Steel Tank?
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Its not quite that simple.
Aluminum tanks tend to become positive by the end of a dive, so you wear extra lead to stay neutral..
Steel tanks stay negative even when completely empty (but only 1-3 pounds).
So you can wear LESS lead on your belt but that does not nessasarily mean no lead.
Many other things (mostly wet/dry suit) effect you weight requirements.
Aluminum tanks tend to become positive by the end of a dive, so you wear extra lead to stay neutral..
Steel tanks stay negative even when completely empty (but only 1-3 pounds).
So you can wear LESS lead on your belt but that does not nessasarily mean no lead.
Many other things (mostly wet/dry suit) effect you weight requirements.
Don Burke
Contributor
I use steel tanks whenever it makes sense as it replaces some weight that would otherwise be on my belt. I end up overall lighter on the boat.
I have to use aluminum to safely dive doubles with my wetsuit as the steel doubles don't give me enough ditchable weight.
I have to use aluminum to safely dive doubles with my wetsuit as the steel doubles don't give me enough ditchable weight.
The issue is not getting weight off the belt, the issue is getting your body back to the surface safely. This is why AL 80s are great tanks, not to mention the cost factor.
1. A diver uses weight to compensate for body composition, exposure-suit insulation and tank buoyancy shift. When you dive steel in the ocean, and remove ditchable weight you can get into big trouble.
2. All tanks have a buoyancy shift as a consequence of breathing the gas and their displacement. AL 80s have about a -1 to +4lb swing, LP&HPs have 7 to -15 to neutral or negative. These are if you empty the tanks.
3. AL you need to compensate for this shift. But, AL 80s have a very small buoyancy shift compared to steel and require minimal weight.
4. What most people fail to grasp is, you dont use a steel tanks weight when full to compensate for insulation buoyancy in the open ocean. They are separate. If you do use it to compensate, and remove weight you will become buoyant towards the end of dive. You are literally dropping weight with every breath. This is also bad. So, if you dive steel correctly, you remain negative no matter what, and this causes problems.
5. Gas volume: If you are really worried about volume, double the tanks or sling a stage/pony/push bottle. An 80 and a 30 is better then a HP 120
6. Trust me, fill a steel 95/98 to 500lbs and try to stay down if you use the tank weight when full to compensate for insulation and dont compensate for tank buoyancy shift. For those of you that say, I dive steel and am never buoyant I would wager that you dont utilize much of your tank, so why spend the cash.
7. You are not lighter on the surface/boat with steel. Steel tanks weigh 10-15lbs more when empty then AL 80s, and even more when charged with gas.
Problems with steel:
Unable to ascend: If you dive Steel in the ocean, you run the chance of not being able to ditch enough weight to swim to the surface.
Unable to control descent: If you dive steel in the ocean, even if your BC works, you run the chance of falling fast enough that your BC will not provide lift.
These issues are compounded when you use a wetsuit because of the compression/loss of buoyancy.
Its your choice of course, but AL 80s are safer for the ocean and offer enough gas. I used twin AL 80s as a Navy Diver. I just made 70+ dives in the Red Sea on AL 80s worked great. I dive twin AL 80s in the Northwest, works great. I can swim/tread water in my rig. (Believe it or not one of the things that killed guys at Dive School in the Navy was treading water with their gear and weight and no BC.)
Bottom line, you really should not use steel tanks as a means to compensate for ditchable weight when diving in the ocean. Do people do it? Yes. Do they live? Yes. Do they die? Yes. You play the odds. It is an unsafe practice. Remember, your goal is to reach the surface.
Take care,
Ryan
1. A diver uses weight to compensate for body composition, exposure-suit insulation and tank buoyancy shift. When you dive steel in the ocean, and remove ditchable weight you can get into big trouble.
2. All tanks have a buoyancy shift as a consequence of breathing the gas and their displacement. AL 80s have about a -1 to +4lb swing, LP&HPs have 7 to -15 to neutral or negative. These are if you empty the tanks.
3. AL you need to compensate for this shift. But, AL 80s have a very small buoyancy shift compared to steel and require minimal weight.
4. What most people fail to grasp is, you dont use a steel tanks weight when full to compensate for insulation buoyancy in the open ocean. They are separate. If you do use it to compensate, and remove weight you will become buoyant towards the end of dive. You are literally dropping weight with every breath. This is also bad. So, if you dive steel correctly, you remain negative no matter what, and this causes problems.
5. Gas volume: If you are really worried about volume, double the tanks or sling a stage/pony/push bottle. An 80 and a 30 is better then a HP 120
6. Trust me, fill a steel 95/98 to 500lbs and try to stay down if you use the tank weight when full to compensate for insulation and dont compensate for tank buoyancy shift. For those of you that say, I dive steel and am never buoyant I would wager that you dont utilize much of your tank, so why spend the cash.
