newbie seeks advice.

sylverbard

ok.

not a new diver, but looking to expand my skillset and abilities. as a photography and video hobbyist a rebreather is eventually in my future, and i want to make an informed, educated opinion on what to buy.

if you have the time, and have dove one or a number of rebreathers, i would greatly appreciate any insight you may have on:


-operating depths;
-maintenance costs and needs;
-ease of obtaining parts in North America or wherever you live.

Many Thanks!

Abbo

Most of us are in denial about costs, but I thought I would give it a go. I've used the Rebreather World Store for US data; costs are far higher here in Japan, but then the diving's better . I have converted all legacy units into modern metric.
Sorb: costs $125 for 20Kg. A 2.5Kg fill officially lasts 3 hours. That's $5.21/hr.
Sensors: are $55 each and you need 3. Assuming a 150 hour life, that's $1.10/hour.
Oxygen: fills are around $10 for a 2.5 litre tin, which lasts around 4 hours with wastage. That's $2.50/ hour.
Diluent: is consumed mostly for inflation. Say $5 a fill lasting 5 hours (it's so small most places fill it for free). That's $1/hour.

The above comes to $9.81/ hour (spurious accuracy there).

Assume a rebreather costs $8,500 (not including instruction, which shouldn't be depreciable if you don't have Altzheimer's). Assume that lasts 10 years at 150 hours/ year. That's $5.67/hour.

The fully-loaded cost works out at $15.48/hour: cheaper than children and way cheaper than my wife. Actually, the depreciation costs are likely to be considerably cheaper: assume a Moore's Law-type of effect - makers are likely to give us better and safer products for less and less money. I expect to replace my Meg for a substantially better product at a dramatically low price in 10 years.

As for the vexed problem of choosing a rebreather, I wish to goodness that somebody would write something on this subject for the library, as the question gets asked about once every fortnight, and the answers get worse, not better, over time.

The major division in rebreathers is into manual and electronic. Advocates of manual rebreathers say they picked mCCRs because electronics and water don't mix. Frankly, I think this argument is specious: all rebreathers use electronics to measure the PO2, and the PO2 measuring is one of the chief weakpoints of all rebreathers. A rebreather is a tool: the choice of tool depends on the choice of job. Allow for mission creep: you may well change what you want to do with it over the life of your rebreather, so buy one that can do far more than meet your present needs. Beyond that, I would merely recommend you read some of the previous 'which rebreather' threads, and attend a tryout session where you can touch and try several units.

Freef

...or SCR vs CCR!

Back to the OP.

If you are diving to 40m max you can use SCR [Semi Closed Rebreathers] over CCR. They work more as a gas extention tool than a 'stay down ages with minimal deco' tool, and they are more limited than CCR-they also bubble a bit.

I dive a Drager Dolphin [a more flexible unit than the Ray]. With a 5L tank I get 2 hours of gas, including a 50 bar reserve, for the weight of an OC single 15 set up. The unit is easy to dive, and known as 'passive' in that the electronics don't control the gas in the loop, only tell you what you are breathing. PADI and the tech agencies do training on the Dolph, it's easy to get one second hand and there are probably more Dolphins in the world than all the other units put together.

A Dolphin costs about half the price of a CCR unit, and uses about 2 1/2 kg of scrubber per 3 hours [again, with a safety margin]. I've done 50+ hours on mine with no problems [apart from one user error!] so far.

Shallower than 40m, no extended penetration [>100m], you don't mind a few bubbles:

SCR Dolphin, Submatix, Azimuth.

Deeper than 40m, or extended penetration [100m+] you don't want any bubbles:

mCCR Kiss, Submatix CCR
eCCR Inspiration, Megalodon

The above lists aren't exhaustive.

The other thing you need to be is disciplined. Rebreathers WILL kill the user if they take short cuts with preparation. SCR's will try to keep you alive because of the way they work, and CCR's can be 'bailed out' into SCR mode, but either is far less forgiving than OC.

Try the following for an overview of the different types of rebreather:

Amazon.com: Simple Guide to Rebreather Diving: Includes Both Semi-Closed Circuit and Fully Closed Circuit Systems...

__________________
David.

Currently owner of two differently sized ankles.

