Teaching Computers in OW class vs tables

[Scubaguy62]

Again, the worst case scenario is that your computer fails, and you have to abort the dive, and not dive for 24 hours.

I guess is hard for some folks to understand, and I once again apologize for making this connection, but on any aircraft equipped with a full autopilot, you set the AP and FMS according to your flight plan, which is based on what???? Charts and approach plates (synonym of dive tables).

If you have consulted your tables during dive planning, and you have set your computer according to the NDLs on the appropriate RDP (21%, 32% or 36%) or the Wheel, and have started your time at the start of the dive, and if according to that, you're still within the NDL, there should be absolutely no reason why, after aborting the dive, you'd have to wait 24 hrs., especially if you have another depth gauge available. Perhaps do a little longer SI and press on.
I agree with this..

What really happens when your computer dies?

Your depth hasn't changed

Your group/deco status hasn't changed

You can still breathe

You can still move

You can still think.....

The PADI AOW manual mentions using the tables as a back up for the computer, and while that isn't incorrect, I prefer the reverse, using the computer as a back up for the tables. I use my Atmos 2 in computer mode all the time, and every time I dive I set it for 1- the EANx mix I'm using (I dive EAN 100% of the time), 2- to my maximum planned depth, and 3- to the NDL for that depth. Then the computer becomes my "autopilot."

 

[diverbrian]

The fact of the matter is that while I might do the nice the friendly ascent, my tables don't cover a good number of the dives that I do. They are not designed for multi-level. Both my SSI and IANTD tables are designed for square profiles.

That being the case, many of my computer dives go off these tables. The 24 hrs. is designed to ensure that your body has completely off-gassed all nitrogen before you hit the water and dive tables by "letter groups" again. This is actually a pretty simple concept and while I might always stay within NDL's (unless I did plan the dive by tables and that is always dive one for the day to ensure that lack of nitrogen thing), I don't feel that playing with DCI is worth the risk. I would wait the 24 hrs. and the hit the water again the next day.

 

[Web Monkey]

The PADI AOW manual mentions using the tables as a back up for the computer, and while that isn't incorrect, I prefer the reverse, using the computer as a back up for the tables.

The computer manufacturer recommend aborting the dive and waiting 24 hours if the computer malfunctions.

Personally, I'm with them and would abort the dive if the computer failed and wait 24 hours as recommended, instead of testing to see if my dive insurance works. It's not worth the risk.

Terry

 

[Scubaguy62]

A ML dive can be planned with the Wheel version of the PADI RDP, which when flipped to the other side, shows 6hrs as the magical time to go from NDL at 130 to Pressure group A.

I agree that the great majority of dives end up, in one way or another, being a ML dive. However, the table assumes the entire time is spent at max depth for the plan, if the dive isn't planned as a ML dive, using the wheel. So, if the plan is to dive to NDL for 70 fsw, for example, which is 40 min NDL according to PADI tables, if the dive ends up being 70, 55, 40, and lasts 40 mins, the diver is already in the conservative end and should not need to wait 24 hrs to dive again, if the computer failed 35 mins into the dive.

Of course, this is all theoretical, and while I don't believe it would be necessary to wait so long, especially in light of careful planning, it's a matter of comfortability and personal preferrence, which neither I, nor anyone else has a right to criticize.

 

[scbababe]

I agree that the great majority of dives end up, in one way or another, being a ML dive. However, the table assumes the entire time is spent at max depth for the plan, if the dive isn't planned as a ML dive, using the wheel. So, if the plan is to dive to NDL for 70 fsw, for example, which is 40 min NDL according to PADI tables, if the dive ends up being 70, 55, 40, and lasts 40 mins, the diver is already in the conservative end and should not need to wait 24 hrs to dive again, if the computer failed 35 mins into the dive. Of course, this is all theoretical, and while I don't believe it would be necessary to wait so long, especially in light of careful planning, it's a matter of comfortability and personal preferrence, which neither I, nor anyone else has a right to criticize.

Hello scubaguy62!(hubby) You know, I respect your opinion and I'm blessed with such an inteligent partner. However, I like the computer and apreciate it's precision. We as divers are lucky for such an invention!

Personally, I hate having to do the tables but it's a tactic that all divers need to know and learn! I tried getting away with learning them but with a hubby like this one is not easy. It's like boot camp at my house, I can't get my dive computer until I know my tables (*%#@!)

