Blindly trust computers?

[Centrals]

I never understand why "table" is no longer taught as standard.
I have came across many divers over the yrs that did not have a clue on NDL as well as the importance of long surface interval. They will jump into water as long as the computer "permitted".
Dive operators love computer because they can sell more dives to the customers especially on day trip! 1 hr surface interval is more or less standard in our part of the world. The operator only care if you had signed in the liability release form.

 

[BRT]

I'm just averaging depths. I can change those 8 minutes at 30 for 8 minutes at 35. Does that change your calcs? That will make it a 66.5' average depth instead of a 66.07. Are you going to say that is "about" 70.5'? You are getting to the problem with depth averaging. It matters when in the dive the deep and shallow parts happen.
For instance lets look at a "different" dive: 8 minutes at 30', 8 minutes at 40', 3 minutes at 50', 12 minutes at 60', 12 minutes at 80', 3 minutes at 90', 6 minutes at 100' and 4 minutes at 110'. What kind of a mental average do you come up with on that? Are you beyond NDL's?

So you are crediting all the shallow times as 70'? How long can one stay at 30' before incurring an obligation?

I'd say the time at 70 (used to calculate your NDL) is more like 40-45 min. See above. That is a guesstimate. If my PDC differs by any substantial amount from that approximation then we have a problem somewhere.

So you average the depth at 70', which is reasonably accurate, but you reduce your bottom time? Would you reduce your bottom time if the 30' depth was 35'?

 

[PfcAJ]

I'm just averaging depths. I can change those 8 minutes at 30 for 8 minutes at 35. Does that change your calcs? That will make it a 66.5' average depth instead of a 66.07. Are you going to say that is "about" 70.5'? You are getting to the problem with depth averaging. It matters when in the dive the deep and shallow parts happen.
For instance lets look at a "different" dive: 8 minutes at 30', 8 minutes at 40', 3 minutes at 50', 12 minutes at 60', 12 minutes at 80', 3 minutes at 90', 6 minutes at 100' and 4 minutes at 110'. What kind of a mental average do you come up with on that? Are you beyond NDL's?

So you average the depth at 70', which is reasonably accurate, but you reduce your bottom time? Would you reduce your bottom time if the 30' depth was 35'?

I would not do that. Working your way deeper is a great way to a) run out of NDL time and B) run past minimum gas.

 

[lowviz]

* Sigh * Those of us who actually understand this simple concept make simplifications to just get a SWAG as to what is reasonable. If the PDC falls anywhere close, then we happily go with that.

You are actually discussing 30' vs. 35'??? OK, so I see it as six and three-quarters hours to hit NDL on air at 30' vs. five hours to hit NDL at 35'.

Time spent there:

 

[BRT]

* Sigh * Those of us who actually understand this simple concept make simplifications to just get a SWAG as to what is reasonable. If the PDC falls anywhere close, then we happily go with that.

You are actually discussing 30' vs. 35'??? OK, so I see it as six and three-quarters hours to hit NDL on air at 30' vs. five hours to hit NDL at 35'.

Time spent there:

View attachment 494814

So do you count the time at 30'? How about if it is 35'? Or don't you count anything above 40'?

 

[PfcAJ]

So do you count the time at 30'? How about if it is 35'? Or don't you count anything above 40'?

Bruh. It’s a *guideline*.

You’re overhere trying to apply precision to something that just isn’t precise.

“Well if it’s 31.5ft do you count it as 32???”

We’re talking ballpark figures so you can at least be aware of what your computer box *should* be telling you. If something is wacky (you or the computer), take the time to figure that mess out and/or play it conservatively.

 

[lowviz]

For instance lets look at a "different" dive: 8 minutes at 30', 8 minutes at 40', 3 minutes at 50', 12 minutes at 60', 12 minutes at 80', 3 minutes at 90', 6 minutes at 100' and 4 minutes at 110'. What kind of a mental average do you come up with on that? Are you beyond NDL's?

Apologies, I think that I see what is jammed in your gears.

Ongassing isn't linear. I can stay forever at 20' but only an hour at three times that depth. So we 'chunk' the dive into depths and times that we can get away with. Play with it. It isn't hard, get a copy of the NOAA Diving Manual. It has all the deco tables in it. You will shortly come to see what matters and what can be ignored for the purpose of getting a valid estimate.

 

[Twoblues]

Suunto settles scary scuba screwup for $50m: 'Faulty' dive computer hardware and software put explorers in peril
I wonder if the divers that brought the suit where conscientious in servicing their equipment yearly?
Pamela Siegman the out-of-air fatality should have carried back up gauges! When careless safety rule breaking sportsmen/women suffer fatalities the families blame everyone (boat operator/manufacturer/etc.) and the sport suffers!

Some folks on SB keep advocating for understanding decompression and gas/time relationship using the simplest tools possible (tables, pre-dive planning, methods to monitor actual gas usage vs expected gas usage). Computers can be helpful, but over-reliance can compromise your safety and abilities as a diver.

 

[Twoblues]

It baffles me time after time that people rather rely on a piece of electronics instead of their common sense and knowledge. I will never understand why.

My rig includes back-up pressure and depth gauges, to complement my OCi wrist computer!

 

[BRT]

Apologies, I think that I see what is jammed in your gears.

Ongassing isn't linear. I can stay forever at 20' but only an hour at three times that depth. So we 'chunk' the dive into depths and times that we can get away with. Play with it. It isn't hard, get a copy of the NOAA Diving Manual. It has all the deco tables in it. You will shortly come to see what matters and what can be ignored for the purpose of getting a valid estimate.

I don't need to do calcs to have an idea if my computer is close to right. I know I can dive the numbers I first gave without a problem. I know the second set won't work. I don't have to do math for that. I still carry 2 computers because I don't want to think too much about it.