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Scuba Tanks: My Faber 95 Doubles October 28, 2008

Posted by Chris Sullivan in Equipment.
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I bought a pair of tanks with bands and manifolds last year for technical diving. These tanks are heavy. When wearing both of them I need about 16 pounds less weight, which means with a wet suit on I need no additional weight at all, and need to add lots of air to my BC to become neutrally buoyant at depth. With my dry suit I’ll wear around 6 pounds of additional weight to be able to do a deco or safety stop comfortably at 10 or 15 feet (vs. 24-27 with a single AL80). These weights are all in fresh water.

Faber 95 Doubles mounted on Backplate and Wing

Faber 95 Doubles mounted on Backplate and Wing

The 95 cubic foot nominal capacity per tank is an exaggeration. This caused me to miscalculate my RMV last year as we all thought the rating was at the rated working pressure. The working pressure of these (Low Pressure Steel) tanks is 2400 PSI, but to fill them to 95 cubic feet you have to use the 10% overpressure allowance by filling them to 2640 PSI. At 2400, it will only contain 86.4 cubic feet. However, the tanks are quite robust and are rated below their actual capability. So I regularly fill them to 3000 PSI which is 118¾ 108 cubic feet, and have seen them filled to 3500 PSI or 138.5 126 cubic feet (although beware of the overpressure relief valve that may have a relatively low relief pressure). There was still lots of air in the doubles at the end of the dive. I like to balance the amount I use to keep my options open.

So my doubles are good to 236.5 216 or even 277 252 cubic feet which can make for a nice long dive. One dive this summer, though, required my doubles plus a staged 80 cubic foot tank at depth, then half of another 80 cubic foot tank for decompression. Bottom time was 2 hours, total dive time 3 hours, mix EAN35, depth about 85 feet. Just the air weighs 18-20 pounds, and the tanks weigh 37.2 pounds apiece (from the chart), so with the valves the whole package weighs about 100 pounds when full. Add to this the backplate and other gear we have a heavy load.

One learns over time to minimize the amount of effort required to lug these things around. If at all possible, I try to transport them in the pickup truck that the owner of our dive shop owns. If they must go in the trunk of my Toyota Camry Sedan, I haul them up on the lip of the trunk (boot for those in the land of 240 volt electricity) , pivot them around so they’re facing the right way, put them on my back, and walk to the boat (or shore or dock). Consequently the plastic cover on the lip of my trunk is pretty banged up. I prefer this, at least for walks under 100 yards, to carrying them on a dolly because I don’t have to lift them. Even if I have stage bottles I can make it with all my gear in 1 trip sometimes. My next vehicle is going to have a tailgate, I think. One of the reasons I do a little weightlifting is to be able to manage this load without hurting myself.

I find it strange that we import something as pedestrian (and heavy) as a tank all the way from Italy. Faber makes good tanks though, and they have a reputation for being able to withstand much more than their rated pressures.

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1. The Big Scuba Gear Purchase, Part 2 « Chronicle of an older diver - November 5, 2008

[…] recreational BC and can be a backup for my technical dives, but the OMS fits me better with the doubles. Back-inflate makes floating on your back more difficult that a standard BC, but I find it much […]

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2. Jim Colton - June 1, 2010

Your calculations do not match up to mine. Where is my mistake?

2400 = 86.4
2640 = 95
2800 = 100
3000 = 108
3200 = 115
3500 = 126

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Chris Sullivan - June 2, 2010

Hmm. Because I was wrong. Thanks for pointing it out – on the 3000 and 3500 PSI calculations I went back to 2400 PSI as the denominator. I’m correcting the original.

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3. Paul R - June 9, 2010

I did the diving doubles from a trunk for a bit, until I needed help standing up while wearing them. Then I switched to an SUV and never looked back. I would suggest avoiding the tailgate though and go for something where the back door lifts up or opens to the side so that you don’t have to slide the tanks to get them to the edge of the tailgate.

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Chris Sullivan - June 12, 2010

Totally agree with you on the geometry of the back door. It’s definitely better if it goes up rather than sideways. Help protect from rain as well if you’re changing clothes or putting on a dry suit and want to keep it that way. The challenge is going to be convincing my wife that my next car should have a door on the back. She’s into comfort, and doesn’t dive so comfort when putting on doubles isn’t much of a consideration for her.

I’m hanging on the Camry until at least next summer unless something serious goes wrong with it.

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