Trapping air under aqualung dimension

[alex-o-matic]

G'day all.

First post here, any thoughts appreciated. I currently dive an Aqualung Dimension BCD. No issues with it, it's been great. However, I have a slight problem - I keep getting air trapped under the BCD - between the BCD and my back. I'm guessing it comes from my regulator exhaust, around my neck and under the BCD and the only way to get rid of it is to roll from side to side, allowing it to escape.

It's a problem that varies from a minor annoyance to something that interferes a good bit with buoyancy - it's extra air that doesn't release when you hit the dump valve. And obviously it gets worse when my work rate is high, which can be an addition to stress loading.

So - has anyone else had this problem? Couldn't find any threads on it when searching. I'm interested if it's likely to be just a problem with this specific BCD, or a technique issue? Would adding a regulator exhaust diffuser do anything?

Cheers!

 

[happy-diver]

Yeah when I'm stuck in a shipwreck like here, it's quite embarsassment that people think that I'm farting

So I get out all red faced and change my trim

Aarhus Dive Site

Queensland ATDW product. Details will load via product api call.

www.queensland.com

 

[alex-o-matic]

Wondering if anyone else has any possible solutions to this (that stop short of replacing the BCD)?

I was out on a dive the other day and it was trapping quite a bit of air between my back and the BCD, and it was starting to toe the line from annoyance into serious issue.

I'd thought maybe of trying to divert the regulator exhaust a bit further, but there's no extended exhaust baffle available for my reg set (Aqualung legend LX series). Thinking if there's some way of closing the gap between the back of my neck and the BCD to prevent bubbles getting in there.

Any suggestions out there?

 

[lexvil]

I’ve never used this b/c so wondering if you can wear it lower on your back (lengthen the shoulder straps) to move it away from you exhaust, if so you’ll want to make sure snug the waist straps so it doesn’t slide up. Trim may have you head down in use, lowering should help that too.

and in SB obligatory requirements you may want to look into a back plate/wing.

 

[jborg]

Any suggestions out there?

Do you have a feeling or guess as to why this happens? My wife used to dive this BCD, and I can't say it seemed more prone to trapping air than any other BCD I've seen...

 

[Landau]

No air trapping issues with my Dimension.... as far as I know. How can you tell itis trapping air? Hard to look and see.

 

[alex-o-matic]

I’ve never used this b/c so wondering if you can wear it lower on your back (lengthen the shoulder straps) to move it away from you exhaust, if so you’ll want to make sure snug the waist straps so it doesn’t slide up. Trim may have you head down in use, lowering should help that too.

Thanks, will see if that's possible - although I don't know if it will be sufficiently secure if I wear it lower down - but can give it a go.

and in SB obligatory requirements you may want to look into a back plate/wing.

I am actually getting started into using a sidemount rig, which solves the problem when I'm able to do that. (This isn't the real reason I'm getting into sidemount - that's more about being able to take a lot more gas along with me, as I vacuum it up, and like the redundancy aspects). I think that I'll need to keep a backmount rig, as I'm contemplating doing my DM later this year, so if I can get away without needing to replace my BCD I'll be happy.

 

[alex-o-matic]

Do you have a feeling or guess as to why this happens? My wife used to dive this BCD, and I can't say it seemed more prone to trapping air than any other BCD I've seen...

I can only think of two factors that may impact. The Dimension seems to wrap slightly more around the body that some that I've seen - which keeps it nice and secure, but creates a bit of an enclosed cavern between the inflated sides of the bladder. The only other thing is that I tend to dive using large steel tanks (Faber 15L steels), which could be hindering the gas escape - although I've noticed it using AL80s too.

But it equally could be how I hold my body in the water, or something completely different. Interesting that it doesn't seem to be a problem others have.

No air trapping issues with my Dimension.... as far as I know. How can you tell itis trapping air? Hard to look and see.

The way to see if you have trapped air is to roll 60-90 degrees to the left or the right, and if you notice bubbles escaping from under the BCD without touching dump valves etc. In my case it's not just a couple of bubbles, it's quite a bit of air that comes out when I roll.

It took me a long time to figure it out. I had noticed some bubbles accumulating under the BCD that only escaped when I rolled, and for a while I thought the BCD had developed a leak, and was leaking into the space between the bladder and my wetsuit. But after a number of tests, I figured out that it wasn't leaking. The only source of bubbles left is exhaust gas from the regulator, which seems to be consistent with it getting worse under high work load.