Hog wrapping a bail out hose under a loop on a rebreather.

[-Sven-]

It is а good thing, that car manufactures are smart enough not to swap pedals))))

Not true.
My car has three pedals, my wife‘s car only two pedals. But for both cars accelerator right and break left of accelerator. Same in a Formula 1 racing car or go-kart, but there you use your left foot for the break. Racing cars up to the 1950th had accelerator middle an break right.
;-)

 

[PfcAJ]

Honestly not in for a ruck here... Please educate me...

With a soft manifold there's two valves at each end of the hose. Should the hose rupture:

• Is the inputs to that hose flow limited though a small orifice in the same way as a SPG connector is?
• If not, then there's going to be an almighty cloud of gas. If there is then it'll take some time to empty both cylinders.
• Assume there's loads of drills to shutdown both sides of the manifold.

My point about using one side only was an assumption that the manifolded bailout is also being used by the CCR as diluent and as the wing inflate. For argument's sake say the LH cylinder is connected to dil & wing; this means if you dive with the manifold closed then you'll use, say, 150 litres of dil + wing (5.3 ft3). As the cylinders are 7 litres, this means the pressure drops by about 25 bar (360psi) per dive. Not a lot agreed. But after a couple or three dives it would mean it needs a top-off.

Whenever I buy gas there's a per-cylinder charge as well as a gas volume. There's often an issue with source pressures if there's no booster. Thus filling one cylinder by a "lot" is cheaper than filling two cylinders by a "little".

Probably all heresy anyway! You dive like that as you want to. I don't as I don't. Both of us are right.

No flow restrictor. I have yet to hear of a rupture, but I suppose yes it would leak aggressively if it straight up burst. I find that to be quite unlikely. A more plausible scenario would be some sort of oring failure.

If you wanted to only top off when your volume got low, consider how many dives you’d have to do before your remaining volume equaled an al80 using a set of lp50s. Many. So that position isn’t really any worse than using a dedicated dil bottle, esp if your shop hits you up with an extra charge just for hooking up the whip.

Does your shop charge you for two tanks when you fill manifolded doubles? Sounds crazy to me.

 

[lermontov]

Then we’d have to go back an re-evaluate your decision to go sidemount, which is a discussion for another thread

In all seriousness, though, you’re absolutely correct. But, the longhose would still be coming from the right post and routed in the “hog loop”, while the left post was either a short hose on a necklace or drives the BOV.

I have no major issues with side mounting bailout (or diving sidemount), and still do it when it’s the more appropriate solution. But I always try to keep the configuration as close to “standard”as possible to keep as much muscle memory intact as I can. And when I do, I’m usually grumbling to myself the whole time about how much easier it would be if I just had my gas on my back

I was teasing really actually i think the back mounted BO ccr combo looks amazing and id use it if it was option, however i couldn't get through places i want to go with that set up. and as an aside i stopped using twins because I have a shoulder injury and cant reach the valves easily

 

[Wibble]

Does your shop charge you for two tanks when you fill manifolded doubles? Sounds crazy to me.

Yes.
Double for doubles/twinset
Sidemount is two cylinders

Worse, it’s common to be charged a fixed amount for a nitrox top-off regardless of oxygen used.

Helium is generally charged per litre/0.03531467ft3

 

[PfcAJ]

Yes.
Double for doubles/twinset
Sidemount is two cylinders

Worse, it’s common to be charged a fixed amount for a nitrox top-off regardless of oxygen used.

Helium is generally charged per litre/0.03531467ft3

Yuck.

 

[ginti]

For a start there’s no central isolation manifold which in OC is the first valve to shut down to preserve gas.

I am not sure if I understand correctly. Why is the central isolation manifold always the first one to close? If you have a leak coming from, say, the left first stage, why wouldn't you close the left valve?

P.S. In fundies they teach the valve drill, which is indeed a drill - not a procedure; the procedure to close the valve in case of a leak from the manifold/first stages/bottlenecks is taught in c1/t1 courses and does not imply to always close the right valve first.

 

[O-ring]

I am not sure if I understand correctly. Why is the central isolation manifold always the first one to close? If you have a leak coming from, say, the left first stage, why wouldn't you close the left valve?

P.S. In fundies they teach the valve drill, which is indeed a drill - not a procedure; the procedure to close the valve in case of a leak from the manifold/first stages/bottlenecks is taught in c1/t1 courses and does not imply to close the right valve first.

In an ideal world you would shut down the problem post first, but the thinking is that you might misdiagnose it so closing the isolator first will have the effect of saving at least half of your gas while you work out which post is actually the problem post.

 

[lostsheep]

or clip the Choptima or Sidewinder to backmount doubles.

Full disclosure, I am a rebreather newbie, I own a choptima that I usually dive sidemount, and the extent of my GUE is fundies. I occasionally dive it with double LP50s.

I didn't want to chime in first but since @grantcobin did I'll throw myself under the bus.

All the arguments for the GUE configured JJ seem to be better solved by just clipping a Choptima (or a sidewinder but I have a choptima) to the front of your standard DIR doubles rig. Literally the only drawbacks I can think of are the chest clutter, which is real, and the added failure point of 1 extra QD hose.

Sufficient bailout volume? The choptima wins, it is scalable to ANY size doubles.
Consistency with open circuit systems utilized by GUE divers? IT IS THE SYSTEM utilized by GUE divers.
Fully redundant with access to all gas and the ability to isolate? Check.
Weight of the system? I suspect the chop is lighter than the JJ with the same tanks. Check.
Does not occupy the position of a stage bottle? Check.

all of the above taken from here

Bringing it all back to on topic and why I chimed in here; a DIR configured set of doubles with the choptima allows for long hose donate without coming off of the loop while meeting or exceeding all of the criteria espoused in the INDEPTH blog about the GUE JJ configuration.

 

[PfcAJ]

Full disclosure, I am a rebreather newbie, I own a choptima that I usually dive sidemount, and the extent of my GUE is fundies. I occasionally dive it with double LP50s.

I didn't want to chime in first but since @grantcobin did I'll throw myself under the bus.

All the arguments for the GUE configured JJ seem to be better solved by just clipping a Choptima (or a sidewinder but I have a choptima) to the front of your standard DIR doubles rig. Literally the only drawbacks I can think of are the chest clutter, which is real, and the added failure point of 1 extra QD hose.

Sufficient bailout volume? The choptima wins, it is scalable to ANY size doubles.
Consistency with open circuit systems utilized by GUE divers? IT IS THE SYSTEM utilized by GUE divers.
Fully redundant with access to all gas and the ability to isolate? Check.
Weight of the system? I suspect the chop is lighter than the JJ with the same tanks. Check.
Does not occupy the position of a stage bottle? Check.

all of the above taken from here

Bringing it all back to on topic and why I chimed in here; a DIR configured set of doubles with the choptima allows for long hose donate without coming off of the loop while meeting or exceeding all of the criteria espoused in the INDEPTH blog about the GUE JJ configuration.

How are you feeding your BOV with the choptima?

 

[tbone1004]

@lostsheep
Sidewinder requires a wonky backplate setup to be used with doubles which is possible as it's been done, but it's weird and puts the bottles noticeably farther off your back.
Choptima would have a really strange long hose routing.

The true sidemount rebreathers actually work best with the DIR setup as they clip in like a stage bottle *though a left side loop bungee is preferred and is easily added in a minute to any backplate*. I regularly use my KissKat with DIR style doubles, or singles for that matter.