Bouyancy difference between Steel and Al?

[Furner]

Whats the difference in bouyancy between a steel tank and an aluminum tank of similar capacity and similar contained pressure? Didnt really cover this in OW class....

 

[Quarrior]

This should help. http://www.diveriteexpress.com/gas/steel.shtml

 

[cool_hardware52]

Whats the difference in bouyancy between a steel tank and an aluminum tank of similar capacity and similar contained pressure? Didnt really cover this in OW class....

Very broad question, so here is my broad answer: In general steel tanks are negative when full and are still (but less) negative when empty. Al tanks are near neutral when full and become positive when empty.

Less broad answer: Air Weighs ~.08 lbs per cuft at 1 amt. If you know the empty weight of the tank, and the capacity in cf you are done.

Best answer: Most tank manufacturers publish this exact info, check their websites.



Regards,



Tobin George

 

[Furner]

Thanks. I didnt notice until you mentioned that most manufacturers list the bouyancy empty and full in their specs.

 

[standrod]

I use about 6-8 lbs less weight when using steel tanks as compared to aluminum 80's.

 

[String]

Try here:

http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi

 

[eponym]

And don't forget--whatever the tank's initial weight, when you're checking your buoyancy you still have to plan to compensate for breathing out the weight of the air in it. In the case of an 80 cu.ft. tank (Aluminum or Steel), that's about five pounds of weight you'll lose (and buoyancy you'll gain) if you breathe it down to 500 psi.