Wisdom of trusting one's dive computer?

[JohnN]

So @JohnN , what would you suggest to someone who owns a Mares Genius that defaults rec is 85/85 GF?

@wstorms, @Fastmarc, @ChuckP, and @rjack321 again this for an unplanned deco obligation (rec diving does not involve deco)

If I had the Mares running 85/85 and had an unplanned deco obligation, I certainly wouldn't do my first stop at 3m.

My primitive understanding of the Buhlmann algorithm is that the GFlo setting won't materially change the amount of deco time. What it will change is where your stops are and how long you need to spend at each stop

 

[Fastmarc]

If I had the Mares running 85/85 and had an unplanned deco obligation, I certainly wouldn't do my first stop at 3m.

That's the thing. You have the knowledge as a technically trained diver to decide on your own to do other than the computer suggests. For someone like me, who is just a rec diver and in the unlikely event accidentally went into deco, we would just be following our computer. Is Mares being irresponsibly or reckless in setting it at 85/85 GF as it's not safe?

 

[JohnN]

That's the thing. You have the knowledge as a technically trained diver to decide on your own to do other than the computer suggests. For someone like me, who is just a rec diver and in the unlikely event accidentally went into deco, we would just be following our computer. Is Mares being irresponsibly or reckless in setting it at 85/85 GF as it's not safe?

It's 'more sporty' than I would prefer. No one understands what causes a person to take a DCS hit, all anyone can do is mitigate the risk. In my experience, you would have to incur a pretty large deco obligation to not have it clear as you ascended so this whole sub-thread could be us considering how many angels could dance on the head of a pin.

Remember, this sub-discussion started with @FeedFlyFreak saying 85/85 was his preferred setting for warm water NDL dives.

 

[ls23]

This is an interesting example. For me, I would not consider 60 minutes at 30 meter a recreational dive. If I run this profile, even with GF100, I end up with 20 minutes deco (17 with ZH-L16-B).

I guess the program is calculating a 60 minute descent to 30m? I hope the OP doesn't plan square profile dives that way.

As for the couple of minutes of deco you get for going over the NDL a bit, 45/85 or 85/85, it's pretty whatever where you spend the deco... be it 6, 5, 4, or 3 meters. Usually most of that gets cleared on ascent anyway before you arrive at stop depth.

 

[rjack321]

@wstorms, @Fastmarc, @ChuckP, and @rjack321 again this for an unplanned deco obligation (rec diving does not involve deco)

If I had the Mares running 85/85 and had an unplanned deco obligation, I certainly wouldn't do my first stop at 3m.

My primitive understanding of the Buhlmann algorithm is that the GFlo setting won't materially change the amount of deco time. What it will change is where your stops are and how long you need to spend at each stop

How much unplanned deco are you going to possibly accumulate? 5mins? 10mins? If you have 15mins of "unplanned" deco that wasn't lack of planning that got you that.

If you have 5mins of deco or whatever you aren't going to have a stop deeper than 6m anyway even if you ran 30/70 or something like that. So 40/85, 85/85 or whatnot doesn't make any difference. You can pretty much do all your <deco> time at 5m just like any other recreational (non-required no deco) safety stop.

 

[Chavodel8en]

Don't let the atypical scubaboard users fool you. Other than in a scuba class I can't recall ever having seen another diver do it any other way than just jump in. End dive on time limit (some boats say you have to be back in xx minutes) or end dive on low gas or end dive when DC tells them that they're coming up on the NDL limit - whichever comes first.

This only applies to "regular" recreational dives mind you. If you're diving at Ginnie Springs or someplace where tech diving and rec diving are both common.. then you'll see people doing stuff other than just following their computer.

I will point out that this is the basic forum, so I would imagine that we're discussing basic recreational dives. But a lot of these posts go beyond the minimum needs for recreational diving, which is fine, nothing wrong with extra discussion, but I agree with you that it is giving a skewed view of "basic scuba discussions"

All my dives are recreational dives, unguided. Most of our planning is more about what we want to see -- which reef or site to swim to, etc. "Lets not exceed our NDLs" and "let's not run out of air" and "turn the dive so you have enough air" are all kinda understood for me, I don't really need to discuss plans about this with my buddy (unless they are a newbie and need advice). Lucky for me, the current's are fairly negligible around Monterey/Carmel, and if there is ever an issue, just surface as gradually as appropriate.

