Double short hose regulator configuration (for non-wreck / non-cave environments)

[DevonDiver]

For me, it's no hassle to just use a long hose on every dive... and the effort of swapping out the hose between one day and another isn't worth any benefit a short hose would give.

If I were going to use a short hose, I'd have to measure an optimal length. I'd want it configured as per a long hose... but without the extra stowed in bungees. It'd have to be as snug and 'torso clinging' as I could otherwise achieve with a long hose.

 

[Remy B.]

@Remy B.

What @Patoux01 said is correct as well. If you are diving in a drysuit, the gas in the wing should only be the gas content of bottles. It's going to be big regardless of if you have 6x al80's, or 2x19l/lp121's and 2x 80's. If you are weighted properly, it is the same amount of gas.

How to calculate buoyancy of a scuba cylinder (metric)

Material: Steel
Capacity: 11 litres
Working pressure: 200bar
Weight: 15 kg
Diving in: Fresh Water
Using Archimedes principle, buoyancy is equal to the weight of the displaced water minus the weight of the cylinder.

The cylinder is made of 15 kg of steel, (which has a density of 7.8 kg/litre).
The steel therefore has a volume of 15 / 7.8 = 1.92 litres, so the total volume is 11 + 1.92 = 12.92 litres.
The density of fresh water is 1 kg/litre, giving 12.92 x 1 = 12.92 kg

Air has a density of 0.0012 kg/litre.
The air in a full cylinder weighs 0.0012 x 200 bar x 11 litres = 2.64 kg.

The cylinder when empty has a buoyancy of 12.92 kg - 15 kg = -2.07 kg
The cylinder when full has a buoyancy of 12.92 kg - 15 kg - 2.64 kg = -4.71 kg


NB - these figures exclude valves, manifolds, regulators, etc..

Material: Aluminium
Capacity: 11 litres
Working pressure: 200bar
Weight: 13 kg
Diving in: Fresh Water

Using Archimedes principle, buoyancy is equal to the weight of the displaced water minus the weight of the cylinder.

The cylinder is made of 13 kg of aluminium, (which has a density of 2.7 kg/litre).
The aluminium therefore has a volume of 13 / 2.7 = 4.81 litres, so the total volume is 11 + 4.81 = 15.81 litres.
The density of fresh water is 1 kg/litre, giving 15.81 x 1 = 15.81 kg

Air has a density of 0.0012 kg/litre.
The air in a full cylinder weighs 0.0012 x 200 bar x 11 litres = 2.64 kg.

The cylinder when empty has a buoyancy of 15.81 kg - 13 kg = 2.81 kg
The cylinder when full has a buoyancy of 15.81 kg - 13 kg - 2.64 kg = 0.17 kg

NB - these figures exclude valves, manifolds, regulators, etc..


________________________________________________________________________________________________

Lets take a example of 4 AL-11L vs 4 Steel 11L both at 200bar, assuming you need 8kg to be neutral yourself with your dry-suit and thermal protection

4 AL, assuming worse scenario of emptying completely = 4 x +2.81 requires 11.3kg to be neutral

4 Steel. assuming the same scenario, = 4 x - 2.07 requires only "cero" kilos but still will be 0.28kg negative

but at the beginning of the dive with tanks full

4 AL will = 4 x +0.17kg = +0.68kg -11.3 = -10,6 Kg

4 Steel will = 4 x -4.7kg = -18.8kg + -0.28 = -19.08Kg

I took the weight from AL and Steel manufactures.

I don't buy this reasoning from both of you, your wing or dry-suit will look like a balloon at the beginning of the dive if using steel tanks, because you have to compensate for that extra weight of the tank material as well not only the gas content.

You are new to proper weighting and what it involves, right? The amount of air in a wing is not a matter of what the tanks are made of. It's a matter of their content.

What Patoux01 said is correct as well. If you are diving in a drysuit, the gas in the wing should only be the gas content of bottles. It's going to be big regardless of if you have 6x al80's, or 2x19l/lp121's and 2x 80's. If you are weighted properly, it is the same amount of gas.

If I understand incorrectly, please correct me.

Source
https://www.subaqua.co.uk/cylinder-...l=steel&volume=&pressure=&weight=&water=fresh

 

[Remy B.]

For me, it's no hassle to just use a long hose on every dive... and the effort of swapping out the hose between one day and another isn't worth any benefit a short hose would give.

If I were going to use a short hose, I'd have to measure an optimal length. I'd want it configured as per a long hose... but without the extra stowed in bungees. It'd have to be as snug and 'torso clinging' as I could otherwise achieve with a long hose.

I agree with you, but your missing the point, the OP seems to have a goal of minimalistic for traveling.

 

[tbone1004]

@Remy B.

I am anything but new to proper weighting. The difference is the ability to properly weight yourself using different tanks and the practicality of doing so. Diving aluminum tanks at depth, especially in a cave is not practical, possible, or safe in many caves in the US. That is why Toddy Style sidemount diving does not exist in the US, that is why the Razor and xDeep units are almost nonexistent in the US, and that is why we have developed rigs with a LOT of lift in them so we can safely dive these caves. Passing bottles off in restrictions is also not possible, so you have to dive long hoses if you want the ability to share air with your buddy if that is part of your plan.

These things are great in theory, but the practicality falls a bit short...

