Stage Cylinder

[Bob Cooper]

OK, I've found they tend to go neutral at about 130bar in sea water.

[wrecksmasher]

There seems to be a fair amount of mixing american and metric sizes here.
When folk talk about 80's here exactly what UK spec cylinder are the meaning?

[Tricky]

I think the 80s mentioned are CE stamped AL80 cylinders. These are approximately equivalent to 11 (and a bit) litres.

[wrecksmasher]

But are these Luxfer 11.1's or a different type altogether? I have never found anything from a UK based supplier that sells AL80's unless someone knows different?

[Tricky]

I believe so.

[Mark Chase]

Originally Posted by Andy Kerslake

Simon

For stage bottles wherever possible we use Aluminum because of the buoyancy characteristics. They typically swing from being negative at the start of the dive to positive when empty, whereas most steel stage bottle would stay negative.

As for which stage bottles to use we (GUE) normally use either 80's, for wreck and cave diving, Ali 7's, or Ali 40's.

However the newer Ali 7's from Luxfer are heavier than the older style 7's and so their buoyancy is not as good.

For Tech 1 type dives I would use either a 7 or an Ali 80, which would be used as a 21m bottle, later if required you could also use an Ali 80 as a bottom gas stage.

I personally use Ali 7's, 80's , 40's depending on the requirements of the dive.

The ali steel argument comes from America where the rules for steel tanks are different and as a result our 235bar fabor light weights are classed as low pressure tanks. As a result the steel tanks the yanks use are massively heavy and negative, like Heiser's. I dived twin 10 Heiser's in Malta and was able to shed 4kg from my weight belt.

Faber light weight steel 7s float arse up at 100 bar and are neutral empty. With A reg on my 7 and it down to 30bar it will hang upside down on the surface in salt water.

My 10 ltr steels float on the surface with 50 bar in an a reg on them.

Apex DS4.


If you planning on being DIR get Ali tanks. Its what they use end of story.

If not then id go for Ali 40s which are really nice and steel dumpy 10s which are infinitely easer to manage than the massive and unwieldy Al80's.
I was told an ali 80 was lovely in the water but when Janous handed off his Ali 80 to me in Vobster I sank like a stone and he went up so I was not impressed at all.

I did a side by side comparison between an ali 80 and a 10ltr steel and the in water difference was 1kg extra for a 235 bar filled steel.

A saving of 1Kg is not worth the hassle of those massive tanks.

If your planning on pushing the duration of a stage cylinder get steels as over blowing alis is not a good plan and they only hold 200bar.

I have dived steel 2 X 7s and possably a 3 and as many as three 10ltrs and frankly if your kit is well balanced then once in the water it makes not much difference at all what your using.

DIR divers have the disadvantage of having all tanks on one side. This means any negative weight is doubled / trebled all on one side of the diver. For this reason they often blow down the tanks to 160 bar to make them floaty / neutral in the water and easier to use.

I find that most dives i do with 7's I could get away with Al40's and the ones where the 7's are needed would be better with the 10's anyway.

A 10 with 160bar in it is as much use to me a a chocolate flipper. When I decide I need 10's I will be needing a damed site more gas than 160 bar.

My 10s are almost always blown to 250

However as I said if you plan on being DIR then get Alis. DIR divers dont do the bottom times in open water to worry about more than 160 bar fills in Ali 80s and if they did they would probably stage the gas somewhere so they didnt have to carry it.

ATB

Mark Chase

[neilh]

Originally Posted by wrecksmasher

I have never found anything from a UK based supplier that sells AL80's unless someone knows different?

Knackers would be distressed
divingniknaks : Luxfer Aluminium cyl. S080 CE white (80cf), Stage / bailout Cylinders

[peterdevlin]

Originally Posted by SoB

All,

So, questions I'm not certain about are Steel or Ali, 5 or 7 if steel or 80 if ali?

Simon,

I'd go for Ali ... abit buoyant when empty, but much easier to manage buoyancy changes (when you take the bottle off) than steel.

Ciao,
Peter

[wrecksmasher]

There seems to be some difference of opinion on just how good alloys are and what the advantages are, or not.
I was considering changing to alloy from steel but on reading this lot reckon it would be a bad move.
With steel cylinders I dive neutrally bouyant and am a bit heavy at the beginning of a dive. As I empty the tanks I return to neutral. If I have to dump stages I am still weighted correctly if I dump them at any stage of a dive. By the time I am at shallow stops I can take them off without adjusting my bouyancy much or at all.
With alloys I will need to add weight and will be heavy if I need to dump stages at any stage of the dive, will still be as heavy at the beginning of the dive as when diving steels so if I dump them I am plummeting to the bottom.
I can't pump alloys as high as steels, afaik can't get them tested within 100miles of my home, they are heavier out the water and and afaik don't last as long......Wheres exactly is the advantage of alloy?
Surely there has to be a reason for folk using them even if I can't see it? Any thoughts?

[bob wippin]

Originally Posted by wrecksmasher

There seems to be some difference of opinion on just how good alloys are and what the advantages are, or not.
I was considering changing to alloy from steel but on reading this lot reckon it would be a bad move.
With steel cylinders I dive neutrally bouyant and am a bit heavy at the beginning of a dive. As I empty the tanks I return to neutral. If I have to dump stages I am still weighted correctly if I dump them at any stage of a dive. By the time I am at shallow stops I can take them off without adjusting my bouyancy much or at all.
With alloys I will need to add weight and will be heavy if I need to dump stages at any stage of the dive, will still be as heavy at the beginning of the dive as when diving steels so if I dump them I am plummeting to the bottom.
I can't pump alloys as high as steels, afaik can't get them tested within 100miles of my home, they are heavier out the water and and afaik don't last as long......Wheres exactly is the advantage of alloy?

Do you mean ally when you say alloy. Steel is an alloy as well!

The advantage of an alloy is that is what you mean is it is more chemically resistant, won't react as quickly with the gas in the tanks, and won't react as quickly with the surtrounding sea water.