Aliminium tanks in the UK

Mal Bridgeman · July 12th, 2006, 04:31 PM

Why do UK divers tend not to use Ali tanks?

I am interested particularly in responses related to twins / doubles.

An S100 would hold roughly the same gas as a 12l steel I think so why aren't they used?

TIA
Mal

**GLOC** · July 12th, 2006, 04:43 PM

My immediate thought is that you still need to have the weight to counter the additional bouyancy of a drysuit and liner. You need the weight somewhere so may as well be on the cylinders, or you are going to have to wear it on a belt.

Unless of course you are Rob who only needs 2kg in salt to get down.

wilbo · July 12th, 2006, 05:34 PM

Mal,

is it not something to do with the buoyancy characteristics of Ali - and opposed to steel?

using: http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi
and a steel and ali cylinder of the same capacity (12l) to the same pressure (200bar) weighing the same amount (13.1kg) there is a difference in positive buoyancy/negative buoyancy (depends how you look at it) when empty of 3.3 kgs per cylinder (metalware ignored)..!

Edit 1: though saying that - the difference between full and empty in both cases is not that different - just the difference in gas, plus the difference in the bouyant force of the material..

so dunno!

I'll get my coat..

Edit 2: the buoyant force of the alis mean you will need to take lots of lead with you when you start the dive..

***Bob Cooper*** · July 12th, 2006, 08:31 PM

Quote: (Originally Posted by Mal Bridgeman)

Why do UK divers tend not to use Ali tanks?

I am interested particularly in responses related to twins / doubles.

An S100 would hold roughly the same gas as a 12l steel I think so why aren't they used?

TIA
Mal

They haven't been readily available in UK until recently. Also, because we dive cold water, we need extra insulation and therefore the buoyancy of that insulation needs to be offset by some negative buoyancy. This negative buoyancy is in the tanks. Also, they are only 11L (approx) so twin Faber 12's are often chosen as the best comprimise.

HTH

Divingniknaks · July 12th, 2006, 08:40 PM

Interesting point that, the brushed Ali 80's (see other ******* thread

) come in at over 14Kg dry, so not that diff to my Heisers.

Of course team gas plans go to hell in a handbasket, 11.2 ltrs instead of 12ltrs. A conversation the "Porridge Gobbler" and I had this very morning.

Ali tanks tend to not last as long as steel ? Neck weaknesses, crack tests etc. Discuss ...........

What about possible steel to Ali corrosion (bands), can't think of the correct term.

But they would look very cool, Rule 6 and all.

Or am I missing a vital point and talking out of my Hariss as usual ?

Maybe I'll join Wilbo under the rock ?

Mal Bridgeman · July 12th, 2006, 08:46 PM

Tanks (sic) guys

so total gas and buoyancy are the issues. I worked out roughly that an S100 at 207 bar would equate to a 12l at 232 bar hence the specific question about S100s.

The buoyancy is a good point though .... I don't carry too much weight so perhaps when I am feeling flush I'll get Phill to put a set together for me to try. I have dived them abroad and they were a delight.... albeit twin S080s.

Rgrds
Mal

***Bob Cooper*** · July 12th, 2006, 08:53 PM

Twin 80's are a delight to dive, in warm (ish) water.

We used them in Mexico with a 200g undersuit and I only had like 2 small v-weights to balance them (approx 2kg).

Also, I forgot to mention that they are only good for 200bar and overpumping them does them no good. They will fail a test on the neck threads with that sort of treatment.

Rick · July 12th, 2006, 09:01 PM

I dived twin 80's in GC and they are a joy to dive, with little added weight req'd(4lbs) to trim them!

As I said to Phil this morning...they may look the dogs nadgers, but unless your team are diving them, then it's a pointless task.

Bob also raised a valid point regarding the fill pressure, which is more than a bit below 232 (unless you get your fills from Stoney), so there not really a viable choice over here.

Phil....the words your looking for are "dissimilar metal corrosion" you auld git!

***Bob Cooper*** · July 12th, 2006, 09:07 PM

They make great stage/deco bottles though!

I'll probably be getting a couple from Mr Knackers to replace my old DOT ones.

Divingniknaks · July 12th, 2006, 09:31 PM

Ah, warms the cockles of me wallet Mr Cooper that does.

Any views on the Ali / steel corrosion thing ?

.

July 12th, 2006, 04:31 PM	#1 (permalink)
Mal Bridgeman(Offline) New Member Join Date: Nov 2005 Location: Suffolk, UK Posts: 703	Why do UK divers tend not to use Ali tanks? I am interested particularly in responses related to twins / doubles. An S100 would hold roughly the same gas as a 12l steel I think so why aren't they used? TIA Mal __________________ Opinions and beliefs are correct at the time of posting but are subject to change without any notice or obligation on the part of the author.

July 12th, 2006, 04:43 PM	#2 (permalink)
GLOC(Offline) Moderator Join Date: Nov 2005 Location: Fleet, Hants Posts: 2,692	My immediate thought is that you still need to have the weight to counter the additional bouyancy of a drysuit and liner. You need the weight somewhere so may as well be on the cylinders, or you are going to have to wear it on a belt. Unless of course you are Rob who only needs 2kg in salt to get down. __________________ Gareth Images of Life Photography DIR Team Foxturd Travels Underwater and Further Afar “Set your expectations high; find men and women whose integrity and values you respect; get their agreement on a course of action; and give them your ultimate trust.” “It is far better to be trusted and respected that it is to be liked.”

