Dive Tables VS Dive Computer

[Rosevb]

Wow, I'm very pleasantly surprised by the scubaboard community! Thanks for all your answers in such a short amount of time! I think what I'm taking away is that a good understanding of tables/what a computer does is useful, but I will also be buying a dive computer
When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

 

[tursiops]

When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because watches rarely fail and if they do you can just end the dive?

I don't carry a watch anymore, but my wife does....she likes the simple display for getting info for her logbook.
My table is in my head....the old "rule of 120." Depth+minutes=120. so you get 80 ft for 40 mins, 60 for 60, 30 for 90. etc. This was a somewhat aggressive approximation for air. I'f I'm diving Nitrox it is quite conservative.
I DO carry a second computer, so in the unlikely event my primary fails, I've still got a way to track my residual nitrogen on later dives. The second computer, of course, is a backup watch and depth gauge as well, in addtion to tracking nitrogen.
Just ending the dive is a terrific strategy...for loss of any gauge, including watch, computer, SPG. you know you were OK up to the time of loss, so surfacing is an annoyance, but not an emergency.

 

[tursiops]

I don't carry a watch anymore, but my wife does....she likes the simple display for getting info for her logbook.
My table is in my head....the old "rule of 120." Depth+minutes=120. so you get 80 ft for 40 mins, 60 for 60, 30 for 90. etc. This was a somewhat aggressive approximation for air. I'f I'm diving Nitrox it is quite conservative.
I DO carry a second computer, so in the unlikely event my primary fails, I've still got a way to track my residual nitrogen on later dives. The second computer, of course, is a backup watch and depth gauge as well, in addtion to tracking nitrogen.
Just ending the dive is a terrific strategy...for loss of any gauge, including watch, computer, SPG. you know you were OK up to the time of loss, so surfacing is an annoyance, but not an emergency.

PS - my wife's watch is a dive watch and displays max depth for the dive as well as bottom time and temp. Everything she needs for her log book.

 

[Celt]

Wow, I'm very pleasantly surprised by the scubaboard community! Thanks for all your answers in such a short amount of time! I think what I'm taking away is that a good understanding of tables/what a computer does is useful, but I will also be buying a dive computer
When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

You can never “just end the dive” the only time a dive can be aborted is on the surface before it starts. Always have a bailout plan should you need to surface.

 

[MargaritaMike]

Yeah, just as ancient as learning how to drive a manual car (that is to say, learning how to properly drive, any idiot can but "D" into Dummy). Look, there's a reason for why you build from the ground up. You can't do it the other way around.

Dive tables are a great tool and you should learn how to use them, there's nothing obsolete about them.

These days I mostly type on a computer and or phone, but that doesn't mean handwriting is obsolete....as "ancient" as it is it still comes in handy.

Another one, spell check, can be a great tool, but you still gotta learn how to spell.

Two comments here. 1) Handwriting is becoming obsolete. In my grandchild's school, they no longer teach cursive writing. I am furious about this but can't do anything about it. How will they read historic documents which were hand written. I guess someone will summarize them and put them on the internet. 2) Not only is spelling important, grammar and word choice is also essential to the most effective communication. You don't gotta learn nothin'.

I dove tables for years because the computer wasn't a thing yet. I never got bent but I was always calculating and rounding numbers to stay conservative. Computers are far more accurate. Their main benefit is to safely allow you to increase your bottom time on many of your dives, especially those that don't have a square profile.

You can use either method just never, ever do it wearing split fins or you will die.

Also, if you don't know how to frog kick in split fins you will die faster.

Well said.
I watched my wife teach "deco theory" and "tables" in a scuba class once. She used a credit-card analogy....you go on a dive and that's like charging stuff on your card. Your card has a limit so you can't charge too much; that's like the NDL. When you surface your SI is like paying off the card, a little at a time; if you don't pay it all off, you can't charge as much on your next shopping trip; that's the residual nitrogen. She introduced all the terms and concepts with the credit card analogy. someone asked, but how do we calculate that for our diving? She said you can use the tables, or a computer. By then, people had figured out the basic concepts and had not been burdened with things they didn't really need to know. i was pretty darn impressed.

