Purchasing Doubles and need some advice from DIR'ers

[jgoodstein]

I am in the process of purchasing doubles for my Fundies class. I am planing on purchasing them soon and diving and getting accustom to them. up until now I have just rented tanks as the cost and upkeep was just not worth it for Rec diving.

I'm trying to decide between the following (all will have 300 Bar din valves installed):

2 X AL80's 3000psi
2 X ALN 80's ( Neutral buoyancy (+.5lb at 500psi) 3300psi
2 X Steel 100's (3441 PSI)

Here's what I need to accomplish:

• I need to dive rec with my friends and dive buddies (so I will dive single tanks).
• I need to dive a bit more technical for scientific diving and other tasks ( photography, archeology, etc).
• needs to have a decent air time. I realize this is dependent on my skills and consumption, and as I improve I get better, but I like to purchase once.

I will have to switch out the necks occasional for the doubles config ( unless there is something that I don't know, but that doesn't really bother me. Eventually I'll get four tanks but for now I am going to start out with two. I'm a big believer in best practices, I love the idea of steels (lots of air, less belt weight), but the weight does concern me. Swimming up with two steels and a busted wing in a wetsuit in the warm waters off of Florida and the tropics scares me. Diving with a single steel in Fl is a bit less scary, but has risk. The standard AL bother me do to their swing in weight and low air capacity as I haven't mastered my SAC (am getting significantly better though). The AL neutrals have a smaller weight swing and seem to be that sweet spot as they are neutral and have 3300psi pressure so I get a bit more air, I feel safe that I could swim up with them, but they do weigh 4lbs more then the standard 80's. The local dive shop is recommending steels (more air, less weight on belt), My NAUI instructor has recommended the standard 80's, I want to find the tank that does everything and I don't know what is best. The DIR shop recommends I choose. I'm looking for advice from those that have more experience then me, that understand the dynamics of DIR and using multiple configs for the tasks that I normally dive.

 

[gsk3]

Don't do the ALN's. From what I hear they will be hard to trim out.

For a wetsuit I'd prolly do the AL80's. For a drysuit, the steel 100's would start to be tempting.

 

[mikemill]

Given your exposure protection, weighting, etc can you have balanced rig in the steel 100s? If not then you'll need to go with the 80s. If you can those would be my preference. Unless you are planning to cave fill then I'll let the other peeps speak on that.

As for changing them out: I really wouldn't. It is just too much work for too little gain. FWIW I do rec dives in doubles with other divers using singles. I like the weighting and balance of the doubles. So I just do two dives on one set of doubles.

 

[FWADIVER]

If you are considering the HP100's i'd look at LP85's instead, little more versatile, and roughly the same gas if you can get cave fills.

 

[ringmod65]

I"ve got about a hundred dives on my AL80N dubs. Love 'em. They are a bit bottom heavy compared to a regular Luxfer or Catalina 80, but they balance my rig and trim me out perfectly as I tend to drop my head.

I've only ever had two problems:

1. I've been refused the 3300 rated fill by one shop; and
2. I've been charged double for a fill because the shop considered anything over 3k psi a HP fill.

Good luck!

Best.

 

[TSandM]

Take it from me -- you are NOT going to switch from using the tanks as doubles to singles and back. Disassembling and reassembling doubles is way too much work for anybody to be willing to do it on a regular basis. Shoot, I don't even like putting cambands on and off a plate, let alone reassembling a manifold! If all you have is a set of doubles, you will either rent singles or dive doubles all the time.

In warm water, regular old Al80 doubles work just fine. They're comparatively inexpensive, can be filled anywhere, and the setup ends up fairly close to neutral empty (the bands and manifold and regs just about offset the positive tanks). They do get butt-light as they empty, which is okay for me, because I dive dry and need about 7 lbs of weight with them, and hanging that off the bottom bolt balances them just about perfectly. With light exposure protection and less weight, the balance characteristics might be more annoying. I don't know; I have never dived them wet.

The "swing" is the same with any tank of the same capacity. Swing is due to gas weight. A steel 80 may go from -7 to -1, and an Al80 from -2 to +4, but the swing is still six pounds.

In light exposure protection, it does not take very much to make steel doubles hopelessly heavy. If you start with a pair of steels which are -1 empty each (and some are -2 or more), add five pounds for the bands, manifold and regs, and then add 12 or more pounds of gas, you're starting the dive 20 lbs negative -- and that's hard to deal with in the event of a wing failure. For this reason, steel doubles and wetsuits are considered a poor combination for DIR diving.

 

[gsk3]

OP - Given that you're diving warm water wet, it sounds like you might be best served by buying AL80 doubles and then two singles. AL80 singles are very cheap, so maybe buy two until you can afford to upgrade them to steel singles if that's what you want. AL80 doubles plus two AL80 singles will be as cheap or cheaper than just getting steel dubs.

I"ve got about a hundred dives on my AL80N dubs. Love 'em. They are a bit bottom heavy compared to a regular Luxfer or Catalina 80, but they balance my rig and trim me out perfectly as I tend to drop my head.

So don't drop your head ;-)

 

[rjack321]

I want to find the tank that does everything

Lemme know when you find these, I don't think they exist.

I would get single 100s for your single tank diving and a set of regular AL80 doubles. If you go dry in the future they are all the same diameter so you could make the steel into doubles and the 80s into singles/stages.

I like to purchase once.

Ahhh the slippery slope begins. You will purchase over and over again. If anything I would avoid the 80Ns, they are the least versatile tanks on your list and most difficult to resell or re-purpose.

 

[lamont]

the worthington X7-100s are somewhat negative, you might want to steer clear of those. you might look for some PST E7-100s[*], or old PST HP100s (small tank neck), or i believe LP85s and LP72s are lighter steel tanks that are more neutral when empty -- although dive buddy who uses them suggests against LP72s since they're head-heavy...


[*] not positive about the buoyancy characteristics of the PST E7-100s, but IIRC they're nearly neutral like the E8-130s.... could be wrong...

 

[rjack321]

At most the Worthingtons are a few lbs more negative than the PSTs. I have both as singles and can't tell them apart. The Faber 85s are for sure lighter than the Worthington 85s and either brand of 100s. I would skip the narrow necks (7/8") its a pain getting good valves which are very very expensive. The angled Genesis valves which you often see on these suck.

If you want steel doubles I think your best bet is to go dry anyway. Until then stick to standard AL80 doubles.