Is a computer actually necessary?

[Theunis]

Well, if anybody decides to dive without a computer, that is his/her decision. If you prefer not to dive with a computer, do it!

However I must admit, it is nice for me to have a computer in my car calculating my petrol consumpsion, etc. It makes it easier. Maybe we are just getting to lazy to do the calculations ourselves. And it is nice having a diving computer doing the job for me. I go for the computer argument.

 

[Kimsey0]

I see you guys are still going at it huh? man never knew my thread would have created so much controversy, especially after all these years, nice to see that it has, and that it has given you guys something to talk about

Mind you i have absolutely nothing against the use of dive computers, but you know it's funny, possibly theres a reason for it not sure, but no one has mentioned the time those divers got bent *because* of a particular model of computer.
As far as i know no one has ever gotten bent/injured because of tables being designed badly/wrong, yet there has been people (2 divers as far as i know/remember, could be more) who were injured for life as the direct result of using a faulty computer model now it's been years since i read this article, but i THINK if i remember correctly it had an error its algorithm (can't rememer if it was improper depth/time reading or what but it had some kind of error like that)
I think the company ended up recalling it.

Anyway i just thought it was odd nobody has mentioned that issue yet, kind of.

 

[flw]

Depends on what you mean by tables - I got bent using an early version of decoplanner - i cut the tables, safety etc, but failed to factor in everything, pushed the limits a bit too far one day on a 70m dive - since then have switched to a gf-based tables, the guy I dive with most hates them and uses a much later version of decoplanner - deco schedules are more black art than real science, though there is now a wider body of experience around, so there are possibly less bends at those kind of depths
it's largely a numbers/statistics thing - al you can do is push the parameters as far as possible in your own favour

 

[Lucy's Diver]

I'm not sure you got the point I was trying to make. I doesn't matter if you sample data a million times/second and calculate out to 20 places when the decompression model is just a SWAG.

Be careful here. DSAT NDL's are a bit more conservative on the first dive but a 60 minute compartment is used for SI credit making repetative dives less conservative.

No! You absolutely are not forced to accept it. You can always choose to dive more conservatively.

Yes but not less. A computer is running the tables for you in real time, and thus allows you more bottom time in a typical warm water tropical recreational dive, which are virtually always multi level.

My point is that the speed and that supposed accuracy is of no real benefit.I know where I'm at and what time it is. Why would I need a computer to tell me that? I not only know what my NDL (or appropriate ascent is) but I know what it will be BEFORE I even take an action for the computer to sample. You see, I know what I'm going to do and whether or not I think it's a good idea BEFORE I do it. I guess, you just do it and see what the computer thinks about it after the fact? It's a little late then isn't it?

You presume that all computer divers, including myself, engage in no dive planning at all. This set of facts would allow you to make the above point. It is, of course, a false set of facts. I plan my recreational dives in general terms. The broad strokes, combined with the computer usage, allows the flexibility to vary the plan based on what happens to be down there. Within the parameters of what I know to be a safe dive, I do indeed do stuff and see what the computer thinks. With that caveat the statement seems rather less flip.

Not only that but I know how much gas that action will require and whether or not I have enough including an adequate reserve should my buddy suffer a total gas loss at the furthest point in the dive. Lets see your dive computer do that. LOL

Again you posit a false set of facts, attribute those false facts the the vast majority of divers, then laugh out loud at it. Indeed no dive computer will plan for gas loss contingencies. They also don't deploy reels, fill lift bags, share air, or climb back on the boat for you. The use of a computer does not relieve a diver of the myriad other things that need to be done to dive safely.

Who says those computers and tables are so conservative?Really? Why do so many divers get bent when using a computer if it puts them "safely in the middle of the cut"? Why would I want to be in the middle of the cut? I know what dives I've done and how I felt afterwards. I know where I set the parameters in my decompresion software and how I pad my decompression given the dive and conditions. How is some computer manufacturer supposed to know or account for that?

LOL, you mean like if a diver just forgets where he/she is or where they've been? I can see where that would be a problem.

Use a computer if you want. I don't need one.

Computers (at least the ones designed for NDL dives) are based on PADI style tables. These are incredibly conservative compared to the set of tables used in the military and commercial diving world. These tables, for example, call for 60 fpm ascent rates and no safety stop in a NDL dive. There's a reason they are normally only used with a chamber topside. Recreational divers largely get bent due to operator error, which includes gaming a computer and diving its absolute limits in repet dives. There are also undeserved hits out there. Tables divers get bent from operator error and undeserved as well, you just don't hear about it as much because they are such a small proportion of the recreational community and the commercial and military community don't really seen to care to air that kind of thing in public.

