Tables for DIR.

[rongoodman]

I'm getting ready for DIR-F in a a couple of weeks and it just struck me that I don't know what they use for tables for NDL diving. I have the PADI tables for air and Nitrox and DPlan on my Palm, but what do they want me to have in my pocket during dives?

 

[amascuba]

I'm sure the people who have taken the class will be able to give you more information on what exactly is taught in the class as far as tables go. I believe all that should be taught in the class though.

You can also look at the minimum deco tables:

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

I also just noticed that Peter put up an article on how to use the minimum deco tables yesterday!

http://dir-diver.com/en/knowledge/min_deco_table.html

 

[rongoodman]

Thanks. I'd forgotten about the minimum deco tables and haven't seen the new article.

 

[SparticleBrane]

It would really benefit me if Peter (or someone else in the know) would do a walkthrough of four dives in one day, as opposed to the two that he does on the website.

 

[ppo2_diver]

Do a search here for the 120 rule. Mike Kane wrote up an excellent article on it. That rule is what I was taught in my fundies class.

 

[amascuba]

It would really benefit me if Peter (or someone else in the know) would do a walkthrough of four dives in one day, as opposed to the two that he does on the website.

Peter's article covers three dives. Doing three dives isn't much different than doing the forth.

 

[Jasonmh]

I'm getting ready for DIR-F in a a couple of weeks and it just struck me that I don't know what they use for tables for NDL diving. I have the PADI tables for air and Nitrox and DPlan on my Palm, but what do they want me to have in my pocket during dives?

The table is pretty simple:

40' 170min
50' 60min
60' 50min
70' 35min
80' 30min
90' 25min
100' 20min
110' 15min
120' 10min
130' 5min

It should be commited to memory, and can be written in your wetnotes.
The esay way to remember it is to use 100feet and 20mins as your starting point, add 5mins for every 10 feet shallower, subtract 5mins for every 10 feet you go below 100.
And just remember that it changes at 60 feet, so just remember that 60 and 50 are swapped (60 feet for 50 mins and 50 feet for 60 mins). This is for diving air.

The stuff they teach on tables is very simple, and I wouldn't worry about it too much before class. If you want to be as ready as possible, pratice bouyancy, trim, and positioning. Without those things, it is extremely difficult to focus on the new tasks being taught.
Have fun,
Jason

EDIT- oh yeah, I forgot about the repetative dives. If the surface interval is greater than 1.5 hours, no residual nitrogen loading is used in calculating the next dive. If it is less than 1.5 SI, double the shallow stops. This is just a guidline, and should be done conservatively. Pay attention to how you feel after the dive.

 

[limeyx]

The table is pretty simple:

40' 170min
50' 60min
60' 50min
70' 35min
80' 30min
90' 25min
100' 20min
110' 15min
120' 10min
130' 5min

It should be commited to memory, and can be written in your wetnotes.
The esay way to remember it is to use 100feet and 20mins as your starting point, add 5mins for every 10 feet shallower, subtract 5mins for every 10 feet you go below 100.
And just remember that it changes at 60 feet, so just remember that 60 and 50 are swapped (60 feet for 50 mins and 50 feet for 60 mins). This is for diving air.

The stuff they teach on tables is very simple, and I wouldn't worry about it too much before class. If you want to be as ready as possible, pratice bouyancy, trim, and positioning. Without those things, it is extremely difficult to focus on the new tasks being taught.
Have fun,
Jason

EDIT- oh yeah, I forgot about the repetative dives. If the surface interval is greater than 1.5 hours, no residual nitrogen loading is used in calculating the next dive. If it is less than 1.5 SI, double the shallow stops. This is just a guidline, and should be done conservatively. Pay attention to how you feel after the dive.

Yes, this is the scheme I use too.
Peter's deco numbers are a bit more conservative and need to be combined with deep stops to get the full picture.

Ascent profile is to start 1 min stops from approx 50% of max depth and continue to 20 or 10 feet and then do a really slow (3-6 min) ascent from there.

And for 32% just take 20% off the depth to get the MDL time.


I've used this for 7 dives in a single day, all averaging 70 feet + with no ill effects.

 

[DIR-Atlanta]

I'm getting ready for DIR-F in a a couple of weeks and it just struck me that I don't know what they use for tables for NDL diving. [...] what do they want me to have in my pocket during dives?

Most of the dives in DIR-F are in shallow water (20-25 feet max), so NDL is not really an issue.

In theory (assuming an infinite gas supply) you could stay as long as you wanted at 20-25 feet without any concerns over nitrogen loading. So for the most part, the choice of decompression device in DIR-F is "it doesn't matter" - you will not really be using one.

More than likely, you will blow through your back gas long before you hit any sort of nitrogen limit anyway.

 

[*Floater*]

I'm getting ready for DIR-F in a a couple of weeks and it just struck me that I don't know what they use for tables for NDL diving. I have the PADI tables for air and Nitrox and DPlan on my Palm, but what do they want me to have in my pocket during dives?

I believe different instructors may teach slightly different things. I was not taught the 120 rule, but instead the instructor suggested to start with 100 ft for 20 min and then add 5 for each 10 ft up or subtract 5 for each 10 down. This is for air. So you get something like this:

70' 35min
80' 30min
90' 25min
100' 20min
110' 15min
120' 10min
130' 5min

Now that should look similar to most tables out there and that's the point. It's just a generic table and easy to remember because of the +/- 5 min per 10 ft thing. Of course, it would look a little funny if you continued the process all the way to shallow depths, so then you can fudge the numbers to say

40' 90min
50' 60min
60' 50min

Now that's for air, but we use EAN32 mostly, so you can either do your EAD conversions, or just drop the time column down by 2 rows for each depth. So you'll get

60' 90min
70' 60min
80' 50min
90' 35min
100' 30min
110' 25min

Again, that should look pretty similar to your basic EAN32 tables from PADI or other agencies.

The shallow depths stop mattering at this point for practical purposes because hardly anyone dives that shallow for long period and if they did they'd probably run out of gas before the MDL were up.

For multilevel dives I was taught to use the tables with average depth. As for SI's, you may be taught the 1.5 hour rule, or to just ignore them or some other rough time to clear. Yuo are of course allowed to vary this for yourself.

A very important part is to do a slow ascent. I was taught to come up at 10'/min from 80% ATA onwards (or about 75% of depth), others use 50% of depth, or do 1 min safety stops at 30'/20'/10' depths in addition to slow ascent, and either to double those shallow stops for repetitive dives or start them deeper. Or you may be instructed to play around with some deco software to figure out acceptable profiles for yourself.