Overshooting NDL and mandatory deco stops

[NAUI Wowie]

If you have a 'recreational dive computer', then it is totally legitimate not to know what table the computer is using.

If you have a computer that is designed for technical diving, i.e. that uses GF to adjust the decompression algorithm. You should know, what the GF settings are - and how aggressive your profile is.
These computers are really designed for those with technical diving training where GF are taught and discussed, at length.

A conventional recreational dive computer is generally very conservative (bend risk low). A technical diving computer can be set (or shipped) for very aggressive profiles which result in a high bend risk.
The VR3 (which has now been overtaken by time), out of the box, the default GF settings where very aggressive - arguably too aggressive to use safely (in the same way that pro planner was too aggressive with its default settings.

IF YOU HAVE GF check the settings, and ensure they are appropriately set.

FALSE and completely false.

I dive recreationally. I bought a tec computer because it is light years easier to use than my junk rec suunto zoop computer. And my computer will be ready if in the future I want to do more than rec diving. So because i spent more money to get an A.I. tec CAPABLE computer I should now behave like a tec diver? I guess I should also know how to do CCR while doing the eagles nest. Wait thats not DIR i shouldnt have a computer at all....

dude ..... riddle me this, is the perdix A.I. more dangerous to dive with than a suunto zoop novo for normal rec dives?

 

[Jay]

Yes I understand how to operate my computer. I dive recreationally now so have zero need to know GF at all. most divers do not need to know this. Useless info for me. I have two dive computers every dive in case one fails that is all I need to know.

FYI, if you want to search my name here you'll see a lot of threads/posts around GFs/algos - I'm not offended if you call it my dive fetish as it was 'all new' to me since returning to diving ... the relevance of GFHi (for rec), and how that setting has a large impact on NDLs on repetitive dives. I have mine (Teric) on 60/90 (the 60 is irrelevant for Rec, but the number seems to fit the gap), and 90 works well on repetitive but I wouldn't do 95 on repetitive (3-4 dives/day, multi days) as it seems too aggressive (relative to other algos, even DSAT). It's interesting comparing some of the dive#3 vs. #4 data with a Fused Tec RGBM and the SI difference.

Then again, if that doesn't float your boat, default is probably Med Consv and will not do you wrong.

 

[NAUI Wowie]

FYI, if you want to search my name here you'll see a lot of threads/posts around GFs/algos - I'm not offended if you call it my dive fetish as it was 'all new' to me since returning to diving ... the relevance of GFHi (for rec), and how that setting has a large impact on NDLs on repetitive dives. I have mine (Teric) on 60/90 (the 60 is irrelevant for Rec, but the number seems to fit the gap), and 90 works well on repetitive but I wouldn't do 95 on repetitive (3-4 dives/day, multi days) as it seems too aggressive (relative to other algos, even DSAT). It's interesting comparing some of the dive#3 vs. #4 data with a Fused Tec RGBM and the SI difference.

Then again, if that doesn't float your boat, default is probably Med Consv and will not do you wrong.

Sooooooo... you are saying Shearwater is only slightly dangerous for my rec dives? I.E. Will it KILL ME to dive with a perdix A.I. at default settings? or even send me to a hyperbaric chamber? I will quite often do 3 or 4 dives a day on nitrox. If you think its dangerous please let me know and you should probably email Shearwater also because they are endangering thousands of divers with their default GF

whatever GF means

ill figure that out whenever I get past rec diving cabo MEX and cebu P.I.

 

[RainPilot]

not being snarky or offensive. But I read your entire post and dont know what you are trying to say.

my question was what happens if you go past NDL limits. my computer wont tell me that if im not doing it.

I was answering what would happen if you go past NDL limits. The videos show what a Perdix display looks like, in addition I tried to indicate what you would see as you ascend (possibly a deco obligation clearing) and why it would not be a good idea to routinely go into a bit of deco, relying on the deco to clear during ascent (as many have done over the years, it seems like a good idea till you think about an emergency, hence I was pre-emptively explaining)

Regarding the relative safety of your dive computer:

Most of the divers who are on this Board are not most of the divers in the world. We are NOT a representative sample. So, when someone here is surprised that you haven't gone into understanding the ins and outs of your computer, don't take it personally. Millions of dives are done every year by divers with NO idea of what their computer is doing under the hood. They are for the most part totally safe.

However, I don't like diving like that, i am a control freak in my diving, so i need to know what decisions are being made regarding my safety, by a machine or boat captain or dive buddy or or or...

Where a Perdix or other tech computer CAN be more dangerous, is where it gives you freedom to decide what you want it to do, but that relies on you having the knowledge of what you are doing. Leave it in Rec mode and out of the box it is set to give you a balance of conservatism and dive time as per what we understand to be best practice at this time.

