How to choose a tank

[nereas]

Dry divers will generally do better with steel tanks as it'lll reduce their overall weight requirement when on deck, or getting back on deck from a dive.

Wetsuited or bare skin divers will require more thought. I prefer steels, but I don't dive thick wetsuits any more. Thick foam suits and deep dives may require aluminum tanks for optimum buoyancy.

As a rule with my inherent buoyancy characteristics though if a magnet won't stick to the tank it's off my "buy it" list. Consider a steel tank a "lifetime" investment if properly cared for. A 6351 Al bottle is scrap now most places since many shops chose to ignore the DOT requirement for eddy current testing and have a blanket refusal to fill them. A 6061 Al bottle is good or 10 to 15 years normal seawater use at best unless exceptionally well maintained and filled ONLY at a "pristine" air source. I still haven't found a consistantly "pristine" air source. I'm still diving some steel bottles older than I am. Considering I've been diving almost 40 years that says a lot for the life expectancy of the steelies.

My simple buoyancy requirement is to always be able to swim up my rig even if the BC looses all lift. Diving appropriately sized single steels FOR ME this isn't a problem as I float pretty well all by myself. Diving doubled high capacity steels requires either a dry suit or lift bag to lift the tanks if the wing gets eaten by an oil rig during a nantucket sleighride. Oil rigs off the MS and LA coast are effectivly bottomless, in that either the water just gets thicker or the depth is deeper than a diver can go open circuit and make it back to the surface still breathing.

FT

Yet another "swim up" candidate. And more gear to split up, ultimately, when the Reaper comes a'callin.

 

[FredT]

Yet another "swim up" candidate. And more gear to split up, ultimately, when the Reaper comes a'callin.

A few quick points,

1. following a death on a rig nobody splits gear, as bodies are almost never recovered. See the last paragraph of the post above.

2. I don't depend on my BC, as I started diving before BCs existed. If you wanted one back then it was necessary to do an over water filight on TWA and "borrow it" from under the seat, as Pan Am's rescue vests sucked as buoyancy devices. I get my buoyancy correct up front, then do my primary adjustment with lung volume. As the tanks get empty the stringer fills up so net buoyancy changes during the dive are minimal.

3. A Nantucket sleigh ride behind a large cobia or AJ is impressive, but one impact with the rig behind a big one will trash a single OR double bag BC. Those barnacles are called cookie cutters for a reason. They are entirely capable of taking a plug out of a 3/8" suit, AND the diver's skin behind it. Barnacle shell openings of 1-2" across are not uncommon. Impacting a 5' diameter pile covered with those at 15 to 20 knots makes "redundant gear" rather redundant.

4. I'm willing to skin out of ALL my gear to surface, and have done so. Free ascents of over 130' are possible starting with "empty" lungs, with a bit of buoyant assist I've done it from over 160'. While I'd prefer to not repeat either of those dives it IS possible to survive a brown world if you don't make other mistakes that prevent your ability to survive a SINGLE error. Most fatalities involve a chain of failures.

DO NOT PLACE YOUR FAITH IN GEAR! Mother Ocean is a hungry wench who WILL be fed if you screw up and have depended on gear that WILL FAIL to save you. Don't screw up!

FT

 

[nereas]

A few quick points,

1. following a death on a rig nobody splits gear, as bodies are almost never recovered. See the last paragraph of the post above.

2. I don't depend on my BC, as I started diving before BCs existed. If you wanted one back then it was necessary to do an over water filight on TWA and "borrow it" from under the seat, as Pan Am's rescue vests sucked as buoyancy devices. I get my buoyancy correct up front, then do my primary adjustment with lung volume. As the tanks get empty the stringer fills up so net buoyancy changes during the dive are minimal.

3. A Nantucket sleigh ride behind a large cobia or AJ is impressive, but one impact with the rig behind a big one will trash a single OR double bag BC. Those barnacles are called cookie cutters for a reason. They are entirely capable of taking a plug out of a 3/8" suit, AND the diver's skin behind it. Barnacle shell openings of 1-2" across are not uncommon. Impacting a 5' diameter pile covered with those at 15 to 20 knots makes "redundant gear" rather redundant.

