Tables & computers

[TMHeimer]

In 23 years of diving, I haven't had to replace my tables.... wish I could say that about computers....

The funny thing is that up here (Great Lakes), the dive profile is basically a square one so it is easily figured with a Wheel or the tables. There isn't really the big advantage here that reef/wall diving gains in computer use.

Mine are basically square as well, as I am almost always right near the bottom looking for shells. For deeper or boat dives I use tables, watch and computer. For shallow dives (30') I don't bother with the computer (one less thing to wash). I have yet to hear my computer ascent alarm, but it's nice to know it's there.

 

[ajduplessis]

Your dive profiles are very conservative and there is absolutely nothing wrong with it. I assume you dive this way to keep things nice and safe? There is only one way to prevent DCS and that is not to dive at all. Tables and computer only will not keep you safe.

It is very good practice to check tables before a dive and compare this knowledge to what you DC is doing. I still do this on even the most basic OW dives. You could extend you dives a lot more and be "safe" with the DC.

There is nothing wrong with small steps.

Safe Diving!!

 

[DiveNav]

I think I said this on another thread ... but it is worth repeating it.

Table vs Dive Computers is like betting on which one is less wrong.

Both are giving you an estimate of nitrogen intake and release of your body (well ... some computers also estimate bubble formation); computers provide a detailed estimate while tables provide a coarse estimate.
But at the end of the day they are only estimates :shocked2:

Alberto (aka eDiver)

 

[fjpatrum]

I think I said this on another thread ... but it is worth repeating it.

Table vs Dive Computers is like betting on which one is less wrong.

Both are giving you an estimate of nitrogen intake and release of your body (well ... some computers also estimate bubble formation); computers provide a detailed estimate while tables provide a coarse estimate.
But at the end of the day they are only estimates

Alberto (aka eDiver)

As I said, this is more a "check and balance" against both that the numbers are somewhat consistent so I know, as a newb, whether or not there is something amiss. I don't have years of experience that allows me to look at either tables or a computer and know "hey, that number doesn't look right". I also don't really care which one is "less wrong".

I have two pieces of equipment that have been validated through years of design and use by other people to be at least mostly reliable. I compare those two "mostly reliable" pieces of equipment against each other as a further check.

I don't blindly trust any piece of gear. I inspect them to the best of my ability. This check, while perhaps not necessary and still not completely reliable, is the best thing I can come up with to "inspect" (and therefore trust) that I'm doing my dives in a reasonably safe manner and still get the "most" out of my dive. The "most" doesn't necessarily mean the absolute max bottom time and it doesn't necessarily mean a 100% guarantee of not getting bent.

This isn't about trying to be conservative or prevent getting bent. It's about my own education, nothing more. I just haven't ever seen anyone else do it and was asking how many people do.

 

[TSandM]

I think what you have learned is that nobody appears to be using the strategy that you have adopted.

I think it's great that you are being thoughtful about this. We all need SOME kind of instrument or methodology to monitor and evaluate decompression status. For a long time, tables were what we had, and they kept most everybody safe. Now we have had dive computers for quite a while, and have not seen a huge uptick in decompression cases. Computers CLEARLY allow more bottom time and therefore, I think it's clear, more nitrogen loading. But the algorithms they are using appear to be very safe as well, and allow for longer dives.

As I say over and over again, all diving involves risk assessment. Among the risks is that of DCS, and each of us has to adopt some kind of strategy for minimizing that. The only problem I see with yours is that you are not going to make your computer-diving buddies very happy, when you want to cut your dive significantly shorter than their (or even your) computer will permit.

 

[mathauck0814]

I tend to plan my dive (if it's something aggressive or out of the ordinary) with desktop software (or more likely with vPlanner for iPhone on the boat) and then transpose the numbers to a slate. That's for safety as a back-up in case both of my computers fail. Once in the water, I tend to stick pretty close to the plan, but I dive by computer mostly.

 

[James R]

The only time I use tables is on a technical dive, which is out of scope for this topic as it's in the basic scuba discussion.

I do use my computer before a dive and between dives to check the approx bottom time at a given depth and expected surface interval so I have a ballpark idea of the NDL/Depth/etc to make a general plan. Lots of times in the lake I may plan 90 feet dive only to find the viz is crap so I adjust on the fly.

Your sac rate may vary

 

[lowviz]

As I said, this is more a "check and balance" against both that the numbers are somewhat consistent so I know, as a newb, whether or not there is something amiss. ....//..... It's about my own education, nothing more. ...//....

Yes!!!

...//....I think it's great that you are being thoughtful about this. ....//.....

So do I.



There is another way to use tables. You are ready.

Figure out your REAL, stressed, RMV. Calculate "worst square dives" for ten foot increments that use ALL of the gas that you have on your back, -this includes any deco obligation. (Yes, I know that this is Basic Scuba Discussions) Buy a used copy of the NOAA Diving Manual. Amazon.com: The Noaa Diving Manual: Diving for Science and Technology (9781568062310): Books All tables and information are within. Calculate the runtime for each dive. Now you know the absolute max time that YOU can stay at any certain depth, limited by gas on your back. Longer than this is sadly academic and pointless to calculate...

fyi: the pic show rock-bottom calcs, but no matter, same idea.

 

[Pullmyfinger]

Since planning has entered the conversation, I'll add this:

I did this as an exercise after my YMCA OW2 class.
I used to compare my planned diving depth against this chart as an additional dive planning tool.

Disclaimer: It was just something I put together using what I was taught at the time, as a student I wanted an overview.
Disclaimer 2: Do your own math.
Disclaimer 3: Just because there are deeper depths listed, does not mean I dive deep on a single tank.....I just wanted to plot it all out.....obviously it's a bad idea. If I'm diving deeper than 80 feet, I use doubles and a similarly minded dive buddy.
Disclaimer 4: There might be some errors due to rounding. Do your own math.
Disclaimer 5: Yes....I realize that my SPG won't be that accurate and that the PSI values on this chart are not what I would see on my SPG.
Disclaimer 6: Yes....I also realize that I can just do a quick math calculation and determine my air supply duration for a given depth, which makes this chart worthless.....but I wanted to do it anyway.
Disclaimer 7: I wanted to get a handle on being able to know what my SPG should be reading...before I looked at it. This was just a tool to help me as I was learning.
Disclaimer 8: .7 is a rough average....determine your own.
Disclaimer 9: If I had any sense, I would be using the Metric system. I can't convince my dive buddies to switch, so I'm stuck with Imperial.


-Mitch

 

[lowviz]

Computers will always be ahead of tables, so tables always lose in a direct comparison. End of story for those who just want a simple answer.

However, if you add personalized gas management to tables the combination becomes the final word. In this particular case, your DC is lacking information...