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

[ScoobieDooo]

Only trying to see how this program works in relation to US Navy dive tables and stuff. I'm just a recreational diver right now, but interested in how these programs calculate, etc. and how combined with a bottom timer might be useful vs using a computer to calculate it all for me...

 

[ScoobieDooo]

Rick,
Ahhh, ok, thanks...I'm seeing that I know nothing about tech or deco diving to date...

 

[WreckWriter]

ScoobieDooo once bubbled...
WreckWriter?

?????????

Wassa matter, you don't like me or something?

First thing, VPM-B is a modern deco model, Navy tales (Haldanian model) are a very old model. A LOT of folks got/get bent running the NDLs to the stops on Navy tables, a big percentage in the 90'-100' range.

Like Rick said, its not an exact science, more art than science maybe. This table will get you on the boat, unbent, pretty much every time. Its simply more conservative.

Leave your conservatism set at 2 unless you're a Navy Seal or a trialthete.

One more bit of advice: don't dive air at 100'

WW

 

[ScoobieDooo]

WreckWriter,
Play nice-a, nice-a...

I just punched 21% in for fun, because lets face it, people DO dive 21% to 120 ft - or thats the MAX DEPTH all the PADI or US NAVY tables recommend.

 

[MikeFerrara]

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

Feel lucky?

Yes what they said!

Pick up 5 different table and you get 5 different answers. Use more than one software and you get more than one answer.

The worst part is that with different settings in the same software you will generate very different schedules.

This is one of my favorite subjects and like most I don't know crap. Except, I have increased the depth and length of my dives a little at a time. You read all the theory untill your certain you understand everything and then you realize that what counts is how you feel. If it works it's good.

Even though some guys seem to have it nailed as far as what works the scientists don't seem to be able to really explain it.

Also since there isn't any money in it it isn't likely anyone is going to do any serious research either.

 

[WreckWriter]

ScoobieDooo once bubbled...
WreckWriter,
Play nice-a, nice-a...

I just punched 21% in for fun, because lets face it, people DO dive 21% to 120 ft - or thats the MAX DEPTH all the PADI or US NAVY tables recommend.

Have I said anything less than nice to you?

Actually the U.S. Navy air tables go to 300', people dive it too, but that doesn't make it a good idea.

WW

 

[rossh]

V-Planner is calibrated to recreational NDL's. The Navy tables are not recreational tables - they are for the navy, and have a significant risk of DCS.

The standard recreational NDL for a 100ft dive is 16 minutes. If you set the conservatism to nominal, then you will find the results your looking for.

Regards
--
Ross Hemingway

 

[padiscubapro]

rossh once bubbled...
V-Planner is calibrated to recreational NDL's. The Navy tables are not recreational tables - they are for the navy, and have a significant risk of DCS.

The standard recreational NDL for a 100ft dive is 16 minutes. If you set the conservatism to nominal, then you will find the results your looking for.

Regards
--
Ross Hemingway

I wouldn't go that far.. PADI (The largest RECREATIONAL agency says its 20 mins!)
I would agree most current dive computers come up with 16 or 17 mins..

No deco tables are usually based on surfacing values which are a bit more liberal than decompression oriented tables.

There are other factors also when looking at the NDL limits each table has its own rules and definition of what bottom time is.. I'll give an example I use frequently

Padi uses 100 for 20 ANDI uses 100 for 23, they look quite different don't they.. but actually they pretty close..

PAdi says BT starts on the decent and ends upon Beginning the ascent..
ANDI says bottom time starts after passing 2 meters/ 5 feet and ends upon reachine the 30 ft stop (I'm not going into the entire ANDI ascent/descent procedure)
But if you take into account a normal ascent rate the bottom times are pretty much the same.. (2 plus minutes of ascent rounded to 3 minutes), so the diver must leave the bottom at 20 minutes..
An instructor giving a class on decompression theory should cover information like this..

 

[ScoobieDooo]

According to Table Tutor dive tables, a dive to 100 ft is more than 16 mins, I believe I am seeing 25 mins. Quite a differance in times, 9 mins to be exact.

 

[Rick Murchison]

rossh once bubbled...
The Navy tables ... have a significant risk of DCS.

That sorta depends on how you dive 'em. For example, in my previous post, where I proposed a series of repetitive dives of 15 minutes bottom time to 100' with one hour surface intervals, the Navy tables actually dictate a far more conservative profile over time (after the first dive - and if a safety stop is used the first dive's allowed direct ascent becomes a moot point) than does V-planner - so if the Navy tables have "significant risk" where does that place V-planner?
Indeed, for air dives at typical recreational depths and times, strict adherence to the Navy tables on repetitive dives will result in shorter allowable bottom times and/or longer surface intervals required than V-planner (or any dive computer, for that matter) just about every time.
Another example: Using the Navy tables, even if we consider the three minute safety stop as a decompression stop, doing a series of 40 minute dives to 60' will require a minimum surface interval of 1:16 between dives one and two, and 2:39 between all subsequent dives. (Using the Navy tables in "no decompression" mode would require surface intervals of 2:59 between dives 1 & 2 and 4:03 for subsequent dives - and using the Navy Tables with doppler limits applied (the SSI modification) would require surface intervals of a whopping 4:26 between dives 1 & 2 and 8:00 (!) between subsequent dives) Using V-planner (VPM-b, nominal), for no-stop dives to 60' for 40 minutes, a surface interval of only 30 minutes is required between dives 1 & 2, and 40 minutes for subsequent dives. So, again, as a practical matter, the Navy table is far more conservative and has a significantly lower risk of DCS than VPM.
It is "common knowledge" that the Navy tables are for young, fit Navy divers and carry a "significant risk of DCS"... but common knowledge, when the actual numbers are crunched, just doesn't hold water. The Navy tables - in recreational no-stop diving, and especially when used for repetitive diving - are in fact very conservative.
Rick