Why do some agencies recommend using a bottom timer instead of a computer

[PfcAJ]

Jablonski's "Baker Dozen for not using a dive computer" is at least 15 years old. Technology has advanced a lot since it was written.

A lot of those points are still true, however.

 

[Kevrumbo]

Learning, knowing and memorizing what a particular deco schedule is going to be after so many iterations of the same range of depth profiles over years of experience, an actively diving and veteran Tech & Overhead Diver can function well with just a digital bottom timer, SPG and wetnotes of contingency profiles and tables.

Obviously where the current technology Dive Computer really has the greatest utility now is for the beginning to novice Technical Diver, where vital practice and experience by rote is just starting to be accumulated and learned. There's nothing wrong with promoting the "Thinking Diver" and not to "blindly follow your computer", but IMHO there should always be a option to revert to dive computer over referencing a gauge bottom timer as needed for the beginner technical diver.

 

[tomfcrist]

Well point 1 and 13 are still valid...the rest are somewhere between questionable and just not true with modern computers.

 

[tbone1004]

IMO
2 is no longer valid
3 is of debatable validity in it's original context, even less so now since you can actually plan the dive the way the computer is going to calculate it
4 is still applicable with some computers, not with shearwater
5 is no longer valid
6 is obviously true, that's what you are using the computer for but it's validity is debatable
7 is obviously no longer valid
8 is no longer valid
9 is not valid with most technical diving computers
10 is not valid with most technical diving computers
11 is not valid with most technical diving computers
12 is not valid with most technical diving computers

So that leaves 1 and 13 as still valid reasons, but in my very strong opinion, they aren't valid enough to warrant not using one, especially when they are negligibly more expensive than good bottom timers....

for those unaware what the bakers dozen are.

1) Dive computers tend to induce significant levels of diver dependance, eliminating the awareness so common and essential to all diving but particularly obvious when diving tables
2) Dive computers do not allow proper planning as divers can’t properly "study" the impact of various mixture and decompression choices.
3) Dive computers are of very limited educational benefit as they do not induce questioning, or proper planning discussions as can be found with tables and most particularly with deco programs.
4) Dive computer programmers often play games with computational process so that they can take insulate themselves from the risk of taking largely square profile data and utilizing it on a multilevel dive. These games tend to result in odd and often ridiculous levels of conservation.
5) Dive computers are expensive and in some cases leave divers with limited resources carrying equipment that is of far less benefit than other equipment that may have been purchased.
6) Dive computers significantly limit the likelihood that divers will track their residual nitrogen groups.
7) Dive computers do not allow for Helium diving in any formats but the bulkiest and most questionable format.
8) Dive computers will often generate longer decompressions than could be figured by an astute, well educated diver with experience.
9) Dive computers often create confusion by giving the user too much useless information, sometimes even obscuring depth and time in favour of blinking CNS and/or deco limitations.
10) Dive computers can become very difficult to properly if a deco stop has been violated. Some computers lock up completely while others just beep or generate erroneous and distracting information. Divers using mixed gasses are likely to often violate computer profiles.
11) Dive computers do not allow for the educated diver to properly modify their decompression to account for advancing knowledge such as the use of deeper stops in a decompression profile.
12) Dive computers do not offer divers as much flexibility in the generation of profiles with varying conservation. For example the right mix would allow 100 min at 60 vs 60 at 60 but I might prefer to do one or the other and indeed might like a compromise. Computers confuse this issue by not providing divers with the proper information.
13) Dive computers users often ignore table proficiency and therefore do not learn tables properly. When confronted with a situation where they can’t dive the computer (failure, loss, travel etc) these divers are at a serious handicap.
-JJ

 

[dmaziuk]

4 is still applicable with some computers, not with shearwater

Is there a plain English translation of this:

4) Dive computer programmers often play games with computational process so that they can take insulate themselves from the risk of taking largely square profile data and utilizing it on a multilevel dive.

The best I can figure, "games" refers to Yount's bubble, Thalmann's linear off-gassing, and Wienke's whatever?

 

[tbone1004]

@dmaziuk conservatism added in for things like short surface intervals, reverse profile diving, rapid ascents, etc. That is not disclosed when and how much the profile will be changed so all of a sudden the NDL's, or in that case TTS number changes and you don't know why and can't predict it. Suunto is particularly bad about it

 

[dmaziuk]

Those are part of "Wienke's whatever" AFAICT. "Programmers playing games" is... one way of putting it.

 

[TMHeimer]

There is nothing wrong with teaching timers and tables. When I dive OC, I never take 2 computers. I have a plan in my wetnotes to follow if needed and a$10 Casio on my wrist to backup my predator.

CCR I have a petrel controller, and a my Predator as a backup.

That being said neither the $10 Casio, nor the shearwater have ever failed me.

One could understandably justify wearing 2 shearwaters and not bothering with written dive plans.

I do the same thing on my (rare) deeper dives--computer with cheap watch backup. Or like you say, 2 computers would also be fine. It would make sense to me that divers usually doing true multi-level dives should lean toward two computers. Those like me who usually do square profiles (I'm always almost on the bottom shell hunting), it makes more sense to use the watch as a backup--or the computer to back IT up.

 

[Michael Guerrero]

So why the difference of opinion?

The answer is pretty simple. Some people feel that you should be able to plan a dive and dive a plan. Some people believe that a dive can be dynamic, with changes to the plan during the dive. Most people recognize the truth in both views, and thus a computer allows you to modify your plan, if needed, based on circumstances--but doesn't excuse you from forethought/planning.

It's really not a big deal, and people who make it as though it is are unnecessarily doctrinaire in my view.

Make a plan, dive that plan, have a computer to help with dynamicity. Enjoy scuba.

 

[NAM001]

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A ScubaBoard Staff Message...

This thread has been split off from another thread as it was off-topic. Nonetheless, it is interesting in its own right. Marg, SB Senior Moderator

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I am not a technical diver but you are a technical dive instructor, so perhaps you can explain this to me. You recommend a perdix or maybe a petrel, I get that they are the best on the market and do cost less than the top-of-the-line computers from major manufacturers. So I understand the recommendation. However, three technical diving agencies (maybe more), GUE, UTD, and ISE all recommend against purchasing a dive computer and using a simple bottom timer, a function that is built-in to many inexpensive dive computers. So why the difference of opinion?

IMO. the agancies you reference have a different concept in diving. its start from the beginning adn proceed to the max with little to no changes in the process. Again IMO its the dir thing. a computer is subject to failing and its primary purpose is to compute deco. To these folks it is un-necessary as they use ratio deco or some dirivative of it. the rest of the computer is a record keeper which is again moot to the hard core dir folks. you need a timer and a depth gage to self calculate deco assuming your gasses are "STANDARD" Computers telling yo to change gas is a no no for them also. you have a gas plan and a dive plan and you use it instead of relying on a contraption. Lastly the money spent on a computer can be used for other more worthwhile items like a SMB's ect. The purpose of the computer is that it does all those functions for you so you don't have to have an in depth knowledge of how to do it. Can I do ratio deco yes but I choose to use a computer. Do I have a plan if the computer fails yes I do. sometimes it involves wearing 2 computers.

There is nothing wrong with these agencies they are all good IMO. The difference lies where the training stops. regular agencies basically stop at OW or AOW. To go any further is icing on the cake. With these agencies each course is a prep for the next course that they assume you WILL be taking.