Posted by northcoast diver on January 23, 2005 at 13:51:22:
In Reply to: Re: Big weekend in Monterey. posted by seahunt on January 22, 2005 at 18:29:44:
I have to work this weekend, or else I would stop by to meet you Eric.
TDI divides up their tech training into the classical nitrox, deco, then trimix portions. I suppose that comes from IANTD. NAUI does something similar.
By the time you get to trimix, the TDI instructors want to make sure that you have minimized your weighting for neutral buoyancy, and that you have really good control of your buoyancy and trim.
Whereas my normal weighting with thick thermals up here is close to 30 lbs (AA-Frank will surely gasp because that sounds so un-cool), with all my tech gear on, my weigh belt is only 10 lbs. The tech gear adds a lot of weight, including the steel tanks, bands, manifold, aluminum backplate, 5 to 6 first stages, 4 to 6 2nd stages, lights, gauges, reels, and argon bottle.
For the early dives, to 150 and 180 ft, any pair of doubles is fine, even twin 80s. Eventually, for dives to 250 and 300 ft however, you would need twin 130s, if you want to stay at depth for 20 minutes. Otherwise your dive time is going to end up being a lot shorter. Or else you would need to skimp on a full Rule of Thirds.
Below is my standard dive plan, from V-Planner, for a 300 ft dive followed by a 250 ft repetitive dive. Note the gas consumption totals. My RMV is 0.75 cu ft per minute while diving, and 0.5 cu ft per minute while on deco.
Note that TDI does not teach repetitive deco diving (to my knowledge -- and something in the manual discouraged it as well). You need to learn that on your own, either from an advanced tech instructor, or from other NAUI tech literature. The general rule is a minimal 3 hour surface interval, and a limit of two dives within 24 hours. For long exposures like this, it is good to have a P-valve as well.
V-Planner 3.43 by R. Hemingway, VPM code by Erik C. Baker.
Decompression model: VPM-B
DIVE PLAN #1
Surface interval = 5 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 3
Dec to 300ft (5) on Trimix 12.0/65.0, 60ft/min descent.
Level 300ft 14:20 (20) on Trimix 12.0/65.0, 1.21 ppO2, 64ft ead, 84ft end
Asc to 230ft (22) on Trimix 12.0/65.0, -30ft/min ascent.
Stop at 230ft 0:40 (23) on Trimix 12.0/65.0, 0.95 ppO2, 44ft ead, 59ft end
Stop at 220ft 1:00 (24) on Trimix 12.0/65.0, 0.92 ppO2, 41ft ead, 56ft end
Stop at 210ft 1:00 (25) on Trimix 12.0/65.0, 0.88 ppO2, 38ft ead, 52ft end
Stop at 200ft 1:00 (26) on Trimix 12.0/65.0, 0.85 ppO2, 35ft ead, 49ft end
Stop at 190ft 1:00 (27) on Trimix 12.0/65.0, 0.81 ppO2, 32ft ead, 45ft end
Stop at 180ft 1:00 (28) on Trimix 12.0/65.0, 0.77 ppO2, 29ft ead, 42ft end
Stop at 170ft 1:00 (29) on Trimix 12.0/65.0, 0.74 ppO2, 26ft ead, 38ft end
Stop at 160ft 2:00 (31) on Trimix 12.0/65.0, 0.70 ppO2, 23ft ead, 35ft end
Stop at 150ft 2:00 (33) on Trimix 12.0/65.0, 0.66 ppO2, 20ft ead, 31ft end
Stop at 140ft 2:00 (35) on Trimix 12.0/65.0, 0.63 ppO2, 17ft ead, 28ft end
Stop at 130ft 2:00 (37) on Trimix 30.0/30.0, 1.48 ppO2, 49ft ead, 81ft end
Stop at 120ft 1:00 (38) on Trimix 30.0/30.0, 1.39 ppO2, 44ft ead, 74ft end
Stop at 110ft 3:00 (41) on Trimix 30.0/30.0, 1.30 ppO2, 39ft ead, 67ft end
Stop at 100ft 2:00 (43) on Trimix 30.0/30.0, 1.21 ppO2, 34ft ead, 60ft end
Stop at 90ft 3:00 (46) on Trimix 30.0/30.0, 1.12 ppO2, 29ft ead, 53ft end
Stop at 80ft 4:00 (50) on Trimix 30.0/30.0, 1.03 ppO2, 24ft ead, 46ft end
Stop at 70ft 3:00 (53) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 4:00 (57) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 6:00 (63) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 8:00 (71) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 11:00 (82) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 7:00 (89) on Oxygen, 1.60 ppO2, 0ft ead
Stop at 15ft 32:00 (121) on Oxygen, 1.45 ppO2, 0ft ead
Asc to sfc. (121) on Oxygen, -30ft/min ascent.
