Gas Management With Sidemount

[lermontov]

Errol,

For me it is simple. I cannot reach my valves due to shoulder injuries. Also, when traveling and I want to dive deeper for longer, it is easier to setup sidemount than to get back mounted doubles. I wish I could reach my valves, so I'd only dive sidemount when diving wrecks and caves. But I can't.

me too I have no deltoid muscle in one arm and leaving the water with twins is hard on my back-with SM I can lower both bottles off a trapeze and jump in and get hooked up (or put one on boat an dh other in water, when exiting , reverse

 

[wetb4igetinthewater]

me too I have no deltoid muscle in one arm and leaving the water with twins is hard on my back-with SM I can lower both bottles off a trapeze and jump in and get hooked up (or put one on boat an dh other in water, when exiting , reverse

To me, there is the downside of reg switches (minor) and if there is an issue with one of the first stages, you can't just close that valve and continue to get air from the tank as you would with backmount. You hopefully can feather the valve. But for me, the pro's heavily outweigh the con's. The con's can be easily address (in my opinion).

 

[lermontov]

To me, there is the downside of reg switches (minor) and if there is an issue with one of the first stages, you can't just close that valve and continue to get air from the tank as you would with backmount. You hopefully can feather the valve. But for me, the pro's heavily outweigh the con's. The con's can be easily address (in my opinion).

I agree the pros are way in favour for me the major ones are :

I dont get sore neck and back after diving sidemount like i did in twins esp out of the water movement
Having everything in front of your peripheral vision is a major plus I feel more in control of my set up,
I like having a smoother profile and less snags points on my back (where i cant see them)

 

[wetb4igetinthewater]

I agree the pros are way in favour for me the major ones are :

I dont get sore neck and back after diving sidemount like i did in twins esp out of the water movement
Having everything in front of your peripheral vision is a major plus I feel more in control of my set up,
I like having a smoother profile and less snags points on my back (where i cant see them)

I agree 100%.

 

[PhatD1ver]

for me, it was a simple question. "Do you want to run out of air EVER again?" and to the forum/group, have you ever run out of air? for reals, you know, slash across the throat, take that last pull and 'calmly' hold your breath while you get your buddies attention like OOG, not oh, my buddy and I watched me breath down and handed over a octopus when I was dry, but an actual OUT OF GAS emergency.

Say what you want, but I've had THREE of these emergencies. There is a story behind each one, but reality is that I as inexperienced, prideful, out of shape, and my instructors and DMs didn't understand my limitations.

So imagine that AOW instructor turning around just as I give him the OOG sign, not the chest thump, but the throat slash. Sure, we were setting up for our safety stop and he had no idea I'd burn thru 70 bar swimming against the current after we drifted past the boat. But it happened.

Imagine a day later that as we are diving as a large group; we have a great drift dive, and are tucked down looking for a shark that's hanging out in the murky blue. And I overstay my bottom time, and now end up with mandatory deco time, and halfway thru, I'm OOG again. And there is my instructor shaking his head and ready to strangle me, if I weren't already low on air.

And then there's the fun of having a 'noise maker' attached to my dry suit hose that I figured was nifty. But really wasn't when I got shoved into my BCD, and then the button got depressed at the worst time possible (70 bar, with a short drift back to the boat left. 2 minutes later, OOG).

And the reality is that even if I don't panic easily when I have an OOG situation (because I'll always be close to the surface, I do manage it that well), my gas management was worse than terrible, and I was an accident waiting to happen.

So, SM was a revelation. You'd think it would be MORE dangerous, but with redundant air, and with the need for switches now drilled into my head, I am constantly checking my SPGs. I use my watch to time my changes too because I know my SAC and can pretty much estimate my switch times for the dive profile I plan. I put my three switches and estimated times on my arm slate.

The methodology shown in the article should be incorporated into the SM manual for every agency. Clear, concise, and certainly the best way to ensure you don't end up with too little air in one tank to have enough to share, and still keep going yourself.

I even modify it just a bit so that when I'm on a trip to Taiwan or Philippines, I can save the crew some headache by only needing three tanks for two dives. Entering the water on my second dive with 120 bar in one and 190-200 bar in the other and adjusting my switch plan.

 

[wetb4igetinthewater]

for me, it was a simple question. "Do you want to run out of air EVER again?" and to the forum/group, have you ever run out of air? for reals, you know, slash across the throat, take that last pull and 'calmly' hold your breath while you get your buddies attention like OOG, not oh, my buddy and I watched me breath down and handed over a octopus when I was dry, but an actual OUT OF GAS emergency.