 

[Patoux01]

If I understand incorrectly, please correct me.

Please don't go all Kev on us throwing needless maths around.

The point is, if you dive negative tanks, you take lead off the diver. If you dive positive tanks, you add lead to the diver.

I'll have to add some "maths".
Assume you're 12kg buoyant, you and your gear, without tanks.
Add 2*12l steel that are 3kg negative each when empty, you now need 6kg of lead to be properly weighted. Your bcd will be inflated at most by 2*12*1.3*230 (assuming 230 bar tanks).
If you do that with S80s, that would get 1kg positive (i don't remember the exact number nor does it matter for the sake of demonstration), you now need 14kg of lead to be properly weighted. your bcd will be inflated at most by 2*11.1*1.3*207 (207b, 11.1l)


Obviously, if you take 14kg of lead because you're used to diving aluminium, and then you switch to steel without changing your weighting, you're gonna be massively overweighted (8kg in the example)

(and I do believe he's kind of a decent sidemount diver)

 

[Remy B.]

Please don't go all Kev on us throwing needless maths around.

The point is, if you dive negative tanks, you take lead off the diver. If you dive positive tanks, you add lead to the diver.

I'll have to add some "maths".
Assume you're 12kg buoyant, you and your gear, without tanks.
Add 2*12l steel that are 3kg negative each when empty, you now need 6kg of lead to be properly weighted. Your bcd will be inflated at most by 2*12*1.3*230 (assuming 230 bar tanks).
If you do that with S80s, that would get 1kg positive (i don't remember the exact number nor does it matter for the sake of demonstration), you now need 14kg of lead to be properly weighted. your bcd will be inflated at most by 2*11.1*1.3*207 (207b, 11.1l)


Obviously, if you take 14kg of lead because you're used to diving aluminium, and then you switch to steel without changing your weighting, you're gonna be massively overweighted (8kg in the example)

(and I do believe he's kind of a decent sidemount diver)

I guess you read as good as you know maths.

 

[Patoux01]

Well, I give up.

 

[Remy B.]

@Remy B.

I am anything but new to proper weighting. The difference is the ability to properly weight yourself using different tanks and the practicality of doing so. Diving aluminum tanks at depth, especially in a cave is not practical, possible, or safe in many caves in the US. That is why Toddy Style sidemount diving does not exist in the US, that is why the Razor and xDeep units are almost nonexistent in the US, and that is why we have developed rigs with a LOT of lift in them so we can safely dive these caves. Passing bottles off in restrictions is also not possible, so you have to dive long hoses if you want the ability to share air with your buddy if that is part of your plan.

These things are great in theory, but the practicality falls a bit short...

I don't dive caves, so I don't know, and if I had to choose high volume tanks I will go for Steel Carbons.

And I guess we got derailed of the OP, because I mention un-clipping one tank, not about how much can a sidemount system lift, I dive with dry-suit I don't use the bladder in my sidemount harness.

If i get to do big dives, then I will opt for double backs in the rest on the sides, like you mention it will become a problem of lift capacity, and for lift wings are kings, but I don't think I will get so far in diving for the moment.

 

[tbone1004]

I don't dive caves, so I don't know, and if I had to choose high volume tanks I will go for Steel Carbons.

And I guess we got derailed of the OP, because I mention un-clipping one tank, not about how much can a sidemount system lift, I dive with dry-suit I don't use the bladder in my sidemount harness.

If i get to do big dives, then I will opt for double backs in the rest on the sides, like you mention it will become a problem of lift capacity, and for lift wings are kings, but I don't think I will get so far in diving for the moment.

carbon tanks don't exist in the US.

If you dive without using the bladder, you are not diving your drysuit correctly or safely. Your drysuit is for exposure protection, not lift. Look up the temperature studies that have been done. By diving with your drysuit for lift, you are staying warmer on the beginning of the dive and gradually losing warmth. By gradually losing warmth, you are also increasing your risk of DCS. Not really significant in a single AL80 because you don't actually need any lift to dive with that tank, but with pairs of tanks or with high volume tanks, the risk is very real.

That said, your comment is why people over there can successfully dive the Razor in cold water, and we can't in the US. We don't wear that much in terms of undergarments, so the lift has to be put into the wing.

 

[Remy B.]

I believe Luxfer sell a Steel Carbon tank in the US up to 300bar, I don't know what a the DOT regulations are on using Medical cylinders as Scuba cylinders.

L7X® carbon composite medical cylinders

They don't advocate to use the Luxfer Type 3 for diving.

Underwater use of Luxfer full-wrap Type 3 carbon composite cylinders

I don't know how for how long people had been diving the Steel Carbons here in EU, I have not hear about issues yet, don't know why in the US they don't want to go that way.

I was taught to dive on my dry-suit, I don't see a problems with that, at least I don't feel cold, I have some how resistance to cold more than others and sweat like a pig in the oven with little ambient heat, I can't do saunas that is for sure, I can't cope with that amount of heat, my issues are my hands and feet. I have dived with a lot of buddies, and always are the show stoppers because they feel cold.

I have done some testing on my self at 10*C for 2 hours diving and not have problems with cold, my buddy didn't do so well, I want to try at 8*C see how I do with my hands and feet, I don't have core temp problems, I know the outcome will be go from 5mm to 7mm gloves.


What are the cave water temperatures there were you dive ?