Caves&Bunnies

Hi,

Maybe I'm missing something, but I dont see a corralation between penetration and the use of a SCR.

Are you recommending that deeper penetrations should only be done on a CCR? If so, can you elaborate on this conclusion? With proper bailout and/or stages, the proper application of the rule of thirds, and not exceeding the max depth of the unit, how does the use of a SCR (Gas extender) lend it to not be recommended for deeper penetrations?

Thank you

Cheers

Mike Edmonston

pete611

Hi...I been diving a Drager Dolphin for 4 years. If you like Underwater Videos and Photos rebreather are for you.I dive the dolphin with a SS backplate and Dive Rite Harness and a 100 lb lift wing. better that twin Tanks and more time....

__________________
Warm Water Only For Me Please.. ><))))°> ><))))°>
WARNING: the rebreather is not broken is a Dolphin!!!

Monkey

I agree and Disagree on some of your points... I agree my diving is way cheaper than my wife... however.... you have neglected to include the ancilary costs of rebreathers...

First you get the rebreather.... then maby 3K worth of electronics... then you want the 2K booster...then you need more tanks to bank drive gas for the booster .... and the nice fill whip kit at 700 bucks.... then you want the compressor to drive the booster... and then you end up with multiple rebreather bottles because you now throw helium into the mix.... and lets not forget the analysers...and then we have lights...and dry suits..and the guy who made your electronics comes out with new handsets...and that only a 1500 dollar upgrade...

I am only slightly in denial...there are some who own multiple rebreathers.

wait till the wife wants one.

The ancilary cost are real... but if you look at the cost of 240 cubic feet of trimix for the OC people.... a rebreather can make a good finacial argument in favor of the rebreather..

but don't fool your self into thinking they are cheap to dive.

when I raced Porsche's, the car ended up being only a small percentage of the cost of racing for a year.... and rebreathers follow the same path.

but boy I don't regret any exspence...they are worth every penny.

Abbo

Car manufacturers say that the more they add safety features the more that people take greater risks, with the result that risk is constant at best. I suspect the same is true with divers: the more we trust our equipment the deeper we go, the longer we stay, and the further we penetrate. I suspect that the equipment-buying is as compulsive as the risk-taking: the more that manufacturers give us better products for lower prices the more we are able to justify our shopping - and the fuller the garage gets!

However, let's leave out the obsessive-compulsive behaviour for a moment and assume an efficient market hypothesis! I switched from OC to CC to save money on the helium: that's a pretty common reason for switching. OC divers spend far more on gas than I do. They therefore have far greater incentives to invest in equipment to allow themselves to make their own mix than I do. You didn't buy the filling equipment because of your switch to CC but despite it. As for the dry suit, OC divers breathe far colder air, so they need dry suits more. I bought a dry suit: the Devil made me do it. I'd far rather freeze my rocks off than put on that thing.

Oops, I didn't realise I was writing in an SCR area. You're going to have to take my word I'm really not trying to provoke an argument, but I never invested the time to understand the attraction of SCRs. My understanding is that they are generally used in the 0-40m region, where helium costs are not an issue, so the cost savings are smaller. They make bubbles, so they are suboptimal for photography. They operate in the part of the water column where increased complexity makes SCRs and CCRs more dangerous than OC. What is it that offsets those increased risks? Being a married man I can argue 24/7 at my slightest whim: I come here to learn.

Flup

Bought my first rebreather when my wife left me. No wife is more money, so why not spend it on a nice tool

Already had a compressor, some stages, lights, O2 and Helium buffers, drysuits etc. etc. So those cost are already made for OC diving (what the **** was that again ), and are not just because of (S)(C)CR diving. The Booster I just ordered, waiting for it to come soon, so ja, that's another 2K going out of the pocket,, invested in fun, pleasure and some leisure

As the wife left, the girlfreind came in, first the MEG, later a life one and yeah, she's now diving a breather too (Dolphin) So there are now 4 units in the garage. (And i still like my hobby )

Correct, but it gives so much fun.

Can completly agree with that. So let's go silent diving.....

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They say i'm all mixed up, maybe that's why i like mixed gas diving !!!!

