Suunto computers....

[DC53]

DC, I would have been happy to look the data over but thats a screwball nitrox mix percentage. I dont have a quick table for 34 and am not willing to figure out EAD for each level to generate an NDL amount. 32 or 36 would have been easier...

Ok when I get a little time I will generate a set of comparison numbers using EAN 32 or 36.

One thing I can say is that if I have say five or six minutes of deco obligation at depth at the end of the bottom time but go up slow with a couple deepstops at 50% of remaining depths, by the time I get to 15 feet the obligation will most likely be gone. (Of course I still always do the non mandatory 3 min stop - and then some.) While there's not substitue for additional training and study (in process and also to come) the process is pretty intuitive (with the assistance of the computer.)

If this sounds like I am being risky, let me again point out that the VEO 250 computer on the other wrist is showing a comfortable amount of NDL time remaining, continuously, during all of this. And yes I am using 50% RGBM attenutation.

 

[DC53]

Interesting that the VEO gives you more NDL at 70' (111 min) than it does at 60' (106min) - or is that a typo?

Should be corrected. Note that these dive planning figures are less than 24 hours after the last dive and so may differ slightly from ones calculated on "fully dried out" computers. I also not that the difference between Suunto and Veo seems to become more and more pronounced with repetitive dives.

 

[Offgassing]

I'll give you a real world example I experienced while visiting my buddy in west palm. He is diving a Suunto Vyper 2; I'm using a Galileo. We stayed together during both dives.

Dive one: N34. Max depth 81 ft, average depth 62 ft, median depth 75 ft.
26 min into the dive, he gives me the the thumb; his Vyper displays 2 min no stop time remaining. My Galileo shows 26 min of no-stop time remaining. We make a slow ascent, do a 3 min safety stop at 15 ft. Total in water time 35 min.

Dive two: N37 max depth 64 ft, mean depth 61 ft.
35 minutes into the dive he thumbs it, 2 min no-stop time left on the Vyper 2; 68 minutes left on the Galileo. Slow ascent, 3 minutes at 15' to increase our safety margin. Total in water time 46'

As you can see there is a vast difference in the algorithms between those two computers. The Suunto has one of the most conservative around; the Galileo is considered moderate, the Veo is among the most liberal. Different models make different assumptions and produce different numbers. Which one is right? You will have to decide that for yourself. I find the Suunto to be way too conservative for me, but my buddy loves it and swears by it. We have both been diving computers for a long time. We are both happy with our choices.

 

[gcbryan]

The bottom line is that deco is a theory and not hard science. The "grey area" between DCS and no DCS is also very large among individuals on a given day.

I saw some figures that indicated that using air at 100 fsw with a 1 percent occurrence of DSC you would get 8 minutes as the NDL time...with a 5 percent occurrence you would get 45 minutes or greater.

If you use two computers it's probably prudent to follow the most conservative. What you don't want to do is pick and choose.

The Veo will be more liberal in most situations but if you do get into deco it will may add on a lot of deco suddenly. It's sometimes the more conservative computer on the second dive as well. So if you are going to use it, use it on all dives (or do something more conservative).

Suunto's are a little too conservative to me in most situations but ultimately I spend a lot of time shallow after a deeper dive anyway so it's not an issue.

One isn't right and one isn't wrong since there would have to be more science behind deco theory for this to be the case (it's more likely that they are both incorrect).

Oceanic is based more on a traditional (Buhlmann) or dissolved gas model. Suunto uses the same theory more or less for their dissolved gas calculations but differ in that they take free phase or bubble mechanics into account so you get more credit for slowing down the ascent and for "deep stops".

It's just a theory but the idea is that traditional models allow microbubble (subclinical DSC) to form or actually for pre-existing nuclei to cause the formation of larger bubbles and then make you wait at shallower stops for those bubbles to dissolve. Bubble theory tries to slow things down and to keep them from forming (or growing past a critical diameter) in the first place.

The differences between dissolved gas and dual phase (RGBM) aren't that great at recreational levels anyway.
Suunto has programmed in certain other penalties.

There are no studies showing a higher incidence of DSC among Oceanic vs Suunto computers. Anyone can get DSC on any day but there are things you can do to minimize the risks.

The best thing is just to learn a little more about deco theory and not trust either model completely and use your own understanding of the theory and your body and what you feel is right for you on a given day.

If you aren't doing reverse profiles, short surface intervals, and aren't making rapid ascents ultimately one ends up being just a little more conservative than the other (Suunto vs whatever).

The NDL's for all computers/tables are based on observed data so within recreational depths there is very little "theory" going on anyway.

I have an Oceanic computer as well as a Tusa IQ-700 which is about as conservative as a Suunto in most regards. I usually use the Tusa but it doesn't really control my dive. I do the dive I would do regardless of the computer used, do a slow ascent with stops, spend a good bit of time shallow and by the time I get out any computer would be satisfied.

 

[NCadiver]

DC53 Oceanic is using DSAT/Powell/Rogers/Modified Haldanean Algorithm and I believe NOAA for the nitrox algorithm. Suunto is using the RGBM Algorithm set for the next altitude level because most of their diving is high altitude lake in Europe.
Oceanic use to be middle of the road for NDL Algorithm, All the real liberal computers are gone now which leave oceanic computer the most liberal now.