7. You are not lighter on the surface/boat with steel. Steel tanks weigh 10-15lbs more when empty then AL 80s, and even more when charged with gas.
Problems with steel:
Unable to ascend: If you dive Steel in the ocean, you run the chance of not being able to ditch enough weight to swim to the surface.
Unable to control descent: If you dive steel in the ocean, even if your BC works, you run the chance of falling fast enough that your BC will not provide lift.
These issues are compounded when you use a wetsuit because of the compression/loss of buoyancy.
Its your choice of course, but AL 80s are safer for the ocean and offer enough gas. I used twin AL 80s as a Navy Diver. I just made 70+ dives in the Red Sea on AL 80s worked great. I dive twin AL 80s in the Northwest, works great. I can swim/tread water in my rig. (Believe it or not one of the things that killed guys at Dive School in the Navy was treading water with their gear and weight and no BC.)
Bottom line, you really should not use steel tanks as a means to compensate for ditchable weight when diving in the ocean. Do people do it? Yes. Do they live? Yes. Do they die? Yes. You play the odds. It is an unsafe practice. Remember, your goal is to reach the surface.
Take care,
Ryan
With my FredT aluminum backplate and 27lb halcyon wing. And a Faber HP100 that is 14lbs negative MT. I don't need a weight belt with my 3mm full suit.... I'm 6'2" Athletic build 190lbs.
And I like to dive this way... It's nice not to have a weight belt... But Ditchable weight is a good thing... I can easily swim up the rig. And carry a Halcyon liftbag. So if I had problems I have another float anyway.... Send it up and wind myself up... And In 4 years... I've never used it.... For that....
Faber HP's are heavy.. Keisers are the heaviest... But well past what I would ever need or use...
Also, Steels only require a VIS. Not a VIS + which is a cost savings every year.. They also if taken care of last longer then AL. I mean pass more hydro's... I know people using there fathers 72's. From the early 60's.
And by the way. Ditching your weight belt at depth of 14lbs isn't the brightest way to assend... It's uncontrolled. Fast... So it is a Last ditch thing... Cause from depth it can kill you too... I'd prefer to shoot a bag and come up on it......
And Swing weight in a AL80 is the same as a HP80.. Air weight is the same at any pressure in any material tank... Only difference is the HP80 holds 80 while the AL80 holds around 77 or so..
Steel is less bouyant because they use less in a tank. The walls are much thinner... Because steel is stronger... Plus Steel is much more forgiving on overpressurization.. If you let the tank sit and RELAX it usually goes back to original state. An Aluminum will hold the expanded shape... Which makes it fail a Hydro... Aluminum has less elasticity..
And I like to dive this way... It's nice not to have a weight belt... But Ditchable weight is a good thing... I can easily swim up the rig. And carry a Halcyon liftbag. So if I had problems I have another float anyway.... Send it up and wind myself up... And In 4 years... I've never used it.... For that....
Faber HP's are heavy.. Keisers are the heaviest... But well past what I would ever need or use...
Also, Steels only require a VIS. Not a VIS + which is a cost savings every year.. They also if taken care of last longer then AL. I mean pass more hydro's... I know people using there fathers 72's. From the early 60's.
And by the way. Ditching your weight belt at depth of 14lbs isn't the brightest way to assend... It's uncontrolled. Fast... So it is a Last ditch thing... Cause from depth it can kill you too... I'd prefer to shoot a bag and come up on it......
And Swing weight in a AL80 is the same as a HP80.. Air weight is the same at any pressure in any material tank... Only difference is the HP80 holds 80 while the AL80 holds around 77 or so..
Steel is less bouyant because they use less in a tank. The walls are much thinner... Because steel is stronger... Plus Steel is much more forgiving on overpressurization.. If you let the tank sit and RELAX it usually goes back to original state. An Aluminum will hold the expanded shape... Which makes it fail a Hydro... Aluminum has less elasticity..
pdoege
Contributor
I'm neutral with my Fabers and about 4 lbs negative with my PSTs.
4 lbs is easily offset with lung volume.
If the tanks are full, that is another couple of lbs. Easy to swim up.
No need for a weight belt or ditchable weights.
Peter
4 lbs is easily offset with lung volume.
If the tanks are full, that is another couple of lbs. Easy to swim up.
No need for a weight belt or ditchable weights.
Peter
I dive steel 72's so if you want to promote saftey in reduced bouyancy change from full to empty, the 71.2 cu ft with a full steel 72 is safer than the 77 cu ft in an AL 80. The steel 72 is also lighter overall, more compact, and less buoyant and will last for at least 30-40 yrs with normal care and maintainence.