Freef

SCR's are time limited in the way that CCR's aren't, and in that way are more like OC than CCR. I get 2 hours out of my Dolph's 5L, at whatever depth. This is like the duration I would get to 30m-ish on my twin 12's. So on a long penetration, particulartly if things start to go wonky you still have a fixed duration of gas-the same as OC. On CCR you could always carry bailout for the return [plus 1/3] and plan the whole penetration on CCR including the return. If at any point you have a unit failure you can get out on OC.

You can also lower the setpoint to conserve O2 if things get really sticky, you can't [easily] do that on SCR.

For long penetrations CCR's are more flexible and a lot less kit to carry than OC, for the SCR operating depth of 0-40m I can't see any real benefit over OC for long penetrations on the safety front. The only benefit is that SCR is lighter for the equivalent gas duration. But if you take the bailout into consideration you can end up with a heavy rig anyway.

By long I mean 100m+. That's a long way in anyones book. I doubt that many divers actually get 100m inside a cave or wreck [wrecks usually have other ways out than the way you got in as well] very often, if at all in their diving 'career' anyway. [In 900+ dives I've managed a total of two, both in 15m and on OC, the longest 175m]

For deeper penetrations [40m+] I see CCR as the way to go. With more flexibility on the depths you can dive compared with OC and longer duration that OC or SCR the benefits are obvious.

I know that the RB80 and the like are used for long cave penetrations, but they are a bit more specialised than anything that the OP is likely to want for getting closer to fish. The problems obtaining one, and the training, are likely to rule one out.

Grumble grumble, bloody CCR lot coming into our forum grumble grumble...

To answer your points:

0-40m, twin 12 duration on the weight of a 15. The weight issue is a major factor [although I dive twin 12's as well for trimix]

They can be used deeper [SCR trimix is feasable] if you understand how to.

The costs of about 1/2 the price of CCR, and decanting from a 15L into the 5L mean that my costs are about £3-4/hour [excluding training and kit], OC would be slightly more, £4-6/hour depth dependant. If I include kit costs, there isn't as much difference [yet] but the more I dive the cheaper it gets.

The bubbles are depth dependant. As there is a fixed surface volume of nitrox entering the loop at 10m the unit bubbles half as often at the surface, at 20m 1/3 as much etc. Also the amount of gas dumped is around 1-2 litres every four-six breaths at the surface, so the bubbles are smaller and quieter than OC-and fish don't get as scared.

SCR's do try to keep you alive. The electronics are for monitoring only, there is a continual flow of nitrox into the loop, and your vO2 needs to be well over 3 for a long time before you will make the loop hypoxic at standard gas and flow rates. If you keep half an eye on your loop fO2 during a dive it will hardly vary. They aren't that complex a bit of kit, and although they do need a bit more kit prep than OC, and a more disciplined diver to go with them, I don't see that they are much more dangerous than OC. If they were I wouln't dive one.

__________________
David.

Currently owner of two differently sized ankles.

Flup

This also goes for SCR, you can (need) to carry enough bail-out to get out on OC in worst case scenario (things go wrong at turning point). This means any diver OC, SCR or CCR are committed to the same bail out gasses, there not much difference in that. Only the 'back-gas' is different --> OC, SCR or CCR, meaning lots of bubbles, less bubbles or no bubbles

Treu, but the use of oxygen on a CCR is so minimised you don't need to do this. (if you take at least a full tank off oxygen)

Like mentioned above, bail out will be closely the same for all the systems. And if you play around a little with your SCR (don't try this at home people ), then you can gain a few advantages to OC. Put your bail-out/deco-gas on the loop (I do that with a minor modification) so you gain lot's of gas duration. Also it enables you to push the 40 mtr limit (watch it, no deeper then 75 mtr's on a dolphin). You go in on deco-gas, on depth switch to your 'bottom-gas' (which has a lower pO2, even trimix if you want to) and out you do it backwards. But like said, don't try this at home, your not diving factory-standard any more.

Correct, but stil there are a number of people who do this on a kind of regular base (like me said the madman ) In the ol' days (OC time) I pushed the Ressel once for about 1000 mtr. Was a very nice dive, with a lot of heavy gear to carry around. Was scootering, so diving the rules of 5-th. (one of the reasons for me to switch to CCR).

Sorry, will try to stay out next time

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They say i'm all mixed up, maybe that's why i like mixed gas diving !!!!