Wisdom of trusting one's dive computer?

[jale]

@CAPTAIN SINBAD
it is one thing to do mental math and another to do approximations in your head and declare it is better than using a calculator. nobody is going full Rainman and running Buhlmann ZHL16-B with GF in their head.

Bulhmann is an approximation.
Bulhmann with GF is tweaking an approximation.
Avg depth, ratio deco,...are approximations
Just choose your approximatiom
Precision don't mean correctness...

 

[abnfrog]

every student in an sdi program HAS to dive with and understand computer diving , it is left up to me as to how much of the tables I teach . I have seen divers who have been diving for years never doing the dive tables , they are at disadvantage when they decide to do a tdi nitrox course, but it just takes them a little longer ....a lot of the table taught divers have forgotten how to do a written out table any ways

 

[EFX]

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

Just to compare GF's I ran my spreadsheet for a 100 ft 30 min dive on air with no deco gases and got this (GFLo/GFHi - Total deco time[ascent time included] - First stop):
85/85 - 16.3 - 20
65/85 - 18.3 - 30
45/85 - 20.3 - 40
35/85 - 21.3 - 40
25/85 - 23.3 - 50

 

[JohnN]

Just to compare GF's I ran my spreadsheet for a 100 ft 30 min dive on air with no deco gases and got this (GFLo/GFHi - Total deco time[ascent time included] - First stop):
85/85 - 16.3 - 20
65/85 - 18.3 - 30
45/85 - 20.3 - 40
35/85 - 21.3 - 40
25/85 - 23.3 - 50

Odd

I just ran a subset of this on my Perdix:
100 ft for 30 minutes on air

85/85 Total Deco 20 min
65/85 Total Deco 20 min
40/85 Total Deco 21 min

I guess the great thing about standards, is that there are so many to choose from

---edit---

Looking at the Perdix, it is using 16c Is your spreadsheet "c" or '"b" ??

 

[EFX]

The spreadsheet calculations were done with Buhlmann ZH-L16C using median depths for ascents and descents. MultiDeco came up with (GFLo/GFHi - Total deco time - First stop depth):

85/85 - 17 - 20
65/85 - 18 - 30
45/85 - 19 - 40
35/85 - 20 - 40
25/85 - 20 - 50

 

[CaveSloth]

Just for fun, I compared what the Teric says to the PADI EAN32 dive table.

Dive table says NDL for 100ft is 30 minutes.

Results from Teric on different GF Conservatism settings:

• Low (45/95): 28 min
• Med (40/85): 23 min
• Hi (35/75): 19 min

 

[Ouvea]

What is the better approach? Trusting the computer or doing pre-dive planning?
The lame thing about the pre-planning is it doesn't really leave any freedom. With the computer, it feels like I am safe to dive without any plan whatsoever, other than making sure not to incur deco.

I'm rather confused at the prior statements. Are you advocating against dive planning? Every training agency, whether Tech or Rec focused advocates creating a dive plan and diving the plan. I don't understand how having a dive plan translates into an inability to making real-time/on-the-fly modifications. That's a lack of a experience in planning dives and executing dives. Maybe it's just me but I find the OP's following statement contrary to what I have been taught by NAUI, PADI or GUE.

"With the computer, it feels like I am safe to dive without any plan whatsoever, other than making sure not to incur deco."

How many dive professionals will advocate this to their new students. How many of you, who are dive professionals, can state that such a statement is in-line with your agency's teachings? There is a HUGE difference in using a dive computer to verify/corroborate the validity of a dive plan and using a dive computer to blindly tell you when you're in deco and your dive deco profile during the dive. Every dive computer that I have owned, beginning with my old Oceanic Prodigy, has a dive planning function. It's something that needs to be done on every dive. Some dive profiles require rigorous calculations and preparations, others do not. A dive to 30ft with an AL80 doesn't require as much planning as a dive to 200ft with two deco gasses. Can you modify either dive on-the-fly? Absolutely! Can you modify the second dive profile as much as the first dive? Probably not...

 

[Graeme Fraser]

I'm rather confused at the prior statements. Are you advocating against dive planning? Every training agency, whether Tech or Rec focused advocates creating a dive plan and diving the plan. I don't understand how having a dive plan translates into an inability to making real-time/on-the-fly modifications. That's a lack of a experience in planning dives and executing dives. Maybe it's just me but I find the OP's following statement contrary to what I have been taught by NAUI, PADI or GUE.

"With the computer, it feels like I am safe to dive without any plan whatsoever, other than making sure not to incur deco."

How many dive professionals will advocate this to their new students. How many of you, who are dive professionals, can state that such a statement is in-line with your agency's teachings? There is a HUGE difference in using a dive computer to verify/corroborate the validity of a dive plan and using a dive computer to blindly tell you when you're in deco and your dive deco profile during the dive. Every dive computer that I have owned, beginning with my old Oceanic Prodigy, has a dive planning function. It's something that needs to be done on every dive. Some dive profiles require rigorous calculations and preparations, others do not. A dive to 30ft with an AL80 doesn't require as much planning as a dive to 200ft with two deco gasses. Can you modify either dive on-the-fly? Absolutely! Can you modify the second dive profile as much as the first dive? Probably not...

No agency or responsible dive pro would advocate diving without at least a basic plan. Doesn't have to be complicated, in fact the simpler the better. It's not just time, max depth and gas planning. Obvious things like exit point should be thought about as well. Easy to stride off a 6ft harbour wall, not so easy to exit if you haven't worked out where the steps are.

Dive computers have transformed diving but, last time I looked AI stood for Air Integrated not Artificial Intelligence.

Remember; plan the dive, dive the wreck, wreck the plan.