Aluminum 90 Tank

Hey Scubaboard,
I had the opportunity to rent an AL 90 to use for a dive trip this weekend. This is the first time I have gone to this LDS and was wondering if anyone on here could provide some more information about this kind of tank. I have only used AL80s and am a air hog. I decided to go with a bigger tank to give me some spare air and I'll be doing a multiple dives throughout the day. Say I get about 45 minutes air time at aboot 60 ft, how would the increase in size increase my time underwater? Thank you!

First of all, discussing spare air which is also a product Spare Air will start a thread you neither want or need.

Second, there is no such thing as extra air, its kind of like extra money.

Although it depends on your dive profile and useage, a tank with 10% more air can give you 10% more time. You may not be able to get the time if your buddy is on an AL80 and ends the dive before you get into the "extra air". Also you will get colder the longer you are down and hypothermia is insidious and can be deadly. And last, but not least, you have to watch to keep from going outside of NDL, at 60' you have only 55 min. on the first dive of the day.

Here is a list of tank specifications for comparison: Scuba Cylinder Specifications

Try out different tanks when you can, some seem sweeter than others and it's whats best to you.


Good luck and good diving.


Bob
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I may be old, but I’m not dead yet.

Thanks for the clarification!

When I first started diving I used so much air that I used an AL100. After about 15 or 20 dives I calmed down, got over it and started using the AL80. When using the larger tank I didn't notice any problems with hypothermia (Florida) or any NDL problems, ascending when either I was getting short on air or my partner wanted to go up, though some of my dives went over 100'. Just keep an eye on your computor and don't worry about it.

You are a bit new to be dedicated to a tank size. Your SAC rate will get better. OTOH if you want a tank and have the $$$ I like the HP 100's. The are about the footprint of the AL80 but hold 20%+ more air. In CA owning your own tank seems the popular choice. Steel tanks are a bit pricey, maybe $350 a tank.

Your times will be based on tank size. So if you can dive for 100 minutes at 40ft on an AL80, you will get 120 minutes on an 100CF approx.

BTW the OP was not talking about Spare Air. :mooner:

i would think that 10% additional gas should give you >10% more time as you dont breath all the air if youu surface at 500 # then you are soing so with 13 cuft in the tank, and uaing 66 cuft,,,,, with the added gas you have now 76 cuft to use and still get to the surface with 13 cuft left. that is a 15% increase in submerged time. significant in my opinion.

chemdog:

Hey Scubaboard,
I had the opportunity to rent an AL 90 to use for a dive trip this weekend. This is the first time I have gone to this LDS and was wondering if anyone on here could provide some more information about this kind of tank. I have only used AL80s and am a air hog. I decided to go with a bigger tank to give me some spare air and I'll be doing a multiple dives throughout the day. Say I get about 45 minutes air time at aboot 60 ft, how would the increase in size increase my time underwater? Thank you!

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