Question Question for Experienced O2ptima CM Divers
- Thread starter rx7diver
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OP
@lostsheep,
I am not sure what additional info you require. Standard (?) dive planning for this kind of open circuit dive assumes a straight drop from the surface to TOD = 165 fsw (so, 2.75 min if descent rate is 60 fpm). Then horizontal out until turnaround (here, RT = 25/2 = 12.5 min). Then horizontal back until begin vertical ascent to 70 fsw.
This is all very basic and straightforward, no?
ETA: I just glanced at your SB profile. Is the info there correct and up to date?
ETA2: I just reread my post. It reads aggressive. I didn't/don't intend it to be. What I meant/mean is, if some of this kind of detail is new to you, I can explain things in a bit more detail, no problem, to the best of my understanding--though I am NOT an instructor. None of this stuff is "deep", IMHO.
rx7diver
Shirley...
I don't even know where to begin to answer that. I am no where near the level of some that have chimed in on this thread. I am but a dilettante when it comes to tech and CCR, that said I do know enough to know that your questions are concerning for those that do know. You really ought to listen to them. I am surely an askhole myself and I am sure at least one of the pros here would agree with my assertion. I want to give you the benefit of the doubt as an askhole myself but you don't seem to be acknowledging their critique. You probably should disregard my critique, but some of these guys actually know what they are talking about and you should listen to them.
@rx7diver you seem to be missing a lot of basic training/understanding, based on your assumptions/questions. Read the thread I just posted about my AN/DP experience, that'll give you an indication of what it takes to plan a 150fsw dive on OC. An entire 30-minute BT dive with deco. Technical Training Report/Review (AN/DP)
When you talk about bailout, it's all about getting to the surface, not continuing the dive. I just ran some quick numbers and I need ~8cuft for the planned ascent to 70ft. Beyond that I'm on 50% mix. Of course there are other ways to plan the dive depending on what your deco mix is.
Again, you're making it way more complicating than it has to be, because you're probably missing the basics. A few instructors already gave you some feedback, but hopefully my dumbed down info sinks in a bit better.
Definitely do a bunch of OC decompression dives before getting on CCR. It's a lot of layers of complexity all at once.
When you talk about bailout, it's all about getting to the surface, not continuing the dive. I just ran some quick numbers and I need ~8cuft for the planned ascent to 70ft. Beyond that I'm on 50% mix. Of course there are other ways to plan the dive depending on what your deco mix is.
Again, you're making it way more complicating than it has to be, because you're probably missing the basics. A few instructors already gave you some feedback, but hopefully my dumbed down info sinks in a bit better.
Definitely do a bunch of OC decompression dives before getting on CCR. It's a lot of layers of complexity all at once.
OP
@boriss,
Yes, I read your post yesterday evening. Congratulations on your course. Sounds like you got some excellent training.
I was certified to the levels of IANTD's "Advanced Deep Air" and "Technical Nitrox", and was doing 200+ ffw dives on Great Lakes shipwrecks in the mid-1990's through early 2000's. (It's all there in my SB profile, I think.) My dive planning is pretty solid, I think, thanks.
I was never trained on rebreathers, though. Never even seen one in the flesh. I used isolator-manifolded HP100's at first, and then isolator-manifolded HP120's for my Great Lakes diving. I broke apart my doubles about 15 years ago. Up to that point, I had been entertaining becoming Tri-Mix-trained (for deeper Great Lakes exposures). I actually purchased a single OMS LP121/125, with the intention of purchasing a second one and doubling them up. And then "life" sidelined my Tri-Mix plans. (I began my family.)
I began this thread because, after recently assembling some "baby doubles" (first OMS/Faber LP 46's and then Faber LP50's) to use with my double-hose regulator, I began wondering whether these baby doubles could be dived with an Optima CM, to at first do the dives I used to do, but on Tri-Mix, and then to do more extreme exposures on Tri-Mix. I still have my doubles back plate, isolator manifold, cold water regs (Poseidon Odins), deco regs (Scubapro) and hardware, and dry suit. I find very appealing the thought of being able to do my old dives, but without the bulk/heft of HP120 doubles!
My gas planning calculations are pretty solid, I think. Since you have just completed your AN/DP course, you should be able to come up with the same numbers I did. Let me know if you want me to take you through the hand calculations.
My numbers suggest to me that, for my own personal level of risk tolerance, my LP50 baby doubles do not have sufficient capacity for use with a Choptima, for me to do my old dives solo, and that I would need larger doubles (though not as large as HP100's or HP120's or LP121's). I posted the details up-thread.
Good luck with your AN/DP-level diving.
rx7diver
flymolo
Contributor
I have a somewhat off topic question related to the choptima (mods, you can feel free to move this to another thread). Because the scrubber is positioned horizontally, as opposed to vertically like most units, does that make it more prone to channeling due to the sorb settling during a bumpy car or boat ride?
Most of the time, no, because most of the time you'll want to use an ExtendAir cartridge rather than pack it yourself with granular sorb. However, if you do pack it with sorb (properly as with any other RB), it should be no more likely to channel than any other scrubber. Think about it... with a "typical" back mount RB with vertical scrubber, isn't the RB typically laying on its side for the car and boat ride anyway? How is that any different to the CM? If you pack it right (tight), it'll be alright. Or just use the cartridge and don't worry about it.
First of all, please re-read and reconsider all the great advice you've received here from several Chop instructors, which so far you have basically ignored. Specifically, that it is unreasonable to plan for 2, 3, or 4 major failures. Let's be clear, when (if) you have to come off the loop permanently at max penetration that is THE major failure for which you are planning your bailout. Expecting and planning for a tank neck Oring, manifold Oring or burst disk failure (the only types where the loss of half your gas cannot be stopped by closing a valve or isolator) on top of that is just ridiculous. I mean, why not plan for a second set of doubles stacked on top of the first in case the isolator valve blows out and you will lose all your bailout gas. LOL
Anyway, I digress. In fact, so much that I will put my real answer to your original post in a separate reply so it is not tainted by this digression...
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