actual NDL calculations

[scc135]

Hrm. I was OW certified in 05. I was taught 60fpm then. But then again, my instructor was serious old school.

 

[j yaeger]

60 f.p.m-padi.....still

 

[LeadTurn_SD]

I only asked because the PADI Dive Planner, and all tables PADI, as is mentioned by the OP has a 30fpm ascent rate. And no I don't know when that changed, but it was definately before 2003 when I finished my Divemaster course, and the U.S. Navy table for No-Decompression dives, Revision 5 (latest revision is 6) is also 30fpm.

I just want to make sure we are all taking the same certification agency here, and not mixing in ratio-deco or some other theory.

Thanks all.

Hi muddiver,

Now I'll need to go check too. My recollection is that at least as recently as the summer of 2007 (when my 3 kids were certified at the local PADI shop) PADI's basic OW texts and RDPs were still using 60' per minute...

But with my memory, I could certainly have it confused

Either way, it does seem that most (all?) are moving to or have already moved to the 30' per minute ascent rate.

Best wishes.

 

[NC Wreck Diver]

Years ago, I was taught 60'/minute. My Edge used this model. Now, I've did some review a while ago, and it's 60'/minute up to 60 feet. Then 30'/minute from 60 feet to the surface (with a safety stop at 15' for 3-5 minutes). My computer seems to follow this algorithum (Uwatec Aladdin Nitrox Pro). I follow this procedure, and my computer seems to follow.

I do incorporate a deep stop on my deeper dives. The is about a minute or two at half my deepest depth. I have read the pros and cons of deep stops, and still feel it is a good program. There has been some interesting articles in DAN's magazine. I'm sure it's covered on DAN's website too.

 

[skynscuba]

... Sure my dive comp says I'm good but when I log it, it shows a max depth of 105 (for instance) with a BT of 35 min, which doesn't make sense on paper.

I don't log dives, so I never run into this problem.

 

[gcbryan]

... Now, I did deep dives and they blow past my NDLs. Sure my dive comp says I'm good but when I log it, it shows a max depth of 105 (for instance) with a BT of 35 min, which doesn't make sense on paper.

It makes sense in a log book it just wouldn't make sense on a square profile dive or using the RDP.

 

[Bob DBF]

In 1980 the PADI Dive Tables was 60' for 60 min with an ascent rate of 60'/min with repetitive groups A to N. It also had some Deco stops and times if you violated NDL.

The 1985 - 1989 PADI Recreational Dive Planner was 60' for 55 min with an ascent rate of 60'/min with repetitive groups A to Z. It "requires" safety stops for times prior to the NDL and for all dives of 100' or greater.

In 2004 or 5 I found out about the 30'/min from 60' feet to the surface because my new computer kept getting PO'ed at me on ascent rate above 60' so I read the manual and also found out I couldn't change it. I never have a problem up to 60' so I guess I've been doing it up to that point.

I don't have a new PADI Recreational Dive Planner so I can't check the copyright of their last change.

My next bit of task loading on the beach is to check the dive planning function and see what the repetitive group turns out to be and see if it makes sense. For a computer failure that group should be more accurate than using a deepest depth and total dive time square profile. Let me know if my thinking is as flawed as usual.

Bob
---------------------------------
Not pushing the envelope just poking at it on occasion.

 

[wve]

Everyone may already know this, but just in case... The PADI RDP and eRDPml calculate Bottom Time differently than computers. This can be important when trying to log dives using the computer, then going back to see what the table would have said about your dive.

According to the RDP, the clock starts when you begin your descent, and it ends when you start your ascent. In contrast, computers start the clock when you descend below a certain depth (say, 8 feet) and stop when your ascent reaches a certain depth (say, 4 ft).

Because of the differences, a computer's bottom time may be significantly longer than the bottom time if using a table.

So, for example, consider a "bounce" dive where one goes to the planned depth then comes right back up at the same rate that you descended (in other words, a V profile). Bottom Time for table use would be 1/2 the bottom time that a computer would record.

The point is, you can't do a dive on your computer, then later look at the bottom time your computer recorded, then use that time to figure out what pressure group you would have been in had you used the table.

 

[Blackwood]

I only asked because the PADI Dive Planner, and all tables PADI, as is mentioned by the OP has a 30fpm ascent rate. And no I don't know when that changed, but it was definately before 2003 when I finished my Divemaster course, and the U.S. Navy table for No-Decompression dives, Revision 5 (latest revision is 6) is also 30fpm.

I just want to make sure we are all taking the same certification agency here, and not mixing in ratio-deco or some other theory.

Thanks all.

The OP is asking about calculating NDL, not how to appropriately use dive tables.

I'm not talking about what they (PADI/their tables) instruct divers to do, I'm talking about what ascent rate is assumed for the purposes of establishing NDL.

As far as I know, for a dive to 60 feet, the PADI/DSAT NDL assumes the diver will have at a minimum one minute of in water decompression, not two minutes.

Also, FWIW, I dug my PADI RDP out of the garage. Ver 1.2 (Rev 02/03) states under General Rules: "Ascend from all dives at a rate not to exceed 60ft per minute."

While that doesn't mean that 60fpm is used in the algorithm, I find it highly unlikely that they would suggest that 60fpm is okay if the algorithm is based on 30fpm.

 

[liuk3]

PADI Max Ascent Rate = 60 fpm
NAUI Max Ascent Rate = 30 fpm (as does pretty much every other agency I've trained with)