Northwest Dive Club

It looks like Luxfer and Catalina are the two main tank manufactors for the aluminum 40.

Dive Gear Express lists some of their specs http://www.divegearexpress.com/gas/aluminum.shtml

Do folks have strong feelings on which tank is a better choice for Puget Sound diving? The Luxfer seems to be very buoyant when empty.

Their table is bogus David (both are ~40cuft yet the swing from full to empty is 3lbs on one and 2.2lbs on the other) - see if you can get specs directly from the manufacturer. I suppose I'd be looking for the one which is closest to neutral (but still slightly negative) when empty and packaged with the valve, reg, and your hardware. I don't have a preference Catalina vs Luxfer - really don't think there's much to differentiate between them. Some folks might still harbor some distrust after the whole debacle of neck cracking with one of the alloys used many years ago but that's ancient history if you're buying a new or relatively recently manufactured cylinder.

I suppose it depends on what you intend to do with the tank. I recently purchased a catalina al40 on the recommendation that they have better buoyancy characteristics when slung as a deco bottle. Apparently the primary difference is how they hang (one is bottom heavy, they other more top heavy).

The luxfer will be about +1.25 in saltwater with a reg installed. It might seem more bouyant than that since it will float (and sink) tail up. The catalina is about the same or slightly more negative but also ever so slightly more "level" floating when empty. I would get a luxfer given the choice, the tail up attitude is an asset if you have to give it or take it from someone.

Hah, this is why you should never listen for advice from a stranger over the internet! I purchased luxfers, not catalinas, just mixed them up when I wrote my last reply.

CaptnJack wrote: I would get a luxfer given the choice, the tail up attitude is an asset if you have to give it or take it from someone.

This is the point someone made in the class last week, but I had too many other things swirling around to remember which brand did this--I could just remember there was a buoyancy position component. Thank you!

question about weight adding for the 40's (when empty)

One friend of mine suggested adding 4pds per tank, but that seems overkill. Around 2pds per tank should work? (For the Luxfers).

Why would you want to add weight to the tank? Correct me if I'm wrong, but the slightly buoyant characteristic when empty is to help move them out of the way. Your overall weighting should be such that with all your tanks near empty, you are neutral/slightly at your final stop.

I've never had a luxfer 40 that was so positively buoyant, that it wanted to float to the surface. The weight of the valve offsets that. The butt end gets floaty but that's it. Adding more weight would just make you that much more overweighted when they are full.

I'm trying to ballpark my weight before I do the 500 psi in all 3 tanks test.

I figure right now I'm probably 2-3pds overweighted already.

With tanks full, I'm fine, but havent done a 15ft hover when they are almost empty test so just looking at collective wisdom on weight addition to cover the empty buoyancy. Specs call 2.2+ empty, +0 full, but as spatty says, I would think regs would offset around a pd of that?

I believe he's asking about adding to himself, not to the bottle, which would be a little weird.

The short answer is you need to be neutral in whatever configuration you make it to your last stop wearing -- which means you have to figure out worst case and weight yourself appropriately. That means without bottles (donated to a buddy or dropped along a cave/scooter/wreck line) and with empty bottles. You need just enough lead to stay neutral at 10 or 15 feet in whichever one of those configurations would make you the most positively buoyant... generally for the smaller bottle scenarios, like a single 40, it doesn't matter very much since they're not very floaty when empty...

Pretty straightforward stuff... and depending on what I ate for breakfast, something <2 lbs is within the margin of error for the day

I guess until I do my low air check, I'll just assume 2 pounds per tank in additional lead, and go from there, thx!

Why would any tanks be completely empty with proper gas management and planning

Only Jesus could walk on water,the rest of us float.

doublesunder wrote:Why would any tanks be completely empty with proper gas management and planning

Because shit happens and it's good to be as prepared for it as possible.

camerone wrote:I believe he's asking about adding to himself, not to the bottle, which would be a little weird.

Yeah... Makes a little more sense now...

spatman wrote:

doublesunder wrote:Why would any tanks be completely empty with proper gas management and planning

Because shit happens and it's good to be as prepared for it as possible.

+1. When shit goes wrong, even the best diver can end up with empty tanks. I used to have the same mindset, but then I heard some first-hand and second-hand stories as well as some articles online. It can still happen even with the best gas planning in the world.

I'd like to bump this Catalina vs. Luxfer thread to say that I happen to love my Catalina Al 80! So far at least. Admittedly, I have no diversity of experience here, but I thought I would share based on a grand total of a couple dives with it. I bought a deco reg the other day and as such was finally able to take it out as a stage filled with 32%. I do not possess video of where it rides, but it feels damn nice in the water! But again, this is only as a stage, and not one that I am ever going to be clipping to my butt D-ring. This sub-forum could also use more activity, so I figured, "A bump? Eh, why the hell not" =P

I just got geeks luxfer 80 but havent dove it yet. All I hear via the interwebs is the luxfers are tail light,and catalina's tail heavy.

Not sure I'll need it though now, since my sidemount bail out rebreather should be on its way shortly and that will be driven by a 40 (SCR, not CCR). But does no harm to have a staged 80 if I ever need it.

I have 6 or 7 Catalina 80 stages. I never could tell them apart from Luxfer 80s, the gas mix inside makes a FAR bigger difference than the manufacturer in how they ride. The good thing is all the hype about Luxfers tends to drive down the prices on used Catalina's