Nitrox in 300bar pony?

[tamas970]

Fully agreed and thx for the reading!

... IMHO, good buddy skills and good dive planning are a much better solution than a pony.

I forgot the weight of the content & didn't know the displacement. Summarizing the math quickly:

displaced water: 5.25L x 1.03 = 5.4kg
Tank weight: 3.8kg
Content weight: ~1.5kg (considering, that its not fully topped up to 300bar)

Result: the tank is NEUTRALLY bouyant at the begining. Considering it would be used as a pony (=used on ascent, most likely not depleted completely) I wouldn't add more than 0.5-1kg lead for compensation.

One small "correction."

Carbon tanks ARE buoyant. Gravity loses once they are taken into the water. However, they are not too positive. The cylinder in question has a displacement of a little more than 5.25 litres (4.7 litre internal volume). This translates as 5.25 kg buoyant effect when empty. While this IS a bit of a pain in the ass, because it would require carrying that much ballast, the overall mass walking around on the boat would hardly be "too much" compared with a steel tanks with similar capacity (a smidge over 1400 litres). Of course, the common item in both a steel and carbon cylinder would be the mass provided by the gas. Filled to 300 bar, the weight of the gas (let's assume air) will be about 4.7 X 300 X 1.2 gm or around 1.6 kg.

I have a buddy who uses carbon cylinders in her CCR. Does just fine with them.

P.S. to a NA centric diver, carbon cylinders may seem exotic and OTT but there's a whole world outside of North America folks...