DM5 Safety stop question

[CandiveOz]

Dear Suunto divers,
I don't own a Suunto but I have downloaded DM5 to play with deco planning module. They recently upgraded DM5 to include RGBM Fused 2 and I find it personally interesting to run different deco profiles to become familiar with the versions of RGBM.

With regards to safety stops, they kick in at 10 meters and deep stops kick in at 20 meters. The safety stop is 3 minutes but if I go into Plan setting and change it to 4 or 5 minutes, the safety stop remains at 3 min in the dive planner. This is either a bug or am I doing something wrong? Or is these safety stop selections (3,4,5) only there to update the computer when you transfer the settings. That's my first question.

My second question is when I plan a deco dive, is the safety stop included in the last stop? For example say your last deco stop is at 3 meters for 10 min. Is 3 of the 10 min your safety stop and 7 min your deco or do you add an additional 3 min to the 10 min deco for a total of 13 min. Specifically, when I plan a deco dive, is the deco profile generated in DM5 only showing the deco obligation and excludes the safety stop?

Here is an example. Dive to 30 meters for 18 min. Suunto RGBM; deep stop off. Safety stop at 3 meters is 3 min. Dive to 30 meters for 19 min (one min more). Deco stop at 3 meters for 3 min. Its exactly the same time at 3 meters as for 18 min but I assume if you disregard these three minutes I you are in violation of the computer where as for 18 min, you could skip the safety stop if desired with no 48 hr lock out penalty. Is it assumed you will conduct another 3 min safety stop?

Say you do an actual dive to 30 meters for 19 min and you deco for the required 3 min. Does your Sunnto computer then recommend a safety stop? If I had a Suunto, I could dive it and discover the answer. but because I don't so I'm asking you who do. Thanks for your feedback.

 

[Zef]

So I ran your dives on my Vyper Air (RGBM) in simulation mode:

Dive sim #1:
Direct Descent to 30 meters (approx 1m) = No-Deco time of between 17 and 18 minutes.
Started ascent when dive time reached 18 minutes and ascended at @ 9m/min
computer indicated 3 minute safety stop at 5.5 meters. Waited 3 minutes and continued ascent....no further stop indication.

Dive sim #2:
Direct Descent to 30 meters (approx 1m) = No-Deco time of between 17 and 18 minutes
Started ascent when dive time reached 19 minutes and ascended at @ 9m/min.
computer indicated 3 min deco stop/obligation with a 3 meter ascent ceiling...this cleared during the ascent.
computer indicated 3 min safety top at 5.5 meters. Waited 3 minuttes and continued ascent...no further stop indication.

Dive sim #3:
Direct Descent to 30 meters (approx 1m) = No-Deco time of between 17 and 18 minutes
Started ascent when dive time reached 20 minutes and ascended at @ 9m/min.
computer indicated 3 min deco stop/obligation with a 3 meter ascent ceiling...this cleared during the ascent.
computer indicated 3 min safety top at 5.5 meters. Waited 3 minuttes and continued ascent...no further stop indication.

Dive sim #4:
Direct Descent to 30 meters (approx 1m) = No-Deco time of between 17 and 18 minutes
Started ascent when dive time reached 25 minutes and ascended at @ 9m/min.
computer indicated 8 min deco stop/obligation with a 3 meter ascent ceiling...this partially cleared during the ascent.
stopped at 5.5 meters until remaining deco obligation cleared. Continued ascent and computer then indicated 3 min safety top. Waited 3 minutes and continued ascent...no further stop indication.

To be clear, each dive was simulated as a "first dive" not a subsequent dive in a series of dives.

Hope that helps.

-Z

 

[KenGordon]

To see what DM5 does you could try concocting a dive that would have a one minute deco stop. If you can’t and the shortest is 4 minutes you have your answer.

Note that some models of Suunto computer include the safety stop in the deco time, so the shortest deco stop is 4 minutes, others split them so the deco stop is shown as 1 minute and then the counter goes back up to 3 for the safety stop.

 

[CandiveOz]

@Zef thank you very much for taking the time to provide these simulations. You answered my question. My Galileo Sol also has a dive planner but it only shows the deco obligation. When you actually dive the computer, it works similar to your Vyper Air in that once the deco is cleared, it adds the safety stop (if turned on in the computer).

Hi Ken, I tried concocting a dive in DM5 with a one minute deco stop and as @Zef described in his scenarios it would first have a 3 min safety stop. As the dive got longer, this 3 min would convert into a 3 min deco stop and as time increased it would become a 4 min deco stop. And as @Zef explained, the 3 minute safety stop is then added at the end according to his simulation on his Vyper Air. I guess the other Suunto dive computers may work slightly differently to DM5, but I was interested in the DM5 diving software itself since I was comparing it to my Galileo Sol's planned deco profiles which excludes the safety stop.

As a side note I was impressed that @Zef Vyper Air had a dive simulator. I had never heard of it. I checked the current models on offer on Suunto's website and it appears only the Cobra 3 has this feature. I wonder why they dropped this feature since it would be a good thing to have to help a diver become familiar with his computer and to plan future dives.

 

[Zef]

The Suunto Vytec, Vyper, Vyper Air, Cobra, Cobra 2, and Cobra 3 all have dive simulation modes as well as a no-deco dive planning mode.

I think the simulation mode was primarily meant as a means for purchasers to become familiar with their computer. It can also be used to run dive simulations where the dive time accumulates 1 minute for every 15 seconds. It is an ok feature to have but in reality is more of a novelty and I suspect Suunto dropped it in the new models to use the memory in the computer to provide different features.

-Z

 

[scubadada]

Hi @CandiveOz

Interesting question and discussion. My Oceanic VT3 and Geo2 do not have deco planning. I have extensive experience with light deco. Whenever a deco obligation is incurred, it is satisfied on ascent, or at the stop(s), and no safety stop is triggered. I pad my deco with a safety stop.

My Dive Rite Nitek Q has no safety stop function in no stop or deco diving.

It would be interesting to hear how other computers handle a safety stop after satisfying a deco obligation.

 

[CandiveOz]

Hi @Zef Thanks again for listing all the previous models that have the simulation. It may be a novelty for experienced divers who are familiar with Suunto but it did answer my question and as you say, it’s a good instruction tool for divers new to Suunto.

Hi @scubadada I agree that reviewing how computers handle safety stops after deco would be an interesting study but we probably should start a new thread on the topic. My Tusa IQ 750 runs PZ+ which is another Pelagic algorithm. When it goes into deco, both deep stop and safety stop are disabled. In other words, safety stop and deep stop are only enabled for NDL diving.

As you know, deep stops are controversial but a single stop during NDL diving, does slow the ascent and may reduce microbubble formation but as far as I know there is no definitive answer regarding this type of single deep stop protocol. With regards to decompression, I guess Pelagic decided to go with what they know versus what they don’t know. They know that decompression is good but they don’t definitively know that adding a deep stop and decompression is better so they made the conservative decision to drop the deep stop. On the other hand, Suunto’s RGBM will include deep stops during NDL and deco diving if turned on. Different models; different approach.

As for dropping the safety stop during deco, I went back through my dive logs. While the safety stop is disabled during deco, the minute the diver goes into deco, the obligation is 4 minutes at 3 metres. On every deco dive I’ve recoded, all start with 4 minutes. So in reality the safety stop is not disabled but incorporated into the deco stop. By padding out your deco with an additional safety stop even allows more off-gassing before surfacing which is a prudent idea.