Aqua Lung Dimension stability issues

[.wilco.]

Hello fellow divers,

First time posting here. I've searched for threads about the same problem, but couldn't find anything similar. If I missed something, my apologies. If you could be so kind as to point me in the right direction, I would be grateful.

TL;DR I bought an Aqua Lung Dimension that's not keeping me stable in the water. I made video's (links below) but Aqua Lung tells me there's nothing wrong with the thing. Am I going crazy?

A little over a year ago, I bought my first BCD. An Aqua Lung Dimension (no i3). I wasn't blown away from the get-go. I just couldn't get myself stable in the water. I kept rolling to the right. I didn't think much of it at the time. I was (and still am) fairly new to diving when I bought it (I have 64 dives to date). And I never used a back inflate BCD. I thought I just needed to get used to it or do a more proper trim.

A couple of months back though, I did a full gear exchange with a buddy of mine during training. When we surfaced, the first thing she asked me was "What the **** is wrong with your BCD?". She experienced the same thing. I let my instructor dive with it. Same thing.

"Okay," I thought, "so It's not just something to get used to." I brought it back to the place I bought it expecting getting it swapped for a new one. That's not what happened, though. They dove with it themselves, couldn't find anything wrong with it, and gave it back saying "It must be your HP hose which is blocking the bladder. Make sure you route it properly and you won't notice anything."

Hopeful (and naive) it was something as simple as this, I tried the thing again. Of course with no luck. I decided to make some videos to show the problem. I went back to the shop, showed them the videos and they agreed it didn't look good and sent it to the international distributor (along with the videos). They couldn't find anything wrong with it though. So they apparently sent it to Aqua Lung in the States. Two engineers looked at it; they can't find anything wrong with it as well.

I'm flabbergasted. And think I'm going crazy. I have a lot of respect for Aqua Lung and their gear, so I can't for the life of me figure out what's going on here. Am I going crazy? Am I expecting something unreasonable (being stable in the water while doing nothing doesn't seem like a stretch goal for a BCD, though)? Am I doing something wrong?

It would be great if you could take a look at these three very short videos and let me know what you think.

> Normal setup. With lead and everything
> BCD only. no lead.
> Loose HP hose (to avoid the "you're HP hose is blocking the bladder" discussion)

I have more where for example I do a fin pivot. When I lift my hands, I 'fall' to the right. If you need that for a better view, let me know, I'll upload it Youtube as well.

Thanks for your help in advance!

 

[Jim Lapenta]

It looks like the air is being prevented from distributing through the wing. Whether its a defect in that unit or a design failure is hard to tell without actually having it in hand.
Clearly, though, you are getting a lot of air in the left side and little to none in the right.
Looking at the specs, the wing for one thing in the large size is ridiculous.
You don't need 42 lbs of lift in a single tank bc.
The wing is too big for a single tank. It's also taco'ing on the side that's inflating. It's too wide.
I've tried to find other videos of it and based on those, the design seems to be an issue.
With some of the stuff AL comes out with, you have to wonder if their engineers have ever been in water on scuba.
Other stuff is cool and well done with high quality.
Some of their BC and fin "innovations" leave you shaking your head.

 

[JackD342]

I can't tell for sure from the video, but it looks like you might have the bladder retraction system unclipped. If you do, that may just make a world of difference for you. Also, is the BCD sized right for you and snugged up, or is it a bit loose on you? Anything that is loose allows air to go more of where it wants to go (up) and less of where you want it to go (sideways). If there is room for the BCD to pull away from your body, buoyancy and trim become much tougher.

A few general notes, in case anything lands with you and helps:

• Air wants to go up not out to the side. Once you get a "high spot" or "bulge" in your BCD from inflation, air will fill from there down, the same way that you clear a mask via displacement. It might take a little bit of a "roll" on your part to move it around a bit. That is the reason many BCDs have a bungeed bladder retraction system - so the resistance makes the air spreads out first, before it stretches the bungee for added volume/lift. Another exampls is the way I sometimes do a brief "dolphin kick" in my drysuit to move the air inside it around.
• Anything else unbalanced on the BCD between left and right? Are weights distributed evenly? If using trim pockets, do you have a good balance between front and back? (I would suggest no more than 30% of total weight in back.)
• Diving overweighted will also tend to cause larger unnecessary volumes of air in the BCD to move around and feel unbalanced.

 

[JackD342]

You don't need 42 lbs of lift in a single tank bc.

This BCD is capable of holding 40 pounds of weight in the supplied pockets between front and back. There are some divers that may max that out or come close, especially when wearing a drysuit.

Considering the recreational diver focus for this and most/all Aqualung BCDs, I for one appreciate them designing the gear so that it will be slightly buoyant at the surface if I remove it when weight pockets are full, rather than watching it take a ride to the bottom.

 

[.wilco.]

I can't tell for sure from the video, but it looks like you might have the bladder retraction system unclipped. If you do, that may just make a world of difference for you. Also, is the BCD sized right for you and snugged up, or is it a bit loose on you? Anything that is loose allows air to go more of where it wants to go (up) and less of where you want it to go (sideways). If there is room for the BCD to pull away from your body, buoyancy and trim become much tougher.