I will admit that recreational tables divers do well tend to be people who are totally squared away in terms of every aspect of gear and dive planning. It is simply not realistic to square away the entire universe of recreational divers to this level. I don't want to be that squared away in my dive planning when I'm on vacation (I am in terms of gear and all the various things a computer does not do). I get enough of that at work (where computers are not used, the topside support does all that, normally I could not see the thing anyway, and besides work dives are neither repet nor mutli-level, so the two big computer advantages are absent).

 

[MikeFerrara]

Yes but not less. A computer is running the tables for you in real time, and thus allows you more bottom time in a typical warm water tropical recreational dive, which are virtually always multi level.

A computer doesn't "allow you bottom time". You can dive as long as you want. The question is...how are you going to manage you ascent?

Why the hang up on multilevel warm water dives that may not be all that typical for the average diver when most of the world isn't in the tropics and so much diving takes place outside of resorts where someone has planned your dive for you? Why don't we talk about Great Lakes wreck diving or something and see how "multilevel" a "typical dive is and what a computer does for you?

I already addressed the nature of those "typical warm water" plans...a deep short bounce and riding the computer up...skip the deep bounce and note how much time you have...or rig for deeper diving and see how much time you have. Either way, I don't need to dive that way.

I don't care to dive a single tank and no redundancy much deeper than about 80 ft. Just treating it as a square profile and using a DSAT table, I've got a half hour. What if I split the dive up into a couple different depth ranges and do a simple time weighted average? Now how much time to I have?

Since I'm in the midwest and not in the tropics lets look at a dive that will be done by thousands of midwest divers countless times over the course of a year at a popular site like Gilboa. The place is full of divers diving the shallow side (60 feet at the tubes, 45 or so at the buss and above 35 or so everyplace else) What do you need a computer for? Let's say we dip over the wall to about 80 ft for a nice view of the wall for about 15 minutes, come back over at the buss and spend the rest of our gas milling around the fish filled (mostly above above 35 ft) area. What would anybody need a computer for? Spend a while shallow after that deep dip, consider it a 50 ft dive and you have all day. Try it with a computer and see if the computer doesn't tell you the same thing. I just don't bother to bring the computer because I know what it will say.

Pick some great lakes wrecks and tell me what a computer is going to do for you?

How about a popular Missouri cave like Roubidoux? Max depth of about 50 ft before the drop, max of about 40 in the cavern and between 130 and 150 for the 1st thousand feet or so...no computer needed, even for the mathematically challenged.

Pick some other popular dives and lets look at them and how to do them without a computer. What about the Gulf or east coast wrecks?

Yet, the kind of dive always used to justify the need of a computer is the kind of dive that I never do, and don't want to do. The only thing that makes the computer seem so useful is the fact that the plan and overall diving style is so silly.

Patient: Doc, it hurts when I do this.
Doc: Well don't do it.

You presume that all computer divers, including myself, engage in no dive planning at all.

If I presume any such thing it's based on experience and knowing what divers are taught. I know there isn't a heck of a lot of real gas planning going on because it just isn't taught.

This set of facts would allow you to make the above point. It is, of course, a false set of facts. I plan my recreational dives in general terms. The broad strokes, combined with the computer usage, allows the flexibility to vary the plan based on what happens to be down there. Within the parameters of what I know to be a safe dive, I do indeed do stuff and see what the computer thinks. With that caveat the statement seems rather less flip.

A also can vary my plan based on what happens and I don't need a computer to do it.

Again you posit a false set of facts, attribute those false facts the the vast majority of divers, then laugh out loud at it.

Let them laugh but I do my laughing with my computer money still in my pocket.

Talk about laughing...you should hear me laugh when I see divers (it's even funnier when it's an instructor) get to france park (max depth of about 28 ft when the water is high) and NOT dive because their computer isn't working...I don't need a computer to do a two hour safety stop but lots of divers do.

Computers (at least the ones designed for NDL dives) are based on PADI style tables. These are incredibly conservative compared to the set of tables used in the military and commercial diving world. These tables, for example, call for 60 fpm ascent rates and no safety stop in a NDL dive.

What does military or commercial diving have to do with this? Why the emphisis on DSAT tables? For example, the buhlman tables are designed based on a 33 fpm ascent but using decompression software, you can specify the ascent and desacent rate when cutting tables.

Again, the PADI/DSAT tables may not be as conservative as you think they are. The DSAT tables are based on a 60 fpm ascent rate and use a 60 minute compartment for SI credit which makes repetative dives less conservative than the US navy tables which use a slover compartment.

