Sidemounts and Manifolds

[ianr33]

These are considerations. You've already stated the option of swapping regs underwater. 2 other options are 1) utilize H valves and/or 2) a bail out bottle.

Another option and much easier than swapping regs is to bum some gas off your buddy.
If you dont have a buddy then consider diving conservatively e.g diving to quarters rather than thirds in a cave situation.

 

[rjack321]

Generally locations with those characteristics are kept strictly secret from bumbling n00bs like myself. The old hands are sick and tired of squeezing past the carcasses of those who have no business off a leash...

This contrasts with the free and easy spirit amongst mountaineers. The skeletons of those who climbed above their ability level are usually festooned with slings and the femurs make good makeshift protection for wide cracks.

True on both accounts.

However, I was just trying to inform you that there are alot of caves in Ontario, some submerged, some dry.

 

[Mark Michaud SELAUSAR]

Bugman is right. The person he is referring to is one of my regular cave buddies. His system is simple and well thought out. He has close to 30 years commercial diving, mixed gas, sat, etc., as well as rebreather, and many years of cave experience. He has a second stage attached to each bottle and a third that comes from a block that he breathes from. When scootering or in tight areas there is no need to swap regs. Any failure, which seem few and far between these days......but always possible, is as simple as a quick disconnect with an isolating disconnnect on each bottle. Once he feels he has all of this how he wants it, as he is still tweaking it, I think I will follow suit. The way it is done, you can't even see it unless you know what to look for. The nice things about this is it is modular. You can have the ease of doubles, same gas in both bottles, and the redundancy of separate bottles without a "hard" manifold between.

 

[divestoclimb]

I was just wondering about the benefit of being able to use the gas in both cylinders if you suffer a failure the requires you to shut one down. With manifolded doubles, if you don't lose the valve and have to isolate, you draw from both cylinders in a balanced manner.

I was thinking that with independent doubles slung, if you lost the functionality of one reg for some reason, you lose the gas from that tank or have to try to swap regs under water.

Are these simply not considerations? Again, just curiosity here, no caves to speak of in Ontario...

I'm not a sidemounter (not really, just with rebreather bailout), but another option you have is feathering the valve on the tank as long as your reg hasn't failed closed. If it's freeflowing or leaking feathering is an option that lets you continue to use that gas at the cost of some task loading.

It's also important to note the distinction between this and backmounted independents. Although independents have the advantage of not being vulnerable to total gas loss, Tech divers no longer tend to favor backmount independents because of the difficulty in doing gas switches properly, slightly increased difficulty in monitoring SPG's, and complications when donating to out-of-gas divers (i.e. with a single 7-foot hose you can only donate from one tank, not either). Sidemount addresses all these issues and adds some other advantages of its own, so the problems that the manifold fixes on backmount don't apply to sidemount.

 

[Dive-aholic]

PADI has a sidemount class wt*f for??

Richard, it's a distinctive specialty that one of the PADI CDs wrote. It's designed to get OW divers into sidemount either during their initial certification or afterward. It is not a no mount class, though. Just a different way of mounting tanks.

 

[Standingbear56]

Bugman is right. The person he is referring to is one of my regular cave buddies. His system is simple and well thought out. He has close to 30 years commercial diving, mixed gas, sat, etc., as well as rebreather, and many years of cave experience. He has a second stage attached to each bottle and a third that comes from a block that he breathes from. When scootering or in tight areas there is no need to swap regs. Any failure, which seem few and far between these days......but always possible, is as simple as a quick disconnect with an isolating disconnnect on each bottle. Once he feels he has all of this how he wants it, as he is still tweaking it, I think I will follow suit. The way it is done, you can't even see it unless you know what to look for. The nice things about this is it is modular. You can have the ease of doubles, same gas in both bottles, and the redundancy of separate bottles without a "hard" manifold between.

Hmmm, sounds like an interesting concept. Any pics of the this set up with the block?

 

[SuPrBuGmAn]

Nope.

 

[Standingbear56]

Darn!:depressed:

 

[DA Aquamaster]

Bugman is right. The person he is referring to is one of my regular cave buddies. His system is simple and well thought out. He has close to 30 years commercial diving, mixed gas, sat, etc., as well as rebreather, and many years of cave experience. He has a second stage attached to each bottle and a third that comes from a block that he breathes from. When scootering or in tight areas there is no need to swap regs. Any failure, which seem few and far between these days......but always possible, is as simple as a quick disconnect with an isolating disconnnect on each bottle. Once he feels he has all of this how he wants it, as he is still tweaking it, I think I will follow suit. The way it is done, you can't even see it unless you know what to look for. The nice things about this is it is modular. You can have the ease of doubles, same gas in both bottles, and the redundancy of separate bottles without a "hard" manifold between.

I still have the gas block I used to use on commercial dives to connect both primary and a bailout gas to a FFM. It is designed so that the block will isolate each source from the other by traveling through an "off" position where no gas flows so that you maintain fully independent gas sources.

It is also easy to set them up with a Scubapro Air 2 or other high flow type quick disconnect but that would serve more as a means to use additional stage bottles, deco gas, etc that coudl be plugged into the two ports on the gas block.

That said, there is really no position where you could draw evenly from both tanks - you would have to manually switch the block from one source to the other. It is simple to do and takes about half a second, but it is still a gas switch.

All of which makes me want to ask the following questions:

1. What gas block is he using?

2. How does he integrate a backup second stage into the sidemount/gas block combination.

3. Where does he incorporate the long hose?

4. What does he do for deco - separate deco bottles or the gas block?

5. If the latter what safegaurds does he use to ensure he does not select the wrong gas?

I also dove independent doubles for a few years and I don't see any advantage of using a gas block for a techncial dive. In managing independent doubles you breath a third from one tank, then switch regs and breathe a hird from the second tank, turn the dive continue breathing the second third and then switch back to the first tank to breathe the second third, leaving 1/3 in each tank. Basically there are still only 2 back gas switches over the entire dive.

With side mounting and any number of stages, you'd modify the amounts used from the two primary tanks to maintain the larger reserve needed for the entire dive, but it would still be only two "backgas" switches.

 

[SuPrBuGmAn]

Those are all great questions for the diver in question, with the blocked sidemount tanks. He's not on the board, so don't hold your breath for answers.

Why's he doing it? Maybe just to get a little extra gas off a tank with a regulator malfunction? *shrugs* Sure, diving independants correctly we'll yeild you enough gas to get out(especially with a little extra conservatism), but there's nothing wrong with a little extra gas still.