Of course, a steel or aluminum 50 would be even "safer" according to the less bouyancy change argument and this obviously runs in to problems at the extreme end of the sacale, so I would suggest the issue is not so much excessive bouyancy change but rather people diving with more air and more tank than they really need.
Ditching weight at depth will usually ensure an unchecked ride to the surface. This is ok for a Navy diver with an on board recompression chamber, but less than ideal for 99.9 of the rec or tech divers out there.
I prefer to be sure I can swim up my tanks, full or empty and to ensure I am not over weighted with empty tanks but rather just neutral at 15 ft. Traditional steel 72's result in 12 lbs of lead weight required to achieve this. But obviously I can still tolerate another 6 lbs of negative bouyancy per tank and can dive larger steel tanks if desired. A pair of 11 to 12 lb negative when full tanks would not be excessive and if it were, I could trade my SS backplate for aluminum and gain another 6 lbs of bouyancy.
Of course, a steel or aluminum 50 would be even "safer" according to the less bouyancy change argument and this obviously runs in to problems at the extreme end of the sacale, so I would suggest the issue is not so much excessive bouyancy change but rather people diving with more air and more tank than they really need.
Ditching weight at depth will usually ensure an unchecked ride to the surface. This is ok for a Navy diver with an on board recompression chamber, but less than ideal for 99.9 of the rec or tech divers out there.
I prefer to be sure I can swim up my tanks, full or empty and to ensure I am not over weighted with empty tanks but rather just neutral at 15 ft. Traditional steel 72's result in 12 lbs of lead weight required to achieve this. But obviously I can still tolerate another 6 lbs of negative bouyancy per tank and can dive larger steel tanks if desired. A pair of 11 to 12 lb negative when full tanks would not be excessive and if it were, I could trade my SS backplate for aluminum and gain another 6 lbs of bouyancy.
docmartin
Contributor
two comments regarding rrh's post:
1. i disagree with the general statement that steel tanks are heavier on the boat than AL. PST's steel tanks weigh less than ALs of the same volume.
2. the shift in buoyancy for AL tanks is not less than for steel tanks. the shift is a function of the weight of the air that is being used. this is the same regardless of tank material. therefore, the buoyancy shift for an 80cf AL is exactly the same as for an 80cf steel. only when comparing a larger volume steel tank to an AL 80 will the shift be greater for the steel tank.
1. i disagree with the general statement that steel tanks are heavier on the boat than AL. PST's steel tanks weigh less than ALs of the same volume.
2. the shift in buoyancy for AL tanks is not less than for steel tanks. the shift is a function of the weight of the air that is being used. this is the same regardless of tank material. therefore, the buoyancy shift for an 80cf AL is exactly the same as for an 80cf steel. only when comparing a larger volume steel tank to an AL 80 will the shift be greater for the steel tank.
Sorry, for the confusion. You guys who advocate not ditching your weight at depth are correct. I was talking about being able to "ditch" a few pounds through losing some gear or drop a pouch. Not jetison some large amount of weight and go for Mr. Toad's wild ride. And as I said, you should be able to swim your rig at depth.
As for the steeel 80 & AL 80, I think PST is discontinuing the tank. I believe this is an issue of economics as the steel 80s cost considerably more than al 80s for little perceived benefit if you dive the steel at rated pressure. Now PST is having their LP tanks rated to 344? PSI. So their 104s are now 130s If you like the steel LP 80s I believe stores are blowing these out. The issue though is diving the rated pressure. I have some friends who dive steel LP 80s at some pretty high pressure...thus adding weight. But, why pay more for a steel that dives like an AL.
Lift bags are good, but if you have a gas problem, time to swim.
All good points.
I still think AL 80s are safer. Honestly, I think you will find that people make the shift to steel without thinking about the alternatives and the weighting and can get into trouble. An example would be a friend who just bought one LP 95, when he could have bought 2 AL 80s and been just as well off, and do twice the diving, or another that watched a diver fall to depth and hit bottom because she was overweighted.
For kicks here is what I will do. I have a set of HP 120s that I do not use...too heavy (for sale cheap as set or broken up), I can get a set of HP 100s and LP 95/98s from friends and I will use my 80s. Thursday, I will run a test.
take care,
As for the steeel 80 & AL 80, I think PST is discontinuing the tank. I believe this is an issue of economics as the steel 80s cost considerably more than al 80s for little perceived benefit if you dive the steel at rated pressure. Now PST is having their LP tanks rated to 344? PSI. So their 104s are now 130s If you like the steel LP 80s I believe stores are blowing these out. The issue though is diving the rated pressure. I have some friends who dive steel LP 80s at some pretty high pressure...thus adding weight. But, why pay more for a steel that dives like an AL.
Lift bags are good, but if you have a gas problem, time to swim.
All good points.
