Tanks

Are Steel Tanks doubles the standard for DIR? I am looking at buying some new tanks, and was just curious if DIR divers had a standard or prefrence in regards to tanks. Thanks.

Nope, the only standard is the right tank for the job/ exposure suit.

For instance, steel doubles are a bad choice for wetsuit diving. Without going into a long drawn out explanation, you'll be overweighted with them. Al80s are a better choice. For drysuit diving, steels are great.

Of course, a single tank is appropriate for a rec dive. If you can swim it up when its full with a failed wing, its cool to use it with a wetsuit.

For doubles (generally), people in the tropics/ warm caves use al80s, steel 100s (or similar) for drysuit diving in the ocean, and 95s or 104s for cave diving or longer ocean dives with a drysuit. Naturally, some people use different tanks, but the above is pretty average.

A few key points about tank selection:

Capacity: Does this tank(s) hold enough gas for my dive plan?
Bouyancy: Can I swim this tank up if my wing fails?(steel doubles) Does it require me to carry a bunch of lead? (Aluminum tanks)
Trim: Am I having to fight this tank to stay in a horizontal position? (Long thin tanks like HP120s, or short, stubby tanks like HP80s)

If all of those can be answered positively, then the tank is a good fit for you and the dive.

Case in point: I love my Faber LP85s as singles. They trim out very well for me, have enough gas for most of my diving (shallow reefs, with the occasional mid-range wreck and reef), and I'm fairly certain I can swim them up with a failed wing. But I don't like my Genesis HP120: it's long so I have to fight it the whole dive to stay trimmed out, it's very negative so I am diving overweighted, and it's generally way too much gas for most of my diving. I generally reserve it for other people to use, so if they are a gas hog then everyone else can have a longer dive or if they need a lot of lead (bouyany body type) then they won't have to carry as much.

But tanks are really a personal preference. I typically recommend HP100s if someone is looking into getting steel tanks because they are very versatile in uses (great doubled or as singles), they trim out well enough on most people, and the 6 lbs of lead they reduce from the weight belt when they switch from an Aluminum tank creates an overall lighter rig as they still weigh about the same as an AL80. It would help, however, if you were to let us know what kind of diving you intend to pursue.

Peace,
Greg

Compensating for the buoyancy of Al tanks only makes you heavier in total.
Really the only 2 things that change during your dive are the weight of the gas you carry (it is not dependent on the tank material, only on the fill weight PxVxdensity) and the buoyancy of your suit (controlled in drysuit and depth dependant in wetsuit diving) So ask yourself: how much is the fill weight in the tanks I carry, and at what depth am I diving? say you carry 4kg of gas and you're diving at 30m in a compressed wetsuit, then you might be around 6-7kg negative at that point.
This is, when you are balanced at the end of the dive; no air in your BCD/Wing at 3m with 30bar. This is about the limit for wetsuit diving. Take any more gas and you'll have serious problems swimming the lot up.

Start balanced, or you'll have more lead and thus more air in your BCD/wing at the start and you'll be more negative when you lose the air in it.

Gr. Ron

Correction: when diving at 30m and in compressed wetsuit (from depth compression) AND YOU LOSE THE AIR IN YOUR BCD/WING, then etc.