ascent. Not a little bit but a lot. I have to either deflate or get back to horizontal position again to not have a rapid ascent. - I never had this with the jacket bcds. I could change position and the Buoyancy was the same. I didnt ascent or decent.

Is this normal for wings or for the cressi commander or do you think its a faulty bcd?

It also takes aaaages to deflate and inflate and after the dive there is a lot of water inside the bladder.

Thanks guys. Dive safe!

 

[rick00001967]

i have never used this particular bcd.

with a rear inflate bcd, the gas in the wing can move around. so when you roll from side to side for example, the gas will move and this will have an affect on your body position in the water.

but what you are describing does sound odd. i would be concerned about having "a lot" of water in the wing.

the only time i see a lot of water in my wing is when doing a lot of manual inflation during a class for example.

otherwise i may have some, but not very much. pls make sure all the fittings for your dump valves and inflator hose, have gaskets, and are tight.

as far as the speed at which the wing inflates or deflates, perhaps it has a larger capacity than you are used to ? or maybe you are not in the correct position when dumping gas ? if you bought from a local shop, you could get them to check the inflator for you.

 

[Oezkan]

Thank you very much for the quick answer! As I'm not used to wings I cannot compare but what you say feels right. It does move inside the bladder when I change my body position. But should it make me ascent? Also what's confusing is when I do head down position the gas and water should go to the top of the bcd and if then make me descent not ascent or no?

Good idea. I let the bcd check I the shop I bought it.

 

[lexvil]

Just a guess but it’s likely that you are staying down by kicking, buoyancy won’t change with position, trim may but the ascent part is the clue.

 

[rick00001967]

what depths are you diving when this problem happens ?

in a shallow pool for example, if you go head down, the gas will go towards your feet (the gas always moves towards the highest point), and since you have now raised your legs, the lower part of the wing is a bit shallower. this would cause an expansion of the gas. this little bit of expanding gas will affect your buoyancy and make you just a little more positive. this could be causing you to ascend.

but if you are testing this in deeper water, you should be able to roll over, or flip upside down and it should have no affect on your buoyancy.

 

[Oezkan]

what depths are you diving when this problem happens ?

in a shallow pool for example, if you go head down, the gas will go towards your feet (the gas always moves towards the highest point), and since you have now raised your legs, the lower part of the wing is a bit shallower. this would cause an expansion of the gas. this little bit of expanding gas will affect your buoyancy and make you just a little more positive. this could be causing you to ascend.

but if you are testing this in deeper water, you should be able to roll over, or flip upside down and it should have no affect on your buoyancy.

I totally didn't think about gas is going to the highest point but it makes sense! But how come a jacket style was no issue doing that?

I indeed tried it today in very shallow water. It was I think 4-5 meters only. I gonna try it in deeper water soon to compare.

 

[Oezkan]

Just a guess but it’s likely that you are staying down by kicking, buoyancy won’t change with position, trim may but the ascent part is the clue.

That's whats concerning me. I do not kick I stay very calm without movement down. And this problem wasn't there with the bcds before.

 

[rick00001967]

I totally didn't think about gas is going to the highest point but it makes sense! But how come a jacket style was no issue doing that?

I indeed tried it today in very shallow water. It was I think 4-5 meters only. I gonna try it in deeper water soon to compare.

it may just depend on the design of the jacket style bcd vs. the rear inflate bcd with a wing. typically there is very little air in a jacket style bcd near your butt. but in a wing (depending on the shape) there may be a substantial amount of gas near your butt.

try it in the deeper water and let us know how it works for you.

 

[lexvil]

That's whats concerning me. I do not kick I stay very calm without movement down. And this problem wasn't there with the bcds before.

Remove your fins and hand them to your buddy, see what happens

 

[Ayisha]

It also takes aaaages to deflate and inflate and after the dive there is a lot of water inside the bladder.

If a lot of water is entering the bladder while you are diving, it is usually because either you are not holding the inflator/deflator at the highest position or you are trying to dump gas when you are underweighted and the BCD is already empty. In both cases, the BCD will take in water.

A wing is similar to a back-inflate BCD, so you have to slightly roll to have the valve at the highest position. For example, if you are horizontal and use the deflator hose, if it's not held high up, it will take in water.

If you're horizontal, we usually use the rear dump valve. You may need to slightly roll and lift the side of your body that has the rear dump valve to make sure it is the highest point.

If you're underweighted, people often tend to keep trying to deflate, which just adds water. If you have a lot of water in your BCD after the dive, chances are you're underweighted or dumping somewhere other than the highest point of the BCD, assuming that your dump valves have a gasket, and are screwed on (finger) tightly.

After inflating or deflating, you do need to give it a few seconds to have an effect. You mentioned that it takes ages to inflate or deflate, so I suspect you are repeating the action and doubling down on what you expected. This can lead to a cycle of correcting and over-correcting repeatedly. For example, you hold the inflate longer or inflate again, start rising rapidly, over-dump, sink too low, and repeat.

Give one or 2 tiny squirts when inflating and ... wait. Same when deflating. If you're using the rear dump valve, make sure you're just pulling the string slightly. Some people tie knots in the rear dump valve string at intervals to help them feel how little they should pull and to not lose grip on it.

Changing position should not change your buoyancy unless you are also changing depth. I suspect the delayed over-filling is what's triggering a buoyancy change. In shallow water, anything you do will be magnified and harder. Once you are neutral at the depth you want to stay at, leave your wing. Use breath control for fine repositioning. If you lose your position, fin back to where you were. There's no need to re-adjust buoyancy to get back to the same depth.

A jacket holds gas all around, so the highest point is readily available and it's easier to deflate. If you started with a back-inflate BCD, you would be more used to the properties of a wing. I started with a ladies back-inflate, so making the switch (10 years ago) to a bp/wing felt the same to me.

There's a lot to unpack there. Hope that helps...