Is a 24 hour wait before flying really necessary?
Now it's time to choose a wrist computer.
- Thread starter SaltyCracker
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Is a 24 hour wait before flying really necessary?
OP
SaltyCracker
Contributor
If you omit a mandatory deco stop, as far as computer is concerned you are at risk of clinical DCS. According to the wiki-of-the-thousand-lies, onset of clinical DCS can take up to 48 hours, but 24 hours covers 98% of the cases.
It's not clear whether "folded RGBM" that runs inside low-end Mares-Cressi-Suunto "recreational" computers can actually work after being "bent" without a 24-hour "reset". Or, for that matter, DSAT: nobody's seen the code. I don't understand VPM well enough to tell but the model is open and anyone can look if interested.
Buhlmann's model doesn't really care if your calculated gas loading is below or above "maximum tolerated" so ZH-L technical computers don't "lock you out" simply because a) it would require additional programming that b) is unnecessary because their target demographic is technical divers who know better.
The Shearwater tissue loading graph is useful in that you can see how quickly the various compartments unload. Even after five dives daily for multiple days in a row, all but the very slowest compartments are back to normal when when you start out in the morning, less than twelve hours after the night dive from the evening before. The small accumulation in the slowest compartments over the course of a week or ten days is nowhere near being problematic.
My own experience and with very limited knowledge on various subjects:
1. Nothing is infallible even a well maintained one eg racing car stranded on the starting grid.
2. SPG is as good/reliable as anything else in the market.
3. Two is one and one is none. Redundancy is useful as long as it is practical. In my case(rec dive) I dive with two entry level computers.
4. 24hrs no fly time is fine with me because I want to be on the safe side.
5."Lock out"? Some divers just do not pay attention or even understood what the computer was telling them. Good or bad idea is debatable. I have no problem with it.
6. Missing deco obligation? I have seen one tec diver missed all the required mandatory deco stops because of lost of buoyancy. Couple of hrs on pure O2 on land and he was back in the water(tec dive) the following day! His choice.
1. Nothing is infallible even a well maintained one eg racing car stranded on the starting grid.
2. SPG is as good/reliable as anything else in the market.
3. Two is one and one is none. Redundancy is useful as long as it is practical. In my case(rec dive) I dive with two entry level computers.
4. 24hrs no fly time is fine with me because I want to be on the safe side.
5."Lock out"? Some divers just do not pay attention or even understood what the computer was telling them. Good or bad idea is debatable. I have no problem with it.
6. Missing deco obligation? I have seen one tec diver missed all the required mandatory deco stops because of lost of buoyancy. Couple of hrs on pure O2 on land and he was back in the water(tec dive) the following day! His choice.
OP
SaltyCracker
Contributor
Okay, I think it's finally sinking in. Higher end tech-diver computers give a person a compartmentalized micro view of tissue loading. Therefore, with extensive experience and higher skill, "technical divers who know better" are able to safely make that judgement. That seems very reasonable to me. And not nearly as reckless as it sounded when it was first casually tossed out there to a brand new diver that shouldn't be considering such activity. I doubt that my diving style will ever graduate to the level necessary to take advantage of that feature but it's nice to know that it's there for my teenage son who likely will due to his future career choice. It's his desire to learn to dive that's even getting me back into the game.
Keep in mind that the models aren't "safe" in some absolute sense: they have a statistical target incidence of clinical DCS and NDL is the point where the chances go from "safe enough" to "not safe enough" -- by the model's authors definition. Which can vary, e.g. the model for young fit able Navy seamen may have a "less safe" cut-off than the one designed for old people on vacation, and both of them are considered "safe".
So there is some wiggle room there, but it's not really about "safe": it's about risks you're willing to take.
OP
SaltyCracker
Contributor
OP
SaltyCracker
Contributor
Yes, exactly. That's why somebody like me has no business diving like this. My SEAC Screen has a liberal-conservative setting of 1-5. I set it to 4 and will see how restrictive that is. I imagine I'll be fine within my rec-diver limits. Even though I was advanced open water certified 20 years ago, I doubt I'll be going much at all past OW limits.
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