Suunto OK for liveaboards?

[Bubbletrubble]

Statistically, I can't provide sound data on the experience that me and my dive buddies all shared with the Suunto vs. other computers, but I can give an anecdotal description. While on a dive trip with 9 of my friends (who are all fairly similar in experience, age, and dive profiles) we did two dives on the Speigel Grove. We all were back on the line (ripping current that day) at roughly the same time, give or take a minute or two. We moved up incrementally and slowly from a depth of about 30 fsw to 15ft on a safety stop. Even though I was at the anchor line before some of my friends and ahead of them in line to exit the water, I was unable to ascend because I had gone into deco. There were 3 of us diving Suuntos on the trip. Through hand signals we were able to determine that only the Suunto divers went into deco. My primary buddy who was diving a Nitek Duo did not. This was confirmed when we finally all were back on board and checked our Suunto computers against the others. This isn't necessarily a bad thing, but it was an odd coincidence (due to the conservative algorithm?). Can this example be scientifically validated? No, but it does create some interesting conversation back on the boat after the dives and here on SB.
Thankfully, my dive buddy didn't mind hanging out with me for an extra 4 minutes while I fulfilled my deco obligation. We both had plenty of gas left and weren't in any hurry to leave the water anyway.

@shannonjon22: I'm not all surprised by your Suunto story. To answer your question, yes, what you experienced can be "scientifically validated" (or at least consistently reproduced). For a given profile, a diver can very easily compare one computer's algorithm to another. Simply attach several different dive computers to a stick and keep that stick level throughout the course of a dive. If you did this with a Suunto and a Nitek Duo, you could subject the stick to a dive profile such that the Suunto computer went into deco and the Nitek Duo did not. Where it gets tricky is correlating the computer algorithm with incidence of DCS. DCS introduces the human element into the picture.

 

[Damselfish]

Statistically, I can't provide sound data on the experience that me and my dive buddies all shared with the Suunto vs. other computers, but I can give an anecdotal description. While on a dive trip with 9 of my friends (who are all fairly similar in experience, age, and dive profiles) we did two dives on the Speigel Grove. We all were back on the line (ripping current that day) at roughly the same time, give or take a minute or two. We moved up incrementally and slowly from a depth of about 30 fsw to 15ft on a safety stop. Even though I was at the anchor line before some of my friends and ahead of them in line to exit the water, I was unable to ascend because I had gone into deco. There were 3 of us diving Suuntos on the trip. Through hand signals we were able to determine that only the Suunto divers went into deco. My primary buddy who was diving a Nitek Duo did not. This was confirmed when we finally all were back on board and checked our Suunto computers against the others. This isn't necessarily a bad thing, but it was an odd coincidence (due to the conservative algorithm?). Can this example be scientifically validated? No, but it does create some interesting conversation back on the boat after the dives and here on SB.
Thankfully, my dive buddy didn't mind hanging out with me for an extra 4 minutes while I fulfilled my deco obligation. We both had plenty of gas left and weren't in any hurry to leave the water anyway.

I can see a deepish squarish dive on a wreck showing the conservatism in comparison with other computers much more. Multilevel reef diving not so much because you tend to get so much time that way anyway, and it's usually easier to modify depth some without missing anything.

 

[Willar]

Another way to incurr added safety stop time on the Suunto is to violate the Rate of Rise by going shallow too fast. I believe Suunto penalizes for a rate of rise greater than 60 ft per minute by adding to mandatory safety stop time. I've inadvertantly violated this during reef dives while going in/out of swim-throughs and found myself with long safety stops while friends with Suunto computers were more careful and did not have long safety stops.

 

[Aspendiver]

Ultimately, DAN's Project Dive Exploration may shed some light on the issue. In the meantime, there are some mathematical estimates regarding relative risk of DCS diving various computer algorithms.

An example can be found in Table 7-6 on page 154 of Bove and Davis' Diving Medicine, Saunders, 2004. Estimates of episodes of DCS/10,000 dives to the NDL limit at 60 fsw of various computers and tables were made. All of the rates were low and they did not vary much by algorithm. The rate of one of the most conservative of computer algorithms, Suunto, was 49 episodes/10,000 dives. The rate of one of the most liberal computer algorithms, Pelagic Pressure Systems, was 68 episodes/10,000 dives. The NDL times at 60 fsw for these 2 algorithms was 50 and 56 minutes. This makes sense to me, the longer the exposure near the limit, the greater the risk. Figure 7-25 on the same page shows the estimated risk of DCS/10,000 dives at 60 fsw as a function of bottom time.