4. I'm willing to skin out of ALL my gear to surface, and have done so. Free ascents of over 130' are possible starting with "empty" lungs, with a bit of buoyant assist I've done it from over 160'. While I'd prefer to not repeat either of those dives it IS possible to survive a brown world if you don't make other mistakes that prevent your ability to survive a SINGLE error. Most fatalities involve a chain of failures.

DO NOT PLACE YOUR FAITH IN GEAR! Mother Ocean is a hungry wench who WILL be fed if you screw up and have depended on gear that WILL FAIL to save you. Don't screw up!

FT

Your point being that since you negatively weight yourself, and I have explained how due to cramping combined with gear failure you may not be able to "swim up," therefore the ocean is likely to claim you, and no one is likely to find your gear, to split it up, well, ...

I certainly agree.

 

[Jimmer]

Your point being that since you negatively weight yourself, and I have explained how due to cramping combined with gear failure you may not be able to "swim up," therefore the ocean is likely to claim you, and no one is likely to find your gear, to split it up, well, ...

I certainly agree.

At what point did you read negatively weight yourself? I read properly weight yourself. I've seen tons of divers with aluminum tanks that were hopelessly negative as well, they're going to be in a lot worse shape if their bladder gets torn than a guy with a steel tank properly weighted. I don't understand why you think someone with a steel single tank and a wetsuit is going to die, you can't seem to back up your statements without saying more crap about people dying, and then doing your little eyebrow thing.

 

[hudson]

As far as buoyancy is concerned, wearing steel tanks is akin to transferring weight from your belt to your rig. I can agree that if you have no ditchable weight on the belt to begin with, as in the case of an already neutral diver, then it makes sense not to add more weight to the rig but I don't know how you can possibly go from that to "wetsuit divers shouldn't wear steels".

Besides, we are talking 5lbs of buoyancy difference here. Even if I had no ditchable weight and I somehow catastrophically suffered the double failure of BC loss and a heavy cramp at the same time while diving solo, I can easily cover that difference by maintaining fuller lungs and swimming up with one leg

 

[rainman_02]

Nereas appears to just be trolling as is his normal MO.





Let's see...

If I cramp...hm, I still have a functioning tank. So, I can breathe. Cool. I can take a rest, stretch it out. I'm just getting closer to neutral with every breath I take.

What else can I do?

Oh! I know! I can turn to my buddy for assistance, since I am not solo diving!

But wait! What if I got separated?


Hm...I guess I could breathe deeper, hold more air in my lungs, and swim with one leg.

Or I could inflate the SMB I have...it will provide some positive buoyancy...at least one and a half lungs-full...added to my normal lung capacity now gives me the ability to shift buoyancy from 0 lungs-full to 2.5 lungs-full of positive buoyancy! Wow.

Oh, I know! I have 14lbs of lead weight on my belt. I can ditch some or all of it! Or, to keep things more controlled, I can ditch my primary and backup lights which all together weigh about -2.5lb...so, now it is just like I'm swimming up an AL80.

The problem with nereas's poor argument is that the required weight DOES NOT CHANGE. 6lbs of it is just non-ditchable now. If you're so far up poop-creek that you need to ditch 20lbs instead of 14lbs to get to the surface...you screwed up a LONG TIME before you got in the water.


Do not listen to his foolishness over a single tank.





For another example: On Guam several years ago, I wore a t-shirt and swim trunks. To dive an AL80 on my borrowed jacket style BC, I needed 8lbs to be neutral at the end of the dive as previously mentioned. If I were to do the same dives on a steel tank, I would probably use an LP85 (0 to -1 empty, -6 to -7 full) or an old LP72 (similar characteristics to an AL80). And I would carry between 2 and 6lbs of lead.

 

[greg98072]

It really depends on whether one or both of your legs is cramped also. And if so, then you can "swim up" -0-. And then you would die. RIP.

Then your buddies will probably split up your gear.

That is where the rest of us here differ from you. If our legs cramp up we can still remove our weight belt using only our hands.

Greg

 

[vshearer]

See what you started ACR? Now ask them what is the best way to tumble a tank.

 

[ACR]

I was thinking that... in fact, I'm going to start a hot-button-topics thread

 

[vshearer]

Actually you have gotten a lot of great info here, sometimes it helps (at least I know it does for me) to have a concept presented by various people for clarity. It keeps it interesting having a devil's advocate for a foil as well.