Ascending without a dive computer
- Thread starter Chris Richardson
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barth
Contributor
Can you provide a scientific basis and research supporting it that the gradient factors you use and/or algorithm is ok to compare to your body.
And what if you are diving in cold/warm water what do you change and how do you still know it is ok to compare to your body?
If it is just a couple or minutes less or more bottom time then it’s just details. Nobody can assure you which methods is best for your body which day... Look at the forresst and not at the trees.
Planning is just a tool to do the dive. You only compare you body to a theoretical model. Nobody can assure you that your planning is perfect, I can assure you it is not....
Photo Girl
Registered
Good for you. Plan your dive with the tables and use your computer. Never ride the NDL line on your computer.Ok, ok, guys! Right, l have bitten the bullet and bought a used Suunto Gekko dc in the interim. I do plan to still use my Divemaster watch, RDP and eRDP as it would be stupid to let them go to waste. Thanks for your help, input and advice guys
caruso
Banned
A good analogy can be made for a car GPS system vs a map and a dive computer versus a bottom timer and tables.
Sure you could use a map, a ruler, and a pen when planning your next road trip, and draw lines on the map and estimate your travel time and arrival time, and you'd get there eventually and you could tell everyone that you don't need a fancy car GPS and people that use car GPS devices don't know what they're doing and feel they can't drive safely without a car GPS system but that would be a bit shortsighted. Because there's a lot more useful information in GPS devices that can make the trip easier, faster, more convenient, more pleasant, and yes, even safer.
The car GPS can calculate real time data on the fly, such as accidents, traffic, and construction delays and stop offs to take a piss or grab a bite to eat, and provide route alternatives while constantly recalculating and adjusting arrival times and mileage so that you know what time you'll arrive which can be rather useful especially when coordinating with other people or arriving at an event. A car GPS can also provide information such as where to find enroute gas stations, restaurants, strip joints, medical care, and other useful data.
You don't find too many people using maps and pens and rulers nowadays do we? For the same reason we don't find too many divers using bottom timers and tables. The technology we have available today is smart, accurate, easy to use, cheap and reliable- although on that last point there are occasionally technology failures- in which case a diver can protect him or herself by carrying a cheap backup computer.
Of course the analogy is not perfect, but it's close.
When comparing dive computers to bottom timers and tables, computers provide the following advantages that tables and bottom timers do not:
1- Even in the unlikely scenario that a diver follows their exact dive plan and doesn't deviate from it, there is no way a diver can calculate their exact depths and times and convert that to N or 02 absorption during a typical dive when they are constantly ascending and descending (even if it's only a few feet here or there), at best they have to round off several times, and they will almost always be forced to shorten their dive because they must use the more conservative, deeper depth calculations. A divers brain will never be a match for a computer- unless perhaps you've got autism like the dude in Rain Man- and even then it's going to be a lot of effort to constantly monitor your depth and time and recalculate on the fly.
2- Computers provide real time feedback and predict the dive time remaining at any particular moment based on calculations that can be derived from as many as 4 different factors including depth, time, 02 and N limitations.
3- Computers take a lot less time and effort and allow the diver to spend more time looking at the wreck or the pretty fish rather than screwing around with slates and performing calculations and remembering them while also trying to enjoy the dive itself.
4- Many computers store dive data (including gas consumption on air integrated models) and allow it to be downloaded to a dive log and create a profile showing times and depths during the dive which if nothing else is pretty cool compared to jotting some notes in a paper log book or manually entering basic data- at any rate its a huge time saver being able to simply pull the numbers off the computer into a digital log book and add a few notes.
5- Other important information is right there on the screen including temperature and time of day and ascent rate (the original topic of this thread).
There is not one valid reason to use dive tables and bottom timers over a dive computer other than perhaps for the sake of using vintage dive gear such as the guys who use early generation regulators and dive with no BCD because it's more "pure" or something of that nature.
Bühlmann's research was extensive, and there have been a number of other studies I have used to determine my decisions on GFs. I do not do this willy-nilly.
We had a recent thread about this, and the word we got about the origin of min deco was that it started as a training exercise of GUE Fundamentals. Students ascended like that in order to give them practice dong staged decompression so they would be ready for the technical training that followed. It was not based on any science saying that was a good way to ascend. It has stuck around, though, and it has become a standard for some people.
I was trained to do this years ago, BTW. It was my standard practice for a while. It was one of the things I questioned, and the more questions I asked, the more apprehensive I became. The standard answer seemed to be "because I said so." So I finally became a thinking diver and relied more on science than doing what I was told.
Dark Blue
Banned
A dive computer is to a bottom timer as a digital thermostat is to an old thermostat with the slider for temperature.
