Steel tank ?..again

[large_diver]

I bought an OMS LP 98 late last summer and have about 10 dives on it -- so far, so good.

I am in the market for another tank this summer -- one factor that may make me look at other steel tanks is that I would prefer a galvanized steel tank to protect against nicks and external rust. I believe that OMS cylinders are simply painted. I do a fair amount of shore diving on the rocky coast of New England.

Anyone have any thoughts on the galvanized vs. non-galvanized tank issue?

 

[large_diver]

FOr those interested in OMS cylinders, see their web site at:

http://www.omsdive.com/

 

[Warhammer]

I too was almost ready to buy an OMS tank and hadn't really considered the paint/galv issue. After talking to a few divers that have the OMS tanks, I changed my mind. They reported paint chiping that easily results in rust if you don't give it immediate attention. I guess you could avoid this by putting a tank protector on, but I don't really care for the protectors. Most of my diving is done from a boat or a pier, but the tanks could easily get skint up while in moderate seas or in the back of my pickup. But I do like the bouyancy characterisics of the OMS tanks, which makes it a tough choice.

 

[o2diver]

I have been diving OMS tanks for 3 Years and have had no problems with them. I own DBL 98s, single 121 and a 46 for a deco bottle. I really enjoy the 121 as I can get two great dives off of the one tank. If I have any doubts about not having enough air I sling the deco bottle for the second dive. I always use the 121 when working with students as it gives me redundant air capacity.
What about the following points?
1) using AL tanks you still have to compensate by adding extra weight for reduced air at your safety stop. Tank becomes lighter..
2) in most cases you are still wearing a weight belt with steel tanks, and if you feel the need to get to the surface quickly, drop your weight belt.

My .02 which isn't worth much considering our dollar.
DSAO
o2diver

 

[Rick Murchison]

My primary doubles are OMS 85's.
Love 'em.
No problems with rust.
Rick

 

[turnerjd]

Originally posted by o2diver

1) using AL tanks you still have to compensate by adding extra weight for reduced air at your safety stop. Tank becomes lighter..

My .02 which isn't worth much considering our dollar.
DSAO
o2diver

O2 diver,

There is a fundamental point you are missing here.

If you have an AL and a steel cylinder of the same capacity (eg 80's) and the same operating pressure, they have the same ammount of air in them. So, when they are both breathed down to practically empty, they will still have the same air in them. The only change in the tank is that they now don't have 80 cuft of air in them.

The buoyancy change will be the same. They will both be 4-6 Lbs lighter than the start of the dive.

Since the steel was ititially more negatively buoyant, when they aer empty, they are still negatiely buoyant, but just less so. As the Al tank was less negatively buoyant that the steel, when it is empty, it is even less negatively buoyant, and in some cases becomes positively buoyant.

The point is, that with both a steel and an aluminium you need an extra few pounds of weight to ensure that you are neutral at the end of the dive. As it is the same ammount of air you use for either type of tank (provided they aer same capacity and operating pressure), it is the same ammount of extra weight you need.

If your .02 isn't worth much, I have to use the féè§"àg euro at the moment. Now, that is worthless (and unnecessary) currency

Jon T

 

[o2diver]

Jon, my oms tanks are 6lbs neg. at the start of a dive, but will be neutrally bouyant at the end of the dive if I suck all the air out of them. The same cannot be said of AL tanks. AL's are not neutrally bouyant, they will be positively bouyant at the end of a dive, which will require the diver to wear more weight than is nessary throught the whole dive.

 

[turnerjd]

O2

My point was that for ANY dive with ANY cylinder, you need to start of 6 Lbs or so negative.

For steel tanks, this 6 Lbs of nagative is taken up by the tanks being heavier, and less buoyant. You don't need extra weight, because you are already negatively buoyant.

Aluminium tanks, which are made from a much lighter material represent less of the total weight, so you need a bit of extra weight on your weightbelt.

Wether the weight is on the weightbelt (Al), or in the tank material (steel) is immaterial, you still need to start the dive 6 Lbs negative to finish up neutral.

Clearer?

Jon T

 

[Rick Murchison]

o2diver
Turner didn't get through... maybe I can
Tank X weighs 38 pounds empty and is 3 pounds positive buoyancy.
Tank Y weighs 38 pounds empty and is neutrally buoyant.
Both hold 80CF of air when full.
Without a tank, I need 6 pounds of lead to be neutrally buoyant.
If I dive tank X, I'll need to wear 9 pounds to be neutrally buoyant at the end of the dive, and I'll start the dive 6 pounds negative (80CF weighs 6 pounds).
If I dive tank Y, I'll need to wear 6 pounds to be neutrally buoyant at the end of the dive, and I'll start the dive 6 pounds negative (80CF weighs 6 pounds).
The only difference is in the amount of weight I need to wear - my net buoyancy change from using 80CF is 6 pounds regardless of the tank's buoyancy characteristics.
Rick

 

[Mario S Caner]

Not to confuse anyone but, there are now neutrally buoyant Aluminum 80's on the market. Every cylinder is slightly different. Bottom line is that you need to check the tamks technical specifications and go from there.