I still think AL 80s are safer. Honestly, I think you will find that people make the shift to steel without thinking about the alternatives and the weighting and can get into trouble. An example would be a friend who just bought one LP 95, when he could have bought 2 AL 80s and been just as well off, and do twice the diving, or another that watched a diver fall to depth and hit bottom because she was overweighted.
For kicks here is what I will do. I have a set of HP 120s that I do not use...too heavy (for sale cheap as set or broken up), I can get a set of HP 100s and LP 95/98s from friends and I will use my 80s. Thursday, I will run a test.
take care,
I dive steel PST HPs. I own two HP100s and one HP120 at present, and a passel of AL80s.
The AL80s are my LAST choice.
An example from last weekend will make the point.
I had a friend who's BC was holed, so she dove my spare BP+Wing. AL plate + STA. She normally needs 12 lbs with an AL tank in her usual exposure suit and a neutral BC, so she packed 8 in a weight belt (the rig is -4), strapped on the tank, and jumped in.
At 65' she though the pack was too loose, and went to adjust it. Unfortunately, she tripped the wrong buckle and the weight belt fell off! Oops! The result was an uncontrolled ascent to the surface which, by the time she figured out what was going on, had brought her all the way up.
FORTUNATELY it happened right at the start of the dive, and she didn't freak and hold her breath, so with no nitrogen load it was not a big deal, other than the freak-out factor.
Now contrast that with my setup. Same deal, except that I dive a steel HP100. The tank is -1 empty instead of +4. I usually would dive with 10lbs of weight for me and my 3 mil suit, plus whatever the tank requires (I'm inherently about +2; 5'11 and 170lbs.) That would be 13-14lbs with an AL80.
With the steel HP100 and SS BP+STA, I need TWO lbs of lead.
If I drop THAT at depth, I'm fine. I can stay down without problems. Until I get within 20' or so of the surface, I can hold depth. So I can now ascend, make my safety stop, and while I'm going to be coming up to the surface once about 20' or so, I can make a perfectly controlled ascent and stop to that point, then come up horizontal for the last 20' to check my ascent rate.
Now which is safer?
1. Enough weight that if you ditch (accidentally or otherwise) you WILL ascend, non-stop, with no way to prevent it.
OR
2. A SMALL ENOUGH amount of weight that accidentally ditched or not you can stay down until close to the surface.
Provided I can swim up the kit from the bottom with a holed wing, I argue that (2) is FAR safer than (1), as a accidental buoyant ascent can be avoided even if I accidentaly drop my weights.
I have seen unintentional ditches many times while diving. I have yet to see a diver intentionally ditch weights - either on the surface or at depth. Therefore, in my experience at least, it is far more important to prevent the consequences of an unintentional ditch than to make an intentional one easier.
The AL80s are my LAST choice.
An example from last weekend will make the point.
I had a friend who's BC was holed, so she dove my spare BP+Wing. AL plate + STA. She normally needs 12 lbs with an AL tank in her usual exposure suit and a neutral BC, so she packed 8 in a weight belt (the rig is -4), strapped on the tank, and jumped in.
At 65' she though the pack was too loose, and went to adjust it. Unfortunately, she tripped the wrong buckle and the weight belt fell off! Oops! The result was an uncontrolled ascent to the surface which, by the time she figured out what was going on, had brought her all the way up.
FORTUNATELY it happened right at the start of the dive, and she didn't freak and hold her breath, so with no nitrogen load it was not a big deal, other than the freak-out factor.
Now contrast that with my setup. Same deal, except that I dive a steel HP100. The tank is -1 empty instead of +4. I usually would dive with 10lbs of weight for me and my 3 mil suit, plus whatever the tank requires (I'm inherently about +2; 5'11 and 170lbs.) That would be 13-14lbs with an AL80.
With the steel HP100 and SS BP+STA, I need TWO lbs of lead.
If I drop THAT at depth, I'm fine. I can stay down without problems. Until I get within 20' or so of the surface, I can hold depth. So I can now ascend, make my safety stop, and while I'm going to be coming up to the surface once about 20' or so, I can make a perfectly controlled ascent and stop to that point, then come up horizontal for the last 20' to check my ascent rate.
Now which is safer?
1. Enough weight that if you ditch (accidentally or otherwise) you WILL ascend, non-stop, with no way to prevent it.
OR
2. A SMALL ENOUGH amount of weight that accidentally ditched or not you can stay down until close to the surface.
Provided I can swim up the kit from the bottom with a holed wing, I argue that (2) is FAR safer than (1), as a accidental buoyant ascent can be avoided even if I accidentaly drop my weights.
I have seen unintentional ditches many times while diving. I have yet to see a diver intentionally ditch weights - either on the surface or at depth. Therefore, in my experience at least, it is far more important to prevent the consequences of an unintentional ditch than to make an intentional one easier.
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