Bent. I guess it really can happen to me.

[Tigerman]

...
yadayada fingerwagging
...

Or you could use the PADI tables and go group Q after the first dive to group E after the SI, giving you an RNT of 18min and and rounded up an ABT of 46 minutes for a TBT of 64 minutes and "barely" above the 56 minutes of NDL - without taking into account the fact that his max depth was less than the 60 feet nor any multileveling..

 

[boulderjohn]

You are certainly right that using square profiles and tables, you were considerably in violation of NDLs, especially given what you say are the ascent rates. DAN's published study on ascent rates compared 60FPM, 30 FPM, and 10 FPM ascent rates, and the 10 FPM ascent rate was the worst. If you were considerably slower than 30 FPM, you were actually adding more bottom time to a multi-level dive. In analyzing the profile of two friends who got bent, we thought their very prolonged (and unplanned) ascent rate was the biggest of several contributing factors.

On the other hand, I have heard that roughly 50% of DCS cases are unexplained (a term I prefer to "undeserved"). It sounds like yours was relatively mild and may have been completely resolved without the chamber ride. Perhaps yours is only one example of one of those cases that defies the statistics.

 

[Scubadude_LA]

If the OP is correct on his profiles, the hit is undeserved Planned or Not:

Straight from V-Planner: Square Profile on Air no Safety Stop!

DIVE PLAN #1

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

Dec to 56ft (1) Air 50ft/min descent.

Level 56ft 41:53 (43) Air 0.57 ppO2, 56ft ead

Asc to 20ft (44) Air -30ft/min ascent.

Surface (44) Air -30ft/min ascent.

OTU's this dive: 8
CNS Total: 5.8%
71.0 cu ft Air
71 cu ft TOTAL
　
DIVE PLAN #2
Surface interval = 0 day 0 hr 43 min.
Elevation = 0ft
Conservatism = + 2

Dec to 56ft (1) Air 50ft/min descent.

Level 56ft 43:53 (45) Air 0.57 ppO2, 56ft ead

Asc to 20ft (46) Air -30ft/min ascent.

Surface (46) Air -30ft/min ascent.

OTU's this dive: 8
CNS Total: 10.3%
74.2 cu ft Air
74.2 cu ft TOTAL

 

[uncfnp]

Jim and Tigerman,

Just to clarify for my own knowledge, isn't ABT from beginning of descent to beginning of ascent? So shouldn't the time at the safety stop be subtracted from the total when using tables?

 

[Scubadude_LA]

Thanks for sharing your story.
Have you started takiong any new meds like blood pressure medication before this dive?

 

[Jim Lapenta]

Jim and Tigerman,

Just to clarify for my own knowledge, isn't ABT from beginning of descent to beginning of ascent? So shouldn't the time at the safety stop be subtracted from the total when using tables?

I was never taught to subtract safety stop time. And don't teach to do that either. And in this case 3 minutes is not going to make much difference. And remember the safety stop is optional so it may actually be skipped, so why subtract it? I teach students to err on the side of conservatism and to plan and track dives as square profiles as my agency requires me to. Even though we know they are not. Standards require me to teach them as such. My PADI classes were all based on square profiles when I got certified. I was not taught to fly the computer. In fact just the opposite. I guess now it's different.

If the computer says it's ok no foul. Just don't expect me to do it. Or dive with those who do.

 

[chrpai]

I was never taught to subtract safety stop time. And don't teach to do that either.

I was. I was taught to use bottom time not total dive time. If I went to 90' for 25minutes and then used 3 minutes to ascend and 3 minute for a stop and 1 minute to ascend to record it as 25 minutes.

 

[redacted]

Doesn't seem fair to call something a deserved hit if you don't know the full profile. Taking max depth and assuming square doesn't seem right to me.

Regarding the "short" 40+ minute surface interval, what's wrong with that? Even assuming a square profile that doesn't put you into the W, X, Y, Z groups that PADI RDP requires a 1 hour SI for. I know the boats I go on < 1 hr SI is normal. 1/2 hour to get to first site, 1 hours in the water, 1 hour to get to the next site, 1 hour in the water and 1/2 hour to get back = 4 hour charter. It doesn't always go that smooth so 45 minutes is likely.

Not much unless you shorten that SI so the boat can get home 15 minutes earlier unless someone happens to get bent. Another 20 minutes and this series would have been back on the tables after adjusting for ascent times and rest stops.

 

[MalibuJerry]

So here is the problem which you probably did not realize when you were doing these dives. If you run v-planner at conservative level +3 then your plan with 3 minute stops at 10' seems fine. But if you add just a couple of feet in depth and a couple of minutes (60' and 45m) to the dive you end up with 14 minutes of deco for your second dive. So this dive plan was on the ragged edge of a decompression obligation and you could be affected by surface pressure and the fluctuations in depth due to surface waves while doing your 3 minute stops. I think the lesson here is for dives that are near ndl's, particularly those that are repetitive dives, one ought to look at the sensitivity of the dive plan and if it is sensitive, go with a more conservative dive plan. Since we are all different even on different days due to hydration, rest and a host of other factors. The bad news is that those who are recreational divers sometimes get "undeserved hits" for the reasons outlined in your dive profile and they typically do not do dive profile analysis prior to the dive.

All of this argues for longer 10' stops as it builds in some more margin.

 

[Tigerman]

I was. I was taught to use bottom time not total dive time. If I went to 90' for 25minutes and then used 3 minutes to ascend and 3 minute for a stop and 1 minute to ascend to record it as 25 minutes.

I wasnt, if I go in at 09:00 and out at 10:00 its 60 minutes as far as the tables is concerned, regardless of how long my safety stop was or how long I used to ascend.
Thats actually somewhat a problem with not including ascent - it may be a lot slower than the recommended MAX ascent rate..