So, who is going to market an inexpensive rec computer running Buhlmann with GF?

[vovanx]

Interesting comment. Do you base this upon going into deco, where GF lo would kick in? Do you dive a Buhlmann backup in order to make this comparison? For 1st dive I can imagine that Suunto could be close to GF hi of 95, doubt that it is true on repetitive dives, particularly with shorter SIs and/or deco on previous dive.

Yes, it is for the 1st dive. I have Suunto and Buhlmann backup set to 35/90, they have somewhat similar NDLs for the 1st dive:
RGBM 30/80? 68 49 34 27 20 16 12 9 8 6
ZHL16C 35/90 67 47 32 25 18 15 12 11 8 7

When I did a planned deco dive they both went into deco at about same moment, both stating something like "8 mins ascend time", and after a bit more bottom time and ascent, they both cleared deco at about same moment.
I did not compare both algos on multiple deep/deco dives at the same day, will post here if I do. However I do not remember them being very different on the NDL time on multiple dives (I always wait at least 60mins surface interval)

 

[scubadada]

I have 480 dives on my Suntoo D6i, had around 300 dives on a D4 and have around 50ish with a Petrel 2 runing 45/90.
I can safely say that Suntoo RGMB really really likes a surface interval, less then a hour between dives (even if the first one of them was fixing a propeller or a discovery) means your NDL is 1/3 of normal, may be less. After about 3-4 hours it does not care as much even if you are doing 2 deco dives it will give you predictable NDLs and deco times.

Major difference is in how much deco it gives you, after 10 minutes of deco Suntoo goes crazy and gives you almost double the deco time of the Petrel.

I often have 20ish repetitive dives in a row during a week and I don't see that much difference between the two on rec dives, Suntoo gives me a bit less NDL depending on the surface interval from last dive.

I dive DSAT as my primary deco algorithm but have quite a bit of experience with a Nitek Q backup running Buhlmann ZH-L16C with GF. @Vicko experience is similar to what I've seen diving with folks using a Suunto computer. The first dive is often not much different than DSAT or a GF hi of 90 or 95. Subsequent dives are often considerably shorter, especially with a short SI. On several occasions, I have done 4 dives/day with a buddy diving Suunto when the SI between dives 1&2 and 3&4 was 30-45 minutes and the SI was 2 hours or more between 2&3 for a lunch break, afternoon turnaround. The NDLs for dives 1 and 3 were not much different than mine, whereas, the NDLs for dives 2 and 4 were much shorter.

my D6i Novo is closer to 35/95

Interesting comment. Do you base this upon going into deco, where GF lo would kick in? Do you dive a Buhlmann backup in order to make this comparison? For 1st dive I can imagine that Suunto could be close to GF hi of 95, doubt that it is true on repetitive dives, particularly with shorter SIs and/or deco on previous dive.

Yes, it is for the 1st dive. I have Suunto and Buhlmann backup set to 35/90, they have somewhat similar NDLs for the 1st dive:
RGBM 30/80? 68 49 34 27 20 16 12 9 8 6
ZHL16C 35/90 67 47 32 25 18 15 12 11 8 7

When I did a planned deco dive they both went into deco at about same moment, both stating something like "8 mins ascend time", and after a bit more bottom time and ascent, they both cleared deco at about same moment.
I did not compare both algos on multiple deep/deco dives at the same day, will post here if I do. However I do not remember them being very different on the NDL time on multiple dives (I always wait at least 60mins surface interval)

As above, not surprising that Suunto would have a similar NDL on the first dive. It a appears that short SIs, and some additional dive factors, such as reverse profiles, rapid ascent, and multiday diving, can lead to shorter NDLs on subsequent dives.

It turns out that Suunto has three flavors of RGBM that are described on their website Suunto RGBM Dive Algorithms Most of their computers run Suunto RGBM. The HelO2 and D9tx run Suunto Technical RGBM, and the DX and EON Core and Steel run Fused RGBM. The computers running Fused RGBM can be set to be quite liberal (P-2) and appear to have NDLs similar to DSAT or a GF hi in the 90s. Martin, @Diving Dubai first pointed this out to me and has extensive experience with an Eon Steel.

Deco algorithms are very interesting

 

[Diving Dubai]

So I know from experience that if I go to P-2 on the Eon I have to accept a compromise. Yes it's less conservative, but it's also less tolerant of deviations.
If I'm my DPV I'm guaranteed to get ascent violations and then get a mandatory stop at 5m
The same dive on P0 then not so much

Now I happen to understand that if I'm dropping from 100' to 160 and riding the deco then I need to make allowances, so I'll sit at 40' until my NDL returns to +99 then do 5 mins at 30' and 6 mins at 15' (unless the computer asks for more). And I have SI's of no less than 90 mins

Back to the cheap computer

The issue is, generally it's new divers or infrequent divers who buy them. These people by any manufacturers guidelines should be setting at the more conservative side.

A manufacturer also has to contend with Young fit regular divers through to fat middle age vacation divers. So their choices of conservatism are a massive compromise.