So yeah, aside from the fun stuff, mostly my planning is basically to just jump in (actually wade in and start surface swimming, but you get the picture).

 

[FreeFlyFreak]

It's 'more sporty' than I would prefer. No one understands what causes a person to take a DCS hit, all anyone can do is mitigate the risk. In my experience, you would have to incur a pretty large deco obligation to not have it clear as you ascended so this whole sub-thread could be us considering how many angels could dance on the head of a pin.

Remember, this sub-discussion started with @FeedFlyFreak saying 85/85 was his preferred setting for warm water NDL dives.

Which was called "aggressive".
And yet as you just stated, it would likely clear on ascent unless you overstayed so long that it wasn't unintentional.

How much unplanned deco are you going to possibly accumulate? 5mins? 10mins? If you have 15mins of "unplanned" deco that wasn't lack of planning that got you that.

If you have 5mins of deco or whatever you aren't going to have a stop deeper than 6m anyway even if you ran 30/70 or something like that. So 40/85, 85/85 or whatnot doesn't make any difference. You can pretty much do all your time at 5m just like any other recreational safety stop.

Exactly my point, and why I set my computer the way I do.

 

[Lorenzoid]

I will point out that this is the basic forum, so I would imagine that we're discussing basic recreational dives. But a lot of these posts go beyond the minimum needs for recreational diving, which is fine, nothing wrong with extra discussion, but I agree with you that it is giving a skewed view of "basic scuba discussions"

All my dives are recreational dives, unguided. Most of our planning is more about what we want to see -- which reef or site to swim to, etc. "Lets not exceed our NDLs" and "let's not run out of air" and "turn the dive so you have enough air" are all kinda understood for me, I don't really need to discuss plans about this with my buddy (unless they are a newbie and need advice). Lucky for me, the current's are fairly negligible around Monterey/Carmel, and if there is ever an issue, just surface as gradually as appropriate.

So yeah, aside from the fun stuff, mostly my planning is basically to just jump in (actually wade in and start surface swimming, but you get the picture).

Who defines "minimum needs for recreational diving"? Even the major training agencies, which have been the subject of criticism (deserved or not) for setting their standards at the bare minimum to keep basic recreational divers safe, appear to have been upping their game in recent years. If I recall some prior discussions correctly, PADI now teaches basic gas planning and has students plan a complete dive on their own. That says to me that dive planning is getting more attention than it did when I took the basic OW class 20 years ago. I was woefully unprepared to plan dives. Many of us suspected that we should be doing a little more than just jumping in and hoping for the best using the information available from our instruments, but few of us did anything to rectify that. I don't know exactly what PADI requires in the basic OW course these days with respect to dive planning, but I am guessing the instructors who take it seriously teach more or less what has been suggested in this thread (aside from the discussion on gradient factors).

 

[Graeme Fraser]

Who defines "minimum needs for recreational diving"? Even the major training agencies, which have been the subject of criticism (deserved or not) for setting their standards at the bare minimum to keep basic recreational divers safe, appear to have been upping their game in recent years. If I recall some prior discussions correctly, PADI now teaches basic gas planning and has students plan a complete dive on their own. That says to me that dive planning is getting more attention than it did when I took the basic OW class 20 years ago. I was woefully unprepared to plan dives. Many of us suspected that we should be doing a little more than just jumping in and hoping for the best using the information available from our instruments, but few of us did anything to rectify that. I don't know exactly what PADI requires in the basic OW course these days with respect to dive planning, but I am guessing the instructors who take it seriously teach more or less what has been suggested in this thread (aside from the discussion on gradient factors).

Correct.

Excerpt from CW dive 5:
4. Complete a simulated dive – Minidive – including: • Plan dive with a buddy

Excerpt from OW dive 4:
1. As a buddy team, plan the dive using the PADI Skill Practice and Dive Planning Slate.

 

[NAM001]

@wstorms, @Fastmarc, @ChuckP, and @rjack321 again this for an unplanned deco obligation (rec diving does not involve deco)

If I had the Mares running 85/85 and had an unplanned deco obligation, I certainly wouldn't do my first stop at 3m.

My primitive understanding of the Buhlmann algorithm is that the GFlo setting won't materially change the amount of deco time. What it will change is where your stops are and how long you need to spend at each stop

Not picking here but isnt materially change the amount of deco time,,,, and how long you need to spend at each stop the same thing. did I miss something.?