bottom time definition?

[Allen42]

We DON'T trust decompression software. We cross reference the output with our own past experience and other models and softwares before we choose to use the profile on a dive. Even then we often use the software output as a starting point and modify the progile from there to suit out tasts. At least we do that until we gain some confidence in a model or piece of software.

I think this may be a bit altruistic. Perhaps this was your pattern, but I'd be willing to bet that for every one of you, there at least two who said, hey everyone seems to use "digiwidgit", so it must be safe.

Same with people and computers. Same with the tables. Where I'm headed is not into an argument with you, but more of a fascinating thought process about trust and faith. It seems to me that in this sport, you can't KNOW something until it or it's converse is proven false, upon which you might die. Wow.

I think most of us are ok with "if it's good enough for most people, then it's good enough for me". So, let's go back to the boat. A person of authority says, here's the plan... and everyone on board nods ands says sounds good. The planner and several of the other divers are all considered to be competent planners, so our specimen trusts them and says "ok, I'm in". Sounds just as realistic as jimbobjoe diver asking a tech buddy, "hey, who's deco formulas, tables, software you using these days?" and figuring they're good enough for themselves. I know of oldtimers who approximate deco. I'm even willing to bet that you probably have blown a plan and done at least one seat-of-your-pants deco profile.

Back to part of my point. I don't think this sport is as regimented as some of the hardcore divers want to make it. Actually, as often as the models, theories, limits, and the "rules" change, I'm sure this sport can't be accurately regimented. Most, if not all, of us did many things "before we knew better" and lived. It isn't more or less dangerous or wrong now that we're more informed, right?

Sorry for the bit of a ramble, and the trolling aspects of this post, but I like to think, hear, and review both sides of things in order to learn.

 

[MikeFerrara]

I think this may be a bit altruistic. Perhaps this was your pattern, but I'd be willing to bet that for every one of you, there at least two who said, hey everyone seems to use "digiwidgit", so it must be safe.

I don't know many people who do much deep diving and decompression that do that. Most dovers I know build up the amount of decompression they do over time and pay attention to how they feel making changes to their schedules accordingly. Some divers deco more agresively and get out of the water much faster and others add decompression time. The software itself is set up for that to some extent. In the case of vplanner you have 4 choices of conservatism and can change the minimum stop time at gas switches. In other software you have gradient factors that can have a huge effect on the output of the program for a given dive.

Same with people and computers. Same with the tables. Where I'm headed is not into an argument with you, but more of a fascinating thought process about trust and faith. It seems to me that in this sport, you can't KNOW something until it or it's converse is proven false, upon which you might die. Wow.

That's why we practice a new thing forst and go only a little further each time. With luck the screw ups will then be little ones and we get another chance. With that line of thought taking a big jump forward while having blind faith in anothers ability to apply principles that we don't understand would be a bad ide.

I think most of us are ok with "if it's good enough for most people, then it's good enough for me". So, let's go back to the boat. A person of authority says, here's the plan... and everyone on board nods ands says sounds good.

Here's the kicker...While this might be common, I can't believe that people do it. The captain and the DM are in charge on the boat. They can set maximums times and whatever for the dive. Beyond that there is NO SUCH THING as a person of authority when it comes to your decompression planning.

Following a DM or anyone else on a deep multilevel dive with no way to plan or monitor decompression status yourself goes against everything that's taught in every scuba class that I know of. I disagree with much of what the agencies do but not a single one is screwed up enough to tell you to do multilevel computer dives without your own computer.

The planner and several of the other divers are all considered to be competent planners, so our specimen trusts them and says "ok, I'm in". Sounds just as realistic as jimbobjoe diver asking a tech buddy, "hey, who's deco formulas, tables, software you using these days?" and figuring they're good enough for themselves. I know of oldtimers who approximate deco. I'm even willing to bet that you probably have blown a plan and done at least one seat-of-your-pants deco profile.

I do calculate decompression sometimes without tables or a computer but that's just because by following certain rules you can modify the schedule to fit different profiles. The root schedule starts with software or tables basically. We don't so much blow a plan as we do have a flexible plan. It's not an exact science.

As an example of not trusting another tech divers profiles...I wouldn't dive the profiles my former trimix instructor does. He uses dplan with the upper gradient factor at 100%. I use 85%. He gets out of the water much faster than I do. Any one who jumps streight to his schedule all at once is asking for it. When we dived together the group used a schedule that was agreeable to all which means it was more like what I use than what he would use if I wasn't there.

Back to part of my point. I don't think this sport is as regimented as some of the hardcore divers want to make it. Actually, as often as the models, theories, limits, and the "rules" change, I'm sure this sport can't be accurately regimented. Most, if not all, of us did many things "before we knew better" and lived. It isn't more or less dangerous or wrong now that we're more informed, right?

You're right. We are always learning more and the rules or at least the popular methods change. That means there are plenty of decisions to be made by each individual diver. I wouldn't leave it up to some one else though.

Sorry for the bit of a ramble, and the trolling aspects of this post, but I like to think, hear, and review both sides of things in order to learn.

Nothing wrong with throwing another slant on it for the sake of discussion

 

[GoBlue!]

To the original question, when I certified, NAUI defined bottom time as start of descent until precautionary safety stop. PADI defined it as start of descent until start of ascent. Not sure if that's still the case with their current tables.

Jim

 

[Pilaar39]

Once again, I thank all that took the time to reply, although it did at times move off into meta discussions.

I am going to go back to the dive shop that trained me and get their perspective.

I am also going to pop over to the equipment forum on this board to get some suggestions on computers for a novice. It appears from this discussion that it is pretty well a must-have.

Once again, many thanks for your input.

 

[s7595]

pilaar39
I too am new with under 30 dives . my advice buy an aries atomos 2 computer , they sell for 400 cdn out in the west ,as for your dive think back to the actualy time you were at 100' if it was less than 20min do not lose any sleep , if it was more than you did the deco stops and were okay , i have been to a hunderd a few times stay about 2-5 mins then come up to around 70-50 and then finish at 15 ' for 3-5 min , I dive with a the comp I told you about ,what I like is the nitgron bar nice and big watch that close and stay out of the yellow zone ,just my 2cents