Say what you want, but I've had THREE of these emergencies. There is a story behind each one, but reality is that I as inexperienced, prideful, out of shape, and my instructors and DMs didn't understand my limitations.

So imagine that AOW instructor turning around just as I give him the OOG sign, not the chest thump, but the throat slash. Sure, we were setting up for our safety stop and he had no idea I'd burn thru 70 bar swimming against the current after we drifted past the boat. But it happened.

Imagine a day later that as we are diving as a large group; we have a great drift dive, and are tucked down looking for a shark that's hanging out in the murky blue. And I overstay my bottom time, and now end up with mandatory deco time, and halfway thru, I'm OOG again. And there is my instructor shaking his head and ready to strangle me, if I weren't already low on air.

And then there's the fun of having a 'noise maker' attached to my dry suit hose that I figured was nifty. But really wasn't when I got shoved into my BCD, and then the button got depressed at the worst time possible (70 bar, with a short drift back to the boat left. 2 minutes later, OOG).

And the reality is that even if I don't panic easily when I have an OOG situation (because I'll always be close to the surface, I do manage it that well), my gas management was worse than terrible, and I was an accident waiting to happen.

So, SM was a revelation. You'd think it would be MORE dangerous, but with redundant air, and with the need for switches now drilled into my head, I am constantly checking my SPGs. I use my watch to time my changes too because I know my SAC and can pretty much estimate my switch times for the dive profile I plan. I put my three switches and estimated times on my arm slate.

The methodology shown in the article should be incorporated into the SM manual for every agency. Clear, concise, and certainly the best way to ensure you don't end up with too little air in one tank to have enough to share, and still keep going yourself.

I even modify it just a bit so that when I'm on a trip to Taiwan or Philippines, I can save the crew some headache by only needing three tanks for two dives. Entering the water on my second dive with 120 bar in one and 190-200 bar in the other and adjusting my switch plan.

I have to commend you on stepping up and admitting mistakes. Stuff like this often gets you crucified on ScubaBoard, though I'm guessing a lot of the harshest critics have made their own set of mistakes, but won't admit to them.

It sounds like you have a higher than average SAC. Nothing wrong with that. SM is a great solution. I'm finally going to get in the water (staying in the shallows) to experiment with my new SM rig. And I may make this my travel BCD and just pay for the extra tanks. Why? My SAC is pretty good, but throw in a massive camera, and I have some pretty extreme drag. So I think that is a good tradeoff, as no additional gear/support is needed from a dive op, other than extra tanks. I have 2 Yoke regulators and 4 DIN ones. For travel, as mostly everyone (afaik) provides Yoke valves on tanks, I'll just set up my SM reg config using my Yoke regulators.

 

[PhatD1ver]

I have to commend you on stepping up and admitting mistakes. Stuff like this often gets you crucified on ScubaBoard, though I'm guessing a lot of the harshest critics have made their own set of mistakes, but won't admit to them.

It sounds like you have a higher than average SAC. Nothing wrong with that. SM is a great solution. I'm finally going to get in the water (staying in the shallows) to experiment with my new SM rig. And I may make this my travel BCD and just pay for the extra tanks. Why? My SAC is pretty good, but throw in a massive camera, and I have some pretty extreme drag. So I think that is a good tradeoff, as no additional gear/support is needed from a dive op, other than extra tanks. I have 2 Yoke regulators and 4 DIN ones. For travel, as mostly everyone (afaik) provides Yoke valves on tanks, I'll just set up my SM reg config using my Yoke regulators.

Yeah, when you are $3.25, you tend to use a little more oxygen to keep all those cells happy while you are diving. I'm not worried about being crucified. I've used those experiences to become a better diver. Since the last time I had an OOG problem, I've logged another 140 dives and I'm very religious about my gas management.

My SAC has actually improved immensely. I'm running about 20l/m these days, where I was about 26l/m a year ago

 

[Kevrumbo]

Yeah, when you are $3.25, you tend to use a little more oxygen to keep all those cells happy while you are diving. I'm not worried about being crucified. I've used those experiences to become a better diver. Since the last time I had an OOG problem, I've logged another 140 dives and I'm very religious about my gas management.

