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[Pierre Farrugia]

Hello WT,
I don't agree with you on "lift bag or DSMB for redundancy if you are diving wet" but then you say "I couldn't imagine being able to control my buoyancy at depth with twins, stages etc just using my drysuit" As most of my diving is done on a wet suit, I feel more confortable using a twin inflator wing, I don't want to be at 50m or more with twin 12's and stages and have to use a lift bag to go to surface, in that case I would prefer a drysuit for boyancy.
As always at the end is diver preference, and as long as you are happy and safe no problem. :drown:

[Davey Willo]

Pierre

As you dive with a wetsuit are all of your cylinders aluminium? From what I've been reading it's common practise to dive steels with a drysuit but only aluminium with a wetsuit, the reasoning being that the rig can then be swam to the surface.. How feasible that is I do not know but it made me wonder exactly which type of cylinders you used when diving wet.

[And]

Hi

I agree Pierre, whatever you feel more comfortable with. The problem with a dual bladder is that if one inflator should malfunction then it may take some time to identify the real one.

As Dave rightly pointed out, diving wet with doubles should be done with aluminium tanks, as they can be swam up.

HTH

WL

[Pierre Farrugia]

I use steel, first of all it's impossible financially for me to have a twinset for wetsuit and an other for drysuit. Also here in Malta no one uses ali cylinders. Also I hate aluminium cylinders, with steel you can shed some lead. Also does it make difference with which cylinders you dive?,as boyance with min (eg50bar) gas in cylinders at 6m will have same boyancy. On the other hand if you don't use any lead and end dive negative is an other matter. I don't think is an option to remove weight weight at depth and then would be impossible to mantain deco depth. What are your views about this?

[Mark Chase]

Totaly agree I dont want to remove weight at depth and would atempt any and all meens of avoiding this. With my rig the removal of lead is not an option so it would meen ditching tourch canister to gain 2kg and then its only stages and you dont want to be dumping them now do you?  

My SMB is a auto gas fill job and you can winch your self up on it. I know I have tryed. Not in anger I should point out just as practice.

Curiously I was diving with Andrew at Stony on Wed and I did shut downs and stage removal. My 7ltr Faber (OMS) steel with 100 bar 85% 02in it was perfictly neutrol I took it off and held it by the top bolt snap and it floated tail in the air at 45 deg. Strange coz I expected it to still be negitive with 100 bar in it.

All good fun

Mark Chase

[Andy Phillips]

Yeh Mark,

I noticed that, I was wondering, what do you think caused that, I know the valve adds a bit of weight, but surely not that much, why would it float tail up. As you were doing it I thought that maybe the compressed gas moved to one end. Closely followed by the thought, "don't be stupid, it's a gas, not liquid". Please someone, tell me why it would float tail up.

Andrew

[rasilon]

Some speculation:

Faber claim that their 7l 232bar British cylinders weigh 7.6kg, plus approximatly 700g for the gas.  The cylinder external volume is about 7.97l (7l WC, plus 0.97l for the steel).  Adding up, this gives the cylinder 300g plus valve heavy and if it was hanging by the bolt-snap then it was a little negative.

Now, the cylinder is almost symetrical and almost neutral, so any weight imbalance will throw it off, in this case, the neck and valve.  The tail end of the cylinder didn't have these weights and was slightly positive, but the top was slightly negative, so the tail went up and the neck down but the whole lot was slightly negative overall so there wasn't enough buoyancy in the tail to lift it vertical.

[Mark Chase]

Wow as speculation goes thats prety informed M8

Ok I was holding the kneck bolt snap so it didnt float away and the tank was floating above the bolt snap at 45 deg. So I think the tank was apx neutrol or slightly boyent which I would expect at empty but I was surprised to see it like that with 100 bar of 85% 02 in.

ATB

Mark Chase

[rasilon]

It's speculation because I'm a novice diver, the closest I've been to a stage cylinder is pictures on the web so I may be missing something.  If I sound well informed, it's because physics works the same underwater as it does on land, and Faber publish all their specs on the web.

Theoretically, it shouldn't have been buoyant with that much gas in it, but I'm assuming that it matches the current spec as listed (7l, BS5045-7:2000, 232 bar, 7.6kg).  If it were a european cylinder (EN 1964-1:1999, 200bar, 7.3kg) then it would be closer to neutral (or buoyant).  If it is as listed, then I've missed something somewhere.

[angleseydiver]

Pierre,
Have you considered the option of ditching weight on end of reel and winding away from it until you can use it again?
I don't know if it would work in practice but theoretically I can't see a problem with it apart from it snagging in  tide.  I've never tried it but if the sh*t hit the fan I think I'd have a go!
all the best,
               Terry