Computer or Tables or Both?

[HowardE]

There's been a lot of discussions on SB about dive tables vs computers in the recreational dive areas on the board... So...

To the tech divers out there... Do you plan a dive from a dive table? Do you cut your own table using desktop software? Do you just dive your computer?

Personally, I run my plan in both V-Planner and MVPlan. I print out and laminate the table with runtimes at -2, 0, +2, +4, and +6 minutes. And 1 column at planned time, but lost deco gas. I carry this in my pocket on the dive.

Then I run the dive on my Shearwater computer (or the Vision Electronics on an Evolution - and use the Shearwater as a backup), and (for open circuit dives) use a backup bottom timer.

What do you do?

 

[rjack321]

Do you run any alternate depths? How many?

Or planned depth last week was 170+. Turns out our max possible (without a shovel) was 115ft. We adjusted on the fly.

 

[Diver0001]

I cut tables on Vplanner and follow those. I usually make 3 plans

1) what I intend to do
2) one for a bit deeper and the same bottom time
3) one for the target depth but 10 min longer
My snafu plan usually consists of looking at what it would take to grind out the deco on back gas.

The computer (a vytec) is backup but I've never needed it.

Other relevant parameters: technical nitrox and open circuit. I think if you're doing trimix these days you really need to think about rebreathers, which might change how you plan your dives.

R..

 

[HowardE]

Do you run any alternate depths? How many?

That depends on the dive itself.

A few weeks ago, I did a shipwreck. The dirt was at 200 feet. The bulk of the wreck was at 180 Feet. I cut 3 different tables all together. 180, 185, and 190 for depth, and then my same schema for time. I have a laminator at home, so it's no problem to print these out the size of a CD cover... Laminate them, and even zip tie 3 together.

The other day. I did a dive to 185 Feet. I KNEW the bottom was a hard 185, as I have both sidescan sonar data, and detailed bathymetry of the area. Also - my plan was to descend to the bottom, and stay on the bottom.

As I said earlier... I just use the tables as a backup...

 

[RJP]

For deco dives I've not done, not done recently, or don't do often I cut V-Planner tables in addition to a +5min plan. My dives are "hard bottom" wreck dives and I plan for max depth. I also add a "lost gas" scenarios.

I write the "main" schedule with a Sharpie on vinyl tape adhered to a wrist slate. The contingency tables are written in my Wetnotes and stowed in my pocket if needed.

On the dive itself I dive the V-Planner plan but also run my Vytec DS computer in computer mode, and then I clear both the V-Planner schedule and my computer before exiting the water. The computer is more conservative then V-Planner with "+2 Conservative" selected but I figure an extra few minutes on 100% at 20' isn't such a bad thing. (as long as you watch 02 exposure, of course.)

For wrecks/dives that I'm familiar with I will refer to V-Planner as a quick check when planning the dive (and make sure I've got backup tables in my wetnotes) but will then dive my computer.

 

[DA Aquamaster]

I use DPlan or Palm VPM (VPM A model) to develop the deco and gas plans, including lost deco gas contingency plans and a plan for an extra 5 or 10 minutes on the bottom depending how deep the bottom is. Generally speaking I do not do a plan for 10-20 ft deeper, unless there is truly doubt about the depth.

My preference for cave dive planning is DPlan as it is very easy to plan numerous segments (up to 7) of various depths and times going in and out of a cave.

Once I know the deco plan and I know the gas plan works, I'll do the dive referencing the computer and ensuring I clear the computer at each stop, but it is basically mirroring the tables so it is not entirely accurate to say I am diving the computer. The computer becomes the primary reference if there is a need to deviate from the plan. Examples of this could include the dive being turned early (no need to do the extra deco originally planned), going deeper than planned on a wreck in order to assist another diver (a non team mate or soon to be ex-team mate) who was significantly deeper than I was, or encountering a significant delay during an exit from a cave that made the planned profiles and contigencies invalid.

Its probably most accurate to say I use the computer. but only after planning with custom cut tables so that I know in advance what the computer is going to tell me and what I will do if the computer stops telling me anything or tells me something that is suspect.

I also carry an Uwatec bottom timer as a back up for depth and time information in the event the computer fails and as a cross check of the computer.

 

[DA Aquamaster]

I write the "main" schedule with a Sharpie on vinyl tape adhered to a wrist slate. The contingency tables are written in my Wetnotes and stowed in my pocket if needed.

Great idea that would save having to clean the pages of the slate. I carry the primary plan on page one of the slate and the contigency/lost gas plans on the front and back of the other two leaves of the wrist slate.

 

[Diver0001]

It's funny you guys would use the tables as a backup for the computer and not the other way around.

Generally, for the dives I do, which are admittedly not the most aggressive deco dives (the maximum I can manage with the kit I use is up to about an hour on the bottom in anywhere up to about 36 metres, which gives run times about 90-95min), I find that the computer has cleared before my "roll-your-own" plan is done, probably because I don't spend the entire time at max depth.

If I had to fall back from the computer to my tables then I'd end up trying to figure out where to put myself back on the map again. The only way I could imagine doing it would be to do all of the stops deeper than the ceiling my computer shows me according to my Vplanner plan so if the computer craps out somewhere along the line I can fall back to where I know I am.... but if I'm going to do that, why not just follow the roll-your-own plan all the way up....?

The way I see it you can't just pick up the backup plan at whatever depth you're on unless you did all the other stops or you'll be missing some (deep) stops which will affect your last stop, probably significantly. What do you do then? Guess?

R..

 

[Diver0001]

Great idea that would save having to clean the pages of the slate. I carry the primary plan on page one of the slate and the contigency/lost gas plans on the front and back of the other two leaves of the wrist slate.

That's what I do too.

R..

 

[HowardE]

It's funny you guys would use the tables as a backup for the computer and not the other way around.

Generally, for the dives I do, which are admittedly not the most aggressive deco dives (the maximum I can manage with the kit I use is up to about an hour on the bottom in anywhere up to about 36 metres, which gives run times about 90-95min), I find that the computer has cleared before my "roll-your-own" plan is done, probably because I don't spend the entire time at max depth.

If I had to fall back from the computer to my tables then I'd end up trying to figure out where to put myself back on the map again. The only way I could imagine doing it would be to do all of the stops deeper than the ceiling my computer shows me according to my Vplanner plan so if the computer craps out somewhere along the line I can fall back to where I know I am.... but if I'm going to do that, why not just follow the roll-your-own plan all the way up....?

The way I see it you can't just pick up the backup plan at whatever depth you're on unless you did all the other stops or you'll be missing some (deep) stops which will affect your last stop, probably significantly. What do you do then? Guess?

R..

I use the table as a backup, because I have a computer that is designed for technical diving (Shearwater Pursuit). It runs the same algorithm as my dive planning desktop software, but in real time. The table is a square profile, which is rarely the case on a real dive. Ascent rate, descent rate, are all very specific on a dive table. Changing those parameters means you're NOT diving the table....