A few general notes, in case anything lands with you and helps:

• Air wants to go up not out to the side. Once you get a "high spot" or "bulge" in your BCD from inflation, air will fill from there down, the same way that you clear a mask via displacement. It might take a little bit of a "roll" on your part to move it around a bit. That is the reason many BCDs have a bungeed bladder retraction system - so the resistance makes the air spreads out first, before it stretches the bungee for added volume/lift. Another exampls is the way I sometimes do a brief "dolphin kick" in my drysuit to move the air inside it around.
• Anything else unbalanced on the BCD between left and right? Are weights distributed evenly? If using trim pockets, do you have a good balance between front and back? (I would suggest no more than 30% of total weight in back.)
• Diving overweighted will also tend to cause larger unnecessary volumes of air in the BCD to move around and feel unbalanced.

Thanks for the help and suggestions, Jack!

I don't have the Bladder retraction system unclipped. That was one of the things my dive shop was thinking as well. We even tried a 'stronger' one (which I use in the video's, by the way). I didn't help, unfortunately.

It's definitely something to do with the distribution of air. I frequently do a barrel roll or something to distribute the air a bit better. That helps for a little while. Never for very long, though. I think the BCD is a pretty good fit as well (it's M/L). I wanted to get an M myself, but the shop advised against it after seeing me in it. I think I could do with an M as well, but it still shouldn't make this much of a difference I think.

I tried everything with weights as well. Using trim pockets, not using them. Making sure everything is distributed evenly. More weights, too little weights. I even ditched everything (gear + weights) in the BCD one dive and went old school with a belt to make sure. Didn't help either. A buddy of mine tried repositioning the tank to see if maybe it was just a bit off center - no luck.

I just can't figure it out. I refuse to believe this is 'normal' for this BCD. Lots of reviews are raving about how well balanced it is. For me, it's MUCH more convenient to dive an Aqua Lung Wave at the moment. I can't help but feel that's not normal. But Aqua Lung is telling me there's nothing wrong with it (through my Dive Shop. I haven't been in contact with them directly)

 

[.wilco.]

It looks like the air is being prevented from distributing through the wing. Whether its a defect in that unit or a design failure is hard to tell without actually having it in hand.
Some of their BC and fin "innovations" leave you shaking your head.

Thanks, Jim. Exactly. I would be very surprised if it is a design failure, though. I think I wouldn't be the first one complaining about it, and I can't find any other people mentioning the same thing. Weird, right?

 

[JackD342]

Thanks for the help and suggestions, Jack!

I don't have the Bladder retraction system unclipped. That was one of the things my dive shop was thinking as well. We even tried a 'stronger' one (which I use in the video's, by the way). I didn't help, unfortunately.

It's definitely something to do with the distribution of air. I frequently do a barrel roll or something to distribute the air a bit better. That helps for a little while. Never for very long, though. I think the BCD is a pretty good fit as well (it's M/L). I wanted to get an M myself, but the shop advised against it after seeing me in it. I think I could do with an M as well, but it still shouldn't make this much of a difference I think.

I tried everything with weights as well. Using trim pockets, not using them. Making sure everything is distributed evenly. More weights, too little weights. I even ditched everything (gear + weights) in the BCD one dive and went old school with a belt to make sure. Didn't help either. A buddy of mine tried repositioning the tank to see if maybe it was just a bit off center - no luck.

I just can't figure it out. I refuse to believe this is 'normal' for this BCD. Lots of reviews are raving about how well balanced it is. For me, it's MUCH more convenient to dive an Aqua Lung Wave at the moment. I can't help but feel that's not normal. But Aqua Lung is telling me there's nothing wrong with it (through my Dive Shop. I haven't been in contact with them directly)

Check yourself against the size chart. Based on the video it didn't look like you have an "out of tolerance" body shape, so this should be a pretty good guide. Also think about what else you are wearing under the BCD, especially for the Over The Shoulder measurement. It is not always possible to get one BCD that fits equally well for use with both a bulky drysuit and just a skin.
BC Size and Lift Chart

 

[.wilco.]

Check yourself against the size chart. Based on the video it didn't look like you have an "out of tolerance" body shape, so this should be a pretty good guide. Also think about what else you are wearing under the BCD, especially for the Over The Shoulder measurement. It is not always possible to get one BCD that fits equally well for use with both a bulky drysuit and just a skin.
BC Size and Lift Chart

I did check the guide before I bought the BCD. For my hips, I should have an M/L, for my shoulders an M. Some of the folks I let dive with my BCD are quite a bitter bigger than me, though. And I have the same problems in both a rashguard and 7mm suit. So I'm fairly confident size is not the problem. Thanks for your tips, though! Much appreciated.

 

[JackD342]

I did check the guide before I bought the BCD. For my hips, I should have an M/L, for my shoulders an M. Some of the folks I let dive with my BCD are quite a bitter bigger than me, though. And I have the same problems in both a rashguard and 7mm suit. So I'm fairly confident size is not the problem. Thanks for your tips, though! Much appreciated.

Just curious - where did you land on the Over The Shoulder measurement?

I can't think of anything else right now. Maybe your air is defective?

 

[JackD342]

Okay, still thinking....

Purely speculation, and I would hope this would have been addressed by your trouble-shooting so far, but here goes:

Pull out a tape measure and check as many dimensions as you can comparing the left side to the right side, both deflated and inflated. Is it possible the bladder is actually off-center, or a little larger on one side than the other? With the exception of valve placement, I think there should be 100% left-right symmetry.