Doing the math

[tursiops]

I remember our instructor teaching us the most simplistic air calculations when I was 13 yrs old. He said, if you plan for 1 cu-ft /min, it is hard (but not impossible) to get into trouble. Seems like that very reasonable approximation continues to be relevant 30 years later.

Although it makes you wonder how they took us on a training dive to 60 ft with no pressure gages and a reserve that was activated around 300 psi..

I think those J-valves operated around 700 or so, between 500-800 if I remember the specs.
And you got to ascend faster then, and no safety-stop nonsense. Ahh, nostagia is just not what it used to be.

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[dumpsterDiver]

I think those J-valves operated around 700 or so, between 500-800 if I remember the specs.
And you got to ascend faster then, and no safety-stop nonsense. Ahh, nostagia is just not what it used to be.

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Yeah we came up faster, but the pressure was not that high.. now you have me questioning my recollection. When i bought my first regulator I got a SPG.. I still had a few reserves, but did not like them.

 

[Ricky B]

Safety Stops have stayed fashionable as a method of adding a safety margin to the NDLs and giving a controlled break in the ascent, e.g. check for boats and things at the surface. They are not mandatory in any algorithm I know of nor are the penalized by most if not all computers, except maybe the Suunto algorithms :depressed:

A true safety stop is not penalized according to the Suunto Zoop manual:

The Recommended Safety Stop, as the name implies, is recommended. If it is ignored, there is no penalty applied to the following surface intervals and dives.

If you ascend too quickly, then the Zoop adds a mandatory safety stop:

If you continue to violate the Mandatory Safety Stop, the tissue calculation model is affected and the dive computer shortens the available no-decompression time for your next dive. In this situation, it is recommended to prolong your surface interval time before your next dive.

 

[DukeAMO]

You're right, I re-read the Mares Puck manual, and rather than requiring the safety stop, it will add deep stops if needed.
My computer didn't add any deep stops on either of these dives; another diver's Suunto did add a deep stop, so we took a break at about 40 feet for a minute or two for her.

However, please explain what this means to me, if the safety stop is always optional:
"[FONT=Helvetica, Arial, lucida grande, tahoma, verdana, arial, sans-serif]The Safety Stop is recommended after all dives (air supply and other considerations allowing), and required on those to 30 meters or greater, and those coming within three pressure groups of the no decompression limit." [/FONT]http://elearning.padi.com/company0/tools/RDP%20InsforUseMet.pdf
The PADI Recreational Dive Planner also says that the safety stop is "required" for those dives.

Does required mean required or not? And do you ignore this if you're diving with a computer?

 

[Basking Ridge Diver]

Interesting. AOW or equivalent is a prereq for Solo.

All I needed to show was 100 dives. No AOW or equivalent was a prereq - not sure why you would need AOW? They are not teaching you to dive - they are ensuring you comfortable under water and have the skill set to Solo - which I had minus the certification and pony...

However, please explain what this means to me, if the safety stop is always optional:
"The Safety Stop is recommended after all dives (air supply and other considerations allowing), and required on those to 30 meters or greater, and those coming within three pressure groups of the no decompression limit." http://elearning.padi.com/company0/tools/RDP%20InsforUseMet.pdf
The PADI Recreational Dive Planner also says that the safety stop is "required" for those dives.

Does required mean required or not? And do you ignore this if you're diving with a computer?

I dont want to blow this up in this forum but think of it this way - Recreational Scuba Diving does not have a "hard overhead" - you can always go to the surface at anytime for any reason. When you are REQUIRED TO STOP that is considered decompression diving - which is not recreational diving. I am not going to tell you to disregard your training or your computer - but I would do some research and decide for yourself.

My Veo 2.0 I can turn on or off - Deep Stops, Conservatism and Safety Stops or completely ignore them if I choose...

 

[tursiops]

All I needed to show was 100 dives. No AOW or equivalent was a prereq - not sure why you would need AOW? They are not teaching you to dive - they are ensuring you comfortable under water and have the skill set to Solo - which I had minus the certification and pony...

From the SDI instructor manual:
23.4 Student Prerequisites
1. Minimum age 21
2. SDI Advanced Diver or equivalent
3. Provide proof of 100 logged dives

I assume the prereq is in part because they want to insure you have some compass skills, for example.

 

[industrious95]

True. I actually knew that the ascent line would be a better place to hang on, but was having trouble applying it. I was the first of a group of six who ascended at the same time, and someone else got the spots on the ascent line that were above 20 feet and below the bar. :-( The captain said that we'd better not get away from the line, and if we did get blown off, we should deploy our SMBs and be prepared to wait at least an hour for them to come get us. So, I was a little overly careful to stay close to the hang bar. What worked reasonably well was keeping a very light grip on the bar, more for reference, and letting it go when it moved a lot, but I was pretty much finning the entire time. It wasn't scary or anything, but it was definitely work. Practice will definitely help.



