Lightweight scuba tanks

[Boarderguy]

Whats SCBA? Where you breath via a hose to the boat?

SCBA = Self Contained Breathing Apparatus
SCUBA = Self Contained UNDERWATER Breathing Apparatus

Used for non submersion activities requiring a source of clean air. Firefighters and certain welding situations come to mind.

 

[lexvil]

As close to light weight, given current pressure parameters is the old steel 72’s pushed up to 3000 psi.

what you need/want is something around the 72 physical size with 6000psi.

call it a VHP 110

 

[Bob DBF]

OTOH, carbon fiber tanks makes sense for SCBA, where reducing the weight the users have to carry is beneficial.

And they are not used for protracted periods in salt water, where they deteriorate faster.

 

[rexman24]

What would be the point, you'd just need to carry more lead to get neutral? Aluminum tanks are sometimes preferred over steel because they're cheaper to buy and maintain, not because they're ligher(with the exception of stage tanks). OTOH, carbon fiber tanks makes sense for SCBA, where reducing the weight the users have to carry is beneficial.

Yes, but unless I'm missing something the 32 lbs aluminum tank is only -1.5 lbs full and +3 lbs near empty buoyancy. So if a tank I describe was created and weighed say 10 lbs. And was say +7 lbs empty buoyancy, it make the system a lot easier for old ppl like me to carry around for Shore dives with long walks/climbs for example.
32+3=35lbs.
10+7=17lbs.

So half the weight. What am I missing?

 

[MarkA]

Yes, but unless I'm missing something the 32 lbs aluminum tank is only -1.5 lbs full and +3 lbs near empty buoyancy. So if a tank I describe was created and weighed say 10 lbs. And was say +7 lbs empty buoyancy, it make the system a lot easier for old ppl like me to carry around for Shore dives with long walks/climbs for example.
32+3=35lbs.
10+7=17lbs.

So half the weight. What am I missing?

The biggest total weight (cylinder + lead) saving you are going to get is by changing from an AL80 to a steel HP80. This will Reduce total weight by approx 8lbs. At this point any reduction in steel will require a corresponding amount of lead added (within a lb). The other way would be to reduce the size of the cylinder.

 

[Edward3c]

From memory one problem with carbon fibre is they can be damaged easily therefore could fail. With fatal results.

 

[rexman24]

The biggest total weight (cylinder + lead) saving you are going to get is by changing from an AL80 to a steel HP80. This will Reduce total weight by approx 8lbs. At this point any reduction in steel will require a corresponding amount of lead added (within a lb). The other way would be to reduce the size of the cylinder.

I was mainly addressing the implication that there would be no advantage to a lightweight cylinder. As far as I can tell there would be.

 

[James79]

Yes, but unless I'm missing something the 32 lbs aluminum tank is only -1.5 lbs full and +3 lbs near empty buoyancy. So if a tank I describe was created and weighed say 10 lbs. And was say +7 lbs empty buoyancy, it make the system a lot easier for old ppl like me to carry around for Shore dives with long walks/climbs for example.
32+3=35lbs.
10+7=17lbs.

So half the weight. What am I missing?

Fundamental to the question is displacement of the tank (total physical volume). Once you get to a tank that is neutral when empty, it weighs the same as the water it displaces... any lighter and you need lead to offset the positive buoyancy. In order to make that work in your favor, you need higher pressures to get the same volume of air in a smaller space (less water displaced) otherwise it's a zero sum game. Most regs are designed to for 3000-3500 psi tanks, get much over that and you increase wear rate and likelihood of HP seat failure. So, to answer your hypothetical "what would it take" to include unobtainium materials, aim for a 10k psi tank 1/3rd the size of an Aluminum 80. If your unobtainium can achieve those pressures at 10 lb total weight, it would be neutral when empty. And bankrupt a small nation to produce. That's where Lex's comment on old school 72's comes in. They weigh about 26 lb, and are neutral empty.... overfilled to 3000 psi they are 85 CF. I have 5 and am always keeping my out for more on the cheap!

Respectfully,

James

Edit so it doesn't read like I had stroke while typing.

 

[rexman24]

Fundamental to the question is displacement of the take (total physical volume). Once you get to a tank that is neutral when empty, it weighs the same as the water it displaces... any lighter and you need lead to offset the positive buoyancy. In order to make that work in your favor, you need higher pressures to get the same volume of air in a smaller space (less water displaced) otherwise it's a zero sum game. Most regs are designed to for 3000-3500 psi tanks, get much over that and you increase wear rate and likelihood of HP seat failure. So, to answer your hypothetical "what would it take" to include unobtainium materials, aim for a 10k psi tank 1/3rd the size of an Aluminum 80. If your unobtainium is can achieve those pressures at 10 lb total weight, it would be neutral when empty. And bankrupt a small nation to produce. That's where Lex's comment on old school 72's comes in. They weigh about 26 lb, and are neutral empty.... overfilled to 3000 psi they are 85 CF. I have 5 and am always keeping my out for more on the cheap!

Respectfully,

James

Thank you for your input James.

 

[MarkA]

I was mainly addressing the implication that there would be no advantage to a lightweight cylinder. As far as I can tell there would be.

My first diving cylinder was a steel Heiser 15l. It weighed 20.4 kg. The modern Faber 15l cylinders weigh about 16.6kg. The difference is an increase of lead. The Faber close to neutral when empty cylinder is more pleasant to dive with. @James79 put this nicely. The total weight carried would be about the same.