V-Planner Dive Plan for NDL dive doesn't look right...

[ScoobieDooo]

Question: I just downloaded V-Planner to start learning about deco dive planning. For the fun of it, I looked at a US Navy Dive Table for 21%. The NDL for rec diving is 100 ft for 25 mins. I entered 100 ft for 24 mins into V-Planner just to see what it would do, and this is what I got...WHY? V-Planner is showing deco stops as so...but in normal rec diving, all that anyone would do for a NDL dive like this IS a safety stop of 3 mins at 15 ft. Whats up?
-Planner 3.10 by R. Hemingway, VPM code by Erik C. Baker.

Decompression model: VPM-B

DIVE PLAN
Surface interval = 0 day 2 hr 0 min.
Altitude = 0ft
Conservatism = + 2

Dec to 100ft (2) on Air, 50ft/min descent.
Level 100ft 22:00 (24) on Air, 0.83 ppO2, 100ft END
Asc to 40ft (26) on Air, -30ft/min ascent.
Stop at 30ft 3:00 (29) on Air, 0.40 ppO2, 30ft END
Stop at 20ft 4:00 (33) on Air, 0.33 ppO2, 20ft END
Stop at 10ft 9:00 (42) on Air, 0.27 ppO2, 10ft END
Asc to sfc. (42) on Air, -30ft/min ascent.

Off gassing starts at 70.8 ft

OTU's this dive: 17
CNS Total: 5.7%

83.1 cu ft Air
83.1 cu ft TOTAL

 

[JeffG]

Hmmmmm Good Question...

Maybe you should not to too quick to sell your Dive Rite Scuba Ni Tek Computer

 

[ScoobieDooo]

Naa,
Thanks, but I find the Bottom Timers easier to use and besides, I'm headed in a DIR direction...computers will rot your brain! Ask Uncle Pug!

 

[O-ring]

I don't use V-planner too often, but for one thing you have the conservatism on +2 so that will make your stops longer. Another thing is that you are comparing apples to oranges...the rec NDLs are based on a dissolved gas model and this is a bubble model that takes into account dissolved gas and bubble formation.

 

[ScoobieDooo]

O-Ring, so what should the conservatism be on?

 

[O-ring]

ScoobieDooo once bubbled...
O-Ring, so what should the conservatism be on?

IMHO, that's a personal decision. Point this thread out to WreckWriter...I know he uses VPM and knows a lot more about it than I do. Actually Ross is on the board now too, so maybe he will answer your question.

 

[ScoobieDooo]

WreckWriter?

?????????

 

[MechDiver]

One other possible thing is having a SI set to only 2 hours. That would signify you still had loading from a previous dive. Not sure what values V-P would use in that case, but it tracks exposure for up to 2 days I believe.

MD

 

[Uncle Pug]

oh... O-ring already said that...

What should the conservatism be on? What are you trying to accomplish?

 

[Rick Murchison]

Not an exact science, is it?
Note that the Navy table with doppler limits applied has a max NDL of 20 vice 25 minutes, and while V-planner will still give you a few minutes more stop time, they're getting closer.
Now, if you really want to have some fun, look at a series of 15 minute dives to 100' with an hour surface interval.
With V-planner (VPM-b, nominal) you can do these indefinitely with a 3 minute stop, while the Navy tables require no stop on the first dive, a 3 minute stop on the second dive, 2 @ 20 and 24 @ 10 on the third dive and on the fourth dive you're up to 9 @ 20 and 28 @ 10, where it finally goes constant.
When you take your decompression course you'll be better equipped to make an informed decision on what to use for your specific dives.
Rick