Is a computer actually necessary?

[bertschb]

This is just what they tell you to get you to buy a computer. LOL

Sheesh! Get over it folks. Nobody had to sell me on the idea of buying a computer. Just like digital cameras, cell phones, GPS receivers, etc - they sell themselves. I like gadgets. I like flexibility in my dive profiles. I don't like screwing with dive tables and I have the money. I bought a computer.

I dove for many years before the dive computer was invented and had a blast. I just MUCH prefer using one than not.

Do you use an abacus instead of a calculator?

Dive computer = optional but cool gadget

 

[Uncle Pug]

bertschb once bubbled...
I bought a computer.

... I bought an expensive one.

And I use it in gauge mode as a bottom timer because I like the additional flexibility and added bottom time I get using it that way.

Tuesday: 93' max 50 minutes TBT

 

[hantzu701]

At my LDS, I went directly from using square tables to using my computer for multi-level dives. The DM's at my LDS think its a waste of money to buy the multi-level dive tables when I have a computer. I still use square tables to plan my dives, but (obviously) the dive plan can signal no dive limits even though I'm no where close to them. Although I am a rec diver, I do realize that my computer can fail, so I am looking to learn how to get around that.

I've read in a few posts how you can calculate the limits in your head. How is this done?

 

[Northeastwrecks]

Uncle Pug once bubbled...

... I bought an expensive one.

And I use it in gauge mode as a bottom timer because I like the additional flexibility and added bottom time I get using it that way.

Tuesday: 93' max 50 minutes TBT

UP:

When you say "TBT", is that the same as what we call "run time", i.e., total time surface to surface?

I'm assuming Nitrox 32 or 30/30? In my head, I come up with about 45 minutes, but that doesn't include multi-level planning.

 

[Don Burke]

hantzu701 once bubbled... I've read in a few posts how you can calculate the limits in your head. How is this done?

The Navy tables follow a pattern:

50 feet gives you 100 minutes.
100 feet gives you 25 minutes.

To get from 50 to 90, lose ten minutes for every ten feet you add, so:

60 feet gives you 60 minutes.
70 feet gives you 50 minutes.
80 feet gives you 40 minutes.
90 feet gives you 30 minutes.

You already know that 100 feet gives you 25 minutes. From there on, lose five minutes for every ten feet you add so:

110 feet gives you 20 minutes.
120 feet gives you 15 minutes.
130 feet gives you 10 minutes.

Some just subtract depth from 120 to come up with a working number. For 60-90 feet, that is spot on. Outside of that, it cuts you short.

Another thing you can do is scroll through the planning mode after the first dive and work the tables backwards to figure out what pressure group the computer thinks you are in. If the computer craps out on the second dive, you can shift to the tables rather than sit out for 12 hours.

 

[Uncle Pug]

Northeastwrecks once bubbled...
When you say "TBT
~~~~~~~~~~~~~~~~
I'm assuming Nitrox 32 or 30/30?

TBT=total bottom time=surface to surface

Yes... I was using EAN32... and all my dives are multilevel.

Average depth was 50'. If we had spent more time deeper then we would have spent more time shallower and kept the average around 50'.

I'm glad we didn't though because we hit a thermocline on the way back up at 20' and it wasn't much fun anymore. I got out with 1500 psi left in the 104 (started with 2900.)

BTW - When I dive with someone using air I treat my EAN32 as though it were air.

 

[Wingtip]

Uncle Pug once bubbled...
and added bottom time I get using it that way.

Tuesday: 93' max 50 minutes TBT

Where's the added BT?

Tuesday: 108' max 52 min TBT - Stayed within my computers NDL too

 

[Uncle Pug]

Wingtip once bubbled...
Where's the added BT?

Tuesday: 108' max 52 min TBT - Stayed within my computers NDL too

None on that dive... it was a bit nippy and 50 minutes was just about enough. Usually we keep it <60 minutes.

Congratulations on keeping your computer happy.

 

[Kimsey0]

I just wanted to let everyone know, that i'm not a troll - this actually happened, and the reason why i haven't posted anymore replies is because i just couldn't think of anything else to say on this subject, since i never did go back to that class. Anyway, i appreaciate the responses thanks

 

[Uncle Pug]

Uncle Pug once bubbled...
Average depth was 50'. If we had spent more time deeper then we would have spent more time shallower and kept the average around 50'.

I don't just use a straight average to figure out my computerless multilevel dives.

I go slower and slower toward the surface the closer I get. You can do this with an infinitely variable ascent rate or with discreet stops of increasing duration.

This is what I do... well at least most of the time.