I'm not, but if they post they need to be prepared to discuss & explain there thinking.Originally Posted by Johan Pretorius
I'm not, but if they post they need to be prepared to discuss & explain there thinking.
Like I say, I've been diving the Z-System for a year now, actually a bit longer. There is no difference in real world WOB. I switch over from back to sidemount regularly. The only difference you will be able to notice depends on the regs you use.
CCR Instructor Trainer
Not at all. Every new concept has to stand up to the scrutiny of peer reveiw and potential critisizm. Otherwise we would all just accept everything at face value and just accept what was being put forward without question.
If the developer of this system can't defend his rationale behind the design or use of the system then he has fallen short of the mark as a designer.
We look for weakness in rebreather design based on our experience and learning which is different for all of us.
If a rebreather designer can defend his techniques or design in this forum then one might be inclined to either adopt or disregard that design. If the designer becomes offended and claims we are picking on him then that tells me either the design doesn't stand up to scrutiny or the designer does not understand his own creation firmly enough. Either outcome will have an effect on who might buy the product or how much credibility the designer of that product has. There is nothing personal in our attempts to find flaws in UTD's logic behind this creation. It is the fact that it is radically different than what many of us have come to regard as conventional thinking that these very detailed questions are being asked.
Would you be so kind as to explain in what possible way that opening post could be construed as 'scrutiny from the community'
You've just pointed out that you have no experience with sidemount rebreathers, so why would anyone with any common sense reply with anything but distain to such a poorly worded and offensive post. If you'd said the same to me, or I suspect anyone with a spine you'd get a similar response.
I really don't have a vested interest in this, it's the unit I dive, it is particularly well thought out and I'd like to share what I know about it with the community. With that in mind I'll be happy to ignore your previous comments and whatever history you may have with Andrew to answer any question you may have that would give you rise to think that the machine is not up to scratch, that is up to my level of training and knowledge of course.
Dave
Kiss Classic
Hi Dave
As i said earlier, i'm not trying to be a PITA about this
The concept of this system is interesting and worth a look, however, it's the rational behind the lp plumming that is my concern
please answer directly......
Why put
Primary Gas addition to unit (mav)
Secondary gas addition (thru bov) (this is immediate, no plugging in to mav etc)
Main bail out system (bov) (again)
Main source of bouyancy
Buddy/team long hose system..........
Through one gas block?? I don't know anyone that plums their system this way, O/C or CCR,
It just seems like you're asking for trouble, there just doesn't seem to be any redundancy, other than plugging into another whip
Again, i'm wanting to keep thing civil and have a discussion
Cheers
Paul
Surly a system should be
Last edited by Curt Bowen; 10th November 2011 at 13:48.
The system would have a lot less failure points (multiple o-rings) by just removing the gas block I.e one additional hose that must run from 1st stage. even with such additional hose I think that the set-up would be cleaner. (maybe add some hose spacer block)
No probem, this might be a bit long but I'll try to be clear and include the background as to how the manifold came about.
Everything in the UTD system of diving relies on the same training methodology, you learn the same skill set in open water as you do in sidemount CCR at the other end of the scale, there are a couple of differences to learn in sidemount but the same principals apply as to our focus on trim, buoyancy the team and having the entire gas supply dontatable through the long hose.
So the progression goes, that from Open Water single tank backmount, if you're going into the overhead you need gas redunancy, so you learn the additional skills to dive doubles and in the overhead. Nothing changes you just add to what you know. Next if you go into deco then we add deco bottles on the left to the existing system, going further we add stages and leash.. everything is just built in steps upon what we already know without any changes in previous procedures. So with the MX we just keep a set of doubles, slide an RB in between them and add that to the existing skill set. So when you learn an RB then nothing is new except the loop, can and a couple of buttons. The compromise here is that the longhose is now clipped off and the necklace is the BOV.
So the question there is that do you either not do the types of dive that require RBs or accept that compromise. I think it's acceptable so I'm happy to dive the MX.
Now move that over to sidemount, we want to go places that require it. So with that in mind it's a case of reworking the skill set to use an existing system, or figure out a way to incorporate sidemount into our existing protocols or just not go at all.
That's kind of the start of the manifold, how to incorporate a looped long hose, necklace and access to all available gas through to both divers. It seems to be about the only way to do that.
The Argument here seems to be that in the case of independent doubles you don't need the hog looped set up, and in a specific case that is true, but it doesn't scale. In single tank rec sidemount it's not possible to pass off a tank, so how do you dontate, 2 regs from one first stage? It doesn't scale with our training if you don't donate the longhose from your mouth. So when you move onto the double tank setup, if you want to utilise 2 short hoses and independent tanks then fine, but it doesn't follow on in any of the UTD classes to change your skill set from the previous class. Thus with the Manifold you've just added another tank to the system you already know.
Now scale that again to the rebreather, and if you have a single Dil/bailout rec setup then again you can't pass the bottle, sure now you have many alternatives from the traditional rebreather train of thought, however they won't integrate completely with the rest of the equipment we use.
So to sum that up, the core is the DIR doubles set up. It's possible to refine that in certain areas, however doing so doesn't fit into the building block methodology of teaching.