Off gassing starts at 248.4ft
OTU's this dive: 161
CNS Total: 72.8%
189.2 cu ft Trimix 12.0/65.0
30.0 cu ft Trimix 30.0/30.0
37.0 cu ft Nitrox 50.0
28.9 cu ft Oxygen
285.2 cu ft TOTAL
DIVE PLAN #2
Surface interval = 0 day 3 hr 0 min.
Elevation = 0ft
Conservatism = + 3
Dec to 250ft (4) on Trimix 15.0/60.0, 60ft/min descent.
Level 250ft 15:10 (20) on Trimix 15.0/60.0, 1.28 ppO2, 57ft ead, 80ft end
Asc to 180ft (22) on Trimix 15.0/60.0, -30ft/min ascent.
Stop at 180ft 0:40 (23) on Trimix 15.0/60.0, 0.97 ppO2, 34ft ead, 52ft end
Stop at 170ft 1:00 (24) on Trimix 15.0/60.0, 0.92 ppO2, 31ft ead, 48ft end
Stop at 160ft 1:00 (25) on Trimix 15.0/60.0, 0.88 ppO2, 28ft ead, 44ft end
Stop at 150ft 1:00 (26) on Trimix 15.0/60.0, 0.83 ppO2, 25ft ead, 40ft end
Stop at 140ft 1:00 (27) on Trimix 15.0/60.0, 0.79 ppO2, 22ft ead, 36ft end
Stop at 130ft 1:00 (28) on Trimix 30.0/30.0, 1.48 ppO2, 49ft ead, 81ft end
Stop at 120ft 1:00 (29) on Trimix 30.0/30.0, 1.39 ppO2, 44ft ead, 74ft end
Stop at 110ft 1:00 (30) on Trimix 30.0/30.0, 1.30 ppO2, 39ft ead, 67ft end
Stop at 100ft 2:00 (32) on Trimix 30.0/30.0, 1.21 ppO2, 34ft ead, 60ft end
Stop at 90ft 2:00 (34) on Trimix 30.0/30.0, 1.12 ppO2, 29ft ead, 53ft end
Stop at 80ft 2:00 (36) on Trimix 30.0/30.0, 1.03 ppO2, 24ft ead, 46ft end
Stop at 70ft 2:00 (38) on Nitrox 50.0, 1.56 ppO2, 32ft ead
Stop at 60ft 3:00 (41) on Nitrox 50.0, 1.41 ppO2, 26ft ead
Stop at 50ft 4:00 (45) on Nitrox 50.0, 1.26 ppO2, 20ft ead
Stop at 40ft 5:00 (50) on Nitrox 50.0, 1.10 ppO2, 13ft ead
Stop at 30ft 7:00 (57) on Nitrox 50.0, 0.95 ppO2, 7ft ead
Stop at 20ft 5:00 (62) on Oxygen, 1.60 ppO2, 0ft ead
Stop at 15ft 24:00 (86) on Oxygen, 1.45 ppO2, 0ft ead
Asc to sfc. (86) on Oxygen, -30ft/min ascent.
Off gassing starts at 196.9ft
OTU's this dive: 121
CNS Total: 72.6%
143.0 cu ft Trimix 15.0/60.0
18.0 cu ft Trimix 30.0/30.0
24.4 cu ft Nitrox 50.0
21.5 cu ft Oxygen
206.9 cu ft TOTAL
DIVE PLAN COMPLETE