Once you go into OC Tec or CC/BO modes, then you have the ability to mess yourself up. That being said, in tech mode, the defaults are actually more conservative than the Rec mode, until you go fiddling with GF etc

 

[Storker]

my question was what happens if you go past NDL limits. my computer wont tell me that if im not doing it.

AFAIK the Perdix uses Bühlmann with GF, perhaps the most common and probably the best documented deco algorithm there is. Get some half-decent deco software¹, find out which GFs your computer is using and plug those into the deco software. Then play. On your computer. It's an interesting exercise.

¹ or search the 'net for a spreadsheet where someone has set up that algorithm; I'm quite certain that you can find something if you look hard enough in the right places.

 

[Storker]

I bought a tec computer because it is light years easier to use than my junk rec suunto zoop computer.

I use a Suunto, and I don't think it's difficult to use. At all. The only issue I have with it is that Suunto is using a proprietary algorithm, so I had some difficulties tracking down the desktop planning program. And that if I should ever go past the NDL, it has a crappy way of handling deco (basically it tells you to spend half an eternity at 3m).

The latter issue is kinda moot, though, because I've never gone past my computer's NDL and if I do, I'll follow the recommendations on the PADI RDP and then sit out any other dives I'd planned that day. I might ask to borrow the O2 bottle for a while, though.

 

[NAUI Wowie]

I was answering what would happen if you go past NDL limits. The videos show what a Perdix display looks like, in addition I tried to indicate what you would see as you ascend (possibly a deco obligation clearing) and why it would not be a good idea to routinely go into a bit of deco, relying on the deco to clear during ascent (as many have done over the years, it seems like a good idea till you think about an emergency, hence I was pre-emptively explaining)

Regarding the relative safety of your dive computer:

Most of the divers who are on this Board are not most of the divers in the world. We are NOT a representative sample. So, when someone here is surprised that you haven't gone into understanding the ins and outs of your computer, don't take it personally. Millions of dives are done every year by divers with NO idea of what their computer is doing under the hood. They are for the most part totally safe.

However, I don't like diving like that, i am a control freak in my diving, so i need to know what decisions are being made regarding my safety, by a machine or boat captain or dive buddy or or or...

Where a Perdix or other tech computer CAN be more dangerous, is where it gives you freedom to decide what you want it to do, but that relies on you having the knowledge of what you are doing. Leave it in Rec mode and out of the box it is set to give you a balance of conservatism and dive time as per what we understand to be best practice at this time.

Once you go into OC Tec or CC/BO modes, then you have the ability to mess yourself up. That being said, in tech mode, the defaults are actually more conservative than the Rec mode, until you go fiddling with GF etc

Awesome fricking post. Thanks for the info

 

[NAUI Wowie]

I use a Suunto, and I don't think it's difficult to use. At all. The only issue I have with it is that Suunto is using a proprietary algorithm, so I had some difficulties tracking down the desktop planning program. And that if I should ever go past the NDL, it has a crappy way of handling deco (basically it tells you to spend half an eternity at 3m). The latter issue is kinda moot, though, because I've never gone past my computer's NDL and if I do, I'll follow the recommendations on the PADI RDP and sit out any other dives I'd planned that day.

it doesnt change the fact that its navigation is clunky and difficult to use. I know I speak for most humans that touch the zoop. maybe 99 percent. I can work it but its a PITA. And you forget and have to remember as it is NOT intuitive at all.

now if you perhaps have an I.Q. above 145 or so it may be simple as pie but for us plebs its a headache.

 

[NAUI Wowie]

AFAIK the Perdix uses Bühlmann with GF, perhaps the most common and probably the best documented deco algorithm there is. Get some half-decent deco software¹, find out which GFs your computer is using and plug those into the deco software. Then play. On your computer. It's an interesting exercise.

¹ or search the 'net for a spreadsheet where someone has set up that algorithm; I'm quite certain that you can find something if you look hard enough in the right places.

again I bought my computer because I wanted air integration and I wanted the easiest user interface and also I wanted a computer I would not grow out of.

I have no intention of going back into college and researching any of what you just posted. I want to dive not land on the moon or bounce dive any deep blue holes.

IF and when I get into deep tec diving and or CCR and or trimix and or cavern then I will modify what they set up. Until then its not needed. at all. I trust shearwater more than suunto not to kill me.

 

[Storker]

if you perhaps have an I.Q. above 145 or so it may be simple as pie but for us plebs its a headache.

I'm pretty certain that I don't have an IQ above 145, and that neither has my two children who also dive. I drive a Cobra with a Stinger as backup, my children both drive Zoops. From playing with their computers, I can tell you that the interface is so nearly identical (except the AI on the Cobra) that I don't notice any difference.

Why Suunto? Because that was the computer that came with my gear when I bought it (used), and I wanted us all to use the same algorithm. Besides, they're fairly affordable and easily available used.

I have no intention of going back into college and researching any of what you just posted.

OK.