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Major Clanger
13-01-2013, 12:45 PM
Can anyone see any issues including the weight of bailout and deco cylinders as part of overall weighting requirement? I get the need to not include removable equipment as part of basic weighting, so, if I don't plan to ever remove the cylinders underwater, is the any reason why they can't become part of my basic weighting? Clearly I'd need to allow for their buoyancy on minimum gas and buoyancy according to gas type eg 50% being more neg than a mix etc.

SoggyBottoms
13-01-2013, 12:48 PM
what about when you need to hand off the cylinders?

GLOC
13-01-2013, 12:50 PM
If you dive the team bailout/support strategy, Charlie's point is valid. Even more important is that if you are handing off that stage, it could be anywhere upto 3kg if you are handing off an AL80 of 50% or 80% (nitrox rather than Trimix).

Regards

Major Clanger
13-01-2013, 01:40 PM
Rtfq ;) The bit where I said if I plan not to hand them off...

Barrygoss
13-01-2013, 01:45 PM
So your bail of 15/50 is all used up and has gone positively buoyant. What do you do? Bag it off... but you can't do that because it started a couple of kg's negative and is part of your weighting......
Stages shouldn't be part of the weighting.
B

nickb
13-01-2013, 01:45 PM
You need to consider the effect of breathing them down. Ali80s are slightly positive once breathed empty, even with a regulator fitted. I've sent on up an SMB line before, which is essentially the same as not having one, so do the maths ;)

[EDIT] Baz got there first!

Major Clanger
13-01-2013, 01:46 PM
So your bail of 15/50 is all used up and has gone positively buoyant. What do you do? Bag it off... but you can't do that because it started a couple of kg's negative and is part of your weighting......
Stages shouldn't be part of the weighting.
B

And if your bail was in a steel cylinder...

nickb
13-01-2013, 01:47 PM
And if your bail was in a steel cylinder...You'd still lose the weight of the gas, which would be the same.

This is basic stuff.

Barrygoss
13-01-2013, 01:49 PM
And if your bail was in a steel cylinder...

What size? What gas? I'll run the maths to find out just what the swing will be :)

Major Clanger
13-01-2013, 01:52 PM
You'd still lose the weight of the gas, which would be the same.

This is basic stuff.

Nick I did acknowledge in the OP allowance for minimum gas in the cylinder.

If I use a steel cylinder for bailout and I've based weighting to include its buoyancy when empty I don't see any reason not to include it which is why I've asked if I missed anything else. Please assume I know the obvious :)

Major Clanger
13-01-2013, 01:55 PM
What size? What gas? I'll run the maths to find out just what the swing will be :)

10 litre with air, though gas type not as critical as buoyancy of empty cylinder. I think that with a 10 litre I can carry about 2kg less lead.

Barrygoss
13-01-2013, 01:59 PM
10 litre with air, though gas type not as critical as buoyancy of empty cylinder.

Ok that's your bail. Now what deco are you going to try to accelerate? Using 50%, 100%? The op said bail and deco...

nickb
13-01-2013, 02:03 PM
Please assume I know the obvious :)I would never assume that mate ;)

Major Clanger
13-01-2013, 02:11 PM
Ok that's your bail. Now what deco are you going to try to accelerate? Using 50%, 100%? The op said bail and deco...

Two or more steels would be quite negative but two 7's for example would be about neg 6 in total full lowering to about neg 3 empty. Steels would be hanging down but if that wasn't a problem to the diver then why not include their empty weight.

Major Clanger
13-01-2013, 02:12 PM
I would never assume that mate ;)

Probably a wise thing to do, I have my moments :)

nickb
13-01-2013, 02:20 PM
There's a reason most people use aluminium cylinders for deco and bailout.

Mark Chase and his pond calculations notwithstanding.

Zero-Viz
13-01-2013, 02:22 PM
so, if I don't plan to ever remove the cylinders underwater.

I would never assume that.

Major Clanger
25-05-2013, 05:52 PM
Came back to this as I can't find anything controversial to say anywhere else. I could have kept this to myself :) I have a confession, I dived two stages, one of which was steel and I liked it...

Never one to go with the flow unless I've tried it and decide for myself, decided to see how a steel stage would handle as bailout with an appropriate gas in it. Two reasons for this, I was thinking of buying another ali 80 but was given a steel 10, plus some comments by Chasey got me thinking...

So today's dive, in a quarry, before a deeper one next week, I had 10/50 as deep bailout in a steel 10 and 50% deco gas in an ali 80 and it balanced out perfectly, one either side. The 10 was clipped tightly and tucked neatly out of the way. So the advantages and disadvantages of using a steel 10 with mix gas for deep bailout over an ali 80...

POSITIVES

On the surface

Smaller, lighter, easier to handle

Underwater[/U]

Slightly more buoyant than the 80, holds more gas (232 vs 200 bar), more forgiving pumped up to higher pressures, becomes more negative as drawn down so less floaty and no problems managing plumbed in bov, no significant affect on trim.

NEGATIVE

It has a boot...



Just another take on the you-have-to-use-ali's-or-be-a-fashion-victim line...

I guess there wouldn't be a huge amount of variation with a less rich mix and something I'll be giving a go when the opportunity arises. For now, if a free steel 10 means avoiding the cost of a new 80 and does the job well enough, then that's alright with me...

Thanks Mark for daring to be different and sharing it.

Fire away ;)

Steve Clark
25-05-2013, 06:22 PM
becomes more negative as drawn down....

That could be really useful. Where do I buy one?

DiverMike
25-05-2013, 07:42 PM
My 232bar 7L Ali cylinders are 1kg negative when fully rigged and empty in salt water (according to my luggage scales). When diving with one bail out cylinder I am weighted to be able to use all my gas but not to ditch the cylinder (which is connected to my OCB).
With 2 stages I subtract 1kg from this.
My steel 10l is slightly more than 1kg negative when empty, but handily in water full is similar to my 7L with 60% in.
My buddy and I plan not to hand off cylinders but if needed can share gas by offering a reg.

Major Clanger
25-05-2013, 09:22 PM
That could be really useful. Where do I buy one?

Good that you appreciate the positives, no idea, mine was free.

Steve Clark
25-05-2013, 10:08 PM
So, is it actually more bouyant than an AL80 with the same gas in it?

(The anti-steel DIR thing comes from the US where the tanks have very thick walls to meet DoT regs for moving them about in vehicles.)

Steve

Major Clanger
25-05-2013, 10:49 PM
So, is it actually more bouyant than an AL80 with the same gas in it?

Steve

No, but i'm referring to CCR deep bailout and matching cylinder/gas characteristics to how you may want it to perform during certain phases of a dive. What it's not, with a mix in, is a behemoth trying to drag you down. Came as a bit of an eye opener, I'd been against them beforehand.

DiverMike
26-05-2013, 08:53 AM
Came back to this as I can't find anything controversial to say anywhere else. I could have kept this to myself :) I have a confession, I dived two stages, one of which was steel and I liked it...




my deep bail out is a 10L steel cylinder. The He in it keeps it from being too negative. I figured I needed more gas than a 232b 7L and Ali 80's are a pig in the water.

Major Clanger
26-05-2013, 09:11 AM
my deep bail out is a 10L steel cylinder. The He in it keeps it from being too negative. I figured I needed more gas than a 232b 7L and Ali 80's are a pig in the water.

Aye. Dive shop very kindly filled my deep 10 to 270 bar unprompted :)