It was a dedicated dive boat a couple hours off of the North Carolina coast, in the gulf stream, so it's a strong current at the surface. Waves were averaging about 3 feet; I think they'll run trips in up to 4-foot waves. The ascent line ran down from the bow, with the current flowing from bow to stern. The hang bar was directly below the boat, running from the ascent line toward the stern. The procedure was to finish your safety stop at the hang bar, then swim well below the propeller and ladder to the tag line, at least 10 feet behind the ladder. Surface, wait far enough back on the tag line that nobody can fall on you, and swim/pull your way back to the ladder along the tag line when it's your turn to get on the ladder. Wait 5 feet back until the crew says to go for it, then get up the ladder (a fins-on ladder) as quickly as possible. We ended up a good 20 feet or so behind the ladder on the tag line, so that was the swim back, and getting up the ladder with fins on was tough. They do exits with fins on and regulator in so you can swim back to the boat (or at least catch the tag line) if you fall off of the ladder. 2 or 3 people fell off each time we finished a dive. Exciting stuff, heh.

Sounds like you did pretty good with your hang, considering the number of divers there. We sometimes run into the same issue, only I usually go with a bunch of spearfishermen, so there's the extra element of spears bouncing around. I always hold mine at chest level, careful to point it away from any one else, but it can get crowded.

None of the boats I've been on in NJ have you take off your fins, same reason as you said. I got thrown off once on a rough day, it would really suck to not have your fins on. Nice reminder to keep the regulator in your mouth too.

 

[NorCalDM]

The dive to 100 fsw on air definitely had NDL as the limiting factor. The DM was checking computers frequently. On that dive, the anchor line was at about 80 fsw, so we got quite a few more minutes by moving up to the high point on the wreck after the guy with the most conservative computer ran out of time. I don't know why they would only offer air in the tanks, but that's what they did. I wouldn't choose that. They probably don't have Nitrox capability. Either that or they like to take their clients on short dives and get home in time for lunch.

The dive to 100 fsw on Nitrox was limited by PSI. I still had about 9 minutes left before reaching the NDL when we headed up to the upper deck at 90 fsw, and then the number went up even more. I forget to how much, maybe to 15 minutes remaining? It sure would have been nice to stay a few more minutes, but our pressure gauges said it was time to go.

Adding a pony bottle for emergencies is actually an intriguing idea. It's less to carry than a full second tank, and if you don't need it, you can use it again on the next dive, and the next dive...

They may not offer it because depth is a limiting factor for Nitrox depending on the mix you are using for example 32% at 1.4 ppo the MOD is aprox 106 fsw. You also still never said how much air you had when you got back on the boat? It's hard to make a judgement of what you should have when you leave the bottom with out knowing the whole story. You need to figure out your limits not what the DM says you should have he is going by the lowest common denominator "the out of shape diver that dives once a year and sucks air". When I'm diving on vacation I follow the rules of the dive op we are diving with but diving on my own here in CA there is nobody to tell me when to go up so I need to know my own limits.

 

[Basking Ridge Diver]

From the SDI instructor manual:
23.4 Student Prerequisites
1. Minimum age 21
2. SDI Advanced Diver or equivalent
3. Provide proof of 100 logged dives

I assume the prereq is in part because they want to insure you have some compass skills, for example.

Ah - I see what you mean - being a long time shore diver - compass skills are rather easy for me. I don't see any value in the AOW classes from what I read on SB - those skills will be learned over time in my opinion. For my son - I would like him to take the class in another year or so of diving - he has 30 or so dives in the last year - currents, low viz, 80 foot dives and so far he has done very well. But for me to take him on a dive boat in NJ - due to his age he needs AOW and a redundant air source.
In the old days with the J-valves we would surface from 50 or more feet - do a 360 for a visual, descend and continue the dive. Then we learned compass diving - so much easier... But back then - it was very minimalistic diving - J-Valve AL80, 7mm two piece, horse collar, good knife and a flag - maybe a catch bag and gauge when lobster season was open.

 

[tursiops]

Ah - I see what you mean - being a long time shore diver - compass skills are rather easy for me. I don't see any value in the AOW classes from what I read on SB - those skills will be learned over time in my opinion. For my son - I would like him to take the class in another year or so of diving - he has 30 or so dives in the last year - currents, low viz, 80 foot dives and so far he has done very well. But for me to take him on a dive boat in NJ - due to his age he needs AOW and a redundant air source.
In the old days with the J-valves we would surface from 50 or more feet - do a 360 for a visual, descend and continue the dive. Then we learned compass diving - so much easier... But back then - it was very minimalistic diving - J-Valve AL80, 7mm two piece, horse collar, good knife and a flag - maybe a catch bag and gauge when lobster season was open.

The best part of diving with a J-valve while lobstering was we could take off the pull-rods and use them to get the bugs out of their holes (tickle sticks were not allowed in Massachusetts) and then put the rods back on before surfacing. Not that I ever did that, of course....