Aspendiver is generally correct, the risk of DCS using any of the commercially available computer algorithms is quite low, but it is certainly not zero for any of them.

Good diving, Craig

That's a great post, and I really appreciate the info-
I just want to point out to everyone who reads it that these are "mathematical estimates"- unless I'm mis-reading, they are not empirical data.

Craig's comment about "no zero risk" is on the money. Safe diving is all about managing risk, not eliminating it. How you prepare for diving and use your computer is likely more important than its algorithm, IMHO.

I use an Oceanic, my brother a Suunto. We have no problems diving safely together.

 

[RonFrank]

The Sunnto algorithms are more similar to others than different. The Suunto is more conservative, but as to bottom time and max NDL that generally means a couple minutes difference at a given depth, so not a lot.

A bigger factor maybe the number of compartments that a particular computer uses to estimate NDL. The more "tissue compartments" a computer measures, the more accurate (theoretically) the computer can gauge the effect of a dive on your body. 9 to 12 compartments are fairly standard, but some dive computers are now using 16 compartments.

I'm not a big fan of Suunto because of their retail policies, and their track record. They've had some issues with some models, and the fact you can not change your own battery IMO is a problem. Maybe some have user replaceable batteries, I have not looked lately.

It's easy to take a liberal computer, and dive it conservatively. The opposite is not so true, and may result in deco obligations for the sake of clearing the computer.

My dive buddy uses a Mares which is older, and appears to be more conservative than either of my two Aeris (Epic/Atmos II). However we have no issues diving together. While on a deep dive on our last livaboard trip, he pointed to his computer to show me had had 2 minutes of time at that depth. I think mine showed 4 minutes, but no worries, we just started a slow ascent.

If you dive a lot of flat deep profiles, this maybe more of an issue, but it's not difficult to hang 5 feet above a buddy if you want to be a bit more conservative.

Computers are a yard stick, but I think most divers need to do a lot of diving to determine their own safety and comfort level. I push NDL's a bit at this time, but it took me a long time to get to where I was comfortable doing so. If you do incur a deco obligation, no worries, just make sure you meet that obligation, and I generally do longer safety stops then required in any event.

 

[ptyx]

Another way to incurr added safety stop time on the Suunto is to violate the Rate of Rise by going shallow too fast. I believe Suunto penalizes for a rate of rise greater than 60 ft per minute by adding to mandatory safety stop time.

It seems to be the case for me as well. On a regular dive, my Vyper seems just slightly more conservative than older (Sherwood&co) computers, and comparable to Mares Puck and friends.

However, training dives, ascent speed violations, inverted profiles or see saw patterns have it go berserk - when some computers just don't seem to notice.

 

[Bubbletrubble]

A bigger factor maybe the number of compartments that a particular computer uses to estimate NDL. The more "tissue compartments" a computer measures, the more accurate (theoretically) the computer can gauge the effect of a dive on your body. 9 to 12 compartments are fairly standard, but some dive computers are now using 16 compartments.

@RonFrank: I agree with most of what you say regarding the business practices of Suunto and the practical use of Suunto computers. However, I don't think that just because an algorithm utilizes more tissue compartments it more accurately reflects the "effect" of the dive on the human body. AFAIK, tissue compartments are an ideological simplification of how various human tissues might load/unload gas and this simplification appears to correlate well with some of the seminal work on DCS incidence. There is no one-to-one correlation of a particular tissue type with a modeled tissue compartment, per se. Validation of the newer 16 compartment models has relied heavily on precordial bubble measurement by Doppler probe...and I still have yet to see one convincing study which gives hard evidence for a causal relationship between Doppler-measured bubbles and DCS, i.e., more bubbling = higher incidence of DCS. For this reason, I treat the "16 compartment algorithms are better than the 12 compartment algorithms" as nothing more than marketing mumbo-jumbo.

I'm not a big fan of Suunto because of their retail policies, and their track record. They've had some issues with some models, and the fact you can not change your own battery IMO is a problem. Maybe some have user replaceable batteries, I have not looked lately.

