Problems for a Kelp diver on a Caribbean dive,rental gear.

[Bombay High]

My computers now will not lock you out and will try to help you as best it can.

It cant drive you to the chamber.

You can change computers all you want, but if you dive badly you will get hurt.

No computer will change that.

 

[boulderjohn]

A computer that models decompression and detects that the diver has ignored the decompression plan and arrived at the surface with a potentially dangerous gas-load, should lock the diver out. That's part if its job.

A computer that does not lock you out is a very valuable piece of equipment in technical diving.

Last year my buddy and I planned a deep dive using V-Planner. Just for kicks he brought along his new Suunto HelO2 and tried to set its options up as much as possible to match the V-Planner algorithm. We followed our V-Planner plan perfectly, doing every one of our stops (starting at 190 feet) precisely as planned. That plan did not match the Suunto's algorithm, though, and it kept giving us constant warnings whenever we did not do something the way it wanted us to. Finally, while we were doing our stop at 20 feet, it went into gauge mode. If we had been using it as a backup to our V-Planner schedule, or if we had been relying on that while having problems it rather rather than intentionally following another schedule, it would have been useless to us at that point in the dive, just as it was useless to us for the next 48 hours.

Contrast that with a computer like the Shearwater Predator. You can input your dive plan and check out that plan before the dive, just as you would with V-Planner. You and your buddy can follow a schedule like V-Planners--with the computers as backups, or you can agree to follow your computers. If you are using your computers as a backup to a plan like V-Planner, it will constantly adjust, no matter how far you are deviating from its algorithm, and it will continue to guide you until you surface. If you surface with time left, it will still be ready to go on your next dive.

Let's say instead that you and your buddy agree to use computers to guide your ascent. You begin your ascent, but perhaps not quite when and at what depth you had planned. Your computers adjust. Maybe you and your buddy did not do things exactly the same, or maybe you have different computers with somewhat different algorithms. Whatever the reason, you are getting different ascent profiles. No problem. You decide which one to follow, and the other one keeps adjusting, no matter how far you have strayed from it. You and your buddy can stay together throughout the ascent. On your final stop, you decide which one you will use. If you decide that the one giving you the lesser amount of time is the one you want, again no problem. The other one will still continue to function, and it will be ready for you on your next dive. If you had a computers that locked you out, then you would have to separate on ascent to follow your individual computers, for fear that you would get locked out.

 

[flots am]

A computer that does not lock you out is a very valuable piece of equipment in technical diving.

Last year my buddy and I planned a deep dive using V-Planner. Just for kicks he brought along his new Suunto HelO2 and tried to set its options up as much as possible to match the V-Planner algorithm. We followed our V-Planner plan perfectly, doing every one of our stops (starting at 190 feet) precisely as planned. That plan did not match the Suunto's algorithm, though, and it kept giving us constant warnings whenever we did not do something the way it wanted us to. Finally, while we were doing our stop at 20 feet, it went into gauge mode. If we had been using it as a backup to our V-Planner schedule, or if we had been relying on that while having problems it rather rather than intentionally following another schedule, it would have been useless to us at that point in the dive, just as it was useless to us for the next 48 hours.

I use vPlanner and a depth gauge and bottom timer.

So far, the printed dive plan has never crashed . . .

flots

 

[boulderjohn]

I use vPlanner and a depth gauge and bottom timer.

So far, the printed dive plan has never crashed . . .

That's how a lot of people dive. That's how I have done it mostly.

That's not how a lot of other people dive, though.

In a thread on this topic several years ago, John Chatterton said that although he does use tables like that, he cannot be sure before a wreck exploration dive how deep he will go or how long he will stay there. He is charting new territory. Because of that, he likes to use the computers. He and his buddy each carry two. They have never had four computers crash.

 

[jimmy71]

I use vPlanner and a depth gauge and bottom timer.

So far, the printed dive plan has never crashed . . .

flots

I have a couple questions and please do not take these as attacks but I have asked this question of many other tech divers.

How many tables to you take underwater with you? Ie how many dive plans do you take? I would love to know what you have been taught and practice.

Jimmy

---------- Post added April 19th, 2012 at 09:22 PM ----------

boulder, I agree so much with what you see as the use of computer in Tech diving. I find it funny that people religiously follow V-planner, but do not trust a live version of V planner such at the liquidvision. Why is that less safe?

