Beach dive planning thoughts.

Not to hijack the dive report thread, I have started a new topic on this subject.

divinman:

The Pro Ultra showed me as having a mandatory stop at 10 ft for 1 minute when we turned the dive and started back up the line. The Source was on the last tick mark in the yellow prior to a required stop. In the two minute ascent from 67ft to 32ft, my stop on the Pro Ultra went away. We completed a two minute stop at 30-35ft and then a 4 minute stop at 20ft. Both my computers showed clear to surface with no required stops. Slow 90 second ascent to the surface.
No my buddy on the other hand is diving a Sunto Cobra and he had an 18minute deco requirement at 10ft.
Thoughts? :06:
Terry

Click to expand...

Reference dives of:
Date: 09/12/04
Dive Location: Ruby E Wreck- San Diego
Dive Location: Pacific Beach Reef

Terry, thanks for the info. I asked because looking at the dive profile (which is sans time and depth reference points) it looked like a long stay at depth and that got me to wondering if it possibly fell outside the standard dive planner (square profile, surface to surface) NDL limits, or would be close to doing so.

Looking back over the past few days at the dives of your dive buddy, it is not surprising this was a deco dive for him. His dives of the previous days were probably a factor in the SUUNTO Cobra placing him in the deco dive mode. SUUNTO uses the dives of the previous 99 hours are in its calculations. I will also confess I am not as adept at using the dive planner as I should be, and often just go with the computer planner. So I am doing more practice with it and basically checking your dive against what I think my recreational planner is showing me.

That brings us to the question of the day: When planning a dive, should we factor in dives of the previous days, particularly if we are frequent divers who dive on successive days and dive deep?

I know that I personally never thought (until recently) to inquire of my dive buddies their dive history in the past 24-48 hours, or of factoring in my own dives of the previous days. If the dives were short and shallow, they are probably not a factor. But I would imagine they would become more important if the previous days dives were riding the NDL, and/or there were multiple dives in the previous day/days particularly if they were deep and long.

I think Sean, just need to be re-classified, God made a mistake, he should have been a fish........no NDL problems. So where did the extra, unplanned, 18 minutes of air come from??

ShakaZulu:

I think Sean, just need to be re-classified, God made a mistake, he should have been a fish........no NDL problems. So where did the extra, unplanned, 18 minutes of air come from??

Click to expand...

He do spend a lot of time in the water. He is certainly getting a lot more time out of his tanks than he did just a few months ago. Anyway you slice it, it looks like it was a fun dive. Not sure I could have done that dive with my AL80.

pasley:

...
That brings us to the question of the day: When planning a dive, should we factor in dives of the previous days, particularly if we are frequent divers who dive on successive days and dive deep?
...

Click to expand...

Really good question.

The Suuntos are good at this, with their air or EANx modes.

I do not know of any technology, other than the computer programs, that can also do it, and they do not do it as good as Suunto does.

It looks like you have discovered a really good reason for using the Suuntos on a dive trip involving multiple days of air or EANx diving. A reason which is undeniable.

The D/M or ITC courses of some of the training agencies (I know of 2 specifically) cover the issue of multiple day multiple diving generally in their training materials. Outside of that forum, I do not believe the issue is taught or considered in much detail.

I took a look at your thread. I don't know how much more I can add. If I had the download software for my Pro Ultra I could send you the last 99 profiles and that would probably give you a better picture. If anyone has a data mouse they want to sell cheap, I will help Pasley out here. I was on the dive with Sean the previous day as well but he has been quite the busy diver lately and I can't keep up. If Sunto is running that far back,( could be a good thing) that would explain the difference. I don't know how long my computer runs back but it stays on and counting until desaturation is completed.

I made 21 dives in 6 days on Nekton in May and yes, my NDL got shorter and shorter as the week progressed. How much? Again, I would need the computer software to tell ya. I am interested to here what others think/believe/know. I haven't taken a deco class yet and I am one of those "lazy" divers that just dive till my computer tells me to come up. My OW class didn't teach multilevel dive planning so its the computer or the square profile table and that is too conservative even for me.

