Dive planning with tables?

[Bzzzz]

Hello,

Not yet fundies trained, however I was wondering how you guys/gals plan your dives?

Obvioulsy, 32% as your backgas, which tables do you use and how do you calculate how long you stay down?

What about multi-level dives?

Thanks!!

 

[Soggy]

32% gives you a 20% advantage over air. So, a 100 ft 32% dive is just like diving air at 80 ft...so you dive an 80ft air table for a 100ft dive.

Multi level dives involve depth averaging....roughly, if you spend 10 minutes at 100 ft and 10 minutes at 80 ft, you've just done a 20 minute dive at 90 ft. Obviously, as the times and depths become more extreme, you need to weight the deeper section.

 

[toodles]

32% gives you a 20% advantage over air. So, a 100 ft 32% dive is just like diving air at 80 ft...so you dive an 80ft air table for a 100ft dive.

Multi level dives involve depth averaging....roughly, if you spend 10 minutes at 100 ft and 10 minutes at 80 ft, you've just done a 20 minute dive at 90 ft. Obviously, as the times and depths become more extreme, you need to weight the deeper section.

Is it common at all times to increase by 20%?....it seems logical if you are using the EAD tables from DSAT..or anyone else.

What do you mean by 'weighting the deeper section'?

 

[Soggy]

Is it common at all times to increase by 20%?....it seems logical if you are using the EAD tables from DSAT..or anyone else.

What do you mean by 'weighting the deeper section'?

Times do not increase by 20%, EAD depth reduces by 20%. Dive whatever air tables you are comfortable, then to get your EAD, subtract 20% when using Nitrox 32. A 100' dive on nitrox 32 is equivalent to an 80' dive on air. This is basic nitrox class stuff. OK, in a nitrox class, you would be taught to calculate the EAD which would end up being 81 ft, not 80 ft, and since you always round up when using tables, you would treat it as a 90ft dive...which is ridiculously overconservative. We all know that the difference between an 80 ft dive and an 81 ft dive is non-existent, so being thinking divers, we make an educated decision to treat 81 ft as 80 ft.

For a dive where I spent say 10 minutes at 120 ft and 10 minutes at 60 ft, I would not venture to say that it was a 90 ft dive because the deep section is much deeper than the shallower section. I would weight the deeper section and pretend that I did 15 minutes at 120' and 5 minutes at 60' and use 100-110' as my average depth.

 

[Reinoud]

Hello,

Not yet fundies trained, however I was wondering how you guys/gals plan your dives?

Obvioulsy, 32% as your backgas, which tables do you use and how do you calculate how long you stay down?

http://dir-diver.com/pdf/minimum-deco-tables/english_metric_A.pdf

(they are also available on that site in imperial)