Past NDL. And then this???

[KeithG]

This problem?
View attachment 420231

You are still a bit too obtuse for me. If you are subtlety referring to the OPs failure to follow the directions of their computer, I am unsure how spending money on a different computer would change the outcome.

 

[Michael Guerrero]

Which problem?

The OP's problem of having a crap computer that uses a crap algorithm.

 

[KeithG]

The OP's problem of having a crap computer.

There was nothing wrong with the OPs computer. It worked perfectly.

If anything, I would claim it was a little too aggressive for repetitive recreational diving. At a Buhlmann 30/70 the OP was in deco multiple times over the trip.

 

[Dan]

You are still a bit too obtuse for me. If you are subtlety referring to the OPs failure to follow the directions of their computer, I am unsure how spending money on a different computer would change the outcome.

You asked an obtuse question and I replied it with an obtuse answer, without subtlety referring to anything. KISS principle - Wikipedia & peace!

 

[KeithG]

You asked an obtuse question and I replied it with an obtuse answer, without subtlety referring to anything. KISS & peace!

i directly quoted a response that claimed purchasing a shearwater product would solve the problem. I was curious which problem the poster was responding to. they subsequently clarified the problem they were referring to.

all is well.

i am still interested in learning about "new" tables / algorithms...

 

[Dan]

i directly quoted a response that claimed purchasing a shearwater product would solve the problem. I was curious which problem the poster was responding to. they subsequently clarified the problem they were referring to.

all is well.

i am still interested in learning about "new" tables / algorithms...

I posted this NOAA Nitrox 32 No-Decompression Table Questions and learnt that table is useless for multiple levels & repetitive dives. It's only good for a perfectly square profile.

 

[KevinNM]

This triggered a thought: "the latest dive tables".

When was the last time someone came up with "new" tables?

This is also indirectly related to the question: When was the last time some one came up with a new algorithm? That has survived?

There are a bunch of different dive tables and algorithms that have been developed in the last 30-40 years and are in use by naval or commercial divers.

What seems to be a decent overview is:
Deep Into Deco: The Diver's Decompression Textbook

 

[Centrals]

Buy a Petrel or Perdix, problem solved.

There was NO problem whatsoever with the computer, the issue is the end user.
What would Petrel or Perdix do when the diver refuse to take note of the info given to him? Physically take him up and start the deco!!!

 

[Miyaru]

Too bad that the focus remains on the computer. It is just a model, a very simplified representation of what is happening in your body.

Switching between computer brands will not prevent DCS. If you understand decompression and offgassing, you can predict what the computer will tell you.

Putting a (recreational) computer in error mode is easy. If you do the same with your body, it doesn't clear automatically after 24 or 48 hours.

 

[blac86]

Hello, I am a beginner with AOW certificate and about 50 dives.

During the 3rd (and last) dive of that day on a multi-day diving vacation trip the following incident happened. The max depth of the dive was at 27meters and I was getting pretty close to my NDL. We had already started our (slow) ascent being now somewhere near 20meters 26 mins into the dive.

I knew from previous dives that my computer (Cressi Leonardo) was quite conservative (compared to my fellow divers’ computers - mostly suuntos zoop, d4 etc) so I didn't worry too much about diving very near my NDL .

Well, something came to my attention few meters below me and I descended 1-2 meters to have a look and that was it. My computer went to DECO “mode”.

I remained calm knowing that that it was not the end of the world (eg my fellow divers had several minutes NDL left, I had plenty of gas etc) and continued a slow but now steady ascent (no more looking around for fish etc – just focusing on the ascent, my gas, the computer and the group).

My question is about the behaviour of my computer. I know Leonardo is not a Deco computer and that it should not be used that way, but still it has made me very confused. It directly gave me 7 minutes total deco time (4 mins deco + 3mins safety) at 3 meters – fair enough. But then, every second I was below 4 meters or so it kept adding (a lot of) deco stop time.

I was hopping that by slowly assenting, deco time would decrease or at least stop increasing. It took me 20 minutes to reach 4 meters - now 45 minutes into the dive. The main reason being I didn’t want to separate too much from the rest of the team (they continued their pre-decided dive profile). By the time I reached 4 meters my computer was asking me to have 35 mins deco plus 3 mins safety!

I remained at about 3-4m for 35 more minutes. Then my air was getting low and I decided to surface (boat was next to me most of this time). By that time the computer was still asking 5 mins deco (I don’t know why). The dive guide took my computer and stayed in the water for another 10 mins or so to make it happy.

Needless to say that everybody else in the group was within their NDL at the end of their dive (70 mins duration) and look at me like an alien or something trying to figure out how the heck I managed something like this. At least they were nice enough not to show even the slightest frustration to me delaying their going back to base for these 20-30 extra mins or so.

Following this I did investigate the dive with Subsurface and I saw that indeed I was outside my NDL time (I know I shouldn’t have been there to begin with). But Subsurface (with the default algorithm/settings) by the time I reached 4m gave me 0 calculated deco time while my computer was giving me 35 + mins deco time! Is such difference normal?

I also investigated SB and I fount out that it is well documented in SB and elsewhere that Leonardo becomes very conservative (compared to other computers) from the 3rd daily dive onward! But such differences?

Please keep in mind that the purpose of this post is to learn. I think I understand the risk and what I did wrong from my side. Please don’t focus too much on blaming/punishing me for my mistake. I could just forget about all these, keep quiet and just keep diving like it never happened. But I don't because I want to know what is going on.

What I am querying about in this post is the behaviour of my dive computer past the NDL. Is that behaviour the right one? Am I asking too much from my computer? And of course the next question is: are the other computers that liberal? Why? Is that ok?

Another less important question: I did check later my computer and “Deep Stop” option was enabled but I don’t know why my computer choose not to suggest a deep stop either.

Thanks a lot for any insight and sorry for the long post. I just wanted to have everything as clear as possible.
Cheers

I can't be assed to read 23 pages of people arguing about computers so I'll just stay this here even if it's been said before. Your ascent rate was dangerously slowly. Slow isn't safer. NDL isn't some magic number that is perfect, and you need a much better understanding of dive theory and dive physics. The reason your deco was so long was because you took so long ascend you kept blowing your stop by not getting there in time. What you thought was being safe was actually critically dangerous behavior. You should ask your aow instructor for a refund.