My Gekko, Vyper, and Mosquito all have user-replaceable batteries. I've changed the batteries in my Suunto Favor, too, although that computer is technically not user-replaceable. No problems with flooding at all. I suspect that even the models marketed with "non-user-replaceable" batteries can be changed out without much problem. I agree that not having a user-replaceable battery would be a deal-breaker in a dive computer. Heck! Who wants to deal with the extra time and expense of sending a computer back to the factory (or authorized repair facility) just to get its battery replaced? I sure don't.
As has been mentioned in several threads here on SB, all dive computer manufacturers at one time or another will have a model which seems to have a higher malfunction rate. The manufacturers typically source components such as depth sensors from third-companies, and these parts have an inherent failure rate. Perhaps the more important question is: What does the manufacturer do customer service-wise in the event of a product failure? Replace/refund/upgrade...or deny that there's any problem at all?

However, training dives, ascent speed violations, inverted profiles or see saw patterns have it go berserk - when some computers just don't seem to notice.

@ptyx: I have not experienced my Suunto computers going "berserk" with see-saw patterns or inverted profiles (whether it be intra- or inter-dive on a repetitive dive day). When I used to wear the Mosquito on my left wrist, I had one incident where I exceeded the ascent rate due to a quick hand movement above my head to dump air from my wing via the corrugated hose. Ever since I started wearing my computer on the right wrist, I've had no problems at all.

 

[Lorenzoid]

I have found my Suunto (D6) to be annoyingly conservative at times, which I think relates to the OP's question. More than once, I have been diving with a group, and while others are content to remain on the bottom for a few more minutes, I see my Suunto about to go into deco mode. I confused people by signing that I had to go up--leading them to believe something was "wrong" that was making me cut the dive short, when in fact all I was doing was trying to avoid a deco stop. One time (a shark dive, when my group was sitting on the bottom for a long time), the D6 told me just a few feet short of the surface that I needed to make a deco stop, but in my hurry to exit the water with the rest of the group and not hold them up, I cut the stop short. Well, I learned my lesson. The D6 locked me out for 48 hours. So I basically just dove without the computer the next day! Is that safer than simply having used a less conservative computer? I don't know. On a later trip, when it again demanded I make a stop while diving with a blissfully unaware group of others, I made sure to make the full stop. It confused the others as to why I was hanging out at a certain depth while they continued ascending right past me, did their safety stop and exited the water. I had to explain that my Suunto requires that I do that or it will lock me out for 48 hours.

That said, I don't have much experience with how a Suunto handles the kind of repetitive dives you might do on a liveaboard. If you really want to do five dives in a day, you might have reason for concern about a Suunto going into deco mode at some point.

By the way, the reason I logged on today was to post a question, and this seems to tie right in: I am looking to buy my wife her first computer, and my question is whether it is not logical to buy her a Suunto, so that our computers (theoretically) will read equal no-deco time?

 

[Bubbletrubble]

By the way, the reason I logged on today was to post a question, and this seems to tie right in: I am looking to buy my wife her first computer, and my question is whether it is not logical to buy her a Suunto, so that our computers (theoretically) will read equal no-deco time?

@Lorenzoid: I hate assessing blame, but the 48 hr lock-out was your own fault, not the computer's. Also, you might want to learn how to signal "deco obligation of X minutes" for future reference. It could clarify things with your dive buddies.

To answer your question...
I dive all the time with a dive buddy who uses a Sherwood Wisdom. No problems at all. We have similar goals, and we communicate well with each other. I actually find it interesting to compare my NDLs to his. At our maximum depth, there's usually only a discrepancy of a few minutes. On the rare occasion when I kick my Suunto into deco, it really puts things in perspective knowing that I'm still diving relatively conservatively (provided that I fulfill the computer's deco obligations). If that happens, he does the deco with me. It's really not a big deal, but then again...we're both pretty laid-back about our diving.

On a side note, I find it rather amusing that you get annoyed with the short NDLs on your D6, yet you're contemplating purchasing another Suunto computer for your wife. It sounds like you dive more often than she does. Hmmm. Maybe this would be a great excuse for you to buy a new, more liberal computer and give your wife the conservative D6. An advantage of getting another Suunto computer is that you won't need to buy another download cable.

Good luck with your computer purchase.

 

[diverdoug1]

I dive with 3 computers when I am on a liveaboard. Suunto Viper2, Suunto Stinger, and a Galiileo Sol. I follow the most conservative for any given dive (not always the same one is most conservative). This works fine on a liveaboard, and I don't feel that my dive time is unneccesarily curtailed.