Gas planning question

[FoxHound]

yeah that comes with breathing off of 2 different tanks.....that's always the case with SM failure or not.

 

[Kevrumbo]

you will consume the same ft^3, just so happens that you will have less ft^3 available to you. Aprox half if you have been keeping the tanks equal.

Say you consume .5 ft^3 per min before losing a tank....you will still consume that same .5 ft^3 after.....you will just go through your gas supply twice as fast due to having half the gas

either way the dive is over and its time to leave.

Correct . . .but assume that you have both cylinders for use --and this is also where IMO the UTD Z-system sidemount trumps all: by virtue of that Distribution Block or Isofold/Maniifold, I can access and combine both available remaining tank volumes in a donation to an Out-of-Gas Buddy.

All my RockBottom/Modified Thirds gas calculations are valid, consistent & applicable between both my conventional backmount doubles and Z-system sidemount doubles diving on Alu 11L cylinders (AL80's). . .

 

[FoxHound]

depends on what the failure is, same with bm, there are failures that will cause you to lose access to a cylinder.

to me personally, the z-manifold has its own possible failure points, I don't like quick connects so I don't, and won't, dive it.

All the power to you for liking it.

 

[Kevrumbo]

depends on what the failure is, same with bm, there are failures that will cause you to lose access to a cylinder.

to me personally, the z-manifold has its own possible failure points, I don't like quick connects so I don't, and won't, dive it.

All the power to you for liking it.

AG has developed and been using the QC6/block manifold system since 1996 and the first Wakulla push beyond 10k linear feet to 14k, on the big old "fridge" PSCR/Pre-RB80 rebreather: no problems with "failure points" back then . . .and none that I've heard about or experienced at all while using the Z-sidemount system.

Development & reasons for the Z-system from Andrew Georgitsis (AG) of UTD:

. . .However, all this banter about "failure" points [of the Distribution Block], detracts from the core and central issue, which is, if you want a system that is consistent with your previous, current or future Hogarthian/DIR/UTD training and skills, that is scalable from single tank to mCCR rebreather, that is capable of mixed team diving, that has interchangeable components and that also allows you to configure and dive a configuration that is best suited for your diving or exploration needs, then the Z-System is the only one that is capable of that.

 

[FoxHound]

I don't want something that is hog/dir/utd.....if i did, id still be diving bp/w

I dive what works, and what works best for me is sidemount.

like i said, happy that the z-manifold works for you....no thanks

Again way off topic

 

[kwinter]

My understanding of the Z -manifold is that it connects the 2 tanks on the LP side. That's the difference between manifolded BM doubles, and the reason I don't support the Z-manifold. IP differences could cause the tanks to not be used equally.

 

[Kevrumbo]

My understanding of the Z -manifold is that it connects the 2 tanks on the LP side. That's the difference between manifolded BM doubles, and the reason I don't support the Z-manifold. IP differences could cause the tanks to not be used equally.

Normally you don't have both sidemount cylinder tank valves turned-on opened and feeding into the Distribution Block or Isofold in Z-system sidemount diving (you trim balance the tanks by alternately turning on one tank valve and breathing off that cylinder with the other cylinder shut -down, and vice versa). --only when you have a contingency like an Out-of-Gas donation, or problem solving a gas flow check would you have the option of opening both cylinder tank valves and accessing the remaining combined volume of both sidemount tanks. . .

 

[Ste Wart]

That not an equipment problem.

Pick a boat that you and your equipment can fit in, and dive how you want.

I can tell you that I'm not going to switch back to BM just to make the dive op happy.

Flots this has nothing to do with a certain dive op, rather the style of diving in the UK.

You get hot-dropped onto most sites. For that environment a single or twin tank BM system is the logical choice due to environment, not stubborn kit preference.

In UK caves SM is the trump card as they are, normally, sump type caves with small restrictions. Therefore SM becomes the tool of choice for that environment.

Same with RB's. For a 30m bimble it's less hassle to fill a twinset and hop in. For dives where time and helium come into the mix then the RB becomes the tool of choice.

I don't limit myself to one system. I choose based on the environment.

 

[kwinter]

Normally you don't have both sidemount cylinder tank valves turned-on opened and feeding into the Distribution Block or Isofold in Z-system sidemount diving (you trim balance the tanks by alternately turning on one tank valve and breathing off that cylinder with the other cylinder shut -down, and vice versa). --only when you have a contingency like an Out-of-Gas donation, or problem solving a gas flow check would you have the option of opening both cylinder tank valves and accessing the remaining combined volume of both sidemount tanks. . .

Sorry, but I still don't get it. I know that you're using only one at a time. The question is what advantage the manifold provides. It is not the same as manifolded doubles that are connected on the HP side with a crossbar before the valve outlet. Closing one post only shuts the outlet and still leaves all gas available to the other post.

Does the Z-manifold preserve the gas if the tank neck o-ring extrudes or the burst disk blows? No, but neither does a hard manifold. But how about other situations? Does it make all gas available to the other post if you shut one valve? No, but a manifold does. How about a LP hose blowout? Nope, you have to shut down the valve. Unless you have inline shutoffs that can isolate the leak while leaving the valve open.

Manifolded doubles have some distinct advantages over independent twins. But I am hard pressed to see the advantage of the Z-manifold over single tanks. The only thing is that in a gas sharing situation, you might not have to worry about a difference in SAC rates. But that is only theoretical because the only time the manifold is functioning is when both valves are open at the same time. And that goes back to my comment about IP differences. You both would be sucking down the same tank if the IP of that first stage was lower.

Please straighten me out if I have misunderstood the Z-manifold.


Please pardon any typos. Sent from my iPhone using Tapatalk

 

[flots am]

I don't limit myself to one system. I choose based on the environment.

You can choose anything that makes you happy. However you don't get to tell everybody else that their equipment choices are inappropriate just because they don't fit on your boat or on your dive site.

People dive what they feel is appropriate for their conditions.