Tank Weight / Buoyancy Differences

[geogator]

I have a quick question. I recently purchased 2 used Luxfer Aluminum S080 cylinders, born in 2002. Is there any weight & buoyancy difference between these and generic Catalina AL80 tanks, both full and empty? I've primarily dove with rented/borrowed Catalina AL80s thus far & noticed that I seemed heavier when I tried them out last week in a local spring but being that they're AL80s too, I would think they should have the same characteristics, however it didn't feel like it as I seemed significantly heavier than usual.

Is there a chart somewhere that can tell me the differences between these, if any? All of my other gear (wetsuit, soft weight, etc.) as well as my body weight was identical to the last time I dove a month ago (also in fresh water), with the exception of a new harness which I don't think would add too much weight to make a difference. (I went from a Hollis Solo to an Elite 2.)

Thanks for any input you may have.

 

[USCScubaboy]

This chart should answer your question.
Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

If the Catalina tanks you were diving with are S80s, you'd see that there is a difference in the buoyancy characteristics of tanks when full and empty.

 

[geogator]

Thanks for the info! It looks like there's almost 2lbs difference when empty & almost 4lbs when full. Glad I wasn't hallucinating! Gonna have to try adjusting my ditchable weight a bit next time.

 

[geogator]

Whooops, scratch that. 1.75lbs empty buoyancy, ~2lb full & tank wt ~ 3.5lbs. Still enough to definitely notice however.

 

[Scared Silly]

If the cylinders you picked up are Luxfer compact 80s (which are 8" in diameter) then you should be able to drop 2 lbs compared to a standard Catalina or Luxfer 80. The buoyancy swing from full to empty will be the same as they all hold the same amount of gas ~80 cuft.

Note while you get to drop 2 lbs of lead to achieve the same buoyancy as before you are actually carrying about 1.5 lbs more in overall dry weight because the compact cylinder weighs 3.5 lbs more than the standard 80s. For some some the added dry weight make compact Al cylinders less attractive. YMMV

 

[henrik242]

Or check out my Scuba cylinder buoyancy calculator, it might be helpful?

 

[sidemount]

Or check out my Scuba cylinder buoyancy calculator, it might be helpful?

Great information, thanks!