For standard dive either Algorithm is good. For tech diving I would use the Suunto because they have a total time to ascent.

 

[DC53]

Here is more detailed information. Comparisons are made between the
PADI EAN32 tables, the Suunto Vyper Air set for 32 Nitrox and zero altitude,
and both with default 100% RGBM and attenuated 50% RGBM, and the
VEO250 set for Nitrox 32……

Depth---NDL ----VEO250-----Delta-----Suunto@---Delta--- Sunnto@------Delta
--------PADI---------------- PADI--- 50%RGBM--- PADI-----100%RGBM---PADI
110-----25--------25----------0----------20------(-)5------19-----------(-)6
100-----30--------30----------0----------25------(-)5------23-----------(-)7
90------35--------37--------(+)2---------31------(-)4------30-----------(-)5
80------45--------49--------(+)4---------39------(-)6------37-----------(-)8
70------60--------65--------(+)5---------53------(-)7------52-----------(-)8
60------90--------92--------(+)2---------72------(-)18-----69-----------(-)21
50-----155-------148--------(-)7-------“>99”------???-----“>99”---------???

A couple of conclusions are apparent. One is that if you accept the
PADI EAN tables as reliable and safe the VEO is pretty close throughout
most of the normal diving range, although a LITTLE bit more “aggressive”.
On the other hand the Suunto even when set at the attenuated 50% level
Is at least 10-20% too conservative between 70 and 110 feet and way more
than that at depths of 60 feet or below. Personally I am a little disappointed
in the Suunto. It has many advantages in terms of user simplicity, lots of
information, air integration, etc., but to have substantial (and unexplained)
variations from accepted norms such as the PADI tables is concerning to me.

 

[gcbryan]

Here is more detailed information. Comparisons are made between the
PADI EAN32 tables, the Suunto Vyper Air set for 32 Nitrox and zero altitude,
and both with default 100% RGBM and attenuated 50% RGBM, and the
VEO250 set for Nitrox 32……

Depth---NDL ----VEO250-----Delta-----Suunto@---Delta--- Sunnto@------Delta
--------PADI---------------- PADI--- 50%RGBM--- PADI-----100%RGBM---PADI
110-----25--------25----------0----------20------(-)5------19-----------(-)6
100-----30--------30----------0----------25------(-)5------23-----------(-)7
90------35--------37--------(+)2---------31------(-)4------30-----------(-)5
80------45--------49--------(+)4---------39------(-)6------37-----------(-)8
70------60--------65--------(+)5---------53------(-)7------52-----------(-)8
60------90--------92--------(+)2---------72------(-)18-----69-----------(-)21
50-----155-------148--------(-)7-------“>99”------???-----“>99”---------???

A couple of conclusions are apparent. One is that if you accept the
PADI EAN tables as reliable and safe the VEO is pretty close throughout
most of the normal diving range, although a LITTLE bit more “aggressive”.
On the other hand the Suunto even when set at the attenuated 50% level
Is at least 10-20% too conservative between 70 and 110 feet and way more
than that at depths of 60 feet or below. Personally I am a little disappointed
in the Suunto. It has many advantages in terms of user simplicity, lots of
information, air integration, etc., but to have substantial (and unexplained)
variations from accepted norms such as the PADI tables is concerning to me.

See post #14 and there is no accepted norm.

Merry Christmas

 

[Jorgy]

I recall a prior thread.......

The PADI dive tables are basically derivatives of the US Navy dive tables.......

Those tables were based on empirical data collected over time and based on being able to work underwater by younger fit military divers.......also a certain amount of decompression illness was deemed acceptable, so post have cited a 5% number.

Again, since this was not recreational diving and a deco chamber was readily evaluable this was felt to be OK......

I would not say that the PADI tables are gospel........

In the end there are cases of "undeserved hits" so there is no real science on this.....

Up to you, what is underwater that is worth a potential hit? My family and I all dive Suunto's and have a great time, when it says go up we go up - usually long before that, only my son has gotten close on deeper wreck dives.....

I have gone into deco on my Sunnto I just clear the obligation prior to surfacing - makes for along safety stop, just amke sure you have enough gas.......

M

 

[DC53]

Thanks for all the input. After consideration, I withdraw my doubts about the Suunto. Better to dive with peace of mind that the computer is erring on the safe side. And, it's super easy for eveything to come out ok even if you do go (a little) over with at least a two minute stop at 40 feet and then 3-5 min at 15.

 

[watboy]

Two bits

On nitrox, Suunto (at least my D6 does) calculates everything 1% more conservative. So if you are running EANx32, NDLs are calculated as if its 31%, FO2 and MOD are calculated as if it were 33%. Thats once source of shorted NDLs.

The second is the diver alert. When you surface, if you have gone particularly deep, near NDL limits, gone into deco or any other thing Suunto thinks is bad like fast ascent, you will get a diver alert warning, the triangle with ! in it. I had go google fu this, but that alert tells you should extend your surface interval. Taking a second dive while this alert is still up will result in your NDL times being severely reduced. Also from google fu, the 50% model modifier will reduce the penalty, but the diver alert warning will always be on. I believe the diver alert will clear after 75mins at the longest. I've run into this problem before, which is most annoying considering how easy it is to trigger a fast ascent warning on a suunto. Raising your hand quickly over head is enough to get the warning.