Dive computers... SO many choices!

[stuartv]

Right, and Craig's already happy with his One True Algorithm(tm)eanic so he's not buying either. So who is the target demo for that custom setting exactly?

Please please please give us the option to manually set gradients, even if it's hidden setting.

 

[dmaziuk]

Well, one can always buy the company and order them to program in whatever. Me, I'd save a million bucks a buy a birdix instead...

 

[ls1dreams]

In the end, I just want a recreational computer with a SAFE algorithm that's based on proper gradients - not old mistaken reduced bubble gradient/deep stop models or models that approximate it with numbers like 20/80, 30/90.

 

[scubadada]

Right, and Craig's already happy with his One True Algorithm(tm)eanic so he's not buying either. So who is the target demo for that custom setting exactly?

Not exactly, see post #32. I have been diving Oceanic and DSAT since 2002, nearly 1250 dives. I've only been diving my current primary VT3 since 2010, 830 dives. I recently gave up my backup Geo2 and have 80 dives on a Dive Rite Nitek Q. The Q has 3 preset GFs, 30/75, 40/100, and 75/95, and full range custom GFs up to 100/100. I have already learned a lot about Buhlmann ZH-L16C and GFs. My VT3 will not last forever. My next computer will run Buhlmann with GFs, maybe a Perdix AI, maybe something else available when the time comes up.

I think the Deep6 computer with 3 GF presets, same as Shearwater rec mode, will be a very nice recreational computer at a great price. Though I like having the custom GFs, I can easily understand why Deep6 would leave them off the initial rec computer. For NDL dives, 45/95 is a reasonable approximation of DSAT (see @stuartv explanation for GF hi entirely controlling NDL dives), 40/85 is close to PZ+, 35/75 is very conservative.

Most all of my dives are rec but about 5% are light deco. I generally have been running 75/95 but have also tried 95/95. I have way too few light deco dives to draw any conclusions. I've never known how DSAT treats deco so have no real baseline to compare. It seems to just pile on time at the shallow stop for my short deco obligations of less than 15 minutes.

Good diving, Craig

 

[dmaziuk]

In the end, I just want a recreational computer with a SAFE algorithm that's based on proper gradients - not old mistaken reduced bubble gradient/deep stop models or models that approximate it with numbers like 20/80, 30/90.

Ah. You win the internets: I nominate the above sentence for the official answer to "what's wrong with giving rec divers custom-settable gradient factors"

 

[stuartv]

Ah. You win the internets: I nominate the above sentence for the official answer to "what's wrong with giving rec divers custom-settable gradient factors"

You imply GF 20/80 or 30/90 are reasonable or appropriate numbers for recreational divers to be using?

I don't know of any rec computers that have those settings, but I agree with @ls1dreams that I wouldn't want a computer that is locked into those settings or an algorithm that yields ascents "like" those settings would.

 

[dmaziuk]

No. OP implies there UNSAFE rec computers, deep stops have any meaning on rec profiles and are intrinsic to "mistaken" bubble models and I'm not quite sure what "it" that' s being approximated with number actually supposed to be.

PS. abusing one of my favourite quotes of all time, "I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a statement".

 

[LandonL]

In which case, why give any options at all? Set it for the most liberal and give no option to change it?

That isn't too smart from an insurance policy standpoint.

Landon was saying that it was too dangerous and/or too complicated.

I stick with my assessment that it is too complicated and confusing to give them the option for 1000+ GF combinations... on a single gas computer.... meant for casual recreational divers……

I really feel like it is overkill, and will be more confusing for them than a simple 0-3 scale.

As for safety.. yeah.. I think its risky to run high values like 95... i realize this coincides with tables, but tables are square profiles, computer based calculations during a dive are not. Its why Buhlmann had a few different variations, the calculations vary differently depending on if square or variable.

ps. The same post also makes it clear that only GF Hi controls the NDL, so, for recreational diving (i.e. this thread), you can already set it to GF 45/99 and it will work exactly the same as GF99/99 (for recreational diving).

I never said the low GF has any effect on the NDL, but yes 45/99 or 99/99 are exactly the same UNTIL you pass the NDL, so if someone does that accidentally I wouldn't suggest decompressing on a 99/99, and I wouldn't really want to be a manufacturer producing a recreational computer that allowed such. You do have to consider your insurance for producing such a product that would do this. If someone were diving that profile they are effectively diving a straight Buhlmann M-line, and have eliminated the safety margin.

In the end, I just want a recreational computer with a SAFE algorithm that's based on proper gradients - not old mistaken reduced bubble gradient/deep stop models or models that approximate it with numbers like 20/80, 30/90.

Buhlmann has been proven to be a safe algorithm, as have the presets mentioned. I am unsure of what you mean by models that 'approximate' it? My reasoning for picking the presets I mentioned was because I believe them to be safe and reliable.

 

[tbone1004]

@LandonL the buhlmann gradient factors when set that low are meant to mimic the ascent profiles of the bubble models by forcing deep stops and making a shallower ascent profile overall.

Personally? for this computer in particular, and realistically everything in the light-tec market and below, I'm OK with following the GF profiles that Shearwater has chosen. They are widely used and accepted, and while they may not be perfectly in line with what you or I may believe, it's fairly inconsequential in the grand scheme of things. If you want that amount of flexibility, spend up for the big boy computers that allow you to do that, but for something like this? KISS

 

[stuartv]

Apologies, Landon. I wasn't addressing you with some of the comments that you took that way.

That isn't too smart from an insurance policy standpoint.

I was being facetious in response to the post I quoted. I agree with you.

I stick with my assessment that it is too complicated and confusing to give them the option for 1000+ GF combinations... on a single gas computer.... meant for casual recreational divers……

I really feel like it is overkill, and will be more confusing for them than a simple 0-3 scale.

As for safety.. yeah.. I think its risky to run high values like 95... i realize this coincides with tables, but tables are square profiles, computer based calculations during a dive are not. Its why Buhlmann had a few different variations, the calculations vary differently depending on if square or variable.

All the Oceanic computers running DSAT are giving NDLs about the same as using a GF Hi of 95....

I never said the low GF has any effect on the NDL, but yes 45/99 or 99/99 are effectively the same UNTIL you pass the NDL, so if someone does that accidentally I wouldn't suggest decompressing on a 99/99, and I wouldn't really want to be a manufacturer producing a recreational computer that allowed such. You do have to consider your insurance for producing such a product that would do this. If someone were diving that profile they are effectively diving a straight Buhlmann M-line, and have eliminated all safety factors.

I know. My comment was a ps on my response to KenGordon.

I also agree with you that presets matching Shearwater should be fine. I was just trying to be devil's advocate for a custom setting, since that is what ls1dreams is asking for. I really don't see it as a big deal, either way. Especially for a $140 computer! I'll be very happy to see y'all finally get that out into people's hands.