What happens in a recreational computer if you go past the NDLs?

[fuzzybabybunny]

So there's absolutely no way to ballpark your deco obligation? 130ft, stayed 5 min past NDL, breathing regular air. All I'm asking for is a ballpark or realistic profile.

 

[tursiops]

So there's absolutely no way to ballpark your deco obligation? 130ft, stayed 5 min past NDL, breathing regular air. All I'm asking for is a ballpark or realistic profile.

Use tables, any tables that have deco info, and you can ball-park the answer immediately,

For example, USN tables (older ones, which i found first), air NDL for 130 ft is 10 mins. 15 mins forces 1 min at 10 ft. 20 mins forces 4 mins at 10 ft. 25 mins forces 10 mins at 10 ft. 30 mins forces 3 mins at 20 ft followed by 18 mins at 10 ft.

Newer USN tables still have 10 min NDL. 15 min > 1 min at 20 ft. 20 ft > 4 min at 20 ft. (same as above) But 25 ft > 17 mins at 20 ft, adn 30 mins > 34 mins at 20 ft.

Buhlmann air tables are also 10 min NDL, with 1 min required at 10 ft. 15 mins > 4 mins at 10 ft. 20 mins > 3 mins at 20 ft and 7 mins at 10 ft. 25 mins > 2 mins at 30 ft, 4 mins at 20 ft, and 12 mins at 30 ft. And 30 mins > 3, 7, and 18 mins at 30, 20 10 ft.

And I would NOT recommend diving ANY of the profiles above! They are all superseded by more modern information, and of course by computers, which use many different algorithms and strategies.

PS - PADI's rule for staying pars your NDL is the rule of "15," which means 3 mins at 15 ft (a normal safety stop) is extended to 3+5=8 mins at 15 ft for over-staying your NDL by 5 mins or less, and at least 3x5=15 mins at 15 ft for overstaying more than 5 mins. The PADI rule is not dependent on your depth, but it does include a mandatory 6h out of the water before another dive for the shorter overstay, and 24h out of the water for a longer overstay. These times are to allow DCS to possibly express itself.....

 

[Narcoz]

suunto computers are interesting in the sense that they will give you a ceiling to to go over. It's what they call continuous deco...

 

[Sunn]

No, you will die unless you are truly an anointed and certified technical diving specialist. End of story.

sure ! brilliant !

Your dive computer will give you deco-stops at X ft for X minutes (according to depth reached and dive time --> tissues saturat.) and eventually the total ascending time, so that you can estimate if you still have enough gas or if you have to pray...

 

[Nianne]

The computer that I have simply says it'll give me a deco profile. That's it. No indication of how long, how many stops, etc. Does a simple 3 min safety stop at 15ft turn into 60 minutes of deco at multiple levels if you go over your NDL by five minutes at 130? It doesn't give any kind of an idea of what to expect.

For a real answer to your question, without trying it underwater, you can download a dive program on your computer, enter the profile of the dive you wanna know info about, enter the algorithm of your computer and you will see what the deco obligation will be.

Keep in mind that staying 5 more minutes at 130ft will make you use between 300l and 500l, depends on your RMV and will put you in a really difficult situation if you're diving a single tank, knowing that you should plan a third of your gas supply for the deco obligation.

 

[JohnnyC]

So there's absolutely no way to ballpark your deco obligation? 130ft, stayed 5 min past NDL, breathing regular air. All I'm asking for is a ballpark or realistic profile.

Sure there is. Tursiops gave you a couple different examples for using tables. Nianne offers the computer program as a solution. However, those examples may or may not have any bearing on what your computer will want you to do. Tables are based on square profiles, whereas computers are constantly calculating your dive profile and decompression information. Deco planning software is making assumptions that you're going to follow the plan it generates.

What algorithm are you running? What implementation of that algorithm are you running? Are you running with any conservatism factors added? Are you running a computer that is capable of running multiple algorithms, and do you know which one you have selected?

As you can see, there are many variables involved in providing a decompression schedule. You can certainly use several methods to ballpark a deco schedule, but they may or may not match what your computer will call for in the event you blow your NDL. Ergo, your manual will tell you that it's going to give you a deco profile. It's not going to tell you what that is in the manual, because it simply can't, even though it already knows what algorithm you're using.

 

[Kharon]

The computer that I have simply says it'll give me a deco profile. That's it. No indication of how long, how many stops, etc. Does a simple 3 min safety stop at 15ft turn into 60 minutes of deco at multiple levels if you go over your NDL by five minutes at 130? It doesn't give any kind of an idea of what to expect.

The reason for that is because every deco profile will be different depending on the dive profile, how long you were in deco, at what depth, after what dive profile, after how many dives, etc. And, most important, the deco plan will change over your ascent dsepending on how well you comply to the deco profile given by the computer as you ascend. It recalculates on the fly. You are asking a question that can't be answered. There is no standard deco profile.

The computer will handle it - at the point you are in deco you need to dive the computer and let it get you up safe. Better yet, watch the computer and don't exceed NDL. That way you don't have to worry about it.

 

[dmaziuk]

So there's absolutely no way to ballpark your deco obligation? 130ft, stayed 5 min past NDL, breathing regular air. All I'm asking for is a ballpark or realistic profile.

I think you should consider the assumptions about your target user base. Perhaps "recreational" divers are assumed to not exceed their NDLs much, so many of their profiles are expected to just be non-optional safety stop, and that's if their deco doesn't clear completely by the time they get to stop depth. They could be expected to want to dive again after an SI, so you might want to program "more off-gassing" into your deco schedule.

On a planed deco dive, OTOH, your user will splash knowing their profile to begin with. What you may want to do there instead is program in tetris to give them something to do during long deco stops.

 

[yle]

The computer that I have simply says it'll give me a deco profile. That's it. No indication of how long, how many stops, etc. Does a simple 3 min safety stop at 15ft turn into 60 minutes of deco at multiple levels if you go over your NDL by five minutes at 130? It doesn't give any kind of an idea of what to expect.

I can tell you what my Suunto D4 did the one time that I exceeded my NDL. It was the second dive of a two dive trip, with a one hour surface interval between the dives. Both dives were to a max depth of around 110 feet, and I think I was using nitrox for both.

I exceeded my NDL by a couple minutes. The computer politely suggested I should stay at 15 feet for an extra couple minutes (beyond the normal 3 minutes for a safety stop.) So I did.

 

[KenGordon]

I'd like to get a better idea of how the computer will behave should you go past the NDLs. The computer will give you decompression stops, but how long will they be and at what depths and how many stages?

If you go to 130ft but don't go past your NDL, a slow ascent with a 3 minute safety stop at 15ft is enough.

If you go to 130ft but stay, say, 5 minutes longer than the NDL, what would a decompression profile look like on a recreational computer versus a tech computer?

More or less the same. What is a ‘technical’ dive computer anyway? One that only comes in black?

When you buy a computer you ge some choices. Some can plan deco dives on the computer, some need pc software to do that and some don’t have the option.

Generally you want to be able to plan a deco dive so you know you will have enough gas for the deco. So one with a pc planner is probably best. Planning on the computer seems like a good idea but is too tedious in general.

To try this out you could take subsurface or MultiDeco or Suunto DM5 and plan two dives to say 30m. One for 17 minutes (probably a no stop dive) and one for 22 minutes (probably a deco dive).

If you want to try it in the water then dive two computers and breath 32%. Set one to air and one to 32% and see how the air one behaves.

Really though training for backgas deco is pretty easy and safe so you could just take the course and have more options in your diving.