Nitrox vs Air
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Before I started "tricking" the computer and creating my own custom algorythms, I would strongly suggest the following:
1. Learning about decompression diving/NDLs/Deep Stop Techniques/O2 and Nitrogen under pressure. There are many advanced deep and advanced nitrox classes which will instruct you on extending your bottom time.
2. Check my current computer's Personal Adjustment Setting to see if I can run on a more aggressive but tested algorythm. Theoretically, the people who program these algorythms are smarter than the average diver (God, I hope so :05: ). For the mosquito, you can learn about this at http://www.aqualung.com/technical_library/Mosquito-ENG.pdf (PDF File Page 57)
3. Compare algorythms between manufacturers and see which one fits your diving better. In some cases, the Oceanic model may be better suited for your diving profiles.
4. If you dive regularly with certain buddies, you should try to dive similar algorythms and coordinate computer usage/purchase.
Personally, the only time I adjust my O2 Level is when I have analyzed the gas and witnessed it to be that specific blend. I would strongly recommend doing the same.
Just my two cents ... Hope this helps.
jcf
1. Learning about decompression diving/NDLs/Deep Stop Techniques/O2 and Nitrogen under pressure. There are many advanced deep and advanced nitrox classes which will instruct you on extending your bottom time.
2. Check my current computer's Personal Adjustment Setting to see if I can run on a more aggressive but tested algorythm. Theoretically, the people who program these algorythms are smarter than the average diver (God, I hope so :05: ). For the mosquito, you can learn about this at http://www.aqualung.com/technical_library/Mosquito-ENG.pdf (PDF File Page 57)
3. Compare algorythms between manufacturers and see which one fits your diving better. In some cases, the Oceanic model may be better suited for your diving profiles.
4. If you dive regularly with certain buddies, you should try to dive similar algorythms and coordinate computer usage/purchase.
Personally, the only time I adjust my O2 Level is when I have analyzed the gas and witnessed it to be that specific blend. I would strongly recommend doing the same.
Just my two cents ... Hope this helps.
jcf
miketsp
Contributor
Just like the Vyper, which I use, you can go even more conservative but not more aggressive.scubajcf:
Just to compare, I have a Vyper and a Beuchat Maestro Pro (made by Cochran under OEM). To make them align on most dives I need to set the Cochran to at least 20% additional conservatism.
I also know one diver that has been in the chamber 3 times due to diving the Cochran to its limit on its 0% conservative setting.
OP
Walter:
Walter, as I don't know how to split answer likw you, please let me give a estensive explanation....
I am sure tables are safer than computers, but tell me if you do square profiles 100% of the time, I would be surprise if you follow your plan more than 20% of the cases. So I believe tables must be used by tec divers, not by recreative divers.
About using the most conservative computer...try this in a drift dive wich 10 divers. I would follow de divemaster that have always been diving in that location, and I can assure you I 've never found a Dive master whoose computer was more conservative than mine.
I 've tried to say that with 24% O2, I 've matched the dive master (more liberal) computer.
And finally, if you are using a computer more liberal than mine, we do exactly the same profile and at the end my computer asks by 20minutes deco and yours asks 10min, who will be bent? If we assume that we can't prove that a more liberal computer will drives you bent, how can we manage that? Because if you can prove...I guess we could see a lot of prosecutes against this factorys.
OP
scubajcf:
Scubajcf, I enjoyed this discussion because most of the people contributed to my better understanding of this situation. I could go directly to the books and decide what is better to me, but this forum concentrates experiences I've never had.
I read Tec Deep manual of PADI and almost gave up diving, but chances are that I am going to die stressed by my boss before doing 40m dives. Of course I could die diving 3m down, but I will take the risk.
My profile :
- SAC around 9-10 SLM - single dives are not the problem, but 4 or 5.
- 90% of the dives, I have a different buddy that I meet on the boat.
- Because that I did my rescue trainning.
- I use the mosquito in the most liberal algorithm possible.
- And I got a error twice at the last two dive trips, whit 10 dives each, the first one was at the last dive, but the last one I got error at the 5th dive (Cozumel) and for nothing I would be out of water 48h waiting for mosquito allow me, when the DM (who I've followed closely) dives everyday at the same condition for years without getting bet.
Life is risky and as many instructors use to say, is easyer get hurt playing bowling than diving (into the recreational limits).
When doing intentional decompression diving I use tables derived for the dive with Dplan on my Palm, which uses a much more conservative bubble gradient model incorporating deep stops. But I still use my computer in dive mode as by the time I clear the longer and deeper deco stops required by DPlan, the nitrogen loading graph is normally back in the green.mattboy:
And you make a good point, decompression is decompression. Whether it requires a formal deco stop, a "recommended" safety stop, or just an ascent rate at less than 30 or 60 fpm, you are off gassing on the way up. If you slow your ascent and extend your stops so that the computer is back in the green after the deco stop, safety is going to be the same as if you just dove with in the NDL's and exited in the same block of the green. (Assuming of course that the computer's algorthym is applicable to and suitable for intentional decompression diving.)
