Two less than perfect dives...

[Qasar]

Well I'm a bit surprised that no-one is back to basic here.
I don't know your rules, in my club we have to surface with 50bars. Whatever minimum you choose, you have then to reverse engeneering:
ascent from 26m (or 23) after more than 30mn bottom time, you should not be far from the NDL, so you need a slow ascent. NOrmaly your computer calculate with 10 to 15m/mn, but a safer approach is below 10m/mn. (and I don't open the discussion about deep safety stops).
If you are an air hog (or stressed) lets take a SAC of 25l/mn
At 20m it's become 25*3=75 l/mn
At 6m safety stop 25*1.6=40l/mn
To ascent from 26m to 6m = 2mn minimum (more recommended).
during these two mn SAC is the average so around 60 l/mn, so 120l
with an Al80 of around 12l volume, it's 10b.
3mn at 6m safety stop: 120l again so 10bars
2 mn more from 6m to surface: 2/3 bars
So at the end of the day you need your security at the surface (50b) + 23b
if you start the ascent with 40b you will surface with 17b.
Of course if your SAC is below you will need less, these calculation are just to show that you need to plan your dive according to your SAC and then decide what you do, not starting ascent with 40b and being puzzled because you run out of air.

 

[maat1976]

No clue Qasar! At no point was I surprised that I had the air I did. In hind sight I needed to be more assertive with the DM to ascend on trouble dive 2. We were less than 10m and There was no need for him to give me his octopus other than maybe he thought I was worried from the dive previous.

Im with a different DM today and tomorrow who seems much more attuned to my gas consumption when I indicate 150, 100, and 50 bar (to ascend). The dive plans are also more tailored to me. I'm back for two more dives with the other guy day after next so we'll see how it goes. Tomorrow we're in Menjangan, which should be fun. We did Pemuteran today.

C

 

[Steve_C]

Agree with earlier post. DM was stretching your air supply. Common practice if conditions are right.

You need to talk to DM ahead of dive about what the plan is. If the idea is to let you use x bar of their air before doing ascent on your gas then you should know that ahead of time. You will be calmer if you know what he/she is doing.

Nervous tension = faster SAC unless I focus on relaxation at least for me. It does not matter if I am trying to heard a roaming dive group or a new dive or looking for something or excited by what I am seeing.

I had the reverse happen in Greece when doing a night dive with a private guide/DM. On the way back she kept getting closer and I kept moving further away so as not to bump her. Finally she got my attention and I figured out she wanted to borrow some air for a while. Turns out that she had grabbed a partially full tank and had underestimated how long I could dive on my tank. Enabled us to swim back under water rather than on the surface.

 

[diver 85]

Concerning dive 2----I had a very short acronym I used at the END of EVERY dive when I started out(this was before computers so you had to go by your watch for BT--it started 'when your head went under the water & ended @ the BEGINNUNG of your final ascent)..........It was simply "AT", stood for Air(dumping your BC) & Time(stopping your stop watch).........Still kinda sorta use it today--& yes I carry a dive watch AND USE IT for 2ndary BT........

 

[rick00001967]

In hind sight I'm not sure why the DM gave me his air on the wreck. I was at 50 at the beginning of ascent from maybe 10m max. He may have done this to check on me or help me conserve my air. Post safety stop I was at 40 bar.


C

sorry if this is repeating what anyone else has said.......if the guide saw you were "low" on gas it is common for them to allow you to breath from their supply. as a buddy of mine once said, "better to share because you want to, as opposed to sharing because you have to". letting you continue to breath from a "low" tank would not be the best option. and remember.....a guide should never allow any diver to surface alone. so he really could not allow you to go to the surface unless of course your buddy went with you. always better to stay together