Aluminum vs Steel Dive Tanks

[newbiesailor]

Originally Posted by JoeDiver

And people think there's drama here at CF.....LOL......

haha, and i still have no tanks..... buhuuuu......

[newbiesailor]

Originally Posted by s/v Beth

And I did not mean to hijack your thread, rather let you know there were options. Good luck with your search.

i don't feel hijacked mate, no problem!!!! when i eventually hopefully before xmas find some tanks i take you for a dive!!!

[downunder]

Skipjack covers it well. I have to agree with he, newt and saucy and go with the steel.

Smaller, much better for bouyancy and smaller for same capacity. essentially steel wall thickness is muh thinner than Al smaller size for same volume.

Go steel.

[skipmac]

One very critical issue with steel tanks. Some steel tanks, like the Pressed Steel low pressure tanks are very negative in the water, even when empty.

You must make sure that you will have overall positive buoyancy in the water with these tanks. If you are warm water diving with a skin or very light wet suit some steel tanks will sink you unless can add air to your BC. If the BC fails you are heading to the bottom unless you ditch the tanks, a skill that many divers are not comfortable with or trained to do.

Bottom line (no pun intended here) you need to set up so you have some kind of ditchable weight (usually a weight belt) that will make you positively buoyant no matter what tank you are using and how full or empty it is in the dive.

News today two divers drowned in the Keys. According to the account in the local paper one diver ran out of air, could not release his weight belt and went to the bottom with the second trying to assist. The ability to achieve positive buoyancy can be life or death in diving.

[amytom]

Originally Posted by skipmac

One very critical issue with steel tanks. Some steel tanks, like the Pressed Steel low pressure tanks are very negative in the water, even when empty.

You must make sure that you will have overall positive buoyancy in the water with these tanks. If you are warm water diving with a skin or very light wet suit some steel tanks will sink you unless can add air to your BC. If the BC fails you are heading to the bottom unless you ditch the tanks, a skill that many divers are not comfortable with or trained to do.

Bottom line (no pun intended here) you need to set up so you have some kind of ditchable weight (usually a weight belt) that will make you positively buoyant no matter what tank you are using and how full or empty it is in the dive.

News today two divers drowned in the Keys. According to the account in the local paper one diver ran out of air, could not release his weight belt and went to the bottom with the second trying to assist. The ability to achieve positive buoyancy can be life or death in diving.

One more thing to think about. Make sure you're only slightly buoyant. If you ditch your weights, intentional or otherwise, you don't want a rocket ride to the surface. I'd rather sink than reach the surface with a bubble in my shoulder and drowning in my own bloody foam.

[s/v Beth]

Wow, I say one snide remark and it gets its own thread :-)
One of the hot buttons that this conversation revolves around is buoyancy. I prefer to be negative at the end of a dive, ascending too fast is a greater risk than staying at the bottom . I want to be neutral all the time , but if I can't make me a little negative . I wear a backplate and very little lead for the same reason , although skips reasons for a wieght belt are sound .

[skipmac]

Originally Posted by s/v Beth

Wow, I say one snide remark and it gets its own thread :-)
One of the hot buttons that this conversation revolves around is buoyancy. I prefer to be negative at the end of a dive, ascending too fast is a greater risk than staying at the bottom . I want to be neutral all the time , but if I can't make me a little negative . I wear a backplate and very little lead for the same reason , although skips reasons for a weight belt are sound .

Yea. See what snide gets you.

I also use a SS backplate, wings and harness instead of BC. And totally agree, you must be negative at the end of the dive, especially at 20' doing a safety or deco stop. The point I'm trying to make is that you need to have some easily ditchable weight (besides your tanks) that will make you positive in case of some major malfunction.

And yes, Amytom's point about being too positive is also critical. Rocket to the surface and risk barotrauma, embolism, bends, etc. But I would also prefer bent to drowned. One can usually fix bent or even pneumothorax, you can't fix drowned. So, one does need the ability to become positively buoyant at any time in a dive, just not overly so.

Many people tend to grossly overweight so the point is a question of balance (yes I stole that line from the Moody Blues) or like the three bears. Not too buoyant, not too negative but just right. .

