Do I really need a computer?

[Dtaine]

Dives in the 60 to 100 foot range make the computer valuable here. I don't know of anyone, except the newest divers, who doesn't use a computer. Call Gerry or Ham at Jupiter Dive, 561-745-7807 and they can give an explanation on why the three tank day requires the computer.

Well I gave them a call, their reasoning was the computer gave extended bottom time and kept better track of surface intervals, etc.

Nothing new to convince me I should have to spend money renting/buying a computer.

 

[Stu S.]

Experts, here is one I don't understand. There's a freshwater dive in Central FL where divers go down to 118 feet for about five or six minutes, then work their way back up. It amounts to a 45 minute dive with an average depth of about 52 feet (according to a computer). This is an air dive. Computers "stay in the green" the entire time. A three minute safety stop is done, no deco time.

Somebody must be using tables to do this, and I can't figure out how.

Thanks guys,

Stu

 

[psychocabbage]

I wont dive without our computers.. Just makes no sense.. There are too many variables in depth to consider when diving in Cozumel..

I can understand doing so in a quarry where the depth may be more constant but when you have swim throughs and whatnot, I wouldnt.

 

[Charlie99]

Experts, here is one I don't understand. There's a freshwater dive in Central FL where divers go down to 118 feet for about five or six minutes, then work their way back up. It amounts to a 45 minute dive with an average depth of about 52 feet (according to a computer). This is an air dive. Computers "stay in the green" the entire time. A three minute safety stop is done, no deco time.

Somebody must be using tables to do this, and I can't figure out how.

This sort of dive can be planned using the PADI wheel.

In Maui I routinely do dives to 100' or so that last 60+ minutes, using an AL80. Obviously these are multilevel dives and would be way off the table if calculated as a square profile dive. Very similar to the freshwater dive you refer to.

There are other ad hoc methods that people have developed, such as using average depth rather than max depth. There are a bunch of caveats on using this method, but within the limitations it works. This method also has restrictions on short SIs, and the one method I'm familiar with puts you into decompression on repetitive dives, and then has you extend the stops on the way back up such that you meet those mandatory deco obligations with extended shallow stops.

Like many things in life, there are a lot of different ways to accomplish the same task, with different benefits and drawback to each method. Also, just like a lot of other things in life, a blend of several methods works better than any one single method.

I primarily rely upon my computer, but use prior knowledge of similar profiles and a very, very rough tracking of average depth to do a validity check of what my computer is telling me.

--------------------------

If all you want to do is to do a rough check of the reasonableness of a multilevel profile, you can use the standard PADI RDP as a multilevel planning tool simply by treating the series of multilevel depths as a series of dives with 0 minutes SI between them. Just like with other averaging methods, there are a bunch of potential problems. You have to have the levels going from deep to shallow. If you dive all the way out the NDLs of the square profile table, then your 60 minute compartment will be within limits, but some faster compartments will slightly exceed limits. (The PADI wheel has MLs or multilevel limits that a a bit less than the square profile NDLs).
Using the standard table like this does work as a general pre-dive sanity check on whether or not a proposed profile makes sense, but then I use my computer to track the actual dive.

 

[goodive]

I have to get to this thread one more time to clear up some comments I made previously.
1. The original question from Apollon was about him loosing his computer and not having money to replace it and if he could dive without one using tables?
Simple answer YES.
2. Sometimes when I try to be funny, I will come across as being a jerk. (Sorry Stu S.). There are of course different tables based on the different algorithms which will lead you to different results.
3. Same apply to diving computers with the addition that you could change certain setting on most computers to make your diving more or less conservative.
4. Diving computer is not a magic box which monitors your body or diving conditions. It is a processor with a database based on the same theoretical algorithms as tables. Please don't tell me (except for Stu S., he has a free shot at me) that there are different models (I know that). They're all just the theoretical models.
Maybe one day there will be a probe which we will stick inside of our body and it will monitor our offgasing :cheeky:, but till that happened we have to live by accumulated experiences of previous divers and theoretical models based on various practical testing.
5. I am personally quite pro-computer (I better be, I spent enough money on the darn things) and as Stu S. rightly said, computer doesn't restrict your dives the way table would. When was a last time you dove a square profile on a recreational dive?
6. It is a personal preference if you dive a computer or tables. Neither choice is only right or wrong.
There are many divers who never use a diving computer and they prefer it that way.
There are many divers who would not dive without one and they prefer it that way too.
And there are many of us who might dive with a computer or two, or a computer in the gauge mode. It all depends on what we're doing in the water that day.
7. I don't have a problem with any of those choices. Just as I said before, be comfortable with YOUR choice, have a clear understanding of your computer or tables, understanding of your bailout procedures, don't blindly follow neither tables nor a computer.
Plan your dive and dive your plan, have a fun, stay safe.

Sorry about the dead horse, I just like to put it in.

 

[Stu S.]

A free shot? Johnnie Walker Blue Label, please.

Cheers!

 

[goodive]

Wow, that is my favourite too. I have the green one only. Actual picture of my liquor cabinet taken couple minutes ago.
Note: Current amounts of liqueur my not be accurately reflected.

 

[TMHeimer]

The computer is good if you are going deep (say below 80 feet?) for the extra safety. Also for the beep that goes off if you ascend too fast. It is also a must for multi level diving, though you want to be conservative here. I always use the tables also, computer or not. If you're going shallow, use the watch--it's easier.

 

[danrlazar]

if you do "square dives" as in most wreck diving,the tables are the way to go, but if you dive warm water reefs, most are multi-level dives, so you need to use the "wheel", and if you can use the "wheel" correctly God bless you. Remember this, we are all doing "computer assisted diving" which in short means stick too the rules, your brain is still the best computer.

 

[NudeDiver]

A while back I lost my Suunto Vyper wrist computer while attempting to gear up off a kayak. I fumbed it as my buddy inadvertently overturned my kayak while I was trying to put stuff on in the water. Anyway, I haven't replaced it because I don't have the money right now.

See my gear insurance thread - it might help you out.

I went back to tables instead. I actually like using the tables. I've gotten to the point where I have memorized a lot of the bottom times at different depths. Most of the diving I do is single tank, 60 to 80 feet max. A lot of the dives are shore dives and so there is most times a gradual decent and accent as we follow the ocean floor out and back in. On the deeper dives or open ocean diving off boats I always do a series of stops starting at 30 to 50 feet depending on what the max depth was.

Has anyone here given up the computer for one reason or another and just gone back to doing the math in the head?

You don't need a computer - but I wouldn't rely on memory either. If you're going to rely on tables, you might want to consider looking at them every time, every dive. Our memory isn't always what we think it is - and when it comes to something like this, why take such an unnecessary chance?[/QUOTE]