I was always told taught in my tech diving to have multiple redundancy with any critical systems. This includes many things including buoyancy, dive plans, air sources, regs, lights ect. I Plan a dive with V planner to get idea of deco obligations, time to surface, gas consumption, ect. I then dive with multiple redundant computers with various contingencies because I can not afford to dive with three top end tech computers. I currently dive with three computers. One VR3 that correctly predicts time to surface based on assumed gas switchs and any gasses can be changed underwater. This is my primary and what will dictate my dive if all functions correctly. My first back up is a recreational computer that allows for three gas changes but it usually very pissed thought the dive. While it allows for gas changes, it does not assume I will and bases the displayed information as If I remained on the current gas for the remainder of the dive and deco stops. Not good for predicting but will get me out of the water. My third computer is my all else fails computer. it is a two gas computer that has my bottom gas and 100% deco programed. This covers if I lost my 50% deco. I will admit I usually bend this computer at the end of most dives. Sometimes I will clear it, sometimes I will not depending on my mood.

My decision to turn a dive is based on many factors and are worked out with dive partner before. We will turn a dive for many reasons including temp, gas supply, or just being plan done. The V planner schedule is my most extreme option and seldom actually becomes my true run schedule. I like the idea of taking a slow assent rate far below a required one. I also do not like the feeling of having to rigorously follow a schedule. I have never liked the idea of doing X depth for X minutes. It always feels like it is pushing things. Anything less might feel like failure. I also think, Hell, if I am going to be punished with the deco schedule of the long dive, I might as well make sure I get all of the bottom time. I just do not see the point.

I will also qualify all of this by saying I am not currently diving below 250 and I am only diving with 2 deco gases. When you are looking at very short bottom times with long deco obligations, I am some of things and views will change.

Just some of my thoughts and I am a little drunk and do not feel like rereading the post to see if it makes any sense. Ask and I will be happy to clarify them while I am sober.

Jimmy

Jimmy

 

[flots am]

I have a couple questions and please do not take these as attacks but I have asked this question of many other tech divers.

How many tables to you take underwater with you? Ie how many dive plans do you take? I would love to know what you have been taught and practice.

No tables, but two dive plans: the planned dive, and a longer one in case something happens to keep me down a little longer.

I run it off on the laser printer, and tape it to a wrist slate with clear packing tape.

The plan is pretty much as it comes off vPlanner, listing depth, stops, etc.

flots.

 

[GrimSleeper]

No tables, but two dive plans: the planned dive, and a longer one in case something happens to keep me down a little longer.

I run it off on the laser printer, and tape it to a wrist slate with clear packing tape.

The plan is pretty much as it comes off vPlanner, listing depth, stops, etc.

flots.

I never thought to try packing tape. Thanks flots, you just saved me the $25 I was going to spend on a laminator, having got bored of writing out plans on wrist slates or in my wetnotes!

Oh, and +1 for planned dive plus a longer one, using V-planner. Have a lot of deep walls here, so also often carry a deeper plan, too, in case something happens to push us far enough past planned depth that it can't be averaged out.

In the past I carried a VR3 as a bail-out in case of being forced way outside the boundaries of the original plan (and to save on deco time if ending a dive really early), but have had so many failures with it - can't get decent batteries out here, and they REALLY don't like voltage fluctuations - that it's basically a paperweight now. Not much use having a bail-out that decides, halfway through a dive, to start a new dive of its own inventing...

 

[jimmy71]

No tables, but two dive plans: the planned dive, and a longer one in case something happens to keep me down a little longer.

I run it off on the laser printer, and tape it to a wrist slate with clear packing tape.

The plan is pretty much as it comes off vPlanner, listing depth, stops, etc.

flots.

So you have a run schedule for you planned depth and time and one for time +5 min I assume? I will also assume by this you also have a limited bottom (ie the sea floor) so that a schedule for additional depth is not needed.

Once again I am not attacking with these questions, I am just curious to learn how other divers think.

What are your plans for a lost deco gas?

Also, If you plan was 200 for 25 min or 60min or X min, do you follow the full deco schedule if the dive is called after 5 min at depth?

Jimmy

 

[flots am]

What are your plans for a lost deco gas?