Maybe I can summarize everyones points.

1. Weight so you can remain negative at the end of the dive with empty tanks at 20' where your tanks and wet suit are most buoyant.

2. Weight so at the beginning of the dive with full tanks and at depth where your wet suit is compressed and least buoyant you have weight you can drop and be slightly positive.

3. Don't over weight.

4. Steel tanks can reduce the amount of lead you need on a belt but should not replace all of it.

[Matt sachs]

1) An out of air situation has absolutely nothing to do with the tank on your back. Its a failure to be trained properly, or ignoring that training.
Out of air drills should be pounded into each and every student.
2) Not being able to ditch your weights is not a tank problem either, its training.
The industry standard is the weight integrated BC. Weight belts (IMO) should go the way of the dive tables and J valves. You can still buy a new non weight integrated BC, but its kinda like buying a car without AC.
3) If you are positive at the end of the dive, you were not weighted properly at the begining of the dive.

[skipmac]

Originally Posted by Matt sachs

1) An out of air situation has absolutely nothing to do with the tank on your back. Its a failure to be trained properly, or ignoring that training.
Out of air drills should be pounded into each and every student.
2) Not being able to ditch your weights is not a tank problem either, its training.
The industry standard is the weight integrated BC. Weight belts (IMO) should go the way of the dive tables and J valves. You can still buy a new non weight integrated BC, but its kinda like buying a car without AC.
3) If you are positive at the end of the dive, you were not weighted properly at the begining of the dive.

Completle agreement on all points. Mentioning the accident in the keys was only meant to point out that the inabiliby to get positive, whether due to panic, poor training, or poor weighting, can be deadly.

Since I don't dive a BC have not looked at the weight integrated models. I assume the integrated weight is in an easily droppable form?

[deepstar]

Ali tanks survive getting scratched just by being scratched.... steel unless you treat them start to rust.

I personally would go for HP ALI 80's - a little bigger than normal but -ve buoyant all the dive.

If you are using steel Tanks, and you choose to fix a rubber boot/sock to protect you boat deck - this is generally where water collects and over a couple of years starts to rust through.

As for a rebreather - combination of all 3ltr, 7ltr, 12 ltr and 15 ltr depending on the dive..... but for prolonged living on the boat a Rebreather is NOT the way to go (IMHO).... too much maintenance and J-size bottles are a nightmare to store.

Just remember: US DOT Tanks are illegal to be filled in the EU/UK - just as UK BS standard tanks are in the US. If you have your own compressor - you have no issue.

[offline]

When on an extended trip I use 53 cu/ft AL for our Draeger Dolphins...

Originally Posted by SaucySailoress

You can more often find steel tanks which have higher pressure ratings than aluminiums. We have some Draeger babies - sit nicely on a rebreather, which is where they're from (but gonna ditch those, they're a pain) - which are rated to 300 bar so also contain 80cuFT. Think they're about 8 litre, but would have to go check.

The point is, they can hold the same amount of air as an ALi 80cuFt (11 litre @ 207bar), and take up waaaay less space on the boat.

[rebel heart]

There are all the technical reasons why steel tanks are better, the one that I notice the most is that I don't get buoyant towards the end of the tank like I do with aluminum.

But aluminum tanks are so much cheaper. I can buy ~4 aluminum 80's for the cost of 1 steel. Space saving is a bit of a wash. I'd rather have 4 tanks than 1 with a compressor (and all the associated work/cost of that).

[rebel heart]

Originally Posted by Matt sachs

3) If you are positive at the end of the dive, you were not weighted properly at the begining of the dive.

It's not so much for me about being positive vs. neutral vs. negative at the end as much as it is your buoyancy changing positions. If I slowly started moving weights from your back to your front, you'd notice it. Your butt will go up easier, you'll have to kick down more, etc.

I've seen a lot of folks with aluminum not realize what was happening to them and dump a lot of air because they take the changing balance for true positive buoyancy.

[s/v Beth]

This must be a first for cf because I think we all agree. I think I would like to dive with a few of you, because you have the same paranoid (safe) mindset . BTW offline and SS, how do the dolphins work on cruising sailboat?

[deepstar]

Sorry I'm CCR