You also see it here where people are most interested in the max NDL - just learn Deco, and understand the limits

I also wonder if the choice of algorithm is a marketing tool - why do Buhlmann computers cost more? do they need additional processing power or is it more of a factor of the above?

Now I'm about to buy either and OSTC 4 or a Perdix just for "tech" I'll probably use the default settings because I know how to max my time with them safely, rather than putting in random GF until I get bent then dialing it down, which is not in my opinion the most ideal method and little different then using GF's I've read about on the internet

I think teh manufacturers are doing a good job covering all bases at the moment

 

[dmaziuk]

I also wonder if the choice of algorithm is a marketing tool - why do Buhlmann computers cost more? do they need additional processing power or is it more of a factor of the above?

I hear Aladin One Matrix is out now with ZHL16 ADT and a price tag of a Zoop, so no they don't cost more anymore. (Technically, it only takes one counter-example to disprove "all Buhlmann computers cost more" statement.)

The issue is not processing power: Moore's Law takes care of that. It's having to make a new computer around a newer CPU. This isn't like cellphones where you can give them a new one every year "free with $100/mo subscription for 2 years minimum", with DCs you have to have the actual sales pay your development costs.

 

[scubadada]

Scubapro's Buhlmann ZH-L8 and 16 ADT MB are used only by Scubapro and are not ZH-L 16B or C with GF used by Dive Soft, Garmin, Ratio/Seac, Shearwater, Divecomputer.eu, or Henrichs Weikamp. Heck, you can call PZ+ Buhlmann if you want.

 

[KenGordon]

So I know from experience that if I go to P-2 on the Eon I have to accept a compromise. Yes it's less conservative, but it's also less tolerant of deviations.
If I'm my DPV I'm guaranteed to get ascent violations and then get a mandatory stop at 5m
The same dive on P0 then not so much

Now I happen to understand that if I'm dropping from 100' to 160 and riding the deco then I need to make allowances, so I'll sit at 40' until my NDL returns to +99 then do 5 mins at 30' and 6 mins at 15' (unless the computer asks for more). And I have SI's of no less than 90 mins

Back to the cheap computer

The issue is, generally it's new divers or infrequent divers who buy them. These people by any manufacturers guidelines should be setting at the more conservative side.

A manufacturer also has to contend with Young fit regular divers through to fat middle age vacation divers. So their choices of conservatism are a massive compromise.

You also see it here where people are most interested in the max NDL - just learn Deco, and understand the limits

I also wonder if the choice of algorithm is a marketing tool - why do Buhlmann computers cost more? do they need additional processing power or is it more of a factor of the above?

Now I'm about to buy either and OSTC 4 or a Perdix just for "tech" I'll probably use the default settings because I know how to max my time with them safely, rather than putting in random GF until I get bent then dialing it down, which is not in my opinion the most ideal method and little different then using GF's I've read about on the internet

I think teh manufacturers are doing a good job covering all bases at the moment

I stopped using the defaults on my Perdix when my buddy on a zoop started leaving me behind on the shot.

 

[Vicko]

Be very carefull of Sunto Fusion RGBM, it really really prefers square profiles and penalizes you for deviations to the point of doubleing deco time for me on some dives + I got locked out of the computer during a dive with almost an hour of deco left because I had to deliver gass to a diver above me.

 

[dmaziuk]

The Wiki of the Thousand Lies claims ZHL-16 ADT is ZHL-16C "modified mostly in middle compartments". ZHL-16B and ZHL-16C are also said to be "modified in the middle compartments" versions of the base ZHL-16 model.

At which point a gissolved gas inverse-exponential parallel compartment model using Buhlmann compartments and Buhlmann equation becomes not Buhlmann?

 

[Bierstadt]

Honestly I never think about Buhlman for pure rec diving. I would rather see a Buhlman DC at the $300-$400 mark for when a diver starts getting into tec diving and as a backup DC for advanced tec diving. And of course for the rec divers who don't do tec diving but have that sort of mindset in wanting to understand and control their dive calculations. I would much rather spend a bit more on a DC to get that than I would to get a color screen and AI. Those are nice to have, of course, but not something I am going to spend on if I don't have Buhlman first. Such a DC might be better suited to being a Kickstarter-type project where a manufacturer gets the buy-in first, then makes the product.

 

[scubadada]

The Wiki of the Thousand Lies claims ZHL-16 ADT is ZHL-16C "modified mostly in middle compartments". ZHL-16B and ZHL-16C are also said to be "modified in the middle compartments" versions of the base ZHL-16 model.

At which point a gissolved gas inverse-exponential parallel compartment model using Buhlmann compartments and Buhlmann equation becomes not Buhlmann?

And....by micro bubble adjustments, and by gas consumption, and by heart rate, and by skin temperature... Scubapro has their own implementation, not reproduced by any other brand. You cannot do planning based on any other implementation of Buhlmann. This is a major defect. Not much different than PZ+, which has undocumented changes to the Buhlmann algorithm.