Manufacturing Materials for SCUBA

[tbone1004]

yes, I am a textile engineer with a background in composites, both civilian and military. Currently sitting in a factory producing yarn out of fiberglass, basalt, carbon fiber, aramids, and hybrids thereof and was in a composite cylinder factory in the UK earlier today. They primarily make driveshafts and fire extinguishers, but do have high pressure vessels as well.

In military applications they don't care about lifespans, they will just replace them, and depending on what they are doing, weight may be critical. Similar to sump diving where these cylinders get used quite frequently, if weight is a concern that's fine and a good compromise.

On CCR, unless you need to save weight, i.e. diving a steel revo without a wetsuit in fresh water, then there's no real point in the added risk and ultimately added cost.

remember that once salt starts getting into the composite through the yarn it can't and won't come out. This will start abrading the filaments from the inside out and cause premature failure. There is no way to really detect this without huge dollar equipment so most people just chuck them instead of trying to rebuild them. They also can't be recycled, so the environmental impact of them is pretty severe compared to aluminum and steel bottles if you care about that sort of thing

 

[Dr. Vinny]

Thank you for your input. I'm currently bringing a Marine friend on-board after a long break in my teaching and diving recreation. I first advised that we buy steel tanks as I had to recycle my AL 80s a while back, an alloy stress issue I understand, and figured that I wouldn't repeat the problem. I see that the AL tanks are widely sold. Do you have or can you point me to any research to give me a warm and fuzzy about this option for tanks? The price of an AL tank is still less than Steel, BUT, not if there is a chance a stress crack is going to appear forcing a re-buy.

 

[tbone1004]

it ultimately depends on what you're doing and why. Steel tanks have many advantages over aluminum for most diving applications especially as primary tanks. Best to scout around your local craigslists and find some used steel tanks. They'll still be a bit more than a new aluminum but have a lot better characteristics. I own more aluminums than steels now, but only because of buoyancy characteristics for stage and deco bottles. My backgas bottles when I can use my own tanks are always steel. I suggest going up into cave country to buy tanks as you are likely to find them cheaper than if you purchase locally

 

[Damselfish]

Lots of people prefer steel tanks but ALs have their place too. ALs are cheaper and less inclined to corrode, which is why they're common rentals. And if you happen to need little added weight (true for some people in warm water) you could actually be overweighted by steel. Just understand the pros and cons and buoyancy characteristics, and how they apply to you.

The aluminum tank issue was with a specific alloy used over 25 years ago by some companies. So that is not a reason to avoid new AL tanks, or recent used ones. But it's something to keep in mind if considering older used AL tanks. (There are many posts that detail the exact tanks that were a problem, but there are dive shops that will have issues filling any tanks of that general vintage or of a certain age even if there's nothing technically wrong with them. Which is bogus, but their compressor their rules.)

 

[Dr. Vinny]

Thanks to all for the help on this "tank reorientation" discussion. In another life while in the employ of the Lockheed Martin Corp., AND, as a note to the classes I taught, "the reason I'm in front of you today is I just have happened to been there before and know a little about how NOT to crash the car" I learned to rely on those that "Bin-there-done-that. So thanks to all, except to the Duff with the snide remarks, Dude! When ignorance is involved education is necessary, not your personal gripe on your mach mode opinions.

 

[KevinNM]

it ultimately depends on what you're doing and why. Steel tanks have many advantages over aluminum for most diving applications especially as primary tanks. Best to scout around your local craigslists and find some used steel tanks. They'll still be a bit more than a new aluminum but have a lot better characteristics. I own more aluminums than steels now, but only because of buoyancy characteristics for stage and deco bottles. My backgas bottles when I can use my own tanks are always steel. I suggest going up into cave country to buy tanks as you are likely to find them cheaper than if you purchase locally

Piranha and Dive Gear Express both have pretty aggressive prices if you know exactly what you want and don't want to drive to pick up. But if you have not already dove that model tank you don't know what you want.

 

[Rred]

" How much lead do you figure it would take to offset the buoyancy of 11 to 15 liters of air?"
Somebody cut class on metric day. One liter is one kilogram of water. One to one. And there are a convenient 1000 cubic centimeters per liter. It's all just "bump the decimal point stuff".
Then if you remember that one kilogram is a convenient 2.2 pounds (close enough)...you need 2.2# of lead to compensate for each liter of air

 

[redacted]

" How much lead do you figure it would take to offset the buoyancy of 11 to 15 liters of air?"
Somebody cut class on metric day. One liter is one kilogram of water. One to one. And there are a convenient 1000 cubic centimeters per liter. It's all just "bump the decimal point stuff".
Then if you remember that one kilogram is a convenient 2.2 pounds (close enough)...you need 2.2# of lead to compensate for each liter of air

So, apparently the "R" does not stand for rhetorical.

We may not be metric yet, but we are inching our way toward it.

 

[Storker]

" How much lead do you figure it would take to offset the buoyancy of 11 to 15 liters of air?"
Somebody cut class on metric day. One liter is one kilogram of water. One to one. And there are a convenient 1000 cubic centimeters per liter. It's all just "bump the decimal point stuff".
Then if you remember that one kilogram is a convenient 2.2 pounds (close enough)...you need 2.2# of lead to compensate for each liter of air

I like to believe that this was mentioned already in post #13