Can you dive again after a minor Deco dive?

[diver_paula]

Karl_in_Calif once bubbled...


I would not expect computer algorithms to vary that much from each other on the NDL side. Maybe a minute or two. I would not expect a big difference. Maybe there is?

I've been diving with my Suunto Solution for years. My NDL times are almost always less than any of my buddy's computers. Many times by more than a couple minutes. The disparity gets larger on multi-level diving but remains fairly constant when doing a square profile on a wreck. I like the conservative side of Suunto's - it's why I chose them.

What is interesting was the first time I went to Truk in 1995. I only owned the Solution at the time and borrowed a friend's computer as a back up for the week. It wasn't a Suunto. For the first three dives of each day the Suunto was more conservative. On either the 4th or 5th dive of the day they flipped and the non-Suunto computer became more conservative. Sure did surprise me the first time that happened.

I now have a Suunto Companion as my backup computer so I don't have to think about two different algorithms.

Paula

 

[DA Aquamaster]

The liberal versus conservative thing is often more complex than just bottom time. My wisdom is liberal strictly in terms of bottom time, but is very conservative in terms of ascent rate and requests a 3 minute saftey stop on all dives deeper than 30 ft. S there really is no free lunch. But personally, I think there is more value and more saftey in a slow ascent rate than there is a slightly shorter bottom time.

The newer tables modified from US Navy tables to reflect doppler ultrasound research help to reduce silent bubble formation, but then so do slower ascent rates, deep stops, and saftey stops so there is more to the issue than strict bottom time.

The PADI RDP is a whole new animal and has some different assumptions. It also uses a 6 hour out rather than the 12 hour out used for off gassing by US Navy based tables. It also has much smaller increments for bottom time and consequently, dives tend to be potentially more "square" in nature with potentially less fudge factor than with a table with broader time increments. If PADI says you have to stay out of the water after a deco dive, I'd believe them. They are designed to provide more liberal bottom time in recreational no deco diving, and as they say, there is no such thing as a free lunch.

For multi-day computer diving, how your computer tracks residual nitrogen and how long it considers it in calculations is also very important. Some computers are conservative over a single dive day, but if longer half life compartments are not considered or if the residiual nitrogren calculations are dropped after 6 or 12 hours, they can become relatively liberal over multiple dive days compared to other computers that track longer half life compartments over a 24 hour period.

This is often one of the reasons why some computers have conservative NDL limits in the first place. I have seen some computers where the manual (that most divers using them have probably not read) states they are not designed for multi day diving.

I know many people who will not dive square profiles with a table as they understand the saftey margins are reduced when they are used that way. But many of these same divers do not recognize that every dive with a computer is essentially a square profile and that the one of the key saftey margins in a computer comes from reduced NDL's compared to tables. They also do not recognize that with some computers, this saftey margin can be eroded in repetetive multi day diving to the point where they are pushing the computer past it's safe limits.

To dive a computer safely and responsibly during repetetive dives over multiple days, you really need to understand how it works and what it's limitations are in various situations, then make adjustments in how you interpret what it tells you and add a saftey margin when appropriate.

 

[String]

Karl_in_Calif once bubbled...

SSI and NAUI(old) tables are all variations of USN. But these are tables not computer algorithms. Different story. Bad analogy.

Eh? All computers use an algorthym based on existing research which can also produce tables. AFAIK no computer uses US Navy tables for its computational model but computers are just a different mechanism of implementing tables - a far more accurate method on an actual dive.

I would not expect computer algorithms to vary that much from each other on the NDL side. Maybe a minute or two. I would not expect a big difference. Maybe there is?

On some definately. The worst ive seen is the computer for our group showing it as a NDL dive with 2 mins left. The other group, identical profile - 8 mins of stops. Both computers had no previous dive "memory" as previous dives were 1 week ago.

I have only dived with my Suunto Vyper dive computer, and I consider all other dive computers as inferior.

So with experience of a sample size of 1, everything else which you never seen or experienced is inferior ?! What tablets are you taking? What about the vytec? How is that inferior. What about the VR3 ? I dive a Vyper but not deluded enough to think everything else around is inferior.

Having stipulated that, I would not stay longer than my Suunto told me I could stay at a given depth on an NDL dive, even though I am acutely aware (acutely, CornFed, very acutely) that USN tables are very, very generous. Nor because of anybody else's NDL computer as well. [/B]

Personal preference really but going into deco on a computer is no different from going into deco by looking at the tables its based on at all. Computers arent some magic black box, theyre based on identical theory that tables are.
A very high % of dives here end up with a deco obligation - we're all still here.

 

[Karl_in_Calif]

String once bubbled...
...A very high % of dives here end up with a deco obligation - we're all still here.

The fallacy of argumentum populorum: Whatever is popular is truth.

If I were to teach that notion of yours here in the USA, I would be expelled from my association of underwater instructors for violation of the standards. If I taught it and someone were hurt, the insurance company would find me in violation of the policy.

