Gas Management With Sidemount

[Razorista]

...as if you have a failure from the tank from which you are breathing, you have in reserve enough gas to get you back.

And if you have the failure in the tank you are not breathing you die.
Not a good system in my opinion

 

[Razorista]

...If the manufacturing process of the dive computers is properly done, there is a vacuum inside, so that there is no moisture in the air, and therefore no condensation. ...

You are forgetting the transmitter contains a battery and a chamber to hold that.
Surface moisture, salt and organic residue is in there too.
It the contacts in there start to corrode that can affect every circuit connected to them.
Antennas in particular are known to age even when fully evironmentaly sealed even on land, frequently dropping them in cold water will always corrode them, it only takes time.

The fire hazard wasn't my point btw., oxygen and temperatures just may corrode objects like that faster.

 

[wetb4igetinthewater]

And if you have the failure in the tank you are not breathing you die.
Not a good system in my opinion

So, 2 failures? That is why you and your buddy have enough air out of one tank (out of 4) to return.

Are you seriously questioning Steve Lewis here?

 

[wetb4igetinthewater]

You are forgetting the transmitter contains a battery and a chamber to hold that.
Surface moisture, salt and organic residue is in there too.
It the contacts in there start to corrode that can affect every circuit connected to them.
Antennas in particular are known to age even when fully evironmentaly sealed even on land, frequently dropping them in cold water will always corrode them, it only takes time.

The fire hazard wasn't my point btw., oxygen and temperatures just may corrode objects like that faster.

And properly maintaining your gear makes that a nonissue. I'm quite retentive when it comes to cleaning my gear.

Cold temperatures will slow reactions. Remember that heat is a catalyst. And you are talking about points that are not exposed to water. If water gets in there, you're regulator needs to be serviced immediately.

Anyway, that's all I have to say. I have noticed you on other threads arguing until the cows come home, so if you wish, please have the last word. I think I've covered the scientific aspect of this debate, so I'm done.

 

[Errol Kalayci]

Whats the fascination with Side Mount? How many people are diving really restricted areas where it is a benefit? The isolation manifold was created to add safety to back mounted doubles that were independent of each other until then. Side Mount seems to add a lot of complexity and introduce more potential issues that are not warranted except in few circumstances where risk/reward balances out (small cave, sumps, etc.). I remember the independent doubles days, was thrilled when I bought my first isolation manifold in 1991 and have not looked back since.

 

[wetb4igetinthewater]

Whats the fascination with Side Mount? How many people are diving really restricted areas where it is a benefit? The isolation manifold was created to add safety to back mounted doubles that were independent of each other until then. Side Mount seems to add a lot of complexity and introduce more potential issues that are not warranted except in few circumstances where risk/reward balances out (small cave, sumps, etc.). I remember the independent doubles days, was thrilled when I bought my first isolation manifold in 1991 and have not looked back since.

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.

 

[kr2y5]

Whats the fascination with Side Mount?

What's the fascination with pancakes? There is healthier, and more nutritious food out there. Eating pancakes, therefore, indicates a gross error in judgment.

 

[Jack Hammer]

At this point in the dive (turn pressure in both tanks and at max penetration), you've used 1/3rd of the gas in each tank and you have 2/3rd (2400 psi) left in each tank. So if you suddenly lost all the gas in each tank, you've still got twice as much gas as you used for the penetration left in the remaining tank.

I'm gonna hope the first part is a typo, as if you were to suddenly lose all the gas in each tank you have nothing... im sure it was meant to say that if you suddenly lost all the gas in either tank... problem is you do not have twice as much gas as you used for the penetration left in the remaining tank, you've used 2400 psi total, 1200 from each tank. You now have 2400 psi remaining in a single tank, the same as you've used for penetration. You have no reserve to resolve any issue, if you are solo or separated you are set up for a very bad day. This is dangerous thinking and a shows very poor gas mansgement planning.

 

[DA Aquamaster]

I'm gonna hope the first part is a typo, as if you were to suddenly lose all the gas in each tank you have nothing... im sure it was meant to say that if you suddenly lost all the gas in either tank... problem is you do not have twice as much gas as you used for the penetration left in the remaining tank, you've used 2400 psi total, 1200 from each tank. You now have 2400 psi remaining in a single tank, the same as you've used for penetration. You have no reserve to resolve any issue, if you are solo or separated you are set up for a very bad day. This is dangerous thinking and a shows very poor gas mansgement planning.

Yes, I meant "either".

It's also an example of straight up rule of thirds planning, and sediment doesn't change the fact that it's an absolute minimum, in a two person team, and in fact the rule of thirds wasn't intended for a 2 person team.

On the other hand, since both side mount divers in a two person team have 2400 psi at max P in all four tanks using this gas management strategy, the loss of any single tank still leaves a total of 3/2s the gas for exit compared to the gas the team used to penetrate. The diver with all the gas lost from a single tank should be able to exit most of the way, if not all the way, and if not, there is still 2400 psi worth of reserve gas for the team.

The thing you also need to consider is that the gas management strategy described is also part of a system and just one factor in the larger dive/gas plan.

First, in our case we dive with a 5' hose on each tank and sharing gas on the exit isn't an issue. (Yes, we've tried it even in narrow restrictions where we're single file).

Second if you read the whole post you'll note I also indicate that I use 1200 psi thirds, even with a 3800-4000 psi fill, so it's padded a bit with 1400-1600 psi left in the reserve third in each tank - not 1,200.

Third, we also tend to poke are heads into offshoots on the way in, while we swim out directly. And of course any jump lines are installed on the way in, and in an out of gas situation they're just left on the way out, which saves a minute or so per jump on exit compared to entry.

Fourth, also as noted previously, the actual turn pressure is adjusted based on the dive conditions. If it's tight and/or silty passage where we know the exit will be longer, we make the turn earlier. It's called "thinking ahead".

All in all means that means we normally end a dive with 1800-2000 psi left in each tank, and I can't actually recall the last time I actually exited with only 1200 psi left per side.

 

[MXGratefulDiver]

Whats the fascination with Side Mount?

It's like sex ... it just feels good. Except that there aren't the unfortunate side-effects ...

... Bob (Grateful Diver)