manual addition...old school?

Icarusflies

zoo_diver

Howdy --

I dive an manual but have buddies that use electronics. They both have their pros and cons and if you read through the archives of Rebreather World you will find that similar threads carry on for weeks. In the end only you can decide what will work best for you. I am a fan of the old KISS (though I dive a MEG) adage -- Keep It Simple Stupid. I can't comment on the unit you are talking about that you say is only electronic. I would not like that feature (rather lack of features) on a CCR.

Good lucK!

Edvin M

Well, the Sentinel level 1 is more like a recreational rebreather, pretty much the same as the Cis-Lunar/poseidon mk6 with a computer which tells you what to do in every cituation lika bailing, go to surface etc and the next levels is more like conventional.

So yep, you have to trust a computer all the time if you choose level 1

caveseeker7

Well, there are two things to be considered:

- the way you dive your rebreather
- the way you plan to act during a failure

Both of those issues are heavily debated, of course:

Either: Dive manually, use electronics as a parachute only.
Or: If I wanted to dive manually I would have gotten a mCCR.

Either: If in doubt, bailout (to OC).
Or: OC bailout is the last resort.

The sport version of the Sentinel, just like the new Poseidon/Cis-Lunar MK-VI, is targeted at sport divers and thus pretty much limited to recreational depths. Which, by the way, goes hand in hand with the initial Rebreather certifications offered, they usually also impose a 40m limit. As does, IMHO, air as a diluent.

Hence their argument is that in case of a malfunction you should bailout to OC and return to the surface. Both manufacturers accommodate this train of thought by issuing their rebreathers with BOVs.

As far as I'm concerned, bailing out to OC is perfectly acceptable, and likely the smart thing to do at a beginner's experience level and at recreational depths.

As far as controlling the setpoint, I'm comfortable doing so, then again I dive a manually controlled rebreather. I did spent some time diving an eCCR, and used the unit as such. I would do a dive a day manually controlled to practice, or at least a large part of a dive. Otherwise let the unit do its thing and just making sure it does. But those are personal points of view, they'll differ from one diver to the next.

One thing to consider is the diving you do, and the diving you want to do down the road. If 70m wrecks are on your itinerary than either of those sport rebreathers are not going to do it for your needs. Unlike the Sport Kiss they have electronics not playing along.

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Stefan



"It is still a good day if you are on the green side of the grass!

Su amigo Roberto!"

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Icarusflies

caveseeker7

Don't know the unit well enough to answer that for certain, and I doubt that anyone else here does as it hasn't hit the market. The electronics are new, and different even from the Ouroboros from what I understand.

But some general thoughts:

- when two cells go bad in close proximity, most CCRs end up "voting out" the good cell which deviates from the majority. AfaIk only SMI has implemented a form of "cell tracking" and Poseidon/Cis-Lunar will go a step further with continual "cell verification" during the dive. On most units up to the user to do a dil flush and verify the cells reading, and monitor the display when the setpoint is raised again.

- computers can hang, crash, whatever you call it. Depending on the display, for example a HUD displaying solid light for OK status can hang when the light is on. It'll stay on, thus giving wrong info. Up to the user to monitor all displays and make sure they're not static.

- solenoids as well as other valves can get stuck open or closed, gas leaks into the loop can develop, changing gas composition. Electronics should notify the diver, but he needs to pay attention and the skills to react.

__________________
Cheers
Stefan



"It is still a good day if you are on the green side of the grass!

Su amigo Roberto!"

Sponsor Lou in Race For Life!

Ant Slegg

Speaking from the Ouroboros standpoint I am suprised when you state that there is no manual O2/Dil add on the Sentinel (this would fail a CE approval???) but can firmly state that with the Boris the electronics controls the ppO2 to a level selected by the diver and the diver maintains a regular (1 per min) check on everything via the display that gives all 3 cells values.

Speaking personally I would only do manual addition during periods when the ppO2 was changing rapidly or when I decided that the electronics was hosed and chose to go to manual control (having bailed out first).

The bottom line is that having spent thousands on electronics most people wouldn't then do the job themselves. If you are determined to do manual ppO2 control as your primary then maybe it is better to simply not have the electronics. In my mind this is akin to am OC diver buying a dive computer and then planning all their deco on tables. In the end there is sure to be conflict.

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Ant' S
Learning to dive since 1990...

caveseeker7

The Sentinel comes in three flavors (MODs):

• 40m
• - no independent secondary
• - no manual add valves
• - air diluent (deco computer)
• 60m
• - secondary display
• - manual add valves
• - normoxic trimix
• 100m
• - gas switch blocks
• - solenoid and ADV isolation valves
• - hypoxic trimix

The 40m sport version also has a 3 ltr on-board diluent tank that is supposed to be sufficient for bailout, the other two versions have 2 ltr tanks.

Anyway, that's what I remember, the features list is on the website.

__________________
Cheers
Stefan



"It is still a good day if you are on the green side of the grass!

Su amigo Roberto!"

Sponsor Lou in Race For Life!

paulraymaekers

Hi steve, if you're in doubth, go for the rEvo hybrid
you can dive it the way you want, manually with electronic backup, fully electronic with constant mass orifice back-up, pure electronic..
it has man add buttons for both ox and dil, and has standard integrated trimix deco

paul

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Pelagian

You will never be able to trust any electronics 100%. All torches, strobes, computers etc will eventually fail.

Having chatted to Kevin about the 3 levels available on the Sentinel, it is my belief that the absence of manual addition valves and a secondary display on the L1 is to make the unit as simple as possible, for the 40m range where if anything goes wrong you simply bailout and get out of the water.

This is reflected in the simplicity of the HUD:

Green = Good
Orange = Check your handset
Red = Bail out

While I'm an advocate and practitioner of manual flight, It has been my experience that the bulk of eCCR divers fly their units automaticaly especially at the entry level.

The Sentinel allows you to progress into increasingly sophisticated options for problem solving, as you yourself progress in your capabilities.

There is an argument for teaching problem solving skills that allow you to stay on the loop, from the very beginning of your training. I think it is a valid argument if you intend to move into a style of diving that requires you to stay on the loop if at all possible. But in the 40m range and a non-overhead environment there is an equally valid argument that it is simply safer to bailout and stay off the loop.

It'll come down to what kind of diving you intend to do, but the Sentinel can take you to wherever you want to go.

Cheers

Seb

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