DIR- GUE Why are non-GUE divers so interested in what GUE does?

[flymolo]

The "backgas" isn’t redundant as they’re also consumed as your diluent. A week's boat diving would need a couple of gas top offs or need different backgas cylinders for different depths. For any dive beyond recreational depths you still require deco bailout(s).

The backgas is redundant because you have two cylinders connected with a manifold which you can isolate. It's true that you only have Dil running off one of the posts, but if for some reason you need to shut down that cylinder you can still close the valve and bail to OC while maintaining access to all of the gas on your back. You can also plug in offboard gas from one of your deco cylinders at a later stage in the dive once you get to the right depth and get back on the loop if you had a good reason to.

On an average dive from anywhere in the 150-220 foot range I consume on average 200-300 psi of DIL, sometimes less than that. I start my tanks at 3500 psi and only top-up once I get to 2600 or so, which means I don't top off nearly as often as you suggested.

A normal** rebreather — such as a standard JJ — doesn’t consume gas from the bailouts (aside from powering up the regulator and test breaths). The standard three litre dil and oxygen cylinders are smaller, cheaper and far easier to manage — than the TWO 7 litre cylinders with special valves on the GUE JJ. Diluent PPO2 is normally different (~1.0) from your bailout PPO2 (~1.4), so your "dilout" would compromise your bailout, probably being hypoxic for moderate depths (60m/200ft) and beyond.

The cost of topping up is the essentially the same. The tanks are never empty or anywhere near it. I personally top up when my tanks are at their rated pressure (2640) and overfill to about 3500 or so.

Normal rebreathers are lighter and smaller thus easier to move around and stow. This is particularly important when carrying kit to a site where breaking it into smaller units may be essential.

My rig is very similar in weight to a set of HP 100 doubles (although I dive a fathom which is a good deal lighter than a JJ). Once bailouts are on, a rebreather in standard configuration is probably very similar to the weight of a rig with backmounted bailout.

The longhose means that you cannot pass over your bottom bailout to a person in need. You will be permanently tied to them whilst they’re consuming your diluent. An OOG donation is more or less the same on a normal rebreather— you pull out your bailout regulator and shove it in their face. Then you unclip your bailout and hand it over to them so they are independent from you.

Not everyone would agree with the approach of passing your bailout to a diver and then separating from them. If a diver is compromised I want to be there to assist them- it's no different than what a diver would on OC. However in a team of rebreather divers I would not anticipate having to share gas as we are all taught to be independent which means carrying enough bailout to bring us to the surface.

Lots of compromises seemingly for little or no benefit.

The gas volumes and redundancy are a huge benefit. And if you've bailed out you are back to diving on OC doubles with a couple deco bottles slung, so your procedures are all the same as on OC. I noticed you haven't addressed the gas volumes, but diving a backmounted set of 50s plus a deco bottle or two means you have more bailout gas than most divers in standard config who seem to typically only carry a single 80 for bottom bailout and a single 80 for deco gas (in the 150-220 foot range).

Have often wondered why normal rebreathers have standardised around the JJ style configuration of a pair of 3 litre cylinders for diluent and oxygen, a large 2 litre suit inflate cylinder and fully redundant bailout cylinder(s). The GUE format JJ stands alone in its design that no other rebreather manufacturers have adopted.

This is not true. Two other manufacturers offer this configuration on their website, Fathom and Divesoft. I've also seen Meg and SF2 divers in this configuration as well.

 

[divad]

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[kierentec]

Have often wondered why normal rebreathers have standardised around the JJ style configuration of a pair of 3 litre cylinders for diluent and oxygen, a large 2 litre suit inflate cylinder and fully redundant bailout cylinder(s). The GUE format JJ stands alone in its design that no other rebreather manufacturers have adopted.



** For this discussion "normal rebreathers" do not include sidemount nor chestmount formats.

Not going to get into each of your issues with onboard bailout, it’s been done in other threads with the reasons for each component and their benefits clearly explained by people with thousands of hours on CCR in various configurations. But it’s not for you (and that’s ok), your mind is made up, so no sense in trying again.

But maybe a question you should ask is why the “standard” recreational (non-military or commercial) ccr configuration is onboard 3L Dil/o2 and the bailout as an afterthought? Just going with what it seems like is the way it is supposed to be done because that’s how everyone has done it since we tried to adapt what the military was doing to recreational diving? In contrast to the GUE mindset of let’s have a specific reason for the placement and use of every single component to create a system that is best applicable to the vast majority of diving conditions.

