Drager Dolphin:

[fins wake]

... a Dräger SCR, right?

which would put your PO2 at 1.20 right after a system flush,

If you're on a constant mass flow SCR such as the Dräger, you won't really need to worry about 'flushes' (i.e. releasing loop gas through the nose three times or so in order to activate the bypass valve) unless you're ascending.

I think you might be confusing, say KISS-style CCR:s and a CMF SCR? Easily done on the web and if one hasn't dived them, so I'm not being sarcastic. I had these problems understanding the different concepts in the beginning as well. :sheepish:

But cruising a long at a steady 30 feet (or 60 feet or whatever) the mass flow system itself will take care of holding the ppO2 reasonably steady. (Remember, it will vary if your oxygen metabolism varies, e.g. due to currents). I do 'flush' upon ascending, however. Good practice.

I am not going to question a person who has 125 dives on the unit to my zero

Absolutely, not my intention to flame Scuba Chip for his personal diving habits. :embarr: :mgun:

Scuba Chip has more dives on his SCR than I do. However, he is advocating something which is specifically argued against by Dräger themselves (on page 17 of the manual, I think) and which is supported by ANDI only provided you do their course and run a different configuration. If one is non-certified or new to the Dräger series one should be aware of this, that's all.

Anyway, enjoy your diving, Jepuskar!

 

[Scuba Chip]

Jason

To answer the questions you posed: You wouldn't use EAN50 on a dive to 120 feet. As you point out, your PO2 would be too high for that rich a mix, at this depth. The mix I use depends on the depth I am going to, but I always try to use the richest mix I can - highest O2 level - mindful of the MOD for that mix. I always plan for moderate workload and use the middle orifice. I have used a PO2 monitor on many dives, but not on all my SCR dives, relying on estimates of inspired O2 on these other dives. In my experience, the manual estimates are reliable. Your actual O2 inspired level will vary, and subsequent dives on the same canister of CO2 scrubber affects inspired O2 levels (obviously). Initially, I was fixated to the PO2 monitor, and not enjoying the dives. All divers need to admit to themselves that when it comes to "rates" for gas absorption, and elimination - whether on OC or SCR - it is all about estimates. We can calculate all we want, but the actual absorption / elimination rates are not exactly what the formulae suggest. Formulae can NEVER account for the physiological variables. I always dive with my integrated UWATEC computer. I am a big believer in slow ascents, and never shy about a deco stop. It's like going to confession - it forgives lots of sins. To aid an effective deco stop, you simply cross your arms in front of you. This arches your back into the rebreather bag of the Drager unit, flushing it, increasing Your inspired O2 level at stop. No harm in that.

I wouldn't use a Drager in 20 fsw. I can get plenty of time from OC at this depth, and there are less details to deal with in OC.
In my opinion, the Dragers are most valuable in the 60' -110' or so, foot range.

I was originally trained on the Drager Atlantis. The Atlantis used vinyl rebreather bags, chrome plated brass fittings, and carried a steel tank for the nitrox. My instructor developed this unit with/for Drager. He wrote a manual for this unit in use today. My insructor was selected to introduce the son of a very famous French ocean explorer to this unit. Parenthetically, this very famous French dive group had never used rebreathers before. That revelation really surprised me.

I was one of the very first - on this side of the Atlantic - to use the "new" Dolphin version of the Drager Atlantis. That was 5 years ago. The Dolphin employs a nylon material for its bags. These bags have a handy plug for cleaning and rinsing which the Atlantis lacked. The Dolphin uses polymer fittings - a plastic type material. It came supplied with an aluminum tank for the nitrox. I remember that first Dolphin dive very well. Six of us, all experienced Atlantis divers, jumped in and promptly found ourselves too bouyant. No one was more surprised at the changed bouyancy characteristics of the aluminum tank than the Drager Official diving with us. It was his 1st Dolphin dive as well.
My personal preference is for the nylon bags and a steel tank - 'cause of the bouyancy characteristics.

I was taught to use these units for decompression diving by Drager officials, and Drager representatives. At least 2 of the technical training/certification agencies that I am aware of, teach deco use of these units. Would I put a rookie SCR diver into a decompression dive? No way! Not anymore than I would place a newbie OW certified OC diver in a decompression setting.

I am very comfortable diving the Dolphin with decompression obligations. In my dives on these units, 45-50% were deco dives. But all of them incorporated a safety stop, required or not.

I have heard the response of my Drager dive buddies (who I continue to dive with) to questions posed regarding modifying the units for use as a CCR, and I can quote their top guy, who unequivocally says, "run the other way."

I have offered my experience, and expressed my opinion without taking any unwarranted cheap shots at anybody. I don't have to. I don't need to impress you with what I read somewhere. I have experience with these units. And for that I am not sorry - mate!

I hope this is helpful to You Jason.
Should you come across an 'experienced' Drager unit boldly sporting "UWATEC" labeling (and there are a number of these in circulation) I can explain that apparent discrepancy to you as well!