July 12th, 2006, 05:34 PM	#3 (permalink)
wilbo(Offline) Senior Chimp Join Date: Nov 2005 Location: UK Posts: 1,504	Mal, is it not something to do with the buoyancy characteristics of Ali - and opposed to steel? using: http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi and a steel and ali cylinder of the same capacity (12l) to the same pressure (200bar) weighing the same amount (13.1kg) there is a difference in positive buoyancy/negative buoyancy (depends how you look at it) when empty of 3.3 kgs per cylinder (metalware ignored)..! Edit 1: though saying that - the difference between full and empty in both cases is not that different - just the difference in gas, plus the difference in the bouyant force of the material.. so dunno! I'll get my coat.. Edit 2: the buoyant force of the alis mean you will need to take lots of lead with you when you start the dive.. __________________ Cheers! Wilbo DIR explorers: DIR Yorkshire Divers: YorkshireDivers One of the Foxturd chimps Last edited by wilbo; July 12th, 2006 at 05:40 PM..

July 12th, 2006, 08:40 PM	#5 (permalink)
Divingniknaks(Offline) Resident purveyor of shiney kit.... Join Date: Nov 2005 Location: Midlands UK Posts: 1,040	Interesting point that, the brushed Ali 80's (see other ******* thread ) come in at over 14Kg dry, so not that diff to my Heisers. Of course team gas plans go to hell in a handbasket, 11.2 ltrs instead of 12ltrs. A conversation the "Porridge Gobbler" and I had this very morning. Ali tanks tend to not last as long as steel ? Neck weaknesses, crack tests etc. Discuss ........... What about possible steel to Ali corrosion (bands), can't think of the correct term. But they would look very cool, Rule 6 and all. Or am I missing a vital point and talking out of my Hariss as usual ? Maybe I'll join Wilbo under the rock ? __________________ Phill ----------------------------- Salvo Lights, DirZone Gear , Frog Wings Dive ? http://www.divingniknaks.com

July 12th, 2006, 08:46 PM	#6 (permalink)
Mal Bridgeman(Offline) New Member Join Date: Nov 2005 Location: Suffolk, UK Posts: 703	Tanks (sic) guys so total gas and buoyancy are the issues. I worked out roughly that an S100 at 207 bar would equate to a 12l at 232 bar hence the specific question about S100s. The buoyancy is a good point though .... I don't carry too much weight so perhaps when I am feeling flush I'll get Phill to put a set together for me to try. I have dived them abroad and they were a delight.... albeit twin S080s. Rgrds Mal __________________ Opinions and beliefs are correct at the time of posting but are subject to change without any notice or obligation on the part of the author.

July 12th, 2006, 08:31 PM	#4 (permalink)
*Bob Cooper*(Offline) Moderator - "Don't stop me now!" Join Date: Nov 2005 Location: South East London, UK Posts: 793	Quote: (Originally Posted by Mal Bridgeman) Why do UK divers tend not to use Ali tanks? I am interested particularly in responses related to twins / doubles. An S100 would hold roughly the same gas as a 12l steel I think so why aren't they used? TIA Mal They haven't been readily available in UK until recently. Also, because we dive cold water, we need extra insulation and therefore the buoyancy of that insulation needs to be offset by some negative buoyancy. This negative buoyancy is in the tanks. Also, they are only 11L (approx) so twin Faber 12's are often chosen as the best comprimise. HTH

July 12th, 2006, 08:53 PM	#7 (permalink)
*Bob Cooper*(Offline) Moderator - "Don't stop me now!" Join Date: Nov 2005 Location: South East London, UK Posts: 793	Twin 80's are a delight to dive, in warm (ish) water. We used them in Mexico with a 200g undersuit and I only had like 2 small v-weights to balance them (approx 2kg). Also, I forgot to mention that they are only good for 200bar and overpumping them does them no good. They will fail a test on the neck threads with that sort of treatment.

July 12th, 2006, 09:01 PM	#8 (permalink)
Rick(Offline) Jock Exley Join Date: Nov 2005 Location: Falkirk/Stratford UK Posts: 730	I dived twin 80's in GC and they are a joy to dive, with little added weight req'd(4lbs) to trim them! As I said to Phil this morning...they may look the dogs nadgers, but unless your team are diving them, then it's a pointless task. Bob also raised a valid point regarding the fill pressure, which is more than a bit below 232 (unless you get your fills from Stoney), so there not really a viable choice over here. Phil....the words your looking for are "dissimilar metal corrosion" you auld git! __________________ Forget Everything And Remember http://phreaticzone.thedeepstop.com/ http://www.dublinbaydiving.com/

July 12th, 2006, 09:07 PM	#9 (permalink)
*Bob Cooper*(Offline) Moderator - "Don't stop me now!" Join Date: Nov 2005 Location: South East London, UK Posts: 793	They make great stage/deco bottles though! I'll probably be getting a couple from Mr Knackers to replace my old DOT ones.

July 12th, 2006, 09:31 PM	#10 (permalink)
Divingniknaks(Offline) Resident purveyor of shiney kit.... Join Date: Nov 2005 Location: Midlands UK Posts: 1,040	Ah, warms the cockles of me wallet Mr Cooper that does. Any views on the Ali / steel corrosion thing ? . __________________ Phill ----------------------------- Salvo Lights, DirZone Gear , Frog Wings Dive ? http://www.divingniknaks.com