Algorithms, Conservative Factors, Altitude, Planned Deco - Questions

[Diving Dubai]

So while RGBM is proprietary and not open source, both companies allow the diver to plan decompression dives if required. A caveat with RGBM; because it is proprietary and takes into consideration and adjusts for multiday, repetitive diving, previous deeper dives and accent rates etc, a tech diver may be reluctant to use this algorithm because it may change the deco obligation during the dive itself which wasn’t planned for in terms of gas reserve

From someone who uses an Eon, I can say that just isn't true, I can back that up by the fact that I run a Shearwater perdix as a back up. I regularly dive multi day repetitive diving (monthly at least) With the Eon at -2 and the Perdix at 45/95 (both the most liberal aggressive setting) they are pretty much identical by the amount of Stop time they give and when they both enter deco. Their deco times are near identical too

I personally would have preferred an OSTC to the Perdix (which is okay but not as special as people on here seem to think) but I couldn't get one to touch and feel before I purchased.

The Eon display is light years ahead of the Perdix. However my dives are all sub 50m and generally no more than 1 hour with only one gas switch

 

[Johnoly]

..What is the future for decompression models and dive computers? ...

Just my opinion, but with battery technology making such huge gains over the last 20 years, I think the future will be more in how much smaller and more efficient CCR's will be.

Just dreaming here, but if you could extract O2 from seawater while underwater as easily as can be done on land currently, that will be the future. I don't think we're that far from it technology wise. And your grand kids will laugh at you for breathing open circuit just like we smile at people today who play vinyl records & 8 track tapes.

 

[stuartv]

Just my opinion, but with battery technology making such huge gains over the last 20 years, I think the future will be more in how much smaller and more efficient CCR's will be.

Just dreaming here, but if you could extract O2 from seawater while underwater as easily as can be done on land currently, that will be the future. I don't think we're that far from it technology wise. And your grand kids will laugh at you for breathing open circuit just like we smile at people today who play vinyl records & 8 track tapes.

I agree with you. I think advances in O2 sensor tech (e.g. the Poseidon solid-state O2 sensors), and advances in scrubber tech will push CCR to be more and more mainstream. To eventually be "the norm" and much less expensive.

But, I don't see that really having anything to do with the OP's question about deco models and dive computers....

 

[CandiveOz]

Hi lv2dive, thanks for your clarification regarding the secondary market for Shearwaters.

Stuartv, thanks for your comprehensive response. Just for my own clarification, when you say you use your Oceanic as back up, do you only use it in gauge mode with a printed bailout table? Or is it so liberal compared to your GF setting on the Shearwater that you let it run in dive mode and if the Teric fails you just follow the Oceanic deco profile?

You also mentioned that the Oceanic was more liberal than the Seabear. Is that because the Oceanic was using the DSAT algorithm versus the PZ+?

Just for your information, my next purchase will be wireless air integration. And I agree, If I want to eventually get a Shearwater, then I should stay within the group that share the same transmitter. But I won't rule out other brands because economically its not a big deal. Say I buy a used Suunto and transmitter for $500 when the original owner paid $1,500. I use it until I buy the computer I really want and then sell the Suunto and transmitter for say $200. My total cost is $300. I could even keep the Suunto as a back up and just sell the transmitter for $50 - $100. There is no big loss (as compared to the original owner). I guess you can call me a bottom feeder who depend on those who enjoy buying brand new shiny things.

I completely understand your tech argument for planning your dive and diving your plan. Good advice. And you are correct, the biometrics of the Scubapro can be turned off if required. But as a previously bent diver I appreciate that these inwater adjustments are trying to make the dive safer and perhaps should be taken into consideration. If it is an issue of gas capacity; then carry more gas. When I started diving, I sucked air like it was going out of style. So back in 2001 I bought a 15 ltr Faber (I think that's 125 cu ft in North America). Since then my SAC has improved but I am still humping that tank on all my dives. My buddies either use 10 or 12 litres so by the end of a typical dive, I've got enough air for the both of us. Also, if I set my computer to be conservative, I can still match my buddy's default air NDL's by diving nitrox which pushes out my conservative NDL's. So with a bit of ingenuity, one can dive conservatively, have enough gas and match your buddies NDL's to surface together.

Now I do consider the Scubapro a bit experimental, but my interest in it is a desire to learn more about decompression. I suspect, like you Stuartv, I'll end up with a number of different dive computers which I'll use depending on different types of dives.

 

[CandiveOz]

KenGordon,
Thanks for pointing out the obvious to use Suunto's dive software. I was able to answer my own question.
From my testing, it appears that the Suunto's Personal settings and Altitude settings are interchangeable. Here are the NDL results using DM5 at 18 meters for the standard RGBM:

51 min = P0A0 (default)
41 min = P0A1, P1A0
34 min = P0A2, P1A1, P2A0
28 min = P1A2, P2A1
23 min = P2A2

I ran the same test for 27 metres with similar results. This makes sense and I realised that my Tusa 750 PZ+ is slightly more conservative at its default setting compared to the Suunto and more or less equivalent to a P2A0 setting when I set my CF to on.

I also looked at the Tech and Fused versions of RGBM and as expected they gave longer NDL's than the default P0A0 at 18 metres. But oddly when I applied the attitude settings, the NDL's are shorter than the standard model. This was unexpected and a bit more testing is required to determine why.

While RGBM is proprietary, Suunto did the right thing by developing software to allow divers to plan their dives and play with the decompression model.