What tables is your computer using and how does it compare to the results you get with other tables, models or software?

There's a reason they are normally only used with a chamber topside. Recreational divers largely get bent due to operator error, which includes gaming a computer and diving its absolute limits in repet dives.

Do you have any data to support that statement?

There are also undeserved hits out there.

I disagree. If you get bent, you did something to deserve it while it may be true that you tables or computer didn't provide you enough information to lead you to expect it. Might be a good reason not to place so much trust in it?

I will admit that recreational tables divers do well tend to be people who are totally squared away in terms of every aspect of gear and dive planning. It is simply not realistic to square away the entire universe of recreational divers to this level. I don't want to be that squared away in my dive planning when I'm on vacation (I am in terms of gear and all the various things a computer does not do). I get enough of that at work (where computers are not used, the topside support does all that, normally I could not see the thing anyway, and besides work dives are neither repet nor mutli-level, so the two big computer advantages are absent).

I don't know how many times I need to point out that the decompression planning I do for a no-stop dive isn't any more labor intensive or time consuming and doesn't take anything away from the dive. For the average no-stop dive, I pretty much just go diving...knowing of course what gas reserves I want for those conditions and having some basic decompression knowledge and staying aware of where I've been and where I am.

 

[MikeFerrara]

Let's clarify something here. I'm not trying to tell folks not to use a computer. If you like them or feel you need them, use them.

My only point is that I dive where I want/can and for as long as I want and manage to do so without a computer. My dives range from simple single tank dives and a swim suit to cold water dives using a dry suit, set of doubles filled with trimix, two or more decompression gasses and a stage or two and I do it all without a dive computer.

I'd have to assume that someone else can do it if I can so to answer the opening question of the thread...No, a dive computer is not necessary.

 

[vicdiver656]

Yikes.....that owner sounds like a real shark! Kinda like my brother! (he was taught on jacket BC, and totally resents the BPW style. Says it's for idiots. [an idea imprinted in his head by his instructor :no ] Anyways, no. A computer isn't necessary, but it is nice at times. I really like them because you can chart your dive and see how you reacted to certain things, and areas for improvement.

 

[Lucy's Diver]

Let's clarify something here. I'm not trying to tell folks not to use a computer. If you like them or feel you need them, use them.

My only point is that I dive where I want/can and for as long as I want and manage to do so without a computer. My dives range from simple single tank dives and a swim suit to cold water dives using a dry suit, set of doubles filled with trimix, two or more decompression gasses and a stage or two and I do it all without a dive computer.

I'd have to assume that someone else can do it if I can so to answer the opening question of the thread...No, a dive computer is not necessary.

I have to assume that since I can rebuild a transfer case, a mechanic is not necessary. For anyone.

We obviously will not agree on this. The thousands vacation only, used the tables once in OW class divers who keep the manufacturers in business are all sheep.

Baaa.

And someone who does a single 60 foot dive within the PADI tables and becomes paralyzed on the airplane over 24 hours after that dive, and whose paralysis is resolved with a chamber ride, is indeed an undeserved hit. I've seen that. Why don't you tell me what he did to deserve that hit?

 

[jviehe]

I have to assume that since I can rebuild a transfer case, a mechanic is not necessary. For anyone.

We obviously will not agree on this. The thousands vacation only, used the tables once in OW class divers who keep the manufacturers in business are all sheep.

Baaa.

And someone who does a single 60 foot dive within the PADI tables and becomes paralyzed on the airplane over 24 hours after that dive, and whose paralysis is resolved with a chamber ride, is indeed an undeserved hit. I've seen that. Why don't you tell me what he did to deserve that hit?

Physical factors that predispose them to DCI? There arent any undeserved hits. You dive, you have a chance of injury.

 

[MXGratefulDiver]

I'm sorry to hear about his passing, I hate to hear when divers are lost...

That being said the issue would be the fact he was on rebreather, not the fact of a dive computer falure.

No ... I think the issue is that you really can't rely on technology to save your bacon when you're diving. The technology can make the dive easier, and more convenient, for sure ... but you still have to have the knowledge and skill to conduct it safely. And you still have to anticipate that technology can fail at any time, and have adequate backup plans in place to deal with it when it does.

A dive computer is a tool ... and like any tool it has an appropriate use. That use does not include using it as a crutch. You should still have an adequate understanding of how it works and why it's giving you the numbers on the display. You should not have to rely on an alarm to tell you that you're exceeding NDL, or ascending too fast.

Dive computers are not necessary ... and they're not necessarily safer. It all really depends on the diver, and how they use the computer to conduct their dive ...

... Bob (Grateful Diver)