Diving with a computer/watch

[Patoux01]

Hi Patoux01:

Of course, I can change the gradient factor or conservative settings for Deco Planne or V-Planner to provides various output. These parameters represent the level of risk you wish to have in planning your dive profiles.

O.

You should do a runtime comparison between your usual gf vs suunto rgbm vs mares rgbm etc. your conclusion could be interesting.



Edit: attached: runtime comparison done by a french guy on another forum.

 

[Storker]

What tables does CMAS use?

I'm not sure that CMAS has one single set of tables. Remember, CMAS isn't a single agency like e.g. PADI, it's a federation of national associations. The associations are responsible for their own curriculum, but to be approved by CMAS and be allowed to award CMAS certs they of course have to satisfy CMAS' minimum requirements.

The Norwegian Diving Federation uses the Norwegian Standard Table. At comparable depths, the NDLs are very similar to PADI's.

Are they BSAC's 88s?

Do you have a link to BSAC's 88?

 

[jboneng]

I'm not sure that CMAS has one single set of tables. Remember, CMAS isn't a single agency like e.g. PADI, it's a federation of national associations. The associations are responsible for their own curriculum, but to be approved by CMAS and be allowed to award CMAS certs they of course have to satisfy CMAS' minimum requirements.

The Norwegian Diving Federation uses the Norwegian Standard Table. At comparable depths, the NDLs are very similar to PADI's.


Do you have a link to BSAC's 88?

The BSAC 88 table was a result from orginal research done by BSAC. The Norwegian standard table was created by the Norwegian government during the pioneer era in Norwegian oil industry, when they noticed that the international commercial diving companies used their own and different tables and procedures, and since it was a lot of cooperation between all those companies there was a need to standardize it. The NST is heavily influenced by the tables used by those companies (mostly from the U.S.A an G.B). If you compare the NST whit the PADI you can see that the NST gives you a couple of minutes more in NDL (remember that the grey out NDLs on the PADI table is mandatory safety stops [basically a decompression stop for 3 min at 5 m]). The biggest difference between NST and PADi rdp is the SI which can be a big difference (I have seen situations where NST says a SI of 10h is needed, while the PADI rdp says 2h). This is because the uses different controlling compartments and the NST was also made for dives with mandatory decompression stops which is a integrated part of the Norwegian CMAS*** training.

I realize now that I haven't answered anyone's question, and I am just rambling on.

 

[dmaziuk]

You are aware that it is fairly simple to find 2 algorithms that can give over 5 minutes of difference in terms of deco, and both are considered safe?

There's a much simpler fallacy in the argument: if you're diving nitrox and a computer-less newbie asks if they can tag along on air, you say no. Unless you are a homicidal maniac actively trying to bend them.

 

[Patoux01]

There's a much simpler fallacy in the argument: if you're diving nitrox and a computer-less newbie asks if they can tag along on air, you say no. Unless you are a homicidal maniac actively trying to bend them.

Well, if my dive is well within an air NDL, I don't mind diving with someone on air and having him "tag along", it's his problem if he loses me though.

I'm not arguing whether it's stupid or not to tag along with someone else, I'm arguing about the need for all the "lawyers blabla" and "you're gonna die" rubbish that is written by some (many?) on this board rather than trying to educate and explain why it can be an issue or why you're not gonna die straight away (eg your "homicidal maniac actively trying to bend them")

 

[dmaziuk]

I'm arguing about the need for all the "lawyers blabla" and "you're gonna die" rubbish that is written by some (many?) on this board rather than trying to educate and explain why it can be an issue or why you're not gonna die straight away (eg your "homicidal maniac actively trying to bend them")

Yeah, me too. I mean, the argument's "I paid all that extra for nitrox, I won't have some noob tag along and limit my bottom time". Well duh, how much did you pay for the whole trip and how would you like to have that cut short because someone had to be rushed to the chamber? Or do you think captain and crew want to play doctors and ambulance? And then someone chimes in with a proof that "all that extra nitrox money" buys you a whooping 2 minutes of bottom time -- assuming you're limited by the NDL in the first place. Seriously, do people even understand what they're saying?

