Aluminum Doubles??

[J_glenn06]

Does anyone dive Aluminum doubles??? Just curious

[OWSI176288]

I've only used double al80's in Mexico due to the caves being so shallow.

Definitely prefer low pressure steel tanks that can be jacked up to a proper "cave" fill for Florida caves.

[Mike Edmonston]

Does anyone dive Aluminum doubles??? Just curious

Hi,

They are used in Mexico with V-weights. I use them when training new divers with doubles. (Wetsuit / SS BP). Weight is still noticable, but not as bas as sticking a pair of steels on their back. Other than that, IMHO, they don't offer enough gas to make it a worthwile choice.

YMMV

Safe Diving

[JahJahwarrior]

I dove aluminum 100s for a while before getting a sweet deal on some Faber LP120s.

I had to wear weight on the belt. I had to wear egads of weight on the belt in a drysuit. I only had 200 cubic feet of gas, compared to....what, 325-350 depending on the fill with my current tanks.

That's 108 usable for penetration compared to 66 usable for penetration, which makes a difference. Plus, I don't need any lead when wet or dry.

You can dive aluminum, and I did for a while, but as soon as I started diving some LP95s, the aluminums' went in the shed and sat there waiting for a day when I couldn't borrow the 95s. Then as soon as a deal opened up on these Fabers, I quickly sold the 100s and haven't looked back.

However the 100s got me through Basic and I did one or two Basic dives after class before putting them, and leaving them, inthe shed

[FW]

You don't see many double 80s in FL anymore, but there isn't a problem, except they don't hold as much gas, and require weight to use with a dry suit.

[Rob Traynham]

Why do you guys prefer Lp over Hp can anyone truly explain the difference. I see all the time that the folks on here are diving LP's. Just curious hopefully this isn't a stupid question. I'm asking because Iam curently looking for my first set of doubles and need reccomendations from the experienced....

[marinediver]

LP tanks hold more gas at a given pressure than HP.

[Rexco]

Most HP tanks have a LP tank that is the same size and weight. When you buy the HP you are paying for that tank getting an exemption (i.e. x 117 etc.) I have seen many a thread that claims the HP and the LP are the same tank but far be it from me to make that statement. The LP just cost less. Of course you cannot always get a "cave fill" mentioned in this thread and having the HP stamp means that you will always get the extra volume of gas.

[Sludge]

LP tanks hold more gas at a given pressure than HP.

There's a little more to it than that. What you're saying is big tanks hold more air at a given pressure than small tanks.

But that's what it all boils down to. Bigger tanks.

For a very long time, steel cylinders were just about all rated at 2400psi. Then some geniuses came out with the high pressure cylinders, and things were no longer as simple as they had been. Instead of sizing them as 95, 104, 120, and so on (comparing apples with apples), we now had the "high pressure 120." Sounds like it's the biggest, but of the three mentioned, it's almost exactly the same size as the smallest. 120 cubic feet at 3500psi and 95 cubic feet at 2640psi is almost the same thing.

Putting 3600psi in a 95, a 104, and a 120 yields 130, 140, and 160 cubic feet, respectively.

So it's not the "low pressure" we're after it's the "bigger tanks."

[Sludge]

Peter, HP cylinders are no longer being sold. The "HP" designation refers to a particular model, one feature being the tiny neck. The "higher pressure" cylinder is correctly refered to an E-Series or X-Series, depending on the manufacturer.

When people confuse these with "HP" cylinders it's a sure sign they haven't been in this sport too long.