What is with DIR and Rebreathers?

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CAPTAIN SINBAD

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Hello guys: I have been intrigued by the DIR style of diving and gear configuration but browsing through these forums, I get the impression that DIRness is somehow not compatible with Rebreathers? Can anyone explain why? I have no experience with rebreathers and basic understanding of DIR approach. I understand that UTD developed some rebreather configurations which have generated some skepticism from rebreather crowd. Can anyone please let me in on this?

Cheers -

CS
 
The one major point with the DIR system (or any Tech system) is the ability to easily, and efficiently donate breathable gas.

Rebreathers are challenging in this regard, as most are not donatable, nor is turning on a bailout, and passing it off (if the OOG diver can't access theirs for some reason) an acceptable practice for primary method of donation of breathable gas.

The newly GUE configured JJ addresses this issue, as there still is a long hose incorporated into the rebreather system in an OC system driven from the CC bottles.

I've SEEN a few in action here in the PNW (GUE-JJ), but I DON'T KNOW JACK ABOUT RB and how they operate, just how my dive team members want me to handle a number of emergencies with their specific units and them when diving as a mixed team.

So with that disclaimer, this is pretty much as much as I can post on this subject.

BRad
 
The one major point with the DIR system (or any Tech system) is the ability to easily, and efficiently donate breathable gas.

BRad

I've got a 5ft hose on my left bailout bottle that goes to a necklace (with excess hose stowed against cylinder). This bottle stays on for the duration of dive. I don't have the necklace ziptied under the mouth piece or anything so I can donate just as quickly as I can on OC with a longhose. This is, however, inherently non-compliant with DIR (longhose on right post, short hose off left to necklace)....but it works well.

Big problem with RBs and DIR is many of over the shoulder mounted counter lungs that directly interfere with configuration and placement of D-rings and everything you clip to them (e.g. where to put backup lights). Also many RB divers incorporate side mount techniques to manage bailout cylinders which again is not perfectly compatible with DIR. Also DIR isn't a fan of replying on electronics (i.e. bottom timer and tables/ratio deco for decompression calculation). This until recently (GUE-JJ) seemed to rule eCCRs out of DIR.

The RB80 has been around for awhile and is DIR compliant.
 
CS,

I don't think DIR and CCR are particularly compatible. If you look to make the switch to CCR, you may want to deal with a facility that does nothing but deal with CCR. DIR type diving has its expertise in OC.

Just my opinion of course.

Claudia
 
There are a couple of compatibility issues from the way I see it.
1. There are certain hard rules that DIR follow that just don't jive in CCR philosophy such as donating long hose off backgas. Let's face it the chance of someone being out of gas when they are carrying their own bailout bottle are so remote as to be non existent. For that matter, a total gas failure on doubles is virtually impossible too but I digress.

2. Reliance on computers. DIR shun electronics and have come up with many contrivances to avoid using technology (Ratio Deco comes to mind) yet will still fall back on desktop software when planning.

3. Staging all tanks on left. CCR makes this cumbersome practice even more cumbersome when you are carrying an additional bottom bailout tank.

4. The DIR philosophy requires a CCR diver transitioning to CCR to complete many levels of advanced OC training prior to being allowed on a rebreather which makes it an unattractive option for those of us with more CCR dives than OC.

UTD tried to incorporate a CCR system that was suppose to be a smooth transition for OC divers to migrate to but in their attempt to make one work with the other they came up with something so very convoluted neither CCR nor DIR proponents could see the advantages. It seems one is just not the other just like a car is not a jet but they both get you places.
 
It seems the "DIRness" has been lost.

When moving to a rebreather, I followed on the forums the various DIR/rebreather threads.
It was more out of curiosity; I wasn't interested in trying to make my rebreather "DIR".

I'm still interested in what is being done. But I fail to see how an eCCR was chosen as the "DIR" rebreather.
 
For a very long time, GUE was skeptical about closed circuit rebreathers, because it was felt that the risks involved in diving such a system outweighed the advantages. The SCR used in their long exploration dives worked well and had fewer failure modes. But the agency has had to adapt, as exploration has become more remote and helium has become prohibitively expensive in many places. Exploration is a pillar of the organization's philosophy, and to continue exploration in the places, remote from deep caves, that GUE wants to explore, something had to give.

GUE has adopted the JJ CCR, and has developed a class for it, but the organization currently does, and probably always will limit the class and the use of the rebreather to Tech 2 certified people who are actually DOING the kind of dives for which the rebreather is necessary. It's a conservative culture.
 
I'm still interested in what is being done. But I fail to see how an eCCR was chosen as the "DIR" rebreather.

the UTD CCR is full manual, no leaky valve - no solenoid. they also use "ratio deco" and don't need a computer for actual deco, there is obviously ppO2 monitoring.

the "original" GUE rebreather is a pSCR, the RB80. Been around for over a decade. Has no ppO2 monitoring in its non-student configuration. plug and dive the drive gases. no underwater computer for deco either, deco planner/table based deco with a gauge.

the GUE CCR has a solenoid because they want it for deep stuff. mCCRs can't go below the fixed IP of the reg feeding the orifice O2, generally somewhere around 240ft. there are workarounds for this but most people wanting to do 300ft dives are using eCCRs. Solenoids are basically about as reliable as orifices in mCCRs which can plug up and "fail" too.

All three have a hog looped OC long hose under the breathing loop to donate gas to an OOA buddy with. So some of the earlier comments on this thread are incorrect depending on which (if any) of these units you'd consider "DIR"
 
There are a couple of compatibility issues from the way I see it.
1. There are certain hard rules that DIR follow that just don't jive in CCR philosophy such as donating long hose off backgas. Let's face it the chance of someone being out of gas when they are carrying their own bailout bottle are so remote as to be non existent. For that matter, a total gas failure on doubles is virtually impossible too but I digress.

It's true that an OOG scenario is very unlikely, just like the need to need to donate from a slung stage. A couple of distinct differences are the gas is an appropriate standard gas chosen for the depth, analyzed before the dive, verified to be on a working 1st stage before and during the dive, 2nd stage is verified during a pre-dive gear check, and the motion of donating is second nature from an O.C. background.

2. Reliance on computers. DIR shun electronics and have come up with many contrivances to avoid using technology (Ratio Deco comes to mind) yet will still fall back on desktop software when planning.

GUE prefers to know where the magic box comes up with the numbers. It doesn't mean the numbers are meaningless, just not baseless.

3. Staging all tanks on left. CCR makes this cumbersome practice even more cumbersome when you are carrying an additional bottom bailout tank.
With backmount bailout, it frees up more room for deco tanks where the DIR diver has known them to always be.

4. The DIR philosophy requires a CCR diver transitioning to CCR to complete many levels of advanced OC training prior to being allowed on a rebreather which makes it an unattractive option for those of us with more CCR dives than OC.

Unfortunately, part of the core training provided is based on knowledge gained in previous DIR training. A crossover would be near impossible unless someone has been training quite a bit in a GUE/DIR team.
UTD tried to incorporate a CCR system that was suppose to be a smooth transition for OC divers to migrate to but in their attempt to make one work with the other they came up with something so very convoluted neither CCR nor DIR proponents could see the advantages. It seems one is just not the other just like a car is not a jet but they both get you places.

That's something worthy of it's own thread...
 

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