There's no real reason to not have a computer (though there are excuses). That doesn't mean diving without a computer or a watch is going to get you in trouble. Diving beyond your capabilities, some of which are provided by the computer, that's trouble.

 

[boulderjohn]

Ok I am going to throw in my $.02, I am a newly certified diver and yes our instructor took care of the dive planning but that was in class where he is responsible for our saftey

I am not familiar with CMAS rules, but with PADI, the students must plan and execute the final OW certification dive on their own. That is the current set of standards; prior to that they were only required to participate in planning the dives. I would have thought CMAS would have similar requirements.

Hm. I was PADI certified, and I can't remember that compass use was covered during my OW class.

Compass use is required for the PADI OW course, both on the surface and under water. Under water, students have to follow a straight line with the compass, turn around, and return to the starting point.

 

[Storker]

I am not familiar with CMAS rules, but with PADI, the students must plan and execute the final OW certification dive on their own. That is the current set of standards; prior to that they were only required to participate in planning the dives. I would have thought CMAS would have similar requirements.

I don't know when PADI put this down as a requirement, but I believe we had it as a national standard over here before PADI introduced it (at least that's my impression from what I've read about PADI OW courses in other countries). No matter if it was CMAS, PADI or - rather unlikely around here - other certifying agencies.

Again, remember that CMAS rules are a lowest common denominator. Any country's diving association is - AFAIK - free to impose more rigorous rules than the CMAS minimum. The minimum standards and syllabi of CMAS certifications can be found here.

 

[Seymour Fisch]

But, to try to answer your question, lets say you're on a dive and your computer is your only timing device, and it goes belly-up during the dive. In this case, you time your safety stop by using your buddy's timing device,
...
you could as a last resort start counting. A nice slow count to 200 ought to do it.

I've pondered this question before (dealing with computer failure, etc.), as even as a new diver, I've already had my computer crap out on me once (low battery, wouldn't go into dive mode). I realized that it takes me about 1:30 to sing the Star Spangled Banner, or O Canada, so if I sing both, that's an easy way to time a safety stop. Maybe adding on La Marseillaise or God Save the Queen would give some extra safety margin. More fun than counting to slowly to 200.


(Aside: I'm pretty good with mental arithmetic, so I've been curious to collect various mental rules-of-thumb and tricks for diving safely with equipment failure. E.g., someone recently mentioned that it was easy to memorize the NOAA O2 CNS exposure table, and indeed from a PO2 of 1.20 to 1.50, everything is nicely linear and easy to remember. Or, I've heard of an old rule of thumb that dive time in minutes plus max depth in feet should not exceed 120 -- which is pretty close to what PADI's RDP shows for typical recreational depthsi; I think 110 would make it strictly more conservative than the RDP. But this is a topic for a different thread, and probably not in the Basic forum, where the message is unequivocally: get a computer, or at least a watch, and know how to plan your dives with it.)

 

[redacted]

I've pondered this question before (dealing with computer failure, etc.), as even as a new diver, I've already had my computer crap out on me once (low battery, wouldn't go into dive mode). I realized that it takes me about 1:30 to sing the Star Spangled Banner, or O Canada, so if I sing both, that's an easy way to time a safety stop. Maybe adding on La Marseillaise or God Save the Queen would give some extra safety margin. More fun than counting to slowly to 200.


(Aside: I'm pretty good with mental arithmetic, so I've been curious to collect various mental rules-of-thumb and tricks for diving safely with equipment failure. E.g., someone recently mentioned that it was easy to memorize the NOAA O2 CNS exposure table, and indeed from a PO2 of 1.20 to 1.50, everything is nicely linear and easy to remember. Or, I've heard of an old rule of thumb that dive time in minutes plus max depth in feet should not exceed 120 -- which is pretty close to what PADI's RDP shows for typical recreational depthsi; I think 110 would make it strictly more conservative than the RDP. But this is a topic for a different thread, and probably not in the Basic forum, where the message is unequivocally: get a computer, or at least a watch, and know how to plan your dives with it.)

I'd just wait until I have to pee again. That is 3 to 5 minutes.