Different bouyancy characteristics between tank brands...

[Jasonmh]

I have 2 sets of doubles, both are put together identically, with the exact same bands, manifold, and regs. The only difference between the 2 is the brand of tanks used. One is using Catalina AL80s and the other is Luxfer AL80s.
This past weekend I used both sets, and was surprised that it seemed to me that the Cat. tanks seem much more "butt light" as they empty as compared to the luxfers.
I had heard that the luxfers tended to be more light on the bottom. Everything else used on the dives were the same, same rig, drysuit, same weight in the same places.
I surfaced with 600# left in the Luxfers and, other than them just being lighter as they emptied, had no problems staying horizontal in the water. The next dive I put on the Catalina tanks, and when they got to about 2000# left, I started to feel light on the bottom, and had to struggle to not tip head-down.
Does this sound right? I had expected that if anything I would have been more butt-light/head-heavy with the luxfers.

 

[Sherwood SCUBA rep.]

http://www.catalinacylinders.com Here is a link to Catalina Cylinders web site for spec's

 

[cerich]

I've found the Cats are not so much "Butt Lite" but neck heavy.

 

[Jasonmh]

I've found the Cats are not so much "Butt Lite" but neck heavy.

Ahh.. well that would explain what I was feeling then. Thanks for the reply

 

[ABQdiver]

Interesting observation Jason! I have only one set of doubles, using Luxfer tanks. I actually feel very controlled with them. I do have several Catalina singles. Might have to try the experiment just for the heck of it and put them together.

Using the Catalinas as singles, I don't notice any thing different........

 

[Jasonmh]

Interesting observation Jason! I have only one set of doubles, using Luxfer tanks. I actually feel very controlled with them. I do have several Catalina singles. Might have to try the experiment just for the heck of it and put them together.

Using the Catalinas as singles, I don't notice any thing different........

I hadn't really noticed this until I got the Luxfers (cause I had the Catalina's first).
I had also been diving with a tail weight on the Cat doubles prior to last weekend. Then when I got the luxfers I did a couple dives without the tailweight, because I had forgotten to put it on. Worked great, so I thought "Maybe I don't have to use that tailweight on the Catalina doubles either". So I kept the weighting and everything the same, but put the Cats on and I could feel a definite head heavy or butt light (depending on how you look at it) tendency.
I agree that with the singles I didn't really notice any difference. Maybe it is because
if the Cats are alittle top heavy to begin with, then you double that (add another tank), then add the manifold and 2 first stages.. maybe it all adds up to make a difference.
I'll have to do some more experimenting.. it is not a really big deal if I am prepared for it, since I can use the tailweight. I loved the way the luxfers felt though.. I might also consider using the catalina's for singles and get some more Luxfers for another doubles set.