Different Shape SCUBA Tanks

Does anyone know of any other shape SCUBA tank that has been tried (successfully or not) other than the standard cylinder? I know the cylinder is typical because of its ease of manufacture and inherent strength, but I was curious if there had ever been another type. I saw the Cousteau special on PBS a while back where they wore slim back pack style units. I know some were rebreather units, and the rest are just housings with regular tanks inside, but that kind of thing would be ideal for streamlining if you could make a tank with that shape.

A wider thinner tank, like a large briefcase size with rounded edges and ends, would be closer to the body and nearer the natural center of gravity. It would also cut down on cross section and potential entanglements. I know all sorts of materials advances have been made just in the last 10 years with Honeycombs, Kevlar laminates and various new alloys. So has this been applied to radically new tank shapes or designs???

Assuming it had the same gas storage as regular tanks I would think the cavers and wreck divers would want this for the obvious benefits.

I agree, but it would make it very expensive. Also you want aminimum if no welding at all, which the present scuba tank offer.

Some rebreathers (the MK series, and, I believe, some odd Russian models) have spheres, which are the 'ideal' shape for containing high pressure. Cylinders are second best, but much more manageable and streamlined.

WRT the high-tech materials you mentioned, some surface (SCBA) cylinders are thinner metal wrapped by a high-tech fiber like Kevlar. The down side of using them underwater (as I understand it), is that the pressure forces the water through the fiber wrapping, and then it is held against the metal, causing corrosion that can't be cleaned or inspected. Also, they are 'disposable,' in the sense that instead of periodic hydro tests, they are used for a few years (5?) then disposed of.

O2BBubbleFree:

WRT the high-tech materials you mentioned, some surface (SCBA) cylinders are thinner metal wrapped by a high-tech fiber like Kevlar. The down side of using them underwater (as I understand it), is that the pressure forces the water through the fiber wrapping, and then it is held against the metal, causing corrosion that can't be cleaned or inspected. Also, they are 'disposable,' in the sense that instead of periodic hydro tests, they are used for a few years (5?) then disposed of.

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The big thing about using those Fiber Wrapped cylinders underwater is they have a wicked bouyancy swing, something like 20 pounds difference from full to empty, so they would be a PITA. I have the book "The Cave Divers" and they used those high pressure Carbon Wrapped cylinders mounted to their scooters, filled with Trimix at very high pressures. The aluminum is so thin that the helium actually leaked out through the metal and carbon/kevlar, the percentages of O2 and N2 went up from the lack of He and they had some serious problems after that.

Why the bouyancy swing unless they contained 250 ft^3 of air.

There was an older aluminum tank that actually had a shape similar to a champagne bottle. Seriously, had one come in to the shop two years back for a visual, moot point, the exception for US DOT had expired and the tank was no longer valid. Can't remember the name of the manufacturer, sorry.

Tim

because they have ultra thin walls made of aluminum, and I'm talking like 1/16 to an 1/8 of an inch, and then wrapped in something that floats. They are built like that to be very lightweight for firefighters running through houses, but they are pretty much like a Buoy when they are empty, incredibly positive.

Most of the units used by Cousteu including the streamlined packs were conventioanl open circuit units containing three small cylinders and often fairly high pressures and they used Mistral double hose regulators. N

Jimmer:

because they have ultra thin walls made of aluminum, and I'm talking like 1/16 to an 1/8 of an inch, and then wrapped in something that floats. They are built like that to be very lightweight for firefighters running through houses, but they are pretty much like a Buoy when they are empty, incredibly positive.

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None of this affects buoyancy swing.

Buoyancy is due to the weight of the gas the container holds and has nothing to do with the weight of material the container is made of.

Jimmer:

because they have ultra thin walls made of aluminum, and I'm talking like 1/16 to an 1/8 of an inch, and then wrapped in something that floats. They are built like that to be very lightweight for firefighters running through houses, but they are pretty much like a Buoy when they are empty, incredibly positive.

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I think what jvdk01 was refering to is the fact that the net buoyancy change is going to be due to gas loss, no matter the material of the tank (assuming the material is not compressible), but maybe the helium loss you talked about....

Buoyance is related to mass, and if you were loosing He at a rate faster than N or O2, the mass would change in addition to the volume, but I ain't interested in running the figgers.