Newbie Post, My 12th CCR, (Shakedown) Dive

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Mastow1

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Newbie Post, My 12th CCR, (Shakedown) Dive

As a new Choptima diver who had not dived it in 54 days, I joined two CCR divers for a shakedown dive. Ergo, check and improve performance under controlled, safest, conditions in preparation for more demanding diving.

During the dive I again noted the O2ptima Nomad LS with chest mount rebreather is very stable, roll resistant, with scrubber, dilutent, and pony bottle under the diver and the buoyancy on top, but slant from my body increasing drag and snag potential. Even with harness straps loose, the rig is self-righting like a sailboat, thus eliminating the stability problem I hated with doubles. Trim and buoyancy were excellent with 2 pounds placed in the top position of the Nomad’s back weight strap (200-pound diver in a 3mm wetsuit, booties, and jet fins, with three handheld lights). The Choptima’s modular type design facilitated positioning the dilutent, pony bottle, and fins at the water’s edge, spreading the weight out over two trips. Superior stability and portability sold me on the Choptima. Unlike my previous mask, my new (kudos to) Diverite tear-shaped mask allowed me to keep the HUD constant in my field of view and to easily pinch my nose. My previous three masks would not. To do: tighten shoulder straps and reposition the hardware on the belt and crotch strap. Work on aligning clip-on cylinders with my body. Record weight parameters in my logbook.

The used dilutent Din regulator that I bought with the Choptima came unscrewed because of lack of lubrication and maintenance. I corrected and will be more vigilant in the future. Several of the low-pressure hoses were too long creating a snag hazard and making it difficult to rapidly check the routing of the hoses. I installed the optimum length.

My plastic dilutent pressure gauge, on a 6-inch hose, was relatively fragile, and a snag hazard. I have installed shorter hoses and two pressure gauges that screw directly into the first stages of the dilutent and pony bottles to streamline my profile and keep the mistress happy.

My gear organization sucked. My save a dive and rebreather support boxes were temporally lost in transit among the four vehicles we used for transport. Now my equipment is in two mesh dive bags.

Like an exotic mistress, a rebreather is less likely to kill you if you treat it well and spend money on it. Buying a buoyancy compensator that was designed to integrate with the Choptima was an excellent use of money. Although they were functioning perfectly on all 11 of my dives, the Diverite manual, directed that it was time to replace the O2 sensors; I value my life too highly to do anything else. One new sensor appeared to be defective until I calibrated it. This is not mentioned in the book, so it gave me pause.

Ready for the Keys!
 

grantctobin

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Newbie Post, My 12th CCR, (Shakedown) Dive
The used dilutent Din regulator that I bought with the Choptima came unscrewed because of lack of lubrication and maintenance.
...
My plastic dilutent pressure gauge, on a 6-inch hose, was relatively fragile, and a snag hazard.
...
Although they were functioning perfectly on all 11 of my dives, the Diverite manual, directed that it was time to replace the O2 sensors; I value my life too highly to do anything else. One new sensor appeared to be defective until I calibrated it. This is not mentioned in the book, so it gave me pause.
Glad you’re self reflecting.

I’m surprised you’re not overly foot heavy in that config and with jet fins.

What do you mean by lack of lubricating the first stage?

Want to post images of your reg config on both of your sidemounted bottles? A 6” brass and plastic gauge is pretty standard and isn’t in the way at all.

Sometimes cells, depending on age and manufacture, have to “wake-up” after prolonged disuse, which sounds like what you were describing, and should have been taught in class. Are you replacing due to time window since putting the cells in your unit? Failed linearity check? Did you elect to replace all four from the same batch of new cells?
 

JahJahwarrior

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Usually you hear the opposite, that something won't unscrew because of lack of maintenance and lubrication! The diluent reg is same as any regulator.

Good call on the mini SPGs for dil and o2.

Anytime you replace cells you need to recalibrate even if they don't seem defective. Good thing you are replacing cells--in general I don't see huge value in extending them past their life even if they are still responding linearly and not current limited, but I also like to rotate cells and replace them throughout the year so I always have different batches and ages of cells in the mix. I'm not nearly as smart or as good at math as people like Bobby and Tbone, so I tossed their math into this basic calculator to let me calculate linearity values. Gas Planning – Dive Blue Heron Bridge (divebhb.com)

Glad you love the Choptima, it's a great unit, and your methodical approach to comfort, safety and skills is the right approach.
 
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Mastow1

Mastow1

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I have been foot heavy with Jet Fins in a back mount CCR. Now, the Nomad-LS I use with the Choptima has a weight strap which allowed me to position weights along my spine to adjust trim. This dive verified that the repositioning and amount of weights I changed since my last dive are optimum.

I regret that my statement on lubricating the first stage was vague. What appears to have happened was that the O ring that the pencil is pointing at was dry and by turning the regulator or normally tightening the handwheel, the din housing (marked in the picture with an Allen wrench set) came loose. Also in the picture you can see my new button gage on the pony bottle 1st stage with the gauge it replaced between the first stages. I tried to position it so I only need to look down to verify the pressures in each of the side mounted cylinders.

Regarding the oxygen sensors, I do not recall my instructor mentioning a “wake – up” issue, but he did advise me on the necessity of calibrating new sent sensors. Either way we now have outlined the issues for other newbies. The sensors come from two different batches. I replaced them because they had all exceeded the, “Do not use after:” dates printed on them. I’m relatively certain that the sensors were still fully functional, but as one of my friends told me regarding pushing the limit with sorb and sensors, “You can probably get away with it, but if you die because of it, we always refer you as the cheap dumb bastard.” Now they will have to settle for dumb bastard.

May all your dives have the surfaces you plan!
 

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