Catalina vs. Luxfer 40cf ...

[jeckyll]

I got a tip from my LDS that the catalina wouldn't be as good, though the guy there didn't remember why (they deal mostly in Luxfer's so I investigated of course).

I found

Catalina S40 3000 40 5.25 24.9 15.9 1.7 -2.6
Luxfer 40 3000 39.9 5.25 24.75 15.3 2.2 -0.8

(columns are: Service pressure, psi Actual air capacity, ft3 Outer diameter, in Length without valve, in Empty weight, lbs (w/o valve) Buoyancy Empty, lbs (w/valve) Buoyancy Full, lbs (w/valve) )

I'm curious why the swing on the Catalina would be so much greater? Anyone know?

 

[toodles]

The Luxfer's are the superior bottle. As you pointed out, there are some characteristics that each bottle has that are a little different.....the most important being is the bouyancy of each.
In my experience, I find that most divers (if they were buying new and had a choice) would choose a Luxfer. (some do not care) I guess it all depends on how picky you are about the bottle itself. Are you using it for a simple redundant pony?......or are you getting into technical diving?
You want the bottle to be as nuetral as it can be at all times during the dive. (in tech/cave diving, you may be taking on/off during dives). When I had Catalina's, this was my biggest issue as they have so much swing in bouyancy.
The Luxfer bottle 'swims' nicer in my opinion......as it is tight to the body and the neck of the bottle is always lower than the tail and swings up nicley behind arm. (Catalina's hang and IMHO always in the way.

I have used both and MUCH prefer the Luxfer's.

tp

 

[JeffG]

I'm curious why the swing on the Catalina would be so much greater? Anyone know?

Its not. 40 ft3 weighs the same in a Luxfer as it does in a catalina.

I'm not sure how the measurements you have were made, but Catalina's are more negative. They hang off you like dead rocks. Thats why they are not recommended.

 

[jeckyll]

Thanks for the answer (Someone locallly is selling a catalina fairly cheap and I'm looking to use it as a pony...).

Jeff: The Catalina swings from -2.6 to +1.7 = 4.3 lb swing
The Luxfer swings from -0.8 to +2.2 = 3.0 lb swing.

I know they are both 40's so I'm confused as to how the swing could be different.

Sources:
http://www.catalinacylinders.com/scuba.html
http://www.luxfercylinders.com/products/scuba/specifications/us_imperial.shtml
and
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

 

[roakey]

I know they are both 40's so I'm confused as to how the swing could be different.

They can't be. Both will swing about 3 pounds from full to empty. That's physics. The Catalina numbers are put out by marketing types on drugs .

Seriously, both will swing 3 pounds. No way they can do anything other than that.

Roak

 

[JeffG]

Jeff: The Catalina swings from -2.6 to +1.7 = 4.3 lb swing
The Luxfer swings from -0.8 to +2.2 = 3.0 lb swing.

I know they are both 40's so I'm confused as to how the swing could be different.

Maybe....just maybe, Catalina made a mistake. (or maybe their air is heavier)

40 / 13 = 3.07

 

[jeckyll]

Jeff: That's what I was thinking. Though I see alot of potential merit in the "air is heavier in their bottles" argument.

It was also the reason for my initial post... in either case, it sounds like I'd be better off just purchasing a new Luxfer.

 

[spectrum]

Must be a Catalina mistake, I found the same numbers on 3 reference sites. Makes you wonder!

Pete

 

[jeckyll]

Must be a Catalina mistake, I found the same numbers on 3 reference sites. Makes you wonder!

Pete

I am still partial to the 'heavy air' theory....

 

[padiscubapro]

Thanks for the answer (Someone locallly is selling a catalina fairly cheap and I'm looking to use it as a pony...).

Jeff: The Catalina swings from -2.6 to +1.7 = 4.3 lb swing
The Luxfer swings from -0.8 to +2.2 = 3.0 lb swing.

I know they are both 40's so I'm confused as to how the swing could be different.

Sources:
http://www.catalinacylinders.com/scuba.html
http://www.luxfercylinders.com/products/scuba/specifications/us_imperial.shtml
and
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

as long as the interal water capicty is the same, that means the gas capacity is the same, then the swing HAS TO BE the same..

the starting and ending buoyancy CAN be different due to total displacement differences by slight differences in displaced volume and cylinder weight.