 

[CandiveOz]

AFAIK the best publicly available info on RGBM is a Wienke - O'Leary article from way back when, and that has a list of -- I'd say "considerations" -- that went into RGBM's conservatism. And I don;t think you'll find even that much for PZ+.

Dmaziuk thanks for referring to the article, I'll have a read.

A caveat with RGBM; because it is proprietary and takes into consideration and adjusts for multiday, repetitive diving, previous deeper dives and accent rates etc, a tech diver may be reluctant to use this algorithm because it may change the deco obligation during the dive itself which wasn’t planned for in terms of gas reserve.

KenGordon and Diving Dubai, thanks for correcting my assumption. Obviously Tech divers do use Suunto Eon since they they have access to DM5 to plan their dives just as Shearwater divers have access to Subsurface and Multi Deco. My comments originated from what I read on the website listed below. Perhaps you would like to comment.

The Best Technical Diving Computers 2017

 

[KenGordon]

But you're talking EON, not Gekko, correct?

Actually lots of Gekko, Zoop, Vyper, Viper Air (which does multiple mixes) and of course Helo2.
Also the odd lost soul with a Mares.

US agencies all traditionally regarded deco diving as the work of the devil, when new agencies came along to promote it they emphasised full on deep and long dives whichever really need accelerated deco and so multi gas computers.

However, back in the old world people were doing actual diving, on wrecks and stuff, where you need a long enough bottom time to be worth while. Since the equivalent organisations were clubs of people already wanting to go diving they didn’t need to worry about the needs of people selling courses to holiday makers and could insist you could perform a deco dive before you were called ‘qualified’.

All these divers were (and aren’t still) doing deco dives on a single gas. There is a progression:

Pretty fish, shallow wrecks, shallow scenic. No deco at all.
Not so shallow wrecks, scenic, deeper reefs. Some deco, but not lots, sensible on backgas.
Deeper or longer wreck dives, scenic. More than enough deco to be sensible on backgas.

The first is what PADI etc target, the third is what TDI etc target. The one in the middle is what BSAC and the CMAS clubs actually do quite often so train people for.

Our club has a new crop of Ocean Divers. They are equivalent to PADI Open Water. We are just working out the logistics of getting them through the Sports Diver training over the winter given most of them do not own drysuits. At the end of that they will be qualified to perform backgas deco dives. They will typically have about 30 or 40 dives at that point.

If I am doing a 30m Channel wreck, especially if the vis turns out nice, I want more than 20 minutes. We train people to go diving, so we have buddies and can fill boats. That is the sort of diving we have. So we train for that.

 

[KenGordon]

Dmaziuk thanks for referring to the article, I'll have a read.


KenGordon and Diving Dubai, thanks for correcting my assumption. Obviously Tech divers do use Suunto Eon since they they have access to DM5 to plan their dives just as Shearwater divers have access to Subsurface and Multi Deco. My comments originated from what I read on the website listed below. Perhaps you would like to comment.

The Best Technical Diving Computers 2017

LOL

That is Andy’s blog. When he wrote that I asked him on here is he had actually dived all the computers. He had not dived the EON, hi s opinion is probably based on the opinion s given on here by all the Suunto haters. This is the very definition of the echo chamber of the net.

 

[Diving Dubai]

@CandiveOz As Ken pointed out, Andy has never dived teh Eon nor (I expect) actually played with it.

A lot of Andy's Negative comments were based on hs personal bias. I found his comments about customisation laughable (I have 4 years and +500 dives of experience with the EOn)

Andy in the same post gav great credence to the Seabear. On this forum when it was first released there was a huge cult following because it was the thing as claimed to be a "shearwaer killer". It turned out to be an unmitigated disaster, with the T1 being withdrawn and lots of promised features never making it to production.

Shearwater (on this forum) has a huge cult following. look at any computer thread - even ones where someone is asking about their first computer and someone will say buy the shearwater (a $1000 USD machine)

I'm not saying its a bad machine, and Shearwater have a reputation for first class customer service, often going above and beyond what is expected in the US.

Outside of the US things aren't so clear. For instance in the Middle East, my nearest service centre in in the UK which is a 3rd party. I've not have to use it but I question whether I'd get the same level of support that one would dealing direct with Shearwater.

Some time ago there where some very long and contentious threads about air integration, it was unnecessary and bad (was one point of view) It was often cited that Shearwater didn't use it. All of a sudden the Perdix AI was released, and suddenly AI was acceptable. Likewise rechargeable batteries vs User changeable AA more debate, until Shearwater brought out the Teric, and now rechargable is acceptable.

That said, the Eon isn't' perfect, but then a lot comes down to your personal preferences. The build quality of the Eon and the OSTC is far superior to teh Perdix (that said teh Eon steel is a heavy beast if you're only divign in a rash vest)

For the type of diving I engage in (to 50m and dive times around the 60 min I have no disadvantages with either.
There is a group of Technical divers here who regularly dive Boxes or OC trimix on wrecks between 70-110m if I was engaged in those dive, then I'd certainly only used teh Shearwater or OSTC because I'd want to plan on the same software etc. But I'm not. For my dives inc deco it's easy to cross plan

Sometimes it's hard for people to get an unbiased opinion, because other peoples reviews are biased or those people don't actually have actual experience with the units and regurgitate what they've read/heard (and often its wrong).

I choose not to point people in any direction I try to give all the facts as I know them with the caveats of my experience and let them choose

 

[KenGordon]

Compasses, don’t forget that integrated compasses are evil too, make the software less reliable...