What's your setup in single tank?
Mostly, as in what do you do for an octo?
As mentioned, short hose as necklaced back up, long hose primary, Spg on 6", LP inflator and drysuit whip. Longhose is tucked into tank with bands and still donate able.
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What's your setup in single tank?
Mostly, as in what do you do for an octo?
That's 50% more complicated than it needs to be.
Begin with similar volumes/pressures in each cylinder (we will say you have 2 AL 80s at 3000 psi starting pressure).
Breathe one third of starting volume in cylinder A (1000 psi, so you now have A=2000, and B=3000)
Switch regs
Breathe one third of starting volume in cylinder B (1000 psi, so you now have A=2000 and B=2000 psi)
Turn the dive
Continue breathing another third off Cylinder B (another 1000 psi, so now you have A=2000 and B=1000)
Switch regs
Breathe a second third out of tank A to the end of the dive, (1000 psi, so you now have A=1000 and B=1000 as a reserve at the end of the dive).
That's just 2 reg switches and it ensures that:
1) At the point of maximum penetration or distance where you turn the dive, the volume in each tank is equal to the total volume you used from both tanks to get there.
2) you never have a differential between tanks of more than 1000 psi, so lateral trim is not a significant issue,
3) you have ample reserve at the end of the dive, and
4) allows you to adjust the reserve up or down with only 2 reg switches and only 2 pressure numbers to remember.
If a 1000 psi per side is too much ( 50 cu ft in this case) in a purely recreational setting, you could reduce it by using larger "thirds" and switching accordingly. 1200 psi would give you "thirds" would leave you with pressure of 1) 1800, 3000, 2) 1800, 600, and 3) 600, 600, for a 600 per side reserve with a 30 cu ft total reserve with 15 cu ft in each tank.
On the other hand in a technical diving situation if a 50 cu ft (1/3rd) reserve is too small, you can reduce the "thirds" you use. In this case if you used 800 psi "thirds" you'd get switch pressures of 1) 2200, 3000, 2) 2200, 1400, and 3) 1400, 1400, leaving a 72 cu ft reserve. So you have the flexibility of tailoring the reserve requirements to the specific dive.
Where I may choose to use 750 psi thirds (A=2250, B=3000), (A=2250, B=1500) and (A=1500, B=1500) like doppler's example, in a recreational setting, would be when diving side mount with AL 80s on a two tank/two dive recreational boat trip. If I do this on the first dive, I use 77 cu ft - a full AL 80's worth of gas, but with an enormous 50% reserve for the first dive. On the second dive, I'll switch to 500 psi thirds - (A=1000, B=1500), (A=1000, B=500), and (A=500, B=500), still giving me 52 cu ft to use on dive 2 with a 25 cu ft reserve. It works well as the greater gas used on dive one maximizes the available NDL on what is usually a deeper first dive. Ad the reduced gas used on dive 2 normally works better with the shallower depths or shorter NDLs you have on dive two, and doubles the reserve you'd have available compared to a single tank rec diver getting out of the water with 500 psi.
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Too many SM divers make the whole gas switch thing too complicated and use approaches that do not ensure an equal distribution of gas at the pint of max penetration, or require frequent reg switches to make that happen. I still prefer to minimize the workload, maximize the gas planing benefits, minimize the number of SPG checks and the risk of making an error by not making any more gas switches than I have to. But some divers still prefer to use an every 500 psi approach. To each his own, but be sure to at least understand why you do what you do as well as the pros and cons.
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Single tank side mount is also a great lighter and lower drag option on a recreational dive, but it has some limitations. With anything other than an AL 80 or an AL72 the lateral trim starts to become an issue and it won't work well with most steel tanks due to either the initial excessive negative buoyancy of the tank and/or the larger swing weight of the tank during the dive.
If you use a pair of 100 cu ft steel tanks in the recreational example above, you'll have bags of gas compared to an AL 80 on each dive, plus a fantastic reserve on each dive, and the configuration is still very clean in the water.
That's 50% more complicated than it needs to be.
Begin with similar volumes/pressures in each cylinder (we will say you have 2 AL 80s at 3000 psi starting pressure).