 

[crofrog]

Trick question! We all know that bailout gas volumes limit bottom time way more than a rebreather's limits.

Do you plan your dives. What would you bring on a 45 minute dive to 75m?

 

[Wibble]

Do you plan your dives. What would you bring on a 45 minute dive to 75m?

I refer the honourable gentleman to my previous answer.

 

[crofrog]

I refer the honourable gentleman to my previous answer.

I'll take it as you don't know how to answer the question.

For someone who seems to act like they do dives like this all the time. I figured you'd know it off the cuff.

 

[Wibble]

I'll take it as you don't know how to answer the question.

For someone who seems to act like they do dives like this all the time. I figured you'd know it off the cuff.

I do and do. But that's my plan based upon the diving circumstances -- especially lazy shot. I wouldn't do 45mins at 75m though -- 2h15+ at deco's a long and cold hang.

Am still curious about the GUE plan for that dive.

 

[wetb4igetinthewater]

@Wibble

Now I haven't taken T1 even, but speaking to a friend that has, GUE focuses a lot of time on dealing with emergencies.

I will hypothesize that this is built upon and extended as you go to T2 ans CCR courses.

With that, if one GUE diver has an issue, that diver and the buddies have extensive training in that situation.

That to me is the strength of the GUE system: consistency. You know what the other diver is going to do. This isn't true of other agencies.

So a GUE CCR diver is likely able to handle being tethered by a longhose to a buddy who's system has failed than I ever will.

I think we have to recognize that fact. Team diving is a pillar of the GUE system.

GUE folks, is this correct?

 

[crofrog]

I do and do. But that's my plan based upon the diving circumstances -- especially lazy shot. I wouldn't do 45mins at 75m though -- 2h15+ at deco's a long and cold hang.

Am still curious about the GUE plan for that dive.

How about 50m for 30min

 

[beester]

Personally I like the GUE setup for wreckdiving... not so much for cave diving.

- I'm using 2x 8,5L tanks, and typically at the beginning of a week of wreckdiving they'll be filled to 250+bar. That's on the inital dives almost 2 80cft tanks on your back, readily available.
- The long hose setup is obviously a compromise for mixed team diving. Yes in a full rebreather team you could have scenarios where you would need to share bottom bail out (the one we have on our back), but that would mean 2 failures (both rebreather and the bailout failing).
- I'm diving with the diluent/bailout on the back AND 2x 3L tanks on the back, 1 is oxygen, the other is argon (air) that connects to my wing and drysuit (yes I keep the regular hoses and I have hoses on all my bailout tanks so I can easily switch if this 1 failure punt fails). The positive about this is that I use 5 to 10 bars of the backgas/diluent per deep dive. So after 6 days of diving I'm still at more or less 200 bars. Of course it's heavy, but compared to a D18L it's still on the light side.
- Bailouts are not shared. Up to 75m (depends a bit on the bottom time) we typically would use a 50% and an O2, and sometimes an intermediate deco gas (36m or 57m). So that's typically 2 decostages (sometimes 3) for dives up to 75m en 50' bottom time.
- Why is it convenient for wreckdiving. I'm carrying 2 less stages than my buddy who's diving the JJ in traditional style. Specifically when there is current it's easier if you can jump in more or less with all the stuff you need vs having to scooter/swim back to pick up additional stages. The same deal with handling yourself on a rolling boat, 2 extra stages makes the equipment stress a bit heavier. (yes there are work arounds, etc... ). Next I don't typically drop stages on wreck dives (unless really tight penetration). So having 2 less stages to work with is convenient. In caves these advantages don't play, equipment stress is less of an issue, you also drop your stages.

So while my buddy is carrying 4 stages (in the traditional jj setup, and yes he's a fully blown GUE diver)

I'll be carrying as stages, just 2.

On deep deep dives team bailout becomes somewhat of a thing. Meaning the main bailout is always per person, but the intermediate deco gasses might be shared within a team. So the full team would carry a 100%, a 50% and deep bailout, but for example the intermediate deco gasses could be shared (1 carrying a 57m gas and the other a 36m gas, which then can be handed over to the team mate in trouble). But the basics remain the same every individual member should be able to do his full ascend with the gasses he's carrying. Of course in a real world scenario if someone gets a CO2 hit, for sure we'll be handing over tanks to the victim, but it's not plan A, more plan B.