Euro Cylinders, round vs flat bottom? which one should I buy an why?

[happy-diver]

Now it can suck less dude, and the crowd cheered, and the crowd roared

 

[Wibble]

• Round bottom are steel, flat ones ar Aluminum.

Something doesn't add up

Wrong.

Flat bottom Euros are superb steel twinset tanks. They stand up too.

The steel cylinders with the flat bottom have an incredibly heavy and thick base. ECS cylinders already have a much thicker base than say Faber for example. If that is of an advantage for you I can't judge, this will depend on your personal trim needs.

I'm not a big fan of ECS, once they get wet inside, the base starts to flake, rather than develop pits. It's a pain to clean up.

They’re not much more heavy and they save on you needing a tail weight

Flat bottom twinsets are much better than round bottom ones.

• They stand up and are stable, vital in a garage to save space
• Much easier to use on a boat as they stand up and only need to be tied on the top (unless it’s incredibly rough)
• The weight is in the right place, saves on having a tail weight
• They don’t have cylinder boots so don’t rot
• They’re surprisingly resistant to rusting on the bottom

Some pics…

Shiny new…

Five years later compared with round

Quiet life as a bank of gas…

 

[Alex Ouroboros]

Yeah my spelling sucks

Wouldn’t apologise, this is neither an English exam or a writing test.

 

[Tanks A Lot]

We should really call them concave (flat bottom) or convex (round bottom) cylinders.

[...]They’re not much more heavy[...]

My comment was more aimed at ECS in general, not all concave cylinders. Seeing as ECS is one of the main suppliers of concave cylinders, is why I went to compare the two. ECS round cylinders tend to be slightly heavier, around 1 Kg overall than a comparable Faber or Vitkovizce cylinder. Unfortunately, or fortunately as in your case, a lot of the weight is in the base of that cylinder.
Take a 12L 232 bar ECS cylinder: It will have a base thickness of 16mm, while a Faber with the same characteristics gets away with around 4.6mm.

Faber has only one concave cylinder for the SCUBA market which is this one:

Water Capacity (L)	Estimated US Designation	Diameter (mm)	Length (mm)	Working Pressure (Bar)	Empty Weight (Kg)	Empty Buoyancy Seawater (Kg)	Full Buoyancy Seawater (Kg)	Real Weight Seawater (Kg)	Empty Buoyancy Freshwater (Kg)	Full Buoyancy Freshwater (Kg)	Real Weight Freshwater (Kg)
12.0		171	660	232	14.5	-0.24	-3.47	14.26	-0.65	-3.88	13.85

ECS is rather coy with their cylinder data but from experience I know that their concave cylinders have just as thick of a base as their convex cousins and are also slightly heavier than a Faber.

One thing you nicely point out is the lack of a cylinder boot, which I see as a huge plus for concave cylinders as well. The downside of a concave base is water will pool in a ring at the bottom, rather than a puddle. This always ends up as line corrosion, for which the failure criteria are much stricter than pits for example. ECS combats this with it's already thicker base, plus flaky behavior of rust that develops. While I love the lack of a cylinder boot, rough handling or scraping along, show much faster than with a boot. Some people love the extra base weight on a ECS, concave or convex, others hate it.

As to their resistance to outside corrosion, from my experience ECS cylinders are far superior to Faber cylinders in this regard. The one area where ECS does worse is with a cylinder boot in place. A non-issue with concave cylinders!

There is no clear better or worse in my eyes, it really depends on your personal needs and usage scenario. Both can be great and have advantages over the other design in certain situations.

 

[Wibble]

One thing you nicely point out is the lack of a cylinder boot, which I see as a huge plus for concave cylinders as well.

The downside of a concave base is water will pool in a ring at the bottom, rather than a puddle. This always ends up as line corrosion, for which the failure criteria are much stricter than pits for example.

Just from personal experience with three of those twinsets over many years (and sidemount, stages, etc.); this isn't the case. Whilst the water will pool at the bottom, you store them in a cool dry place -- garage -- which doesn't have pools of water. In reality, the cylinders are dry by the time you've got home.

I never rinse cylinders. Just never seen the point of it. I'm also never fussy about scraping the bottom if it was put down or dragged a bit; just part of the normal life of a cylinder.

Rust forms when there's plenty of moisture/humidity. The myriad chips and gouges are normal and don't turn into rusty blobs.

Cylinder boots on the other hand...

 

[Tanks A Lot]

Just from personal experience with three of those twinsets over many years (and sidemount, stages, etc.); this isn't the case. Whilst the water will pool at the bottom, you store them in a cool dry place -- garage -- which doesn't have pools of water. In reality, the cylinders are dry by the time you've got home.

Apologies, I should have clarified that I was talking about inside pooling of water from wet fills, not outside. I have not worded this great, my bad!

 

[tridacna]

Wouldn’t apologise, this is neither an English exam or a writing test.

NOR a writing test.

SB Grammando Squad.

 

[grantmac]

If we could get flats here I'd dive them in a heartbeat

 

[Gone for diving]

If we could get flats here

We can but they are awful big tanks.
Flat bottom is not technically right.

All industrial weld cylinders are like this.