I just quickly glanced at a small array of different dive tables and it appears that they all agree that anything after a 12 hour surface interval is not considered a repetitive dive.

No more than a handful of tables were used when I did my quick check and I do not have any RGBM tables. I would be interested in seeing those some day. I think everything I have is based on the US Navy tables.

A 24 hour SI is what I still consider my min. time before I'll fly, so I'm not sure how that figures into the equation.

I'll be very interested in hearing people's comments on this one.

The only time I ever dove with a computer was with an Orca Edge "many moons" ago. I borrowed it from the dive shop. It was like carrying a little brick with me. Needless to say, I'm somewhat table oriented.

Christian

divinman:

.... I haven't taken a deco class yet and I am one of those "lazy" divers that just dive till my computer tells me to come up. My OW class didn't teach multilevel dive planning so its the computer or the square profile table and that is too conservative even for me.

Click to expand...

Ahem, Uhmmm, guity as charged here too. Hence my quesiton. 151 dives and the last time I got the dive planner out before this week was, well, my BOW course. But tomorrow is a new day and I am trying to improve that by learning. I do kind of have an idea in my head of limits, and the dive profile caught my attention as being in that neighborhood. But, I am clueless about multi-level planning.

Soooo, I thought I would use the dive profiles you furnished to start a discussion (I rarely dive below 40 feet so yours are more interesting and useful for the discussion).

V-Planner 3.43 by R. Hemingway, VPM code by Erik C. Baker.

Decompression model: VPM-B

DIVE PLAN #1
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 70ft (1) on Air, 50ft/min descent.
Level 70ft 33:36 (35) on Air, 0.65 ppO2, 70ft ead
Asc to 10ft (37) on Air, -30ft/min ascent.
Stop at 10ft 3:00 (40) on Air, 0.27 ppO2, 10ft ead
Asc to sfc. (40) on Air, -30ft/min ascent.

Off gassing starts at 50.4ft

OTU's this dive: 13
CNS Total: 5.7%

81.4 cu ft Air
81.4 cu ft TOTAL


DIVE PLAN #2
Surface interval = 0 day 1 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 70ft (1) on Air, 50ft/min descent.
Level 70ft 33:36 (35) on Air, 0.65 ppO2, 70ft ead
Asc to 20ft (36) on Air, -30ft/min ascent.
Stop at 20ft 2:20 (39) on Air, 0.34 ppO2, 20ft ead
Stop at 10ft 9:00 (48) on Air, 0.27 ppO2, 10ft ead
Asc to sfc. (48) on Air, -30ft/min ascent.

Off gassing starts at 50.4ft

OTU's this dive: 13
CNS Total: 9.2%

88.0 cu ft Air
88 cu ft TOTAL

DIVE PLAN COMPLETE

Since they didn't do a square profile, just playing with the numbers, I can get the second dive to be a deco dive, just by changing the BT to 35min, instead of 30min (don't know the SI, safety stop depth, and is estimating BT's and depth). Very difficult to know what is actually happening, unless you dive the exact dive plan/profile as planned??? Guess we can ask one of the TECH divers to comment.............

18 minutes of deco on a Cobra..... you mean when he got to 10 he still had 18 minutes?? If so, my experience with Suunto comps would tell me he got into deco and stayed there without ascending.....

Usually, Suuntos will go into deco and give just a few minutes of obligation. If you do nice safe ascent, before you get to the stop it's cleared or reduced dramatically. If you don't start ascending, you start racking up the obligation. Happened to me once on a photo dive.... 14 minutes of deco, and it meant it. I got to 10 feet and had to do 14 minutes, no credit for the ascent....I downloaded the profile and discovered to my dismay I went into deco at 60 ft while photographing a subject, and stayed there for five minutes, racking up more time.

You should have your buddy download the profile, find out when he went into deco and for how long before ascent, I'd bet it's a good while.

Chris

That's what happened. I am aware of how it works so I knew I would have to do the additional time. I was hoping it would be reduced when I went up, but I can see my tissue saturation was over 100% until I finished the extended stop. Is going into deco always a bad thing? Is it a line you never cross? If your going to do the time, can you do the crime?

Sean