Are Suuntos really more conservative for rec diving?

[EireDiver606]

Everyon hates Suuntos.

I can understand why for technical dives, but they’re perfect for rec dives.

 

[admikar]

Best to dive with the same algorithm (Suunto is fine) that your dive buddies use. Otherwise, somebody is going to be unhappy.
In the US, I see few Suuntos; elsewhere, many. It is very much a marketing and distribution thing, not a an algorithm thing.

Beware, however, the VERY different approach to customer support: Shearwater is probably one of the best, Suunto, not so much.

I'm happy to dive with a buddy sporting a Suunto. Just have our expectations known beforehand. One of the reasons I went for SW is your last sentence.

 

[dmaziuk]

However, isn’t it true that any dive computer penalizes these actions too, in the form of shorter NDL times? If you have a short surface interval, for example, your tissues have less time to rid themselves of Nitrogen.

It's not quite that simple: e.g. DSAT's driving tissue compartment off-gasses to half its original loading in 1 hour, whereas Cressi RGBM's "slowest" compartment is 480 minutes. So DSAT considers you "clean" in 6 hours while by RGBM you'd only off-gassed 50%. On the flip side if you had significant gas loading in those slower tissues, DSAT could consider you "OK" after a shorter surface interval that in reality is too short. (DSAT comes with a warning: no more than 6 consecutive days of diving, for that reason.) That's the theory, whether it works out that way in practice is a different story.

Another example is, again in theory, bubble models could calculate "smaller bubbles" at safety stop than at the surface and therefore faster off-gassing at SS. So for the same (long) SS and SI a bubble model could conceivably calculate less residual gas loading.

In other word the differences are non-linear and highly profile-dependent.

Besides, Suuntos comparable to Shearwaters are the Eon line whose conservatism settings apparently aren't quite as "conservative" as those of Gekkos and Zoops everyone whines about.

 

[svs]

I have Suunto (old one, so I don’t know if they fixed that problem or not) and more recent Veo. On many dives NDL difference is not so bad, within few minutes between computers, but I did have a problem with Suunto on some multilevel dives. E.g ledge 60 to 100 ft. If in the beginning of the dive I dropped to 100 ft, both computers showed say around 20 min NDL. Then, during dive, I tried to stay on the top of the ledge to extend dive. As soon as I am up to 60 ft, Veo gives me 40-45 min NDL but Suunto remains at 20 min and both continue to count down. So at the end of the dive I get 20-25 min dive on Suunto and 40-45 on Veo and this is a big difference.

 

[Xoom]

Thank you all for the incredibly informative replies.

I agree that conservatism is not a bad thing, and if I want, I can add stops for longer period, longer SI's etc to be more conservative myself.

I am leaning towards a Shearwater which I could always set to high conservativism. My only concern is it might be too tec focused for me. I'd like to see Suunto, Garmin etc. continue to develop modern, color interfaces with air integration.

 

[Steve_C]

Dove a scuba pro ALadin and a ZOOP for a number of dives. Typical trip is 60-100 ft off a boat over a wreck or ledge. EAN 32 %, Multilevel. SI is about an hour. Tank is HP100. First dive they are about the same. Second dive ZOOP gave about 15 minutes less of NDL. On the second dive my dives are usually NDL limited and not air. ZOOP was also much slower in giving credit if I went up a little bit to get more NDL. Sold the ZOOP and now dive two Scubapros. Note: I do slow ascents, a full safety stop, etc etc. Also slow from the hang bar up.

 

[Xoom]

It's not quite that simple: e.g. DSAT's driving tissue compartment off-gasses to half its original loading in 1 hour, whereas Cressi RGBM's "slowest" compartment is 480 minutes. So DSAT considers you "clean" in 6 hours while by RGBM you'd only off-gassed 50%. On the flip side if you had significant gas loading in those slower tissues, DSAT could consider you "OK" after a shorter surface interval that in reality is too short. (DSAT comes with a warning: no more than 6 consecutive days of diving, for that reason.) That's the theory, whether it works out that way in practice is a different story.

This is very illuminating, thanks!

While I see what you are saying - that they aren't easy to compare in a general sense - would you say the Bühlmann ZHL-16C that Shearwater uses is more similar to RGBM than it is to DSAT for multi day dives? I had read that Buhlmann's slowest compartments also use 400-600 minutes.

 

[AJ]

I am leaning towards a Shearwater which I could always set to high conservativism. My only concern is it might be too tec focused for me. I'd like to see Suunto, Garmin etc. continue to develop modern, color interfaces with air integration.

Take a look at the Teric or the Perdix. Both have recreational mode and do all the things you want.

 

[dmaziuk]

This is very illuminating, thanks!

While I see what you are saying - that they aren't easy to compare in a general sense - would you say the Bühlmann ZHL-16C that Shearwater uses is more similar to RGBM than it is to DSAT for multi day dives? I had read that Buhlmann's slowest compartments also use 400-600 minutes.

The other key bits are "M-values" -- if you don't know they're the same for ZHL and a given RGBM implementation (I don't), then you don't know if you're comparing apples and oranges. Secondly, in ZHL you can effectively modify M-values by "gradient factor", whereas bubble models modify them by a formula whose output depends on a number of factors not modeled in ZHL+GF. Including e.g. max depth of the preceding dive.

 

[EireDiver606]

The real question is: do you want your computer to tell you what to do or vice versa?

100% in agreement with this.

A few days ago I was diving 30m and my computer hit my nil quicker than everyone else’s. I wasn’t using my computer for the NDL time because I know what I have in my head.
Nitrox 32
30m 30mins
27m 40mins
24m 50mins

And so on...