not bent yet?

[caverdave]

So it was RJP's idea and I have been having fun.

I took a dive to 130 for 40min (28%). the total calculated dive time was 110 minutes.

then i added a stop at 80 for 10 minutes (40%) and a stop at 40 for 10 min (50%) and then one at 30 for 5, and 20 for 5 and got the total dive time down to 82 minutes. but still a 7:40 deco obligation on O2. at one point I had the deco down to :40 and i am still playing with it to minimize both the deco obligation and the total dive time.

It will take me some re-reads to understand what was posted above. I am a little slow that way. I have to see what is behind the formulas I can not just absorb them as is.

The playing helps- keep it up.

If you are questioning why it shows up as deco in this example vs the 1st dive- - you've taken a huge leap in bottom time (40 minutes vs 5).
Pending your tanks that jump up may not even be plausible (mentioning as sometimes playing can lead one into odd scenarios).

For your playing also suggest comparing back to your original tables too; with your above stops you should see a difference between the two.

A very rough generalization that may help for understanding (but not to be read into too much) would be that you are off gasing while ascending and taking on a new average depth when stopping at more shallow depths. Lots of "fun" to be had watching the dive computer go from full red need deco to no deco as one "watches fish" at 30-20' (vast overgeneralization but may help mentally picture...)

If you haven't taken or has been awhile you might get some significant insight from an Adv nitrox deco procedures class...

Dave

 

[SailNaked]

Yes as soon as the stars align I will take Adv Nx. I was wondering if the 40min was unreasonable, I got it down to a total dive time of about 72 minutes but then i was trying to remove the deco obligation and found I would have to add more time to the total. fun game.

 

[caverdave]

Yes as soon as the stars align I will take Adv Nx. I was wondering if the 40min was unreasonable, I got it down to a total dive time of about 72 minutes but then i was trying to remove the deco obligation and found I would have to add more time to the total. fun game.

before anyone "complains" / just in case...
I wasn't saying it wasn't reasonable / doable.
I was calling into mind that pending your tank size that time/depth may have you staying way longer than possible (i.e. stretching for sake of example- i.e. if you were on an Alumin 80 you wouldn't have enough gas- unless your SAC is amazing and/or there is no allowance for a buddy & emergency etc)

Let the fun continue... (but no diving the profiles until the stars align)

Dave

 

[ianr33]

then i added a stop at 80 for 10 minutes (40%) and a stop at 40 for 10 min (50%) and then one at 30 for 5, and 20 for 5 and got the total dive time down to 82 minutes. but still a 7:40 deco obligation on O2. at one point I had the deco down to :40 and i am still playing with it to minimize both the deco obligation and the total dive time.

You're really not minimizing the deco though,you're just moving it around.Nothing wrong with that, just don't fool yourself into thinking you are reducing the deco. Look at this profile:

Conservatism = + 2

Dec to 130ft (2) Nitrox 28 60ft/min descent.
Level 130ft 37:50 (40) Nitrox 28 1.38 ppO2, 116ft ead
Asc to 50ft (42) Nitrox 28 -30ft/min ascent.
Level 50ft 50:00 (92) Nitrox 55 1.38 ppO2, 14ft ead
Surface (94) Nitrox 55 -30ft/min ascent.

OTU's this dive: 147
CNS Total: 58.5%

121.8 cu ft Nitrox 28
77.1 cu ft Nitrox 55
198.9 cu ft TOTAL


Is that a deco dive or an NDL dive with a long stop at 60ft on 60% ?? Obviously its a deco dive because at 40 minutes you have a substantial deco obligation.

 

[SailNaked]

Conservatism = + 3

Level 130ft 27:24 (30:00) Nitrox 28 1.38 ppO2, 116ft ead

Level 70ft 7:00 (39:00) Nitrox 44 1.37 ppO2, 40ft ead

Level 40ft 20:00 (60:00) Nitrox 44 0.97 ppO2, 19ft ead

Level 20ft 4:00 (64:40) Oxygen 1.60 ppO2, 0ft ead

Surface (65:20) Oxygen -30ft/min ascent.

OTU's this dive: 89
CNS Total: 39.9%
75.4 cu ft Nitrox 28
35.0 cu ft Nitrox 44
3.6 cu ft Oxygen
114.1 cu ft TOTAL

Very easy with Al80 doubles(28%) an 80 Deco/ travel of 44% and a small O2 maybe hung or carried. Includes redundancy and might even be a recreational dive

this profile was a total dive time of 65 min, and used the deep stops to eliminate the Deco obligation but there was certainly a deco obligation upon leaving the deep part. I would not do this dive because it took me awhile on the computer to make it up and if anything happened it would go out of whack quick. The times had to be played with. a computer would guide this kind of thing but since it is so specific I would not want to do it. that and of course I am not trained

I have been Internet training for more than a year, I know all about 1/3s buddy requirements, lost gas and redundancy and I still grouched at my wife when her computer showed a few minutes of deco in Coz that cleared after going up 10 ft.

Im happy to do regular dives till I get my hazard card, no worries on that, but this has been a very interesting exercise.