What defines a "Deco" dive?

[DwayneJ]

I wonder what NDL plan was being followed... As originally planned 6+ mins of deco.
Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 90ft (1) Nitrox 32 50ft/min descent.
Level 90ft 40:12 (42) Nitrox 32 1.19 ppO2, 73ft ead
Asc to 20ft (44) Nitrox 32 -30ft/min ascent.
Stop at 20ft 0:40 (45) Nitrox 32 0.51 ppO2, 13ft ead
Stop at 10ft 6:00 (51) Nitrox 32 0.42 ppO2, 4ft ead
Surface (51) Nitrox 32 -30ft/min ascent.

Off gassing starts at 51.6ft

As dived...

Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 100ft (2) Nitrox 32 50ft/min descent.
Level 100ft 20:00 (22) Nitrox 32 1.29 ppO2, 81ft ead
Asc to 75ft (22) Nitrox 32 -30ft/min ascent.
Level 75ft 20:00 (42) Nitrox 32 1.05 ppO2, 60ft ead
Level 75ft 2:00 (44) Nitrox 32 1.05 ppO2, 60ft ead
Asc to 10ft (47) Nitrox 32 -30ft/min ascent.
Stop at 10ft 1:00 (48) Nitrox 32 0.42 ppO2, 4ft ead
Surface (48) Nitrox 32 -30ft/min ascent.

Only a minute of deco. Using +2 level of conservatism but even at +0, the first dive was still a deco dive. Ratio deco to find max NDL? Navy tables max NDL?

By the by - Found a link to the NOAA tables... http://www.ndc.noaa.gov/pdfs/nitrox32.pdf

 

[DwayneJ]

Does it matter?

The boat assuredly knew they were not up, via the comment "one crew member even mentioned the fact that she had lamented that, “If they’re going to do this long of a dive, they really should let us know beforehand.” "

I'm not asking what the boat said or how long they were down for, I asking how do you get an NDL dive out of 40 mins/100'/32%?

 

[Jax]

Just wondering the relevance?

 

[DwayneJ]

I'm cool -

...FWIW, GUE profiles consist of depth averaging if you're not doing a square profile and require a "min deco" ascent, rather than blasting up to 15 feet to hang out for three minutes...

Nicole

Nicole explained GUE/Min Deco Ascent.

 

[DwayneJ]

and not noticing for the better part of 1/2 hour

Well first off, it was not half an hour....

I've assumed the boat speed as its a big boat/displacement hull.

27 Minutes/0.5 Miles
Mins
~1-------Engine(s) Start
~5-------Accelerate/Cruise/Decelerate 0.5 Miles/8Kts (boat speed ~9Kts due to current)
~5-------Position
~11------Total
Difference
~16---Dealing with other divers getting on board (boat and divers drifting away from the public mooring)
---------------- ~3 Feet Per Second (1.5Kts) Drift Speed

Secondly, the ~16 minutes includes the time to get diver(s) out of the water, off the back of the boat, gear off and secured.

What have I learnt out of all this -

1. GUE Min Deco profile as detailed is flawed. ZHL16 with GF30-80 would have me doing 12+ minutes of deco for 100'/40 mins/EANX32% Update - there were posts from Nicole stating it was a non technical/NDL dive, but reading the original post, Nicole did say "on their 40' stop..." so they were diving a deco dive. Not sure why the confusion about NDL/Deco.

2. Dont trust public moorings.

3. I've learnt current sucks big time and stay put is the right choice.

 

[GrumpyOldGuy]

Well first off, it was not half an hour....

I've assumed the boat speed as its a big boat/displacement hull.

27 Minutes/1620 Seconds/0.5 Miles
Secs----Mins
60------1-------Engine(s) Start
310-----5.17----Accelerate/Cruise/Decellerate 2600'/8Kts (boat speed 9.5Kts due to current)
300-----5-------Position
670-----11.17---Total
Difference
950-----15.83---Dealing with other divers getting on board (boat and divers drifting away from the public mooring)
----------------2.74 Feet Per Second (1.5Kts) Drift Speed

Secondly, that 950 seconds includes the time to get diver(s) off the back of the boat, gear off and secured.

What have I learnt out of all this -

1. GUE Min Deco profile as detailed is flawed. ZHL16 with GF30-80 would have me doing 12+ minutes of deco for 100'/40 mins/EANX32% Update - there were posts from Nicole stating it was a non technical/NDL dive, but reading the original post, Nicole did say "on their 40' stop..." so they were diving a deco dive. Not sure why the confusion about NDL/Deco.

2. Dont trust public moorings.

3. I've learnt current sucks big time and stay put is the right choice.

In 3rd or 4th grade I learned that if I analyze something is very precise units (such as seconds in your case) and thow in a lot of meaningless detail I could sometimes BS my way through an argument. It worked great then, not so well with adults.....

Just saying, whats the point? The crews screwed up, not real big in the end but enough to upset a customer and many other people reading the thread. They could have defused the situation with a little caressing. Now the wound is infected and its a bigger mess than it needed to be.

 

[Hepcat62]

1. GUE Min Deco profile as detailed is flawed. ZHL16 with GF30-80 would have me doing 12+ minutes of deco for 100'/40 mins/EANX32% Update - there were posts from Nicole stating it was a non technical/NDL dive, but reading the original post, Nicole did say "on their 40' stop..." so they were diving a deco dive. Not sure why the confusion about NDL/Deco.

GUE min-deco for a 100' dive (up to MDL) is a 30fpm ascent to 50', followed by 1min at 50', 40', 30', 20', and 10'. Each 1min stop is actually a 30 second stop, followed by 30 seconds of travel to the next stop. So assuming this was an MDL dive (due to averaging), there is still actually a 40' stop in her ascent profile.

 

[DwayneJ]

In 3rd or 4th grade I learned that if I analyze something is very precise units (such as seconds in your case) and thow in a lot of meaningless detail I could sometimes BS my way through an argument.

LOL - I have 20+ years of measuring micro and milliseconds so I absolutely missed that 3rd grade lesson. How about "when the big hand is on the one and the little hand is on the two?"

 

[TSandM]

I don't know how they are doing things these days, but I learned to use 100 for 20 as a baseline air dive; add five minutes for each 10 feet shallower. Using 32%, figure the 80% EAD, so you'd be looking at 80 feet, where you would have 30 minutes of "MDL" time -- meaning you could stay up to 30 minutes and do a 30 fpm ascent to 40 feet, and 10 fpm ascent from there to the surface. A 40 minute dive with an average depth of 100 feet would be a staged decompression dive, requiring more than "minimum deco". But in DIR diving, all dives are deco dives, and ALL dives involve stops. Even if I did 100 feet for only ten minutes, I'd still do the minimum deco.

 

[drbill]

Not sure I understand you Lynne, but then I'm not very conversant with DIR terminology or standards. Personally I only refer to a dive being deco if it involves a mandatory stop based on tables or some algorithm. According to DIR, ALL dives are deco? Even one to a maximum depth of 30 ft for a total dive duration of 60-70 min? Understand that I'm not questioning you or DIR, just trying to understand how DIR defines a "deco dive."

Of course any dive can be considered a deco dive based on one's definition. We are all hoping we off-gas appropriately for whatever dive we do. Regardless of whether I'm in "mandatory" deco, I do multiple stops on deeper dives and try to modify my mandatory deco stops to extend them as long as I can... it's an old body I'm in and I try to treat it well.