Carbon Fiber Tanks

[crpntr133]

Once carbon fiber is damaged that tank is to be condemned! The carbon fiber isn't the first layer on these tanks but one gouge and it might be damaged.

 

[WD8CDH]

From their website:Full or nearly empty? Fresh or salt water? It can't be all of these. When marketeers make statements like this, it triggers my avoidance response.

The manufacturer makes a choice of three different removable weights that you can select according to the diving conditions.

By the way, the Interspiro system holds about 140CF but weighs about the same as an 80 single.

 

[WD8CDH]

...guess I'm still trying to figure out the point of carbon-wrapped or composite scuba tanks rated to whatever bazillion psi when we live in a world of shops/boats only providing 3000 - 3500 psi-ish fills ? ...just do the math, if these super-duper futuristic tanks are only filled to 3000-3500 psi, compare their 'real' cubic feet capacity with boring/old conventional AL/steel tanks and see if one can call that "progress". ...plus, these 'futuristic' materials tanks are more 'floaty' than AL/steel tanks, requiring you to ballast them with more lead anyway.

True, if filled to only 3500psi, there is little point. But 4500psi fill capability is getting much more common. I live within 20 miles of 3 shops that can fill to 4500psi.

While you do need to add more lead, the total weight including the lead is quite a bit less than conventional tanks of the same rated capacity.

 

[WD8CDH]

Probably an even better choice than Carbon Fiber for very high pressure SCUBA tanks would be a 7000 series aluminum alloy. Luxfer makes a few 300bar 7000 series tanks in europe that would be very good for SCUBA if made in the right sizes. For example, if the AL40 was made out of 7000 series alloy with the same wall thickness, they would handle over 5000psi. At 4500psi, they would hold 60CF and make a really nice to dive set of doubles while being more rugged than Carbon Fiber.

 

[DA Aquamaster]

True, if filled to only 3500psi, there is little point. But 4500psi fill capability is getting much more common. I live within 20 miles of 3 shops that can fill to 4500psi.

"Can" and "will" are very different terms. Many shops will do 4500 psi fills in response to the paint ball market, but they usually charge disproportionately more for it and if the air bank only fills to 4500 psi, you many not get an actual 4500 psi in your tanks due to both heating during the fill and loss of pressure in the bank.

And you probably won't be able to get a 4500 psi fill as fast or as reliably as a 3000 psi fill.

That is of course on top of the easily damaged and at best limited life nature of the tanks and their high acquisition cost.

 

[Leadking]

Why would you want one? The less a tank weighs the more lead you have to wear!

 

[WD8CDH]

"Can" and "will" are very different terms. Many shops will do 4500 psi fills in response to the paint ball market, but they usually charge disproportionately more for it and if the air bank only fills to 4500 psi, you many not get an actual 4500 psi in your tanks due to both heating during the fill and loss of pressure in the bank.

And you probably won't be able to get a 4500 psi fill as fast or as reliably as a 3000 psi fill.

That is of course on top of the easily damaged and at best limited life nature of the tanks and their high acquisition cost.

So far, every shop that I have checked that "Can" fill to 4500 "Will" fill to 4500psi any tank that is rated to 4500psi.

Those shops in my area that charge higher for HP fills charge only $1.00 extra over 3500psi.

The commercially available (but not in the US) SCUBA tanks from Interspiro have unlimited life, but they are expensive.

 

[WD8CDH]

Why would you want one? The less a tank weighs the more lead you have to wear!

As mentioned several times before, the very high pressure tanks plus the extra lead still weighs substantually less than even HP steel tanks of the same capacity.

To go with an extreme example, with the ultra high pressure Titanium tanks that I used to own, I could put about 200CF of tanks and the lead needed to make them neutral in a briefcase and still have room for a mask and my lunch. I could carry all of my gear for two dives in one trip when everybody else had to make two trips.

 

[Rhone Man]

The raw materials for carbon fibre are always going to be lighter than those aluminium or steel. The weight of gas (cu ft for cu ft) is always going to be the same (although you might have more gas in one or other).

I accept what you say that for a dive op, you only need one V weight system for each diver, making the tanks much easier to lug around, assuming you have more than one tank for each diver.

I suspect if they can be made robust enough, the world will eventually move to carbon fibre tanks, but given how slowly Al 80s wear out, and how many there are around at the moment, the move is not going to come quickly...

Speaking for myself, you can't even get HP Steels filled to 3,500 PSI in this part of the world, so we have a long wait.

 

[WD8CDH]

Lets say hypothetically that Carbon Fiber fire fighter tanks were legal for SCUBA and compare divable weights of different tanks setups with similar air capacity. Using real published data:


The Luxfer L87R SCBA (87CF) tank weighs 10.1 pounds plus 10 pounds of lead to be neutral empty for a total of 20.1 pounds.

An LP85 steel SCUBA tank weighs 31 pounds and is neutral empty without adding any weight.

The Luxfer S80 SCUBA tank (77CF) weighs 31.4 pounds plus 4.4 pounds of lead to be neutral empty for a total of 35.8 pounds.


So the CF tank divable weight is 10.9 pounds less than the steel tank and holds 2 more CF of air and is 15.7 pounds less than the divable weight of an aluminum 80 while holding 10 more CF of air.

So the real weight savings of 4500psi tanks is more than ten pounds even for recreational air capacities and would be even more than twice that for a "tech diving" rig. The savings compared to HP steel tanks would be less, but still quite noticable.

I would pay and extra buck a fill for the weight savings. And remember, you only need one extra hunk of lead per Diver, not per Tank.