Why is domed bottom steel tank more popular than flat one?

[nohappy]

Why is that most of the steel tanks are made with domed bottom while aluminum tanks are mode with flat bottom in scuba industry?

 

[Tokenwiz]

The shape is an artifact of the manufacturing process. Because of the nature of the materials steel cylinders are made using a deep draw process, aluminum use a backward extrusion. The former results in a rounded bottom as a result of the manufacturing process and the latter gives a flat bottom. Choice of cylinder is generally made based on buoyancy characteristics rather than shape and to make the round bottom cylinders able to stand up, people attach plastic or rubber boots to flatten the bottom out.

 

[nohappy]

Thank you @Tokenwiz for your reply. I'm aware of that process, but I also know that both steel and aluminum can be made with both shape. I'm not selecting them by their shape and I know they both have boots. I'm only curious.

 

[Tokenwiz]

I haven't personally come across flat bottom steels or round bottom aluminum that I can think of so I'd suppose if they exist they are less popular because of ease of manufacturing. Also, a steel tank that had extra material to make the bottom flat would result in an excess of material and mass on the bottom (as compared with a normal tank) making the buoyancy characteristics of the tank quite horrible I guess.

 

[Storker]

I haven't personally come across flat bottom steels

There are concave bottom steels to be had, though.

 

[Protondecay123]

Here's a great video showing how steel cylinders are manufactured.
Here's one for the aluminium cylinders.

 

[Divin'Papaw]

Thank you @Tokenwiz for your reply. I'm aware of that process, but I also know that both steel and aluminum can be made with both shape. I'm not selecting them by their shape and I know they both have boots. I'm only curious.

They can? I've never seen a round bottom aluminum tank nor a flat bottom steel tank. I'm not a metallurgical engineer but I'm not sure your statement is correct. I'm open to being corrected but I've sure never seen any examples in my 15+ years of diving.

 

[Storker]

I've never seen a round bottom aluminum tank nor a flat bottom steel tank.

Me either. I've seen both round bottom and concave bottom steels. Lots of them. I can't remember ever having seen a flat bottom steel tank.

Can't speak about Als, though. They're not particularly common where I've been diving (Europe)

 

[Degenerate]

Me either. I've seen both round bottom and concave bottom steels. Lots of them. I can't remember ever having seen a flat bottom steel tank.

Can't speak about Als, though. They're not particularly common where I've been diving (Europe)

Same, I have seen plenty of concave bottom steels, never seen a flat one (although OP might be thinking of concave and calling them flat).

I haven't personally come across flat bottom steels or round bottom aluminum that I can think of so I'd suppose if they exist they are less popular because of ease of manufacturing. Also, a steel tank that had extra material to make the bottom flat would result in an excess of material and mass on the bottom (as compared with a normal tank) making the buoyancy characteristics of the tank quite horrible I guess.

Concave bottom steels are not uncommon here in Scandinavia, I can't say if they are more bottom heavy than their convex counterparts but that wouldn't necessarily be a bad thing.
My convex bottom D12 232b tanks are rather top heavy and that is usually countered by a butt weight, which could easily be swapped for a V weight to offset the heavier bottom part of concave ones, my fundies instructor was using a pair and he did not mention anything about buoyancy being horrible, nothing but praise from him on them tbh.
I also love the fact that you can just straight up stand your rig up on a flat surface without having to lean it against anything if you got concave bottom tanks.

 

[Johnoly]

While not a traditional "scuba tank",,,,most bank bottles are steel and flat bottomed. Some hold 6000psi.
Another reason for round bottoms vs flat bottoms is for weight savings. A round bottom distributes the pressure more evenly than a square flat bottom so less material is needed to achieve the desired strength. That also is why we have curved arches in bridges, similar concept.