Personally I moved from DIR doubles to the Z-system about a year and a half ago, I had some concerns initially as did the general community. I dove it recreationally then moved on to cave with it as I figured out that the problems the manifold creates have simple solutions. The skill set was a simple crossover and when I actually started diving the unit with other DIR divers it was instantaneous integration, after explaining the slight differences and nuances within the system.
Now when I went to backmount rebreather the transition was easy, the only new thing to learn was a couple of buttons to control the PPO2, and the buoyancy. Click the switch and I'm 200% familiar with the backmount doubles settup I'm now diving. For that reason I could almost say my last few hundred dives DIR have been training dives for a rebreather class, it's one small step to add on top.
Switch that over to the sidemount rebreather and we have the manifold again, with which we already know the problems and how to deal with them. So rather than come from diving independent sidemount I simply had to add top my current skills, the rebreather skills. It makes it a very simple transition, and if you'd like to see it in action watch the MX-Z video on the UTD site. That's my mCCR1 class and my first confined water session in the sidemount rebreather, maybe an hour and a half total time on an RB. It's one small step from the system I have a year and a half of experience on and you can see that easily.
So after all of that the question would be for me, do the benefits of all of the above outweigh the disadvantages of the manifold?
so:
BOV is on the manifold, ok. I don't want to loose the BOV at all, I won't dive a unit without a BOV given my current thinking on RBs. So what's the alternative, put it on a first stage. Which tank? a protected static LP manifold would have less chance of failure than a dynamic system like tank valve or first stage. If either tank fails then I still have my BOV.
Primary Gas addition to the unit. I would consider this as a non issue, I can swap out the QC6 to the dil injector easily before my PPO2 drops below 0.16-0.18
Secondary Gas addition to the unit through BOV. Disconnect the DIL and plug the second stage to it. Gas addition now means seal the loop, take a breath from the reg and blow it back into the loop. To have to do this you've already had to loose both injectors and the manifold. So therefor although not difficult to do I wouldn't contingency plan for this, too many failures on one unit. I'd have gone to OC by now breathing from my dil tanks.
Main source of buoyancy. Well actually padi taught me to oral inflate many moons ago, I might have to get on my knees in the sand to remember how but I reckon I could still do it :D On the other hand the point is valid if multilevel cave diving. If I know there will be the need to descend again to exit, then there must be a backup in place and for this for sure you would add inflator hoses to each of your first stages. I'd say this is included in proper dive planning. As the manifold is LP you could open it up to inflate at a push without loosing too much gas.
Team/Longhose. Well this goes back to the heart of DIR. We are willing to accept that a right post or manifold failure will take the long hose out of the game, that's one reason we have a team. We don't plan on 2 HP dynamic failures in DIR backmount, so we don't plan on 2 LP static failures in sidemount. In actual fact there is the added redundancy that the worst case manifold failure still leaves me with my lowest pressure tank on top of sharing gas with my team. The HP manifold is often the first point of contact with the cave, the Z-manifold is protected in that is cuts almost no profile over your back.
Right... that did drag on but I wanted to be concise. So with my knowledge of the for and against arguments for the manifold, yes there are downsides but they are far and away outweighed by the upsides. I'm not claiming it's perfect or everyone must dive this way but I do hope that explains a lot of the legitimate questions behind the system.
Dave
CCR Instructor Trainer
Thank you for your elaborate reply. It does lay out a lot of the methodology behind the system but there are still some items that might be perceived as flaws in your philosophy for those of us who might not put the same amount of importance on certain small details like where the long hose is routed etc.
The one that comes most immediately to mind is the comment above. It has been mentioned by myself and others that putting all your gas through a common failure point (gas block), exposes you to a certain "eggs in one basket" level of failure mode. What that means is with a CCR the gas in your lungs is part of a very limited supply in the event of a loss of the ability to provide gas volume. Therefore in the event of a failure of your diluent delivery system using the volume in your lungs to inflate the wing will not really provide you with any additional bouyancy for the same reason that taking a deep breath on a rebreather does not cause you to float up.
Last edited by wedivebc; 11th November 2011 at 01:01.
Yo' let's keep this thread in check, I'm ALREADY tiring of the amount of time required moderating it (hint)!!
No Problem. Obviously I agree that taking a breath from the loop and inflating the wing won't do any good.
So the options off the top of my head are to oral inflate the wing then:
1, hot plug a dil tank to the dil injector
2, Plug the spare 2nd stage to a dil tank and use that gas to inflate the wing
3, Plug in the spare 2nd stage to the dil tank, breathe out into the loop then switch to OC to sort yourself out using the loop.
4, Temporarily reopen the manifold to inflate and allow that minimal gas loss. I'd say this would probably be my first port of call.
5, ok this is possible and I can't think of a situation in which you would do this, but you could unplug the O2 supply and connect the dil to that injector. (edit to add that we will be using standard mixes so the bottom mix should be at 1.2PPO2, anything hypoxic and we would be carrying a deco mix that would be breathable to 100% rich at whatever depth we are at.)
Hope this helps,
Dave
Last edited by Dave1981; 11th November 2011 at 19:48.
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