The digital thermostat constantly monitors the temperature and adjusts accordingly on a dynamic basis. It can be set so that the room temperature is lower during the winter or higher during the summer during periods that comfortable temperatures are not required. The result is typically a large savings in energy and $. The slider thermostat either needs to be adjusted several times per day to get something close to the effect of a digital thermostat or if left as it is, a huge waste of energy and money. The technology is available, why not use it other than because "I like to do it the old way".
The digital thermostat constantly monitors the temperature and adjusts accordingly on a dynamic basis. It can be set so that the room temperature is lower during the winter or higher during the summer during periods that comfortable temperatures are not required. The result is typically a large savings in energy and $. The slider thermostat either needs to be adjusted several times per day to get something close to the effect of a digital thermostat or if left as it is, a huge waste of energy and money. The technology is available, why not use it other than because "I like to do it the old way".
scrane
Contributor
As a rule of thumb, without any other reference as to your ascent speed, go with the bubbles.
barth
Contributor
Actually I do have navigation on my smartphone and also in my car. But I don’t use it that often. When I go to work, diving, visiting friends and things like that I don’t need it. I don’t like the voice in my car telling me what to do. I don’t like it to set my navigation.
It is the same like diving. Most of the dives I do are shallow dives. It is very easy to make a diveplan for me, even a multilevel dive. I don’t have to use my smartphone or wetnotes. I don’t have to change setting in my computer. I don’t have to put in the right nitrox mixture.
Tech 1 dives is the same. For most tech 1 dives I don’t need to open my wetnotes or deco software on my smartphone. I don’t have to set the right mixtures. I don’t have to do gasswitches at my computer.
Because me and my buddy did plan the dive in details most of the time it saves a lot of time underwater because we don’t need to communicate bottomtimes and deco.
When I started diving I did use a computer, that was in 2004 till 20066 I think. I’m using a computer in gauge mode for 12 years now.
For the dives I do a computer doesn’t give me more bottomtime. Most of the dives I thumb is because low temperature and minimum gas.
1 My planning is pretty accurate. It is not a big problem if I could do 1 or 2 minutes more bottomtime or 1 or 2 minutes less deco.
2 Your computer can tell you the divetime is left at the depth you are diving now. But it can’t give you the dive time if it is a multilevel dive and it does not know your plan. I can tell you that underwater.
3 I can’t remember when I opened my wetnotes underwater for checking tables. I did plan the dive. Most of the times this mean I dive the plan. If the plan changes I can change my planning without checking tables. After 12 years of diving without a computer this is no problem for me anymore.
4 If my computer is in gauge mode I can still download data. I did that for 200 dives or something like that. I did check the profile. But I did stop logging my dives. If I really want to tell I can tell you where I did dive when. I do use my camera for almost every dive. Most of the divesprofiles I don’t care. Sometimes I do check a profile after the dive. But that is it’s a profile that is different than dives I did before.
5 Sometimes more info isn’t better. I like a display with only info I need/want. I don’t care about ascent rate and time of the day.
But thank you for your response. It took me a long time to find out why I do like my computer in gauge mode.
I do understand what you mean. But if you have 3 average divers, one would have a PFO. What I mean is that it is just theorie. There are also a lot of factors like temperature , dehydration and more. It is hard to tell which model and or gradient factor will work best for a diver. Nobody can actually tell me if my diveplanning is good or not good. It’s not black/white like one planning is good or another is wrong. It is just a grey area. But if I do almost the same dive as you do and use your methode, the planning wouldn’t be perfect. Prefect would be if I do no minute more stops than I need. Because in the perfect situation you don’t want to spent more time doing deco than you need to. Or is the perfect planning when you are really concervative and doing a lot more deco than you need?
Maybe a method is not validated. But everybody decide what he/she uses. But if there is an update of a divecomputer or deco software, what do you do? Do you check the software by yourself and check what they did exacly change or do you trust the software?
I did change things after courses. I did change my gf in my iphone decosoftware.
Thank you for your response. I will think about it. There will be a day when I will put my computer in oc tech mode and give it a try (again) ;-)
I do the same thing I have always done. I read carefully and make a decision. I have made a number of changes in my decompression practices over the years, and each change was carefully considered. In the past couple of years we on ScubaBoard have been blessed (or cursed, depending upon your point of view) with several rollicking debates that included some of the most famous names in decompression science, with references to all the major studies. I read those very, very carefully, and my current plans are based on the decisions I made during those debates.
In contrast, during a Webinar back in the days when I was learning to use Min deco, the owner of the agency was explaining the approved decompression process, a process that was not only different from ALL the strategies commonly used by other divers, that difference was trumpeted as proof that all the others were wrong. One of the students on the Webinar asked for the science behind that approach. "You have to have faith," the owner of the agency said. "Faith in you?" she asked. "Yes," he answered.
So, there you have it. Two approaches to choosing a decompression strategy. I prefer the first.
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