Do I need a Dive Computer?

[Chad Carney]

But did it, (the $8 LP table), come with a warranty? :1poke:

I only found it at LP, I didn't buy it. (Warranty? ... at LP, pretty funny!)

I received my OW through SDI, and we focused on using a computer, although we did go over tables briefly. Mike

The SDI text has an awesome tables instruction section; highlighted and crystal clear. You can rip it out, and laminate it if you want. (Saves $8 off the kit.)

It's great when OW students have seen their computers in the pool, learned to use them, have seen downloaded profiles of other's dives before making their own. Finally they dive on their computers and then compare their own profiles!!!

Chad

 

[m7scuba]

I'm a new diver (doing my OW cert dives in March) and I already bought my computer (Mosquito). I am familiar with the tables and how to use them. I even figured it out before taking the class from stuff on the internet. It's easy. Our instructor pulled out a series of dives she did on one of her trips. She ended up getting about double the dive time by using her computer as if she had used the standard dive table. Another thing that I really like is the ability to download dive profiles.

I suppose this falls on deaf ears on a recreational board, but you can get significantly more bottom time using tables (particularly computer generated ones) than you can with just about all of the dive computers out there. (This assumes good physical conditioning and a willingness to push the limits.) You can easily plan multi-level with tables. That, plus learning to keep track of your average depth is all you need. If you don't want to push any limits you can still get the same bottom time you would with a computer that you would dive conservatively. It is a matter of understanding this stuff and it isn't rocket science.

As a computer geek, your above statement caught my attention. I don't think that I would want to use tables as my primary for recreational muti-level dives, but being able to generate them would be helpful. Is there a good thread that discusses this or a good place to look? I'm also not the type that would want to push the envelope - at least not for quite a few dives while I'm still learning and getting comfortable under the water.

 

[m7scuba]

You should always plan your dives (with the computer or tables), but with just a watch you have to remember to set the countdown timer before the dive, start the stopwatch when you descend, stop the stopwatch when you ascend, and start the countdown timer when you get to your safety stop. A computer does all this automatically, so in my opinion, a computer will handle much of the workload for you, as well as giving you longer bottom times on mult-level or repetitive dives.

I fully agree about planning. Even with a computer you should be able to figure out what your max bottom time is for your planned depth and probably the next deeper depth as well.

I have a Timex Helix DM as my backup. Since it water activates at 5 ft, it will start the stopwatch for you. It will also stop it once shallower than 5 ft. I guess you would still need to remember when you started your direct ascent and time your safety stop since it doesn't have a countdown timer. It also says to not press the buttons under water.

How would you handle a computer failure during ascent? Could you just use a standard profile? For example - if my max depth was 60 ft, then I would take the time that I exited the water and subtract 5 min to determine my bottom time (3 min safety stop, 30 fpm assent x 2 min). It would probably be off of the tables which would end my diving for the day, but maybe not.

 

[RTodd]

She ended up getting about double the dive time by using her computer as if she had used the standard dive table. Another thing that I really like is the ability to download dive profiles.

As a computer geek, your above statement caught my attention. I don't think that I would want to use tables as my primary for recreational muti-level dives, but being able to generate them would be helpful. Is there a good thread that discusses this or a good place to look? I'm also not the type that would want to push the envelope - at least not for quite a few dives while I'm still learning and getting comfortable under the water.

Yes, as standardly taught the typical dive table is limiting. However, you can dive average depths using dive tables and you can calculate multi level dives using dive tables if you know what you are doing. Although this is an oversimplification of the calculations, it is all your computer is really doing.

Personally, I use decoplanner because it is no frills and the other stuff gets in my way. It is on the GUE website. There are quite a few other software programs that work fine too. Choosing which one evolves into a debate about the quality of the model. Which, in my opinion, is not too important in the real world for typical recreational dives.

To put this in context here are two very typical mulit-level dives. I picked these because I dive them all of the time on recreational trips and could confirm them on dplanner (palm version of decoplanner) to make sure there was no deco involved.

Using 32% nitrox:

95ft/70ft/50ft. Spending 20 minutes at each depth. 45 minute surface interval and do the exact same multi-level profile except spend 15 mintes at each depth. (You could spend 25 minutes at 50 on the second dive if you wanted to do so.)

Now, if you actually dived at these depths or kept your average depth during each time range at these depths, very few people could make an aluminum 80 last this long. I am not advocating diving to the ragged edge of models, but that is what this table model "allows." You have to use your own brain to add the conservatism or you can have the software enter it in for you when you generate the tables. Try doing these dives while actually staying near these depth with just about any computer and see if you can keep it out of deco. The point is that computers don't actually give you any more bottom time. You can go to the trouble to truly plan your dives and still have as much or more no deco time as any computer diver.

 

[m7scuba]

Using 32% nitrox:

95ft/70ft/50ft. Spending 20 minutes at each depth. 45 minute surface interval and do the exact same multi-level profile except spend 15 mintes at each depth. (You could spend 25 minutes at 50 on the second dive if you wanted to do so.)

WOW...
I just plugged those dives into SDM and can really see the difference. The first dive was no problem, but the second dive had a deco obligation - 10 ft ceiling, 29 min ascent time after 45 min down. Actually there was a deco obligation after the first 14 minutes (10 ft ceiling, 9 min ascent time).

 

[DiverDusty]

You should get a computer. By now you probably wished you would have purchased at least something different than the dive gear you bought when you were first certified. The same principle applies here. You WILL get more bottom time with the dive computer, and BTW make sure you get one that has a Nitrox setting as well as air. For a few more bucks you might be glad.