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Hello you all,
I'm thinking about buying lightweight composite double 15 litres.
Does annyone have expierience with these sets? How do they handle your balance? Are they easy to use one your basic deeper dives with Trimix and stagebottles?
In addition to unsatisfactory buoyancy characteristics, composite tanks aren't satisfactory in durability for day-to-day repeated banging around a boat use either. They are designed for limited duty emergency use, and that's what they're good for.
Rick
"You can have peace, or you can have Freedom. Don't ever count on having both at once." (Heinlein)
"... they saw the deeds of the LORD, his wondrous works in the deep." (Ps107:24)
They’re several materials that the wrapped cylinders use, carbon fiber as you mention and fiberglass. There are two major problems with using any kind of wrapped cylinders for diving. Though light above water they’re horribly buoyant in the water; you’d have to carry a LOT and I do mean a lot of extra lead to get below.
The weight belt you’d have to carry would offset any gain you realized in the lighter cylinders.
Secondly, the wrapping around the metal shell is porus and will allow water to be trapped against the [very thin] metal wall that’s the gas tight “seal” that actually holds in the gas. This will cause corrosion to set in fairly quickly, possibly resulting in a bomb.
Leave the composite cylinders for the firefighters.
For what it's worth concerning composit cylinders. I use a carbon fiber composite cylinder on the Nitrous Oxide system in my hotrod boat, the cylinder is the same one used by firefighters on their Scott airpacks. I use this type of cylinder because it is lighter than the aluminum bottles and in Drag Racing every pound counts, however I can tell you that they would make lousy scuba tanks not only for the bouancy problems, but as Roak mentioned the material can and does absorb water ad this would be bad. The cylinder in my boat is never underwater but even evryday humidity at the boat races and general splashing causes it to absorb water, so I could not imagine them as bing good scuba tanks.
The confusing comments you're seeing is because no one here in the US is familiar with the composite tanks made by Interspiro, they're not popular here in the US because of their high working pressure.
(nearly impossible to get a full fill)
Interspiro is the only manufacturer that I'm aware of that makes composite bottles suitable for scuba use.
That being said, I LOVE the balance of my steel Interspiros, even if they are a pain in the neck to get hydroed and filled.
The valve design also eliminates a whole host of entanglement hazards as well.
In "The Technical Diving Handbook" by Gary Gentile
Page 20 has a picture of Clark Pitcairn wearing steel doubles with 3 composite tanks attaced to them. he is also carrying a stage bottle. (the bouyancy of the composite tanks helps offset the negative bouyancy of the steel)
it also mentions that the cylinders are experimental.
man.... that looks like a lotta air.
it also mentions that these tanks are used mostly in European Countries and that few shops in the US can pump to 4,500 psi
Do you know if they are DOT approved and if approved, if they have a “lifetime” of 15 years like other DOT composite cylinders?
I kinda doubt if the composite bottles are DOT approved, but I'll check. Some of their old steel cylinders were made in West Allis (Milwaukee) of all places.
The composites are supposed to be good for a 40 year minimum.
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