If You are serious, and willing to spend a couple of bucks, I can connect you with an expedition (forming now) that will get you rebreather certified, give you about 25 rebreather dives, and provide you the diving experience of your life! PM me for details.

May Your dives be long and Your surface intervals short

 

[Tigerscuba]

I have dolphin, well at least an atlantis with dolphin guts. Overall its a pretty good rig. I think what it all boils down to is what do you want out of it. You see there are people who who enjoy reefs and wrecks in the mid ranges, say 50'-100'. If this is your dive profile then the dolphin will indeed be an outstanding unit for you. But if your a trimix diver who likes the wrecks at 150+ then a ccr is the only way to go. I think if you posted your experience level, typical dive profile, and goals you may get better advise from us. The best approach in my opinion is to set down and write down your profiles, intended goals, and what you want out of diving, both now and down the road. Then pick the best tool for the job.

 

[Jaytor]

Hi folks -

I'm not as experienced a rebreather user as many (most?) on this list, but I'll add my two cents. I owned a Draeger Atlantis (which I think is very similar if not the same as the Dolphin) 4-5 years ago. After diving with it for a while, I decided to sell it and switch back to OC. For me, the advantages didn't outweigh the disadvantages.

I'm a semi-pro underwater photographer (meaning I sell my photos but don't make a living at it) and was hoping that the SCR would allow me to get significantly closer to marine life. The Atlantis has some advantages over OC, but not much. It still generates bubbles, although they are reduced compared to OC and come out of the back of the unit instead of in front of your face. However, unlike OC, you can't hold your breath for a minute while you approach to avoid bubbles. The oriface is open all the time whether you're breathing or not.

My bottom times with OC (Alum 80) are typically 70-90 minutes. I generally don't like to stay down longer even if I have air in my tank and often come up with >1000psi left. I had a hard time finding >EAN40 at most dive locations, so my bottom time with the standard tank on the Draeger was no longer anyway. And my theoretical MOD was reduced compared to my typical EAN32 OC mix.

I was always somewhat paranoid about the scrubber, so changed the scrubber material between almost every dive, particularly if I was down for >60min. This meant that my maintenance time for the rebreather was on the order of 30min during surface intervals. This left relatively little time to work on my cameras, and I often found the other OC divers had to wait for me.

I am quite interested in rebreathers, and would consider getting a CCR unit. A CCR unit would virtually eliminate the bubbles and provide real advantages in stalking marine life. Most have a scrubber and gas capacity that will easily allow 2-3 hour long dives with minimal maintanence between dives.

I don't think the SCR units are significant safer than the better CCR units. Both require considerable training, diligent maintanence, and careful attention while diving.

Once I had the Draeger configured the way I wanted (PO2 sensor, pony bottle on each side to balance weight), my investment wasn't that much less than a CCR rebreather.

So, if you're serious about getting a rebreather, you might want to take a closer look at the CCR units before making a final decision. Hope this helps.

- Jay

 

[fins wake]

... honest to God, I don't want to start a flame war with a fellow RB user. I enjoy a ruck, but not with someone who has more dives on the specific unit than I do. (Nah, I don't want to impress anybody, I do have experience on the units myself, I do want people to follow manufacturer's recommendations and live long etc etc. Peace!)

Point is, I still think the Dräger's a much worse decompression device than the Inspiration, say, and not just because Dräger themselves say so ...

Anyway, to end on a lighter note, a quick flash-back from memory:

My insructor was selected to introduce the son of a very famous French ocean explorer to this unit. Parenthetically, this very famous French dive group had never used rebreathers before.

The father of Jean-Michel, the great Jacques actually did experiment with very early and simple rebreathers before joining up with Emile Gagnan to make the first 'modern' regulator, the aqualung. He describes it at the beginning of his seminal work, Le Monde du Silence. Basically he oxtoxed and almost killed himself, which really ties the knot to the hyperoxia threads on this forum (the 'narrowing white tunnel' etc.). End of experiment. No more rebreather diving for him. The rest is history.

So, if you're serious about getting a rebreather, you might want to take a closer look at the CCR units before making a final decision.

Amen! But dive safe. And since the great Jacques has been mentioned, let me briefly cite another of his sayings: Happiness for a bee or for a dolphin is to exist. For Man, it is to know this and ponder upon.

Dive safe, y'all.
K.
(with apologies for my French translation.)

 

[jepuskar]

A system flush in the Drager is considered by me to be getting rid of the entire contents of the inhalation bag....it is a pretty wise thing to do right before ascending or even throughout the entire ascent. Some people even go as far as saying switching to OC for the ascent.

Maybe a system flush in a CCR is different, but I definetly want to know what I am breathing when ascending...especially for lower mixes.

Jason

 

[fins wake]

Some people even go as far as saying switching to OC for the ascent.

Never! I think - and hope - this is an area where Chip and I will be in complete agreement. I've never switched to OC for ascent on either CC or SC, and never will use it as SOP.

