Matching GF between main and backup computers?

[steinbil]

The table says 100 ft, 30 minutes, which it seemed like you questioned the validity of.

GUE uses 30 min @ 30 m as the rule of thumb, which is the same as 30 min @ 100 ft in the PADI table. (Since that's the deepest allowed by the GUE table that forms the basis of the rule of thumb; that's not the case in the PADI table so perhaps a different rule of thumb becomes more natural.)

View attachment 807956

The PADI RDP for 32% would be a rule of 125, not 130. Even the Navy/NOAA tables don't support 130.

The GUE MDL table jborg posted allows for it. With a standard GUE MDL ascent, that gives a Surfacing GF of 90% for 27m/90ft and 24m/80ft at its most agressive. Around GF85% for 30m/100ft and 21m/70ft. Actually a tad lower if you follow the recommendation of slowing down from 3m to the surface. Just like with the PADI RDP, it would be a bad idea to dive at the very limits of the table and do a quick ascent.

 

[dmaziuk]

I dive with a Perdix 2 (main) and an Apple Watch Ultra (backup, I really like the compass), and liked the fact that they both use the same algorithm. I just noticed that their "default" Gradient Factor settings aren't the same:

Perdix 2 "med" conservatism:
40/85

AWU "default" conservatism:
70/85

I feel like these should match, but I'm really not sure which to chose as I find GF a bit of a confusing topic.

Apple default reflects the more modern thinking: GFLo = 0.83 * GFHi. Shearwater default dates to before NEDU bruhaha, but you can change the setting to whatever you want. As others pointed out, the difference only matters if do into deco.

 

[scubadada]

Apple default reflects the more modern thinking: GFLo = 0.83 * GFHi. Shearwater default dates to before NEDU bruhaha, but you can change the setting to whatever you want. As others pointed out, the difference only matters if do into deco.

For SW OC rec you have access to custom GF. I dive 80/95.

 

[tursiops]

The table says 100 ft, 30 minutes, which it seemed like you questioned the validity of.

GUE uses 30 min @ 30 m as the rule of thumb, which is the same as 30 min @ 100 ft in the PADI table. (Since that's the deepest allowed by the GUE table that forms the basis of the rule of thumb; that's not the case in the PADI table so perhaps a different rule of thumb becomes more natural.)

View attachment 807956

The "rule of X" is a tangent-linear approximation to a curved line. You get it by looking at the table and finding the smallest sum of depth (feet) and time (mins). On the PADI table it is 125, which is accurate for 89 and 90 feet, and conservative for greater and lesser depths.
The GUE table you've posted indeed gives 130 for its "rule,' and appears to be accurate for 79, 80, 90, and 100 feet, which is very strange...it suggests the GUE deco curve is a straight line over those depths...not a curved line like other tables. Where does the GUE table come from; what is it based on? I thought the GUE tables were based on Buhlmann, with a GG-Hi of 85, but I guess not. GH-Hi of 85 would give a rule of 118 for 32%; GF-Hi=95 would give 125; and GF-hi=99 would give 127.

 

[Twiny]

There is no deco in GUE Fundamentals, so the GFlo won't apply. Actually the GFhi probably also won't come into play as (1) it's all about doing skills in shallow water, and (2) you learn to dive with a bottom timer/gauge mode.

As far as I know, 20/85 is only used by GUE for TRAINING PURPOSES, as it gives more stops, and GUE teaches to be a thinking diver and to keep up with current research. I don't know any GUE divers that dive 20/85.

Hi, in order to select the proper GF to adapt your deco to your type of diving, gases, age, fitness level, ... : do NOT necessarily follow recommendations coming from computer manufacturers nor training agencies.
Rather keep directly updated by diving researchers like Prof. Simon Mitchell (Scubaboard member).
Pretty sure you won't talk anymore about 20/85 for long !

 

[tursiops]

Where does the GUE table come from; what is it based on?

It appears to mirror the 2012 NAUI table...

 

[steinbil]

Hi, in order to select the proper GF to adapt your deco to your type of diving, gases, age, fitness level, ... : do NOT necessarily follow recommendations coming from computer manufacturers nor training agencies.
Rather keep directly updated by diving researchers like Prof. Simon Mitchell (Scubaboard member).
Pretty sure you won't talk anymore about 20/85 for long !

I think you missed the part in bold where I specified that 20/85 is only for training. And also the part where I said that GUE teaches you to keep up with the latest research.

 

[Twiny]

I think you missed the part in bold where I specified that 20/85 is only for training. And also the part where I said that GUE teaches you to keep up with the latest research.

No, no, I was just quoting you because we think the same, just as positive reinforcement ! against 20/85 for challenging dives on air

 

[inquis]

I was looking at the GUE 32% table last night, as a matter of fact, and equivalent GFs are somewhat variable. Some of the times are equivalent to GF x/90+, and I think 60 ft worked out to x/95. Based on my (possibly imperfect) understanding of the MD ascent, I also assumed a 10 m/min ascent to half depth and a 3 m/min ascent from there.

 

[steinbil]

I was looking at the GUE 32% table last night, as a matter of fact, and equivalent GFs are somewhat variable. Some of the times are equivalent to GF x/90+, and I think 60 ft worked out to x/95. Based on my (possibly imperfect) understanding of the MD ascent, I also assumed a 10 m/min ascent to half depth and a 3 m/min ascent from there.

Almost right. 9m/min to half depth, then 3m/min to 3m, and even slower last 3m to surface.