what is a good steel tank for warm water

[LIVES4SHARKS]

I dive a ST 120 using a SS BP with a 360 wing with 36lb lift. I also use ST 100's. I add no additional weight when diving SW with a 5mil wetsuit unless conditions dictate. I may add an additional 2-4lbs at most.

Carolyn:shark2:

 

[Rhone Man]

Thank you for the information. Could you give an example of what size tanks you use and how much lift your BC has. My main concern is being overweighted.

I use a steel 72 overfilled to 3,000 PSI (which makes it, what, an 88?). I have a 17lb wing with a Kydex backplate. I wear 5lbs of lead with a steel tank, or 8lb with an aluminium.

 

[Blue Sparkle]

Also consider that with a 17lb wing, you don't have a whole lot of wiggle room ...

I'm very new at this, but my calculations showed the same thing.

After diving with an AL63, and feeling much more comfortable with a shorter length tank, I was looking over a chart of tank weights and sizes - just thinking about buying a tank, and wondering if there might be a steel tank that would be shorter (than an AL80) and yet give me a bit more capacity than the AL63.

From what I found, it did not seem like this would work with the 17# wing I have, but that I would need a larger wing (I knew going into it that I was buying the 17# wing for warm water, aluminum tank diving). The steel tanks (at least in the size range I was considering) were all fairly negative.

I suppose it might be different for you than me, but if I were you I would add up everything that is negative on your rig + the most negative the steel tank would be, and then see if you would have enough lift to compensate for that figure (or if you might need a new wing to go with a steel tank).

Here is a chart that shows the figures for various tanks so that you can do the math for yourself:

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Sik_Z33]

With a steel back plate and a steel tank you will be overweighted. With your wetsuit on you'll be roughly 2-3 lbs over weight depending on your tank size. If you do go with steel I suggest going with nothing larger than and 80 cu.ft. tank, depending on the brand it'll have a buoyancy between -7 to -8 lbs and have slightly larger capacity then your current Al-80 (the al-80 is actually 77 cu. ft. while an HP or LP Steel 80 tnk is exactly 80 cu. ft.). The Al-80 is -1.5 lbs full and about +4lbs when it nears empty so keep that in mind when trying to calculate the difference a steel tank will make.

 

[fjpatrum]

With a steel back plate and a steel tank you will be overweighted. With your wetsuit on you'll be roughly 2-3 lbs over weight depending on your tank size. If you do go with steel I suggest going with nothing larger than and 80 cu.ft. tank, depending on the brand it'll have a buoyancy between -7 to -8 lbs and have slightly larger capacity then your current Al-80 (the al-80 is actually 77 cu. ft. while an HP or LP Steel 80 tnk is exactly 80 cu. ft.). The Al-80 is -1.5 lbs full and about +4lbs when it nears empty so keep that in mind when trying to calculate the difference a steel tank will make.

Did I miss something from the OP that indicated the weights they normally use with an AL80? How can you make the assertion that the OP will be overweight without knowing more about a "normal" rig for them?

As for buoyancy characteristics, Walter mentioned that an AL80 is approximately +2 when empty, but you say +4 and a steel 80 is approximately -6 full and neutral when empty while you say it's -7 or -8 (I'm assuming full.) Is that depending upon manufacturer or are you folks just throwing out numbers based on rough estimates and personal experience? IE is there really that much difference between one steel 80 and another or one AL80 and another?

 

[scubadobadoo]

I have a 6 pound back plate and if I use a steel tank in warm water with a 3mil I am over weighted. YMMV.

 

[Jan Kruger]

Found this insightful discussion about diving cylindres : Diving cylinder - Wikipedia, the free encyclopedia Hope it works !

 

[spectrum]

You really need to look at the whole equation. I know I keep a few AL80's around for shallow fresh water dives in the summertime. With my HP steels which are not terribly negative I'm over weighted. If you'd happen to have something like the Fabers that are ultra negative then it could be even more severe.

Of course I associate warm water with limited neoprene. If you're wearing the full Monty in "warm water" then go steel for sure. It's the exposure protection, not the water temp that drives this discussion.

Pete

 

[ameneon]

As mentioned above you might not need any weights if you go with a steel tank. But many want that for the safety of being able to drop your weightbelt during emergency. So before deciding on a steel tank you might want to decide if you are comfortable without ditchable weights.

 

[Sik_Z33]

Did I miss something from the OP that indicated the weights they normally use with an AL80? How can you make the assertion that the OP will be overweight without knowing more about a "normal" rig for them?

As for buoyancy characteristics, Walter mentioned that an AL80 is approximately +2 when empty, but you say +4 and a steel 80 is approximately -6 full and neutral when empty while you say it's -7 or -8 (I'm assuming full.) Is that depending upon manufacturer or are you folks just throwing out numbers based on rough estimates and personal experience? IE is there really that much difference between one steel 80 and another or one AL80 and another?

He didn't mention anything about carrying weight so I figured he didn't since he's diving warm water with minimal protection (3 mil) with a SS back plate.

I use my Transpac for warm water diving in south florida with both steel 80's and AL80's. In my 3 mil wetsuit I carry no weight with my steel tank and 4 lbs if I'm using an aluminum tank, and keep in mind my transpac is slightly positive to begin with.

The numbers I use are from a scuba cylinder specification chart (link below) that's accurate in my experiences. On the chart a standard Luxfer AL80 is -1.4 lbs full and +4.4 empty.

As for steel the exact numbers are:

PST (E7)HP80: -8.5 full, -2.5 empty (My cylinder of choice for it's compactness)
PST HP80: -9 full, -3.3 empty
PST LP80: -7 full, -1 empty
Faber 80: -7.55 full, -1.7 empty


Specification Chart


With the rest of his configuration and exposure protection remaining constant simple math can be done to see how a change in tanks will affect his buoyancy at the beginning of the dive.

Current set up with no weight
SS backplate: -6 lbs
AL80: -1.4 lbs (full)
Total: -7.4 lbs

New set up with smallest practical steel tank
SS backplate: -6 lbs
Steel (80 or 72): -8 lbs (full)
Total: -14 lbs