The issues that arise however are that the stop is no longer optional and that losing bouyancy control, running out of gas, or lacking redundancy in the event of a regulator failure are not acceptable options.
emelotto:
It's easy, just highlight the text and click on the quotation symbol at the top. To indicate who said it, type "=name" after "quote" inside the [] brackets. Always make sure you have a close quote "/qute" inside [] for every begin quote. Preview your post to double check.
emelotto:
Not necessarily.
emelotto:
I plan most of my dives with a computer. I stopped using tables for most dives almost 20 years ago.
emelotto:
Poor choice of terms.
emelotto:
If you're not happy with it, get a different computer.
No two divers ever have exactly the same profile.
emelotto:
No two divers ever have exactly the same profile, but for discussion's sake are you assuming we skip deco? Assuming exactly the same profile (impossible, IMO), one of us will be more likely to get bent than the other, but that will come from factors such as fitness, hydration, did one of us exert ourself during or after the dive, did one of us sit in a hot tub, is one of us older than the other, did you drink coffee (I never do).......... The more of these factors stacked againsty you, the more conservative you want to be. Decompression theory is exactly that - theory. There are things we can do to increase or decrease our chances of getting bent. A more conservative table or computer will decrease our odds of DCS, but will not eliminate them.
emelotto:
I have no idea what you mean by this.
I think he is just noting overall that you can have two computers on the same profile and have one call for deco and have one say it is ok to surface.
When I first got a new computer the old one went along as backup and for comparision purposes. The newer and more liberal computer was ok with a direct ascent on many dives while the old computer often wanted a 1 to 3 minute deco stop. Of course the new computer also more or less mandated a 3 minute stop at 20 feet on all dives below 30 ft to add extra safety to the "liberal" algorthym, so it is pretty safe to say that while it would allow you to skip the stop and ascend without going into violation mode, it was not "safe" to do so.
The last part of his statement I think refers to the fact that deco theory is just that and that there are so many variables that we cannot tell for sure what will be 100% safe for all divers in all situations. Consequently all computers (and tables for that matter) involve some degree of risk. The only thing you can do is be smart about it, understand what is at work and the limitations of the theory and then adjust your personal level of conservatism accordingly based on how you feel after each dive. If you are feeeling overly fatigued, achy or have flu like symptoms, your body is probably telling you to back off a bit and offgas more conservatively.
In my opinion the availablilty of a nitrogen loading bar graph on the computer is a great asset to have, and not surfacing until you are in the green is a very wise practice to follow regardless of what brand of computer you have.
And one last time, if you worry about having to quit first due to a conservative computer, just move up to 32% nitrox. For example on a 110 ft dive, you would have an NDL of 15 minutes on air but would have 25 minutes on 32%. That extra 10 minutes is more time than what your buddies will be granted by their more liberal computers. At shallower depths, the differences get even greater with nearly 20 minutes more bottom time allowed at 70-80 ft.
When I first got a new computer the old one went along as backup and for comparision purposes. The newer and more liberal computer was ok with a direct ascent on many dives while the old computer often wanted a 1 to 3 minute deco stop. Of course the new computer also more or less mandated a 3 minute stop at 20 feet on all dives below 30 ft to add extra safety to the "liberal" algorthym, so it is pretty safe to say that while it would allow you to skip the stop and ascend without going into violation mode, it was not "safe" to do so.
The last part of his statement I think refers to the fact that deco theory is just that and that there are so many variables that we cannot tell for sure what will be 100% safe for all divers in all situations. Consequently all computers (and tables for that matter) involve some degree of risk. The only thing you can do is be smart about it, understand what is at work and the limitations of the theory and then adjust your personal level of conservatism accordingly based on how you feel after each dive. If you are feeeling overly fatigued, achy or have flu like symptoms, your body is probably telling you to back off a bit and offgas more conservatively.
In my opinion the availablilty of a nitrogen loading bar graph on the computer is a great asset to have, and not surfacing until you are in the green is a very wise practice to follow regardless of what brand of computer you have.
And one last time, if you worry about having to quit first due to a conservative computer, just move up to 32% nitrox. For example on a 110 ft dive, you would have an NDL of 15 minutes on air but would have 25 minutes on 32%. That extra 10 minutes is more time than what your buddies will be granted by their more liberal computers. At shallower depths, the differences get even greater with nearly 20 minutes more bottom time allowed at 70-80 ft.
dougaldiver:
I second such statement.
If your dive computer's conservative NDL bothers you, you should consider replacing it rather than working around it. And if it bothers your buddy, I will certainly choose someone else to dive with.:05:
in_cavediver
Contributor
emelotto:
First, making changes in paremeters to one model may yeild similar times for another model over a small range but that is not guarenteed over the entire range. Its that lack of complete knowledge of the entire range that should scare you. (Think very agressive no stop times in some repetive dives that no other 'liberal' model may give for instance)
In reality, your best bet is to do one of two thing. The first and best choice is to dive nitrox. It will give you everything you asked for. The second option is to buy a computer with a different deco model. (IE more liberal).
Mike
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