LP 95 Buoyancy characteristics?

[laikabear]

I have an LP 95 and I'm trying to figure out the buoyancy characteristics. It's a Faber, born on date 2003, and also stamped XS Scuba. It's a white painted tank.

On several of those spreadsheets that contain tank specs, I see a Faber LP 95 listed as -1.2 empty and -8.325 full. However, the tanks for sale currently on DRIS, etc., and the Blue Steel site are listed as +1.69 empty and -5.37 full.

I'm just wondering if there is a way to determine the specs just by looking at the tank. I emailed Faber with no response. I tried Blue Steel and they replied but did not know the answer. It looks like their partnership with Faber began in 2004 so maybe that means this tank is the more negative one?

 

[tbone1004]

faber hasn't really changed the tanks at all, the difference you are seeing is that the huron chart listing -1.2 is with a valve, and the blue steel charts are without valve. Valves weigh 2-3lbs depending on which ones you use, so it's pretty accurate.

What is more important than the actual numbers is the relative numbers. As long as you know your ballast requirements with one of the tanks on the Huron chart, you can move to another easily. I.e. if you know your weight using say a Luxfer al80, then using the huron chart, you see that you will need to remove 5.6lbs when going to a Faber 95.

 

[laikabear]

Aha, I didn't realize one chart was including the valve and one isn't.

Hmmm. Well I don't see my HP100 on the Huron chart (that chart just has the 3180 tanks and mine's a 3442), but it is on the Blue Steel page. So looks like I would need 4 more lbs of weight with the LP 95, even though it's 3 lbs heavier than the HP 100. Not ideal.

 

[tbone1004]

yes, so if you have the Faber 3442 100's *brilliant tank btw*, the buoyancy delta is 1.69+.59=2.28lbs, so with the 95 you'll need to add about 2lbs to compensate for the tank difference. Remember it is relative difference, not absolute difference, so if the tank you are familiar with is the fx100, and you are going to a l95, then you have to add the difference in buoyancy for that, have to stay on the same chart. Conversely if you were going from the FX100 to an AL80, you'd go to the following math
FX100 to L95 is 2.28lbs less lead, and the l95 is 5.6lbs less lead than an al80, so if you were to go from your FX100 to an AL80, you would need to add 5.6+2.28=7.9lbs, so you have an 8lb advantage using the FX100 vs a Luxfer AL80.

Most 8" tanks have less than favorable buoyancy to weight ratios as compared to their skinny 7.25" cousins. This is compounded going to galvanized tanks, and HP tanks. HP tanks will typically be more negative than LP tanks due to more metal on the tank itself *look at the Faber L120 vs the FX149 which are basically the same tanks dimensionally, but the 149 is 6lbs more negative while only being 2lbs heavier. 7" tanks vs 8" tanks, FX120 is the same height as the FX149, but is 2lbs more negative and 7.7lbs lighter. Painted vs hot dip is another extreme where the galvanized tanks are heavier and more negative due to the zinc that is put on them.

You are experience a double trouble of 7" vs 8" and lp vs hp so you are experience two of the three variables leading to less than favorable buoyancy vs weight vs capacity.

 

[Beau640]

In case others stumble across this and don't know where to find these charts:

I prefer:

http://www.indianvalleyscuba.com/se...ction/information/CYLINDER SPECIFICATIONS.pdf

Other:

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan