I'm curious about sidemount

[decompression]

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.

 

[stairman]

I just keep both tanks within 300 PSI of each other or so. No big deal whatsoever. I only sidemount cavediving currently and breathe 1/3 of my gas from each tank and turn the dive leaving 2/3 for my exit and emergencies. To me sidemount is totally redundant. 2 regs, 2 SPG's, valves easily assessable for shutdowns and /or feathering and I run a wing inflator hose off each reg since I have a dual Nomad wing. I can shutdown a bad reg and exit with SPG and auto inflation and feather it if need be.

 

[Dive-aholic]

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.

----

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.

I have to disagree with your example here, Larry. Steve's example does require one additional switch but is much safer. Check out this article - Sidemount Gas Management « Rob Neto - for an example of how your example might not be safe.

 

[beanojones]

The quoted is a great post, but the first line is unintentionally ironic

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.

.

That's all more than 50% more complicated.

Switching regs, and checking SPGs is silly easy, and not the least bit complicated. That above math is complicated.

Doing all that math and stuff may reduce the number of switches, but it is not less complicated, it is more complicated.

The reason we switched from tables to computers is because most people make math mistakes at times, and eliminating the possibility of them is a huge step forward in safety. The above complicated procedure is reintroducing the possibility of math errors into diving.

Check SPG, switch reg, is easy.

 

[MSargeant]

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...

...

You don't have to carry your cylinders down to the waters edge separately... you can just clip them on (using the bottom clip as normal and using a clip on a choker/piece of bungee around the neck to your shoulder D ring) walk them to the water and then apply the bungee look and unclip then go, do it in reverse when you get out.

If you've only done trial stuff then do an actual course and learn that all these "counter points" are worked out easily.

- Long hose is stowed down the side of the right cylinder, easy to deploy and re-stow much like a stage bottle

- Proper dive briefing and buddy checks negate the issue of having different configurations (if their are any). As long as you know how to donate and your buddy knows how to recieve/how you are going to donate, only things left are the releases.

- I dive sidemount for pleasure and dive backmount when i'm with newly passed open water divers or trainees... Just practice in your spare time, very hard to forget so "re learning" isn't an issue.

In other news UTD have brought out a manifold for their Z system but i don't dive it so i won't encourage.

Safe Diving

 

[djcheburashka]

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.

None of that's really accurate. If you want you can attach the tanks to your rig (using safety bolt snaps instead of the bungie at the top of the tanks while you're walking) and walk them to the water just like backmount doubles. This is how you enter when side mounting from a boat. So the "extra trips" are only if you feel like it, for example if you don't enjoy carrying doubles long distances...

The "relearning" time, for me, from backmount to sidemount, was 7 minutes.

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)

Those are configuration choices. Poor ones in my view-totally not necessary for sidemount.

realize there is a different config for every diver in SM basically so team diving can get interesting if it goes south.

This bothers me a lot less than I thought it would. If you think about it, there are basically two circumstances in team diving where it *really* matters for your buddy to know your gear-a gas failure (buddy helps with the first stages on the manifold, spots bubbles, etc) and if you're unconscious. With SM, you can do yourself all of the gas failure things that in backmount require a second person.

Most Sm divers love it and never want to go back, I just don't see the need to eliminate the manifold

The redundancy you lose, is in backmount you still have all your backgas (but can't donate) if there's an unfixable failure in one of your regulators. In SM, you'd have to move the reg from one tank to another, which is actually possible, I guess. What you gain is fewer failure points in SM, and all of the gas failures are much easier and faster to deal with.

Other sm downsides: you're less likely to have readily accessible pockets, it's not obvious where to stow your lift bag/smb, the hoses can be a job to manage getting set up, and if you're diving a single tank heavier than an al80 you have to think about balancing yourself out laterally.

On the other hand, I can take both sm tanks off, hold them in front of me, and easily swim through a hole smaller than many of the divers on this board without worrying much about snags

Also it looks really cool.

I hate doing multiple trips in a dry suit when it's 100 degrees and humid. But that's me.

This is so weird... Why don't you just clip the tanks on?



Sent from my iPad using Tapatalk HD

 

[Glenn08]

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 ?

 

[jago]

I'm afraid, this is a little more complicated than OC in BM where a "standard" tec config (Hogarthian) can be used as a reference.

Usually HP hoses are shorter in SM and stage tanks than BM. But gauges ?

Unless you can not dive with 2 same cylinders (both volume and pressure), I recommend to use both (like Steve Lewis explained)* and not dive on one, keeping the other as a back-up / pony tank**.
* in this case a 2nd reg would not be helpful.
** in this case a 2nd reg would be recommended.

 

[FoxHound]

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 ?

Most side mounters will use either a 6in or 9in hose with a standard pressure gauge.....i prefer a 6 inch pointing up so i can see both of them without having to use my hands.

In general you will have 1 second stage per first stage.......the other tank is your backup, no octo required

in single tank side mount you will see an octo on the reg set for obvious reasons.

as for a pony bottle, your second tank is essentially a pony bottle.....its your back up.....you breathe the tanks so that if either tank/reg set has a problem, you can get out safely on the other tank.

 

[CaveMD]

I generally use Steve's method. Gas management in sidemount is so easy it's hard to believe people actually consider it "task loading"