72 cf aluminum

[Fishpie]

If you do find a Catalina 67 you'll find that they have about the same buoyancy characteristics as a steel 72 but in a shorter fatter package....the 53 too btw.

 

[JLambus]

If you do find a Catalina 67 you'll find that they have about the same buoyancy characteristics as a steel 72 but in a shorter fatter package....the 53 too btw.

I have one of these 67's and i never dive it... its way too heavy out of the water. I think its probably heavier than my 72's... its the only aluminum i own since it was given to me and i havent been able to give it away ever since.... heavier and holds less air... Boo says I.

 

[WD8CDH]

Back in the old days ('70s), Luxfer made a 2475psi aluminum 72. It was called "the floater". It was about 4" longer than a 3000psi AL72 and really a pain to dive with. The 3000psi AL72s have good buoyancy characteristics.

Hy-Mark cylinders have a heavier neck mostly to eliminate a machining step. With 6061-T6 alloy, it's not really necessary to be that thick.

 

[captain]

Back in the old days ('70s), Luxfer made a 2475psi aluminum 72. It was called "the floater". It was about 4" longer than a 3000psi AL72 and really a pain to dive with. .

They made very good buoys to mark sites.

 

[wedivebc]

Specifically, look at this shot -- anyone think this might help prevent possible issues with neck cracking? Not being an engineer I wouldn't know, but it seems plausible at least.

I don't believe there has been any problems with SLC since manufacturers started using 6160-T6 alloy about 20 years ago.

 

[DA Aquamaster]

Specifically, look at this shot -- anyone think this might help prevent possible issues with neck cracking? Not being an engineer I wouldn't know, but it seems plausible at least.

Back in the 1980's until 1991, Walter Kidde made tanks with heavier than average necks, but they were still prone to SLC issues. They were great tanks, they just had 6351-T6 alloy.

Still, I think there is some potential benefit in a heavier neck as eventually I think we will start to see some neck cracks in older 6061-T6 AL tanks - not nearly to the same extent as with 6351-T6 alloy but some cracks will no doubt occur due to stress risers from tool marks, folds, etc in the manufacturing process. A little more metal in that area may help ensure the crack is detected before it starts to leak through the neck.

 

[SparticleBrane]

wedivebc -- that is most likely the case, but I have heard of the occasional 6061 cylinder coming up with neck cracks. Doesn't mean it is extensive or prevalent, but definitely possible.

 

[tgsmith]

Is the actual capacity of a Hymark AL72 72cuft? If so there's a huge benefit that wasn't directly mentioned. An AL80 is only 77cuft in actual capacity, so you've got a tank that swims(supposedly) way easier from everyone I've seen write about them yet is only 5cuft less. That's really no difference in capacity. Not to mention all the buoyancy advantages that was explained......

In addition to VA Scuba, contact Dive Right In Scuba from Plainfield, IL. He was putting together a group buy over on thedecostop.com for hymark cylinders, including AL40's, AL80's and AL72's. He stated our buying price would be less than what the cylinders usually cost HIM. Deal.

I still might buy Al80's just cause you can get them used for so cheap!

 

[WD8CDH]

The Hymark 72 is a true 72 CF at 3000 psi. The Hymark 80 is 78 CF at 3000 psi.

 

[Gilldiver]

Here are the numbers from the Aluminum 72 I found in the dump a number of years ago. The inspection mark is Industrial Analysis, but I don't know who's mark that is between the month and year of the first hydro.