Bouyancy characteristics for hp steel tanks

[formernuke]

I'm looking at getting HP steel 100's for single tank diving. The options are new fabers or used PST.

Does anyone know the bouyancy differences between these tanks?

 

[Kupu]

Have you seen this thread?

 

[rsingler]

Faber FX100 is 100cuft at 3442psi, if you can get it, and has an empty buoyancy of -0.6lb.
7.25" x 25"

PST special permit 100 is 102cuft at 3500psi, if you can get it, and has an empty buoyancy of -1.3 lb.
7.25" x 24"

 

[formernuke]

Ok I feel like an idiot I searched instead of just reading the top post.

 

[Bob DBF]

Or if you can find a Faber MP 100, 100cuft @ 3498# (3180 +10%) -7.25 empty, nice for cold water. 7.25 X 24", 38.7# empty.



Bob

 

[Doctor Rig]

What ARE the “buoyancy characteristics” of dive tanks? The compiled tank table values might be a great resource for the experienced diver, but not to me.

Can anyone provide some insight on how to use this data to select a tank that will give the diver the most manageable buoyancy through-out a dive (full to empty) and help optimize the least amount of lead required for the dive?

I’m guessing there are some preferred tanks (either aluminum or steel) that are are better for buoyancy optimization than others. I’d love to hear what your favorite tanks are and why!

 

[Kupu]

Can anyone provide some insight on how to use this data to select a tank that will give the diver the most manageable buoyancy through-out a dive (full to empty) and help optimize the least amount of lead required for the dive?

I will offer an example of of how I used the spreadsheet for a recent tank purchase when looking for an alternative to AL80s. For single tank, warm water dives with wetsuit the goal was to minimize added lead without being over-weighted by the tank itself. I wanted a tank that is close to neutral at the end of the dive rather than positively buoyant.

Looking at the spreadsheet, my Luxfer and Catalina AL80s have 77.4 CF capacity and are about 1.5 lbs negative at the beginning of the dive but over 4 lbs positive at the end. The OMS steel LP85 has 85 CF capacity and is about 6.5 lbs negative full and is neutral at the end of the dive. Using the OMS LP85 allows me to remove 4 lbs of lead from my weight belt with no loss of air capacity and about the same tank dimensions.

 

[Doctor Rig]

I will offer an example of of how I used the spreadsheet for a recent tank purchase when looking for an alternative to AL80s. For single tank, warm water dives with wetsuit the goal was to minimize added lead without being over-weighted by the tank itself. I wanted85 a tank that is close to neutral at the end of the dive rather than positively buoyant.

Looking at the spreadsheet, my Luxfer and Catalina AL80s have 77.4 CF capacity and are about 1.5 lbs negative at the beginning of the dive but over 4 lbs positive at the end. The OMS steel LP85 has 85 CF capacity and is about 6.5 lbs negative full and is neutral at the end of the dive. Using the OMS LP85 allows me to remove 4 lbs of lead from my weight belt with no loss of air capacity and about the same tank dimensions.

@Kupu Thanks for sharing. Did your LP85 change your trim or weight placement any?

 

[broncobowsher]

The chart gives numbers but does not tell the whole story. I have found that the steel tanks rest on your back better. They are heavier, but the weight is in the right place. You don't have a floaty aluminum tank pulling up while weights are pulling down. A steel tank just feels more relaxed on my back. I just trim out better. In both wet and drysuits.

 

[Kupu]

@Kupu Thanks for sharing. Did your LP85 change your trim or weight placement any?

Yes, as described by broncobowsher above. The horizontal trim I am looking for comes easier using steel LP85s and LP80s rather than AL80s.