Different AL80 weights?

[Aloha Joe]

sorry if this has been covered, couldn’t find anything on my phone and am on a dive trip.

I’ve been diving AL80s on Oahu, 2 different charters. Weight and trim has been great (10lb on belt, 8lb cam bands) diving a 6lb plate and 7mm full suit.

I just dove off Hawaii Island and my trim was so bad I ended up perfectly vertical! I swapped the 8 vs 10 location, and even had to move 4lb from weight belt to chest harness.

Can this be due to different tank brands? Nothing else should have changed and I did confirm the recent tank was an AL80.

Being that far out of trim ruins the dive for me. I’m now going to Maui and diving steel so I need to understand my baseline.

 

[aquacat8]

This is from DGX
“There is a line of aluminum "compact" high pressure tanks that offers somewhat improved buoyancy characteristics when compared to standard aluminum tanks. However, some divers felt the uneven distribution of weight in the early designs of compact aluminum tanks caused them to be bottom-heavy in the water and they have not proven to be popular although later designs addressed that concern.”

 

[aquacat8]

If you are going to dive steel next your trim will change again anyway

 

[aquacat8]

If you had one of those “neutral buoyancy” aluminum tanks thrown in you could have been overweighted as well.

 

[Aloha Joe]

Maybe it was a neutral weight tank. I actually dropped a pound and still had plenty of ballast at 600psi. It felt tail heavy, like all the weight was at the small of my back. It was 3000psi though so not compact HP.

If the tank is the cause then I can just take 6lb from my cam bands and should be good with steel.

 

[aquacat8]

Yeah probably just a flukey tank... rental tanks come in all kinds

 

[Aloha Joe]

2 tank dive though... Both were weird.

 

[aquacat8]

The neutral tanks are bottom heavy, they put extra aluminum on the bottom, you probably got two of them.

 

[AdivingBel]

Yep, could have been neutral AL 80s. I dived them in St. Croix this winter. The OP told me in advance so I dropped a couple lbs.. They were nice.

 

[Aloha Joe]

Nice...when you know about it! I had one dive where I was fighting not to be standing straight up, and another holding a weight from sliding on my harness.