I guess I'll have to stop diving. I got rid of all of my credit cards (except one for travel) and only deal in cash. If I don't have the cash, I can't afford it.

Wow, I'm very pleasantly surprised by the scubaboard community! Thanks for all your answers in such a short amount of time! I think what I'm taking away is that a good understanding of tables/what a computer does is useful, but I will also be buying a dive computer
When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

Congratulations on your certification. I think it is admirable that you are asking these questions instead of just blundering ahead. Everyone has their opinion regarding tables and computers. I think you got the right take-aways from the posts. MY OPINION: Tables are effective in planning dives IF you understand what the table is telling you. They are also effective if you dive to a certain level, stay at that depth, and then surface (a square profile). They also provide a very conservative calculation for residual nitrogen. Computers are more accurate for multi-level diving which is typical of recreational diving. IMHO your decision to get a computer is a good one. My only suggestion is that for whichever computer you get, read the manual until you understand every nuance of your computer. Also, learn how to access and read all of the functions of the computer. Also, the computer should be Nitrox capable. You may not be diving Nitrox now, but you may in the future and then you will be ready.

Again, congratulations and good luck with your diving. Enjoy your new hobby.

Cheers -

 

[gr8jab]

Wow, I'm very pleasantly surprised by the scubaboard community! Thanks for all your answers in such a short amount of time! I think what I'm taking away is that a good understanding of tables/what a computer does is useful, but I will also be buying a dive computer
When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

I don't have a watch or tables. I take my wife's computer as a spare, when she is not with me.

A second dive computer isn't for increased safety. It is mostly a convenience thing, allowing you to continue diving if the primary computer fails. If you only have one computer and it dies, you're done for the day.

If you are paying thousands of dollars for a scuba vacation (airfare + resort + food + diving package), then a couple hundred more for a spare computer is an excellent insurance policy. It really sucks to pay $200 for a day on the boat, only to have the computer die on the 1st dive. But, in such a case, you can usually rent a replacement the next day.

My first dive computer, bought around 2001, failed several times. I later found out (here on scubaboard) that they were prone to problems. My current dive computer has been rock solid, and I generally don't worry about it failing.

I suggest you start with one dive computer, and then consider a 2nd if you are going on an expensive trip. If you do have two, they both go in the water with you, so they both track your nitrogen loading and surface intervals.

 

[Chavodel8en]

When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

Necessity of a back up computer/watch for NDL diving

Above is a recent thread in the "Computers" sub-forum which will discuss your question -- in fact, more discussion than you prob care to read. Also a poll as to what if any backup folks have.

My 2 cents - I dived for years locally without any backup. Like you pointed out, if my gear failed, I would just end the dive and drive home. Note that you'd need to ascend using visual clues or other clues to know your depth.

However, If I was going on an expensive diving trip, I'd probably have a backup computer. I wouldn't want to rely on a watch, depth gauge & tables for backup, as they wouldn't maximize my diving.

 

[Bob DBF]

When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

Ending the dive is the right answer. There is no way to convert the computer information to the tables or from tables to computer, so if the computer dies you are done for the day. Tables don't break so no problem there.

If I was going on a big expensive dive trip I might pick up a backup computer for insurance.


Bob

 

[Vitesse2l]

It doesn't hurt to sit down with tables and plan a dive, including gas planning (OP may not have covered this in class) and get an idea of time/depth etc before getting wet. I find that helps get my head around what I expect to happen in the water as I'm extending my limits. With a bit more experience you know what ballpark to expect.

Enjoy your diving OP.

 

[loosenit2]

Wow, I'm very pleasantly surprised by the scubaboard community! Thanks for all your answers in such a short amount of time! I think what I'm taking away is that a good understanding of tables/what a computer does is useful, but I will also be buying a dive computer
When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

When I dive with a computer I do not wear a watch, but I bring one in my dive bag. I always bring dive tables with me, to aid in dive planning. I find the dive tables easier to use for planning than scrolling through the dive planner in my computer that has similar, but more accurate NDL limits. Unless I am doing a lot of repetitive or deep diving I generally find that my limiting factor in how long I can stay down is not NDL or nitrogen loading, it is air supply. So understanding your air consumption rate (SAC/RMV) is also a key step to effective dive planning.