Ill make a stab at it. when fecis hits the rotary oscillator the OW is taught to CESA which has "Max effective depth of the 60" area. Aow teaches additional skills to replace the last resort CESA for making deeper dives. Evern is those skills are no more than heightened awareness to better prevent ooa situations.
Changed depth limit for PADI Open Water
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marcushall
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My son in 14 years old, and just got "Junior Advanced Open Water" certified. We were discussing why the 70' limit, and I suggested that it was likely to stay well away from possible narcosis situations and a still developing brain. (Well, presumably developing..) If the 60' OW limit is not related to this, though, does it seem that the 70' junior limit is?
I believe you are correct in your suggestion. 70 ft is 10 ft deeper than the OW recommendation, so is sort of Advanced, but not much. I'd recommend when your son turns 15 and the "Junior" goes away that he do a 100 ft dive with an Instructor, or even do the Deep specialty.
kafkaland
Contributor
Use of the pony bottle is not a part of any of the standard AOW options. Your instructor evidently threw that in for you. If you take the deep diver specialty, you are supposed to breathe from an alternative air source during a simulated emergency decompression stop, and the pony bottle is an option for that. The AOW deep dive can count as the first dive of the deep diver specialty, but the alternative air source exercise is not on that first dive.
klausi
Contributor
A bit of an odd situation, since most people with OW cert only will have few dives, and do their AOW soon. It does not make sense that you should dive to 18 m only. In many places, the operators will understand. In some of the larger shops in QLD, that might be a problem.
george_austin
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Kev - OMG
---------- Post added August 8th, 2015 at 09:32 AM -------
---------- Post added August 8th, 2015 at 09:37 AM ----------
geez, whatever happened to Plan your dive and dive your plan? Personal responsibility in the nanny age, I suppose. If you can't plan your dive within your limits, maybe you should stop and find another sport like checkers or bicycling and this isn't directed at the original poster. Just a general observation.
I dont know anyone who would handle this OOA like as a rec diver while with in NDL limits. If it was my buddy i would give them air proceed directly to half depth at 60 ft per minute. Slow to 30 ft per minute to 20 ft and access the spg for a minute as whether to continue to the surface. My first concern would be to get them to functional CESA depth. 100 ft at 40-50 ft is a minute. 40-50' to surface is less than a minute if necessary Yes the dive site has a lot to do with it. Is there boat trafic ect. Your ascent scheds calls for 26 per diver. I figure
4 ata 1min (100 ft)
2.5 ata 1 min (40-50 feet) 50-60 ft change
1.5 ata 1-2 min (15-20 ft) 30+ ft change.
surface
your total is 26.5 and mine would be 7. This is a tech process that is being adapted to rec diving. Its not a very good fit.
Another aspect the i dont see is the time for depth change. no other normal ascent calls for ascend and stop every 10 ft for one minute. The time to ascend covers the stop times you list. A steady ascent at 30-60 is supposed to cover the stop time. Given that it should take 2-3 minutes from 100 to surface in a with in NDL ascent. I understan d the process you are using however i dont think it really applies to the situation you give.
Probably in more direct answer to the OP's question, OPINION, todays OW classes teaches skills for dives to 60 ft because of CESA as a last resort surface technique being a <60 ft method. To the OP. My class in the 60's was the same as the entire pipeline to Master diver in one course. Some other factors is that in my observation and dicsussions with OW's is that they dont know about rock bottom calculations and the like to be able to properly plan a deeper dive. Ill stick my neck out here. Most OW's dive till the air gets to 5-600 and then surface from their 40 ft depth. That process just doesnt work so well when starting at 100 ft. Relativily speeking you are doing a deep dive with shallow diving skills and planning.
4 ata 1min (100 ft)
2.5 ata 1 min (40-50 feet) 50-60 ft change
1.5 ata 1-2 min (15-20 ft) 30+ ft change.
surface
your total is 26.5 and mine would be 7. This is a tech process that is being adapted to rec diving. Its not a very good fit.
Another aspect the i dont see is the time for depth change. no other normal ascent calls for ascend and stop every 10 ft for one minute. The time to ascend covers the stop times you list. A steady ascent at 30-60 is supposed to cover the stop time. Given that it should take 2-3 minutes from 100 to surface in a with in NDL ascent. I understan d the process you are using however i dont think it really applies to the situation you give.
Probably in more direct answer to the OP's question, OPINION, todays OW classes teaches skills for dives to 60 ft because of CESA as a last resort surface technique being a <60 ft method. To the OP. My class in the 60's was the same as the entire pipeline to Master diver in one course. Some other factors is that in my observation and dicsussions with OW's is that they dont know about rock bottom calculations and the like to be able to properly plan a deeper dive. Ill stick my neck out here. Most OW's dive till the air gets to 5-600 and then surface from their 40 ft depth. That process just doesnt work so well when starting at 100 ft. Relativily speeking you are doing a deep dive with shallow diving skills and planning.
Kevrumbo
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Originally Posted by Kevrumbo
Look at this objectively from the perspective of Air Sharing in an Emergency Out-of-Air Contingency for two novice divers at 30m:
A Quick Contingency "Rock Bottom" Calculation and Gas Plan Estimate for Open Water. . .
Given: For a single 11 litre tank (AL80), a total of 11 litres/bar metric tank rating and a volume Surface Consumption Rate (SCR) of 22 litres/min -same as a pressure SCR of 2 bar/min*ATA (divide 22 litres/min by 11 litres/bar)- using an example NDL air dive to 30m (4 ATA) depth in Open Water.
Emergency Reserve/Rock Bottom pressure calculation, from 30 meters with one minute stops every 3 meters to the surface,
-->Just "tally the ATA's":
4.0
3.7
3.4
3.1
2.8
2.5
2.2
1.9
1.6
1.3
Sum Total: 26.5
Multiplied by 2 bar/min*ATA equals 53 bar Rock Bottom absolute reading remaining on your SPG. --this also happens to be the pressure in bar needed for one person in an emergency contingency to reach the surface with the above minimum decompression ascent profile.
So ideally for a two person buddy team, multiply 53 by 2 which is 106 bar for both to reach the surface (sharing in a buddy Out-ot-Gas contingency).
But realistically, for two experienced divers stressed: 106 bar plus 30% of 106 bar equals 138 bar Rock Bottom SPG reading.
For two novice divers stressed: 106 bar plus 100% of 106 bar equals 212 bar (!!!)
--->obviously then, two novice divers on single 11L tanks should not be diving to 30m for any significant length of time. . .
The point is to have a gas management contingency plan -either as conservative as in my example with plenty of margin for error on a slow emergency air sharing ascent; or as arbitrarily loose or liberal as yours with a faster and hopefully in control ascent- and stay within that gas plan above the Diver's maximum certification limit.
The major lesson to learn in either mine or your example is to quantitatively & objectively show the drastic consequences to the novice open water diver buddy team on how truly fast a single tank supply can dwindle if going far beyond the 18m/60' Basic Open Water Certification Limit, for any significant length of time.
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