 

[Charlie99]

The computer manufacturer recommend aborting the dive and waiting 24 hours if the computer malfunctions.

Personally, I'm with them and would abort the dive if the computer failed and wait 24 hours as recommended, instead of testing to see if my dive insurance works. It's not worth the risk.

It's your COMPUTER that's broke, not you.

Would you really wait 24 hours if it was the first dive of the day, and it was a 40' dive that you know was only an hour long?

While I'm not part of the "computers rot yer brain" crowd, I do believe in keeping track of my depth and time in sufficient detail to know at least roughly what my N2 loading is.

If I've done agressive dives and am heavily loaded, I would probably call it a day after a computer failure. But if I'm well away from the limits (the MODEL limits, not the square profile table limits), then I'll move over to the table and dive conservatively, and add shallow hang time. I'll also do the common sense check of looking at my buddies computer to see that it is saying what I expect it to.

OTOH, I find it unecessary to blindly follow a "get out of the water for 24 hours" edict by a computer manufacturer that is forced by liability concerns to be overly conservative.

 

[Charlie99]

I use my Atmos 2 in computer mode all the time, and every time I dive I set it for 1- the EANx mix I'm using (I dive EAN 100% of the time), 2- to my maximum planned depth, and 3- to the NDL for that depth. Then the computer becomes my "autopilot."

This might work well in Broward county where the 3rd reef doesn't have much height to it and therefore your dives are reasonably close to square profile, but in other locations where there is a lot to look at over a wide range of depth, this method of planning is, IMO, overly restrictive.

I prefer to do a rough multilevel plan using the RDP.

 

[ShakaZulu]

Ok, I have question for all the table dewds.......... I always log my dives to the logbook after a dive.

Diving Air

Dive 1

Dive Time - 28min
Max Depth - 99ft
Ave Depth - 62ft
Safety Stop - 3min (stayed within the NDL limits as shown by the computer)

Dive 2 (SI 1:09)

Dive Time - 25min
Depth - 85ft (last time I looked, the computer stopped working)

Immediately accended with my buddy and did a 3min safety stop. When can I do my next 85ft dive again?

 

[Scubaguy62]

This might work well in Broward county where the 3rd reef doesn't have much height to it and therefore your dives are reasonably close to square profile, but in other locations where there is a lot to look at over a wide range of depth, this method of planning is, IMO, overly restrictive.

I prefer to do a rough multilevel plan using the RDP.

You're right about the reef structure in So. Fla.; we don't do a lot of wall diving here. On the other hand, when diving the Spiegel Grove, for example (a definite ML dive), I use the wheel to plan my levels, and set the max time on the computer for what the RDP says. Then I use the computer to monitor my plan while diving it.

Usually the second dive after the Grove is at French Reef, which is so close to the SG that the SI ends up being 20 mins or less, and that reef has areas where the depth ranges from 30 to 60 fsw. Overly restrictive??? perhaps, but I much rather err on the side of caution.

It's like boot camp at my house

C'mon babe, it's not that bad...at least now there's a greater motivation...the 35% emp. discount..

 

[Scubaguy62]

Ok, I have question for all the table dewds.......... I always log my dives to the logbook after a dive.

Dive 1

Dive Time - 28min
Max Depth - 99ft
Ave Depth - 62ft

Dive 2

Dive Time - 25min
Depth - 85ft (last time I looked, the computer stopped working)

Immediately accended with my buddy and did a 3min safety stop. When can I do my next 85ft dive again?

Need more info... Right off the bat, I'd say take a rest for the rest of the day.... and spend the rest of the day monitoring yourself for signs of DCI.

On the other hand, was the dive on air, or any form of EANx? How much of an SI did you have between dives 1 and 2? It would also help to know how long were you at 99 fsw, and how long were you at your average depth. If we figured the 28 mins at 100 fsw (99 fsw rounded up), and assuming the gas was 21%, you exceeded the NDL, according to the PADI RDP by 8 mins. In that case, the second dive aggravated the N2 loading.

If on the other hand, your gas was 32%, even if the entire time was spent at 100 fsw, you're 2 mins under the NDL for 32%, but you should have also done a safety stop at the end of Dive 1, and you're not saying you did. At any rate, I would wait anywhere between 6 - 12 hrs. to dive again.