Breathe one third of starting volume in cylinder A (1000 psi, so you now have A=2000, and B=3000)
Switch regs
Breathe one third of starting volume in cylinder B (1000 psi, so you now have A=2000 and B=2000 psi)
Turn the dive
Continue breathing another third off Cylinder B (another 1000 psi, so now you have A=2000 and B=1000)
Switch regs
Breathe a second third out of tank A to the end of the dive, (1000 psi, so you now have A=1000 and B=1000 as a reserve at the end of the dive).
That's just 2 reg switches and it ensures that:
1) At the point of maximum penetration or distance where you turn the dive, the volume in each tank is equal to the total volume you used from both tanks to get there.
2) you never have a differential between tanks of more than 1000 psi, so lateral trim is not a significant issue,
3) you have ample reserve at the end of the dive, and
4) allows you to adjust the reserve up or down with only 2 reg switches and only 2 pressure numbers to remember.
If a 1000 psi per side is too much ( 50 cu ft in this case) in a purely recreational setting, you could reduce it by using larger "thirds" and switching accordingly. 1200 psi would give you "thirds" would leave you with pressure of 1) 1800, 3000, 2) 1800, 600, and 3) 600, 600, for a 600 per side reserve with a 30 cu ft total reserve with 15 cu ft in each tank.
On the other hand in a technical diving situation if a 50 cu ft (1/3rd) reserve is too small, you can reduce the "thirds" you use. In this case if you used 800 psi "thirds" you'd get switch pressures of 1) 2200, 3000, 2) 2200, 1400, and 3) 1400, 1400, leaving a 72 cu ft reserve. So you have the flexibility of tailoring the reserve requirements to the specific dive.
Where I may choose to use 750 psi thirds (A=2250, B=3000), (A=2250, B=1500) and (A=1500, B=1500) like doppler's example, in a recreational setting, would be when diving side mount with AL 80s on a two tank/two dive recreational boat trip. If I do this on the first dive, I use 77 cu ft - a full AL 80's worth of gas, but with an enormous 50% reserve for the first dive. On the second dive, I'll switch to 500 psi thirds - (A=1000, B=1500), (A=1000, B=500), and (A=500, B=500), still giving me 52 cu ft to use on dive 2 with a 25 cu ft reserve. It works well as the greater gas used on dive one maximizes the available NDL on what is usually a deeper first dive. Ad the reduced gas used on dive 2 normally works better with the shallower depths or shorter NDLs you have on dive two, and doubles the reserve you'd have available compared to a single tank rec diver getting out of the water with 500 psi.
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Plus you now need to carry down your tanks separately to the dive site (if land based) then retrieve everything and go diving. It lowers you vertical profile and is nice in the water, but too many extra trips for me, and relearning if your back mount.
It also means your hard clipping your light and kinda complicates the long hose deployment in certain situations (long hose stowed, and tank off as some do)
I don't dive it other than some trial stuff.
So...
To each their own..
If you want, go for it, learn how to rock it, but realize there is a different config for every diver in SM basically so team diving can get interesting if it goes south.
Most Sm divers love it and never want to go back, I just don't see the need to eliminate the manifold and I hate doing multiple trips in a dry suit when it's 100 degrees and humid. But that's me.
Not trying to rain on anything here, but counter points can be useful...Didn't notice the forum I was in. So if your into it, have fun...
Plus you now need to carry down your tanks separately to the dive site (if land based) then retrieve everything and go diving. It lowers you vertical profile and is nice in the water, but too many extra trips for me, and relearning if your back mount.
It also means your hard clipping your light and kinda complicates the long hose deployment in certain situations (long hose stowed, and tank off as some do)
realize there is a different config for every diver in SM basically so team diving can get interesting if it goes south.
Most Sm divers love it and never want to go back, I just don't see the need to eliminate the manifold
I hate doing multiple trips in a dry suit when it's 100 degrees and humid. But that's me.
Some stupid questions = do you use custom / special short hose pressure gauges ? Do you use one second stage on each reg, or do some SM divers add an octopus to one of the regs ? Does anyone add a pony as a back-up ?