So, what is truth?

 

[padiscubapro]

ScubaAaron once bubbled...
My dive buddy and I have differing opinions on this matter. He states that if you exceeded the no-deco bottom time on your computer, go into deco, then do the required stop(s) you are not allowed to dive again for 24 hrs. I am only talking about a few minutes deco. Is this correct? I believe that as long as you follow the stops per your computer and surface "not in deco" then you are OK to dive again.

And as a follow up: If I am correct and my buddy is wrong, is there any increased danger to going a few minutes into deco? As in increased bubbles? Other than if you do an emergency assend you will assend without doing the required stops.

Thanks in advance for your comments,

Aaron.

Yes it is possible when planned and trained. Those without formal training should not be doing deco dives.. Doing deco dives and completing deco on AIR is just plain stupid.. Deco should be completed on the proper gas..

ANother danger about flying a computer and not knowing what is was designed for is how you get credit for surface intervals.. many computers out there are designed for "EMERGENCY" decompression, not to follow blindly.. The biggest problem is that many dive computers use the 60 minute compartment for SI credit.. in deco diving this could be a big problem especially if the proper gases aren't used.. SOmeone decoing on air may still be ongassing the slow tissues while the fast tissues are offgassing.. The slow compartments are the ones that can withstand the least amount of bubbles... Pain only bends are usually the result of the slower compartments...

Recreational tables like PADI's RDP are strictly for no deco diving they make certain assumptions.. This is the primary reason they have special rules attached when you hit the ndl and some other conditions. If you compare the RDP against tables such as the NAVY you will see that your repetitive credit happens much faster with the RDP this is primarily padi uses the 60 minute tissue compartment for surface credit.

If you plan on doing deco diving.. Get FORMAL training...
There are computers that are designed to AID deco diving but are never a substitue for proper pre dive planning.

 

[String]

All i can assume from that comment is if what you say is true the training agencies and 20 years behind the real world and the "sue now, sue often" society over there is worse than i thought.

By the nature of diving here, most of our dives are mandatory decompression dives. Our club alone probably gets through several hundred per year.

Decompression diving is not some mystic art - it is in pracitce no harder to perform than diving within the NDLs, it doesnt require the brain of einstein of the physical dexterity of a top athlete - its something anyone can do after training.

As for "whatever is popular is truth" i have no idea what you are on about - every single person i have dived with this year has done deco dives and they're all still there (or very good models). 2/3 of all bend incidents from last year were from people diving WITHIN the NDLs.

As for expelled from your association, i have no idea. Certainly deco theory is taught for the basic course here and the second qualification (rough equiv to the PADI AOW) a deco dive or simulated decompression dive with planning is mandatory to earn the qualification - the final wording on the certificate includes "enables the diver to plan and carry out dives requiring mandatory in water decompression".

NDLs are not a clear cut yes/no event. Every dive is a deco dive and just staying 60 seconds the right side of it as opposed to going 60 seconds over it isnt as different as you seem to believe.

 

[cornfed]

Karl_in_Calif once bubbled...


The fallacy of argumentum populorum: Whatever is popular is truth.

Would you please start addressing the questions you've been asked. Despite what you may think, your little tutorials on rhetoric do not answer provide the questions. I (and a lot of other people) are waiting for you to provide sufficient conditions to support you claims. And frankly, at this point I'd be willing to accept a few necessary conditions instead.

We can start with and easy one. Why do you say that the “USN tables are very, very generous”? What are they generous in comparison to?

 

[flw]

Karl_in_Calif once bubbled...


The fallacy of argumentum populorum: Whatever is popular is truth.

If I were to teach that notion of yours here in the USA, I would be expelled from my association of underwater instructors for violation of the standards. If I taught it and someone were hurt, the insurance company would find me in violation of the policy.

So, what is truth?

Different country, different organisation, different expectations - we teach deco right from the very start of a divers training, much UK diving is square profile, limited (10-15 mins) deco is the norm. SAA and Scotsac use Buhlman tables, Bsac use their own, tables are taught with the expectation that at the recreational end of deco, computers will be used.
F

 

[Karl_in_Calif]

flw once bubbled...



Different country, different organisation, different expectations - we teach deco right from the very start of a divers training, much UK diving is square profile, limited (10-15 mins) deco is the norm. SAA and Scotsac use Buhlman tables, Bsac use their own, tables are taught with the expectation that at the recreational end of deco, computers will be used.
F

I was wondering why there had been so much flame throwing on this issue. Makes total sense now.

 

[100days-a-year]

What a ma-roon,stay on him cornfed.Oceanic =lo cost,not very likely.Uwatec is not the only computer that has recalls or failure rates.The beloved Suunto is mentioned in this forum much more often than any other for problems.HS Explorer and VR3 are Ok I guess,mebbe that full-up RGBM stuff is alright?Dude needs to throw away his Deep Air notebook and give up his Rodales subscription.120 rule?