Big Mistake

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I once had a similer experance but it didn't put me into a deco mode. I have a Cobra. Had been making repetive multilevel dives 2-3 dives a day for 3 days. On the last dive I was at 40' or so still had a bit of air and the computer showed more dive time left before deco than air. remaining. A pod of dolphins showed up and I went to 15' to check them out and take pics. My buddy and the D/M stayed at 40 ft. When the dolphins left I still had showing a longer dive time than air so I droped back to 40 ft for a couple of mins and checked out a puffer fish. The computer gave me a stop message on the decent back to 40' but still showed I had dive time left. On the accent it added an extra min to the safety stop. According to the computer (I also roughly check out my dive profile useing a padi wheel) I never busted a NDL but because of the bounce profile at the end of the dive it added to the safety stop. Could have been since you "bounced from 70' down to 90' that it became more conservative and penilized you. I understand that the Suuntos are very conservative when it comes to a sawtooth, Bounce or reverse dive profile.
 
Suunto computers are known for long shallow stops. I once ran my Vyper in air computer mode on a 180/20 dive and it wanted me to do all my stops at 10'. Problem is that if you don't, it locks out. They're great in gauge mode but that's it.

WW
 
Ok. I'm going to try and steer away from the obvious questions regarding why you planned for 12 and then threw that plan out and started diving your computer.

However playing with my suunto planner, I can't for the life of me figure out how you could have encurred a 12 minute deco obligation. You seem to imply a lot of bouncing in your dive, and that's going to cost you.

However can you download the profile, and give us the profile numbers for all the dives in the series and the surface interval times? I tried running it and had to overstay for almost 40% longer than the NDL to get the thing to kick to 12 minutes deco @ 10.
 
Anyone have any insight to my earlier post

Off gassing at your safety stop occurs during the process of breathing. If you slow your breathing down to conserve air on your safety stop, aren't you also slowing down the offgassing process? Wouldn't this increase the time required for the deco stop? It seems like conserving air at the safety stop would be detrimental to the whole deco stop process.

If I were in SeaJay's fins on this particular safety stop, I would have not conserved my air like SeaJay did. I would have breathed normally and sucked my tank all the way down to maximize the offgassing process... would this have been the right thing to do?

Anyone?...
 
I'm really not sure, but, my guess would be that lowering your breathing rate (by relaxing for example) would NOT have much an effect on offgasing, you would just breath off more N2 per breath, with the total ammount off-gased within 5 minutes (for example) being the same whether you have a RR of 10 or 20 breaths/per/min, provided you are not breathing shallow/skip breathing.

Off-gasing is mostly a function of perfusion (the blood going to the lungs), the ventilation just blows it off.

Again, this is just my guess. I'd conseve the air and stay down as long I could.
 
MASS-Diver once bubbled...
Snip

Again, this is just my guess. I'd conserve the air and stay down as long I could.

I'm with you, it's the time on the stop not the respirations that off the N2.

After diving with a few people on Suuntos, I certainly would not buy one, ridiculously long deco time at ridiculously shallow depth.
 
Spectre once bubbled...
However can you download the profile, and give us the profile numbers for all the dives in the series and the surface interval times? I tried running it and had to overstay for almost 40% longer than the NDL to get the thing to kick to 12 minutes deco @ 10.

Sure, man... Maybe you can shed a little more light on this.

Okay, dive 1, salt water, AL80 (77.4 cuft of 21%), 3000 psi.:

0-5 min: decended to 90' constantly
5-15 min: "bottom" of dive, max depth of 102', but averaging about 95'
15-28 min "hung" at 75 feet
28-31 min ascend to 18 feet
31-34 min safety stop at 15 feet
34 min: END. Roughly 700 psi left.

Surface interval: 1 hour, six minutes (apparently longer than I remember - perhaps I'd forgotten to add in time for gearing up and all)

Dive 2, salt water, AL80 (77.4 cuft of 21%), 3100 psi.:

0-3 min: descend to 75'
3-5 min: ascend to 65'
5-7 min: descend to 86'
7-10 min: ascend to 80'
10-12 min: descend to 94'
12-13 min: ascend to 71'
13-16 min: level at 72'
16-18 min: descend to 98' (rock bottom; interestingly, my logbook shows 1 minute of NDL, not what I saw as I described... 3 min NDL. As I said, I think I overswam the computer at this point.)
20 min: My logbook says that my dive computer showed 0 NDL at 88 feet. From here, I quickly begin to add deco time.
20-30 min (!): I ascend at a constant rate to just under a 10-foot ceiling (holy smokes! That's a perfect 8 ft/min for ten minutes! I mean, the graph's got a perfectly straight line...) I max my deco obligation at 45' and at 27 minutes to be a whopping 18 minutes of deco.
30-42 minutes: 12 minute deco at just under 10 feet, including the 3 minute "safety" stop.
42 min: END. Roughly 150 psi left (!).

Wow... How amazingly educational...
 
Over 50% of the responses to my poll on computers were users of Suunto computers. I don't have one, but they sure are popular with the members of this board. There were a few that checked the bottom timer box, but not that many.

The behavior of Seajay's computer is consistent with some other profiles of fellow divers that I have seen, where a deco obligation is incurred on a second deep dive of the day and rather than clearing on the ascent the legnth of the stop increases.
 
The Oceanic cleared 17 minutes sooner than the Suunto

A wall dive . We planned this dive for 15 minutes at 130 feet for a total run time of 29 minutes including deco on EAN 44 - deco time was minimal so we didn’t need to go to a higher % O2 so we just topped up a our 40 cf cylinders that were at EAN60 with clean air – and we stilled planned to dive our air computers until they cleared any deco obligations.

We dove the profile as outlined following our run time to depth right on the nose this time. Our last stop was planned to 15 feet and it was at 33 minutes into the dive my Oceanic (again only programmed on air) computer cleared any deco obligation. However the Suuntos didn’t clear until 50 minutes into the dive. I had the most fun watching the barnacles scooping in nutrients with their little feather like appendages; they were all over the wall at 15 feet.
 
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