This is typical OC-induced ludditeism. Unless your loop is flooded, or you're really spooked for whatever reason, you never really come off the loop! This goes for both SC and CC.

I do my flushes after ascending, not before. There's really no point in doing it before, you just waste diluent.

Jepuskar, I believe you're ready for the course. Go for it, mate!

/Edit: 'flushes' separated from 'after' in italics.

 

[saturated]

There alot of Dolphins in closets, mine included. The reason they are in closets is quite simple. A low pressure steel tank with a good fill gives me as much bottom time as the dolphin with half the hassels. Now a ccr on the otherhand is a huge leap forward and is well worth the added setup/teardown time. Dolphins are pretty good units. the problem is most guys I know outgrew them to fast and now have a $3500.00 rb collecting dust(Complete setup). If I had to put my stamp on something it would def be the inspiration. Your not likely to require more than it has to offer.

The flush prior to ascending is taught to provide a known mix prior to ascent. Most guys dive these units with no way of knowing their mix, so having a known mix prior to ascent may not be the worst thing to do. In reality though it is more for sanity than anything else.

 

[undah20]

I think you'll like the Dolphin a lot, it is a good, reliable unit for most people.

First a re-read of tigerscuba's post seems appropriate to me. It seems a good summary, and then I can post my own rambling here.

Some of the things I've found with my expeirience using the Dolphin: Excellent for the experienced OC diver who wants to try something new and venture into something other than OC (all with PROPER training of course). You 'learn' a new way of diving, and don't rely upon your past OC experience as thinking it will make you good with SCR diving - keeping an open mind of course.
The lack of bubbles do help you get closer to the aquatic animals, but not tremendously so. Both language has a lot to do with it also. And if you are with other OC divers nearby, forget it. (Jaytor have you tried purposely creating an exhaust before approaching the shot ? - this acts similiar to the breath hold technique you employ in OC). But there is a periodic exhaust unlike CCR. You might really like the far more quiet aspect of the SCR versus the minimized bubble aspect (if you can understand the difference)? I think the effect of the better silence is an asthetic that will draw you more into SCR and beyond.

I have always employed BOTH the Drager Oxygauge and Uwatec Oxy2transmitter with XO2 wrist unit for diving on the Dolphin. I cannot see why SOME Drager divers feel they dont need ppO2 monitoring? To me it is like diving without a depth gauge and thinking it doesn't matter as you know the reef like the back of your hand. Things can always change - workloads, comfort levels, ANYTHING). I have the best of both worlds. I may have overkill redundancy, but with 3 monitors - I know both my breathing concentrations and real-time inhalation loop as well (as the two different units are in use in different areas). It you have to choose just one, IMO, the Uwatec combo FAR benefits outweighs the oxygauge - you know real-time actual breathing loop O2 concentration).

I flush the loop (through nose exhalation) at the end of every dive at the shallowest of safety stops). I want the benefits of inspiring the loop prior to exiting the dive. Bailout is there as secondary bailout, not for gas switching to avoid hypoxia.

I find that even after extensive DCR/SCR (depth air consumption/surface air consumption) rate configurations, workloads do end up changing as experience increases. The limiting increase of of ppO2 for dives in and around 115ft +/- 10 feet to be very limiting with the Dolphin or any SCR. Benefits for shallow dives are outweighed by increased comfort and experienced levels as well. Now, at the point where I am able to make 90-120 min dives (irregardless of target depth - considering no-decompression recreational dive profiles) on 80AL single tanks with 75bar/1000 psi reserve upon surfacing, I've outgrown the purpose of the the Dolphin. Making strictly 30-40 ft dives with OC, I can easily match the Dolphin profile with less maintenance and cost.

Being a deep freak, and very comfortable at depth, again I've outgrown the manufacturer's Dolphin intent. I've been looking extensively into restructuring it for KISS, etc, use, but WHY? I mean, for the cost and headaches, there are CCR out there with much better results (ie Prizm Topaz - same size and weight as Dolphin).

My opinion/post is just to say that with a great deal of experience, you can quickly outgrow the Dolphin. Don't get me wrong, I really like the design and functionality of the unitand I'm not talking about you amking the jump to CCR. I think taking the training on the Dolphin, diving it for a while, renting the unit in your area or on vacations for a good many dives, is a better option and save you a great deal of money in the long run. If you end up getting a Dolphin, you'll be all the more experienced and pleased. If you end up passing it by, going CCR, or staying OC, you'll be pleased with the knowledge and experienced gained by the addition of another diving feather in your hood.

 

[undah20]

ha ha ha ha, that was funny!

I meant "Body language has a lot to do with getting closer to aquatic life also!"

ha ha ha ha....I'm running for my XL Latte now!

And all you CCR divers, are you totally enamored by the total love of no bubbles? Must seem strange to think backwards to OC and SCR with all those bubbles in the water...
aahhh, nothing but the wonderful blue and the sounds of the ocean!