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Re: Re: Andria Doria diving on todays Disc Channel


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Posted by ks on May 10, 2006 at 16:02:16:

In Reply to: Re: Andria Doria diving on todays Disc Channel posted by Dave on May 09, 2006 at 07:32:28:

In case you are wondering, here is an example of an open circuit profile for a dive to 225 ft for 25 mins. The bottom mix is TMX 15/60, the lean and travel mix is EAN50, and the final deco mix is 100% O2. The model is VPM-B.

At my level of conservatism (+3) and my respiratory minute volume (RMV), you would need twin 130s plus two 30+ cu ft deco bottles for a dive to this depth for this long. Most divers would use 40s for deco, however. I also use 40s.

As to whether the CCR divers could get away with anything smaller than 30s, I doubt it. Maybe you saw 30s and thought they were 20s on TV.

A CCR diver is able to deco more efficiently during the first phase of deco on bottom mix because the CCR keeps the ppO2 constant by varying the O2 fraction, whereas with open circuit the ppO2 is constantly decreasing during the ascent. That would explain smaller deco bottles for the CCR divers. However they would then not be able to use the deco bottles for bailout, if their CCR units failed for some reason.

And with a CCR you normally cannot buddy breathe either. Some of the newer CCR unit manufacturers claim that there is a switch mechanism on them that now allows you to buddy breath, but I haven’t ever seen it in real life.

CCRs are a great idea for filming. But other than that, I would not use them.


Decompression model: VPM-B

DIVE PLAN #1
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 3

Dec to 225ft (4) on Trimix 15.0/60.0, 60ft/min descent (EAN 50 TRAVEL MIX TO 30 FT)
Level 225ft 20:35 (25) on Trimix 15.0/60.0, 1.17 ppO2, 49ft ead, 70ft end
Asc to 160ft (27) on Trimix 15.0/60.0, -30ft/min ascent.
Stop at 160ft 0:50 (28) on Trimix 15.0/60.0, 0.88 ppO2, 28ft ead, 44ft end
Stop at 150ft 1:00 (29) on Trimix 15.0/60.0, 0.83 ppO2, 25ft ead, 40ft end
Stop at 140ft 1:00 (30) on Trimix 15.0/60.0, 0.79 ppO2, 22ft ead, 36ft end
Stop at 130ft 1:00 (31) on Trimix 15.0/60.0, 0.74 ppO2, 19ft ead, 32ft end
Stop at 120ft 2:00 (33) on Trimix 15.0/60.0, 0.69 ppO2, 15ft ead, 28ft end
Stop at 110ft 2:00 (35) on Trimix 15.0/60.0, 0.65 ppO2, 12ft ead, 24ft end
Stop at 100ft 3:00 (38) on Trimix 15.0/60.0, 0.60 ppO2, 9ft ead, 20ft end
Stop at 90ft 4:00 (42) on Trimix 15.0/60.0, 0.56 ppO2, 6ft ead, 16ft end
Stop at 80ft 5:00 (47) on Trimix 15.0/60.0, 0.51 ppO2, 3ft ead, 12ft end
Stop at 70ft 3:00 (50) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 3:00 (53) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 4:00 (57) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 6:00 (63) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 10:00 (73) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 5:00 (78) on Oxygen, 1.60 ppO2, 0ft ead
Stop at 15ft 27:00 (105) on Oxygen, 1.45 ppO2, 0ft ead
Asc to sfc. (105) on Oxygen, -30ft/min ascent.

Off gassing starts at 180.6ft

OTU's this dive: 126
CNS Total: 57.2%

189.2 cu ft Trimix 15.0/60.0
30.0 cu ft Nitrox 50.0
23.7 cu ft Oxygen
242.8 cu ft TOTAL


DIVE PLAN #2
Surface interval = 0 day 3 hr 0 min.
Elevation = 0ft
Conservatism = + 3

Dec to 225ft (4) on Trimix 15.0/60.0, 60ft/min descent (EAN 50 TRAVEL MIX TO 30 FT)
Level 225ft 20:35 (25) on Trimix 15.0/60.0, 1.17 ppO2, 49ft ead, 70ft end
Asc to 160ft (27) on Trimix 15.0/60.0, -30ft/min ascent.
Stop at 160ft 0:50 (28) on Trimix 15.0/60.0, 0.88 ppO2, 28ft ead, 44ft end
Stop at 150ft 1:00 (29) on Trimix 15.0/60.0, 0.83 ppO2, 25ft ead, 40ft end
Stop at 140ft 1:00 (30) on Trimix 15.0/60.0, 0.79 ppO2, 22ft ead, 36ft end
Stop at 130ft 1:00 (31) on Trimix 15.0/60.0, 0.74 ppO2, 19ft ead, 32ft end
Stop at 120ft 2:00 (33) on Trimix 15.0/60.0, 0.69 ppO2, 15ft ead, 28ft end
Stop at 110ft 2:00 (35) on Trimix 15.0/60.0, 0.65 ppO2, 12ft ead, 24ft end
Stop at 100ft 3:00 (38) on Trimix 15.0/60.0, 0.60 ppO2, 9ft ead, 20ft end
Stop at 90ft 4:00 (42) on Trimix 15.0/60.0, 0.56 ppO2, 6ft ead, 16ft end
Stop at 80ft 5:00 (47) on Trimix 15.0/60.0, 0.51 ppO2, 3ft ead, 12ft end
Stop at 70ft 3:00 (50) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 3:00 (53) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 4:00 (57) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 6:00 (63) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 10:00 (73) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 5:00 (78) on Oxygen, 1.60 ppO2, 0ft ead
Stop at 15ft 32:00 (110) on Oxygen, 1.45 ppO2, 0ft ead
Asc to sfc. (110) on Oxygen, -30ft/min ascent.

Off gassing starts at 180.6ft

OTU's this dive: 134
CNS Total: 75.1%

189.2 cu ft Trimix 15.0/60.0
30.0 cu ft Nitrox 50.0
27.3 cu ft Oxygen
246.5 cu ft TOTAL


DIVE PLAN COMPLETE




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