My SAC has actually improved immensely. I'm running about 20l/m these days, where I was about 26l/m a year ago

Given a arbitrary nominal volume SCR [SAC rate] of 22 liters/min per ATA (that's 0.78 cuft/min per ATA in US Imperial Units, a reasonable & achievable volume SCR for most divers):

Cylinder Size | Pressure SCR
11L/bar tank (AL80): 2bar/min per ATA;
12L/bar tank (Steel HP100): 1.8bar/min per ATA;
13L/bar tank (AL100): 1.7bar/min per ATA;
15L/bar tank (Steel HP119): 1.5bar/min per ATA;
16L/bar tank (Steel HP130): 1.4bar/min per ATA;
11L Twins (Double manifolded AL80's): 1bar/min per ATA;
12L Twins (Double manifolded HP100's): 0.9bar/min per ATA;
16L Twins (Double manifolded HP130's): 0.7bar/min per ATA.

---
Notes: How to Derive a Pressure SCR (Surface Consumption Rate)|

Example: Given a volume SCR (also called SAC rate or RMV) of 11 liters/min*ATA, divide it by the Tank Factor Rating of the Cylinder in use. For an AL80 cylinder with a tank factor of 11 liters/bar:

11 liters/min*ATA divided-by 11 liters/bar equals 1 bar/min*ATA.

 

[Razorista]

In my opinion draining one of the tanks by accident is a common mistake for anyone switching to independent doubles, regardless of the place they are carried.

Draining the second one happens easily on small tanks or when entering the water with partially used tanks, but will 'never happen' to anyone with typical tank volumes for technical or advanced sports dives.

When an equipment failure happens on the 'underused' side this might become a real problem, however.

Normally you should never run out of gas, since the first tank you drain will alert you about the problem you might have in a few minutes in a way nobody is likely to ignore.

I think it is a good way to try to achieve something like a 10 or 20 bar rhythm for a time after switching to sidemount config, for training purposes.
However...:
after a few hundred dives this gets rather tedious and accumulates a lot of memories of dives when it failed, leading to a spiral of pressure and disappointment.

You miss a switch sometimes at least.
An unexpected large animal will distract most people enough to just forget for 20 minutes, people carrying cameras might even do so on purpose for longer than that, many get almost suicidal while the red light is burning.
Many, probably most, have a hard time reestablishing a rhythm once they have lost it.
They get distracted, feel stressed, think about something totally uneccessary more than actually required for a successful dive.

I stopped using any fixed rhythm after finding myself a few times too distracted when an unexpected problem occurred seconds after realizing I had forgotten a switch for a significant amount of time.

In my opinion this is one of the primary mistakes of modern sidemount training.
Tanks should be equalized as much as possible, anything else is just an approximation and should only be used as such.
Training for any fixed rhythm has no practical value, when equalized tanks are your real goal.

 

[Coztick]

In my opinion draining one of the tanks by accident is a common mistake for anyone switching to independent doubles, regardless of the place they are carried.

Draining the second one happens easily on small tanks or when entering the water with partially used tanks, but will 'never happen' to anyone with typical tank volumes for technical or advanced sports dives.

When an equipment failure happens on the 'underused' side this might become a real problem, however.

Normally you should never run out of gas, since the first tank you drain will alert you about the problem you might have in a few minutes in a way nobody is likely to ignore.

I think it is a good way to try to achieve something like a 10 or 20 bar rhythm for a time after switching to sidemount config, for training purposes.
However...:
after a few hundred dives this gets rather tedious and accumulates a lot of memories of dives when it failed, leading to a spiral of pressure and disappointment.

You miss a switch sometimes at least.
An unexpected large animal will distract most people enough to just forget for 20 minutes, people carrying cameras might even do so on purpose for longer than that, many get almost suicidal while the red light is burning.
Many, probably most, have a hard time reestablishing a rhythm once they have lost it.
They get distracted, feel stressed, think about something totally uneccessary more than actually required for a successful dive.

I stopped using any fixed rhythm after finding myself a few times too distracted when an unexpected problem occurred seconds after realizing I had forgotten a switch for a significant amount of time.

In my opinion this is one of the primary mistakes of modern sidemount training.
Tanks should be equalized as much as possible, anything else is just an approximation and should only be used as such.
Training for any fixed rhythm has no practical value, when equalized tanks are your real goal.

Ok one of us is having a little stroke, I don't know what you're trying to say...
Personally I can't speak to overhead protocol but I can tell when one side is 300# lighter. This is when I like to switch for trim. I check the spg on both each switch.