Are Suunto dive computers so conservative, they're useless?

[airsix]

In comparing my Stinger to other divers computers the time difference was what I thought to be minimal (i.e. 2-3 minutes). Honestly, I don't want my computer to push the limits and ride the line. I would rather have some built in conservatism.

I'm in the same boat. A computer is life support equipment. I like my life support to be somewhat conservative.

-Ben M.

 

[ArcticDiver]

In comparing my Stinger to other divers computers the time difference was what I thought to be minimal (i.e. 2-3 minutes). Honestly, I don't want my computer to push the limits and ride the line. I would rather have some built in conservatism.

This whole idea of "conservatism" is more of a marketing statement than anything else. It equates dive time with being safer, or less safe. Certainly dive time is one component of a safe dive. But it is only one component of several that are very important.

Given that divers don't get bent when using just about any popular computer or algorithm how do you know where "...the line" is? For that matter how do you know what "...conservatism." is as differentiated from just making a dive shorter or longer?

The point is that if there was a demonstrable difference in divers getting hurt when using any particular algorithm, whether in a paper table or in a computer, it would show in accident statistics. As of today I know of no such data.

So, use any computer you want. Or, use paper tables with a timer and depth gauge. Do whatever you are comfortable with. But, the data doesn't support the idea that one computer is more, or less safe/conservative than another.

The standard advise I was given and which I follow and give to others is: No one really knows why one person gets DCS and another on a similar profile doesn't. There are some educated guesses. But no one actually Knows. So, pick an algorithm you are comfortable with; understand it thoroughly and follow it precisely. Blindly following any algorithm without understanding it is in the same category as doing a Trust Me dive.

 

[WarmGoingCold]

This whole idea of "conservatism" is more of a marketing statement than anything else. It equates dive time with being safer, or less safe. Certainly dive time is one component of a safe dive. But it is only one component of several that are very important.

Given that divers don't get bent when using just about any popular computer or algorithm how do you know where "...the line" is? For that matter how do you know what "...conservatism." is as differentiated from just making a dive shorter or longer?

The point is that if there was a demonstrable difference in divers getting hurt when using any particular algorithm, whether in a paper table or in a computer, it would show in accident statistics. As of today I know of no such data.

So, use any computer you want. Or, use paper tables with a timer and depth gauge. Do whatever you are comfortable with. But, the data doesn't support the idea that one computer is more, or less safe/conservative than another.

The standard advise I was given and which I follow and give to others is: No one really knows why one person gets DCS and another on a similar profile doesn't. There are some educated guesses. But no one actually Knows. So, pick an algorithm you are comfortable with; understand it thoroughly and follow it precisely. Blindly following any algorithm without understanding it is in the same category as doing a Trust Me dive.

You are correct in the fact that DCS is not an exact science. There is a general belief though that the Suunto dive computers are more conservative than others and that belief is based upon our experience diving with those computers and making the observation that when our computers are telling us to ascend, other divers with other computers are not se being told to ascend by thier dive computers. This is based upon diving with those same divers over the same period of time. I personally have no issue with this and I like the fact that I dive with a computer that forces me to ascend perhaps a few minutes earlier than others. That is just my personal view.

I do agree with you though that a person should use what they are comfortable with.

 

[PerroneFord]

One computer telling you to go up sooner than another doesn't make it more or less conservative. It simply removes time from your dive. The algorithm on the SUUNTOs is *supposedly* based on RGBM. It specifies different decompression profile shapes than the common Haldanean profiles.

A computer more conservative would have you doing deep compression stops along the ascent, and requiring longer stops the shallower you got. That would actually EXTEND the dive time, not lessen it. This is to allow more time to offgas and remove more nitrogen from the body.

I'll post a custom cut profile for a 60ft dive for 50 minutes (the SSI limit and apparently the time when the SUUNTO says to leave the bottom) from V-Planner:

V-Planner 3.72 by R. Hemingway, VPM code by Erik C. Baker.

Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 5

Dec to 60ft (1) Air 50ft/min descent.
Level 60ft 48:48 (50) Air 0.58 ppO2, 60ft ead
Asc to 20ft (51) Air -30ft/min ascent.
Stop at 20ft 28:40 (80) Air 0.33 ppO2, 20ft ead
Surface (80) Air -30ft/min ascent.

Off gassing starts at 43ft

OTU's this dive: 11
CNS Total: 6.9%


THAT is conserative. Your 50 minute bottom time dive is now an 80 minute dive with conservatism turned up to the max.

 

[tangfish]

I really like the Suunto form factors and interfaces, but you're right that they're very expensive and pretty conservative. Conservatism and consideration for micro-bubble formation is nice, but I've been diving an Oceanic VT Pro and have plenty of friends with different types of computers and so far no one has suffered DCS purely as a result of following a computer that wasn't conservative enough. I'm trading up to the Atom 2.0 soon and looking forward to it. I'd base my decision more on price and interface if I were you, rather than the RGBM (for it's positives and negatives).

 

[ChrisA]

The Suunto can be set to three levels of conservatism. But even if set to "very conservative" it will still let you stay down underwater longer then a dive table if you are not doing a square profile. I typical dive I do about once a week s to go down to 70 or so feet until the computer starts giing me single digit time remaining. Then se swim up the inclide of the bottom slowly to about 45 feet and hang out there for a while. The computer gives me back a lot of time once I reach 45 feet. Ok, we stay at 45 until we see air getting to 1000 or so and then slowly head in to shore. I watch the computer and by the time I'm at 30 feet it is giving me 99 minutes NDL because the display only has two digits

If all your dives are really are square, still the computer can give you more time then a table. With a table you have to round all the numbers to the conservative side. The computer does not round. So a dive to 76 feet does not count as a dive to 80 feet and you will get "credit" for a very slow 30 foot/sec acent because the computer can treat your slw acent as a multilevel dive. Those runding erros more then make up for the Suunto being conservative. When you do multiple dives the table's _really_ add rounding and it adds up to shorter then needed time of your third dive

And what is wrong with "conservative"? Beats the heck out of "bent"

 

[Dave83]

You guys are right that the chance of DCS sickness is subjective and dependant on the person. Most dive computers were designed for recreational divers and not to be used for decompression dives. I think the intent is to offer a decompression plan in the event a NDL limit is surpassed. Most are designed not to be used for technical diving. I think they are a very useful tool to a recreational diver that does not plan to surpass NDL limits but gives them a plan in case they do.

 

[Azza]

I have a Suunto Vyper and I have loved it right up until today. It died on me today right at the start of a days diving.
It wouldnt turn on automatically like usual and when I manually turned it on it was reading a depth of 19 metres with about 40 minutes of deco time.
Grrr

 

[El Orans]

And what is wrong with "conservative"? Beats the heck out of "bent"

 

[PerroneFord]

And what is wrong with "conservative"? Beats the heck out of "bent"

Ok, just stay above 40ft then. And you can take the computer off. Nothing wrong with being conservative right?