Share my buddy's, or use my back gas (lost deco gas is in the dive plan).

Also, If you plan was 200 for 25 min or 60min or X min, do you follow the full deco schedule if the dive is called after 5 min at depth?

I know the NDLs for various depths, and if it really was a 5 minute dive, I'd have no problem just doing a normal ascent with a few minutes @ 15' or 20'.

If it was 15 or 20 minutes instead of 25, I'd follow the plan.

Dive computers are nice for recreational diving and I use one all the time, but that's because the risk incurred by a failure is minimal. If the computer is whacked out, the surface is always available.

When the penalty for a hardware failure is injury or death, I much prefer a printed plan.

Multiple different computers really isn't a fix, because different computers use different algorithms and they'll never agree (a man with two watches never knows what time it is).

Multiple instances of the same computer isn't a fix either, since a software problem in one, is likely to be replicated in all of them.

flots.

 

[jimmy71]

Share my buddy's, or use my back gas (lost deco gas is in the dive plan).



I know the NDLs for various depths, and if it really was a 5 minute dive, I'd have no problem just doing a normal ascent with a few minutes @ 15' or 20'.

If it was 15 or 20 minutes instead of 25, I'd follow the plan.

Dive computers are nice for recreational diving and I use one all the time, but that's because the risk incurred by a failure is minimal. If the computer is whacked out, the surface is always available.

When the penalty for a hardware failure is injury or death, I much prefer a printed plan.

Multiple different computers really isn't a fix, because different computers use different algorithms and they'll never agree (a man with two watches never knows what time it is).

Multiple instances of the same computer isn't a fix either, since a software problem in one, is likely to be replicated in all of them.

flots.

Ok I suck at the multi quote option. And once again I love discussion on these things so do not take any of them as an attack. I do not fault anyone for diving any way they want as long as the accept the risks and benefit and are comfortable doing so. This is the last time I am making this disclaimer.

"Share my buddy's, or use my back gas (lost deco gas is in the dive plan)."

So you have a run schedule for back gas only with you on your dive?
Lets say you are diving with 50% and 100% deco. You lose your 50%. Your plan is to share your buddies. Plan is for him to to finish/complete each stop and then you on his 50% gas. Are you on gassing on those deeper stops while not on the O2 rich deco? You can safely ignore the possible off gassing. What about your buddy as he waits for you to finish your time at a stop? Do you have an additional run schedule for this?


"I know the NDLs for various depths, and if it really was a 5 minute dive, I'd have no problem just doing a normal ascent with a few minutes @ 15' or 20'.

If it was 15 or 20 minutes instead of 25, I'd follow the plan."

Ok, it was 60 min at 150 dive plan, You do thirty before it is turned. Do you follow your orig run schedule?
How would this not be considered best guess? If you had your laptop and a printer at depth with you, Would you be willing to follow the new run schedule V planner calculated?


"When the penalty for a hardware failure is injury or death, I much prefer a printed plan."
The vast majority of equipment we dive with is hardware and we assume ANY and ALL can/will fail. This is why we have redundancy in all systems that may lead to injury/death. I do not see of this is any different. While I have never had a Knife fail on me, I assume it can/will and consider it a critical system and thus have at least 1 if not multiple backups. I can lose a slate and a run schedule can get damaged. You do have redundancies, but of course you would because it is considered a critical system.

"Multiple different computers really isn't a fix, because different computers use different algorithms and they'll never agree (a man with two watches never knows what time it is)."
Multiple computers running multiple algorithms is a benefit and a safety feature as I see it. Feel free to clear them all. If you do not like what a computer tells you, do not dive it. I do not own suuntos as the algo is to conservative and I do not like what it tells me, so I do not dive them.

"Multiple instances of the same computer isn't a fix either, since a software problem in one, is likely to be replicated in all of them."
Vplanner is software. Do you plan your dive with multiple DIFFERENT deco planning software? The usually practice is for each member of the team to plan the entire dive based on the same gasses/settings and then come back together and compare the run schedule. They should all agree. This decreases the risk of someone entering incorrect data or misinterpreting the plan. It is unlikely that two people would make the same mistake if they independently entered in all the data. This is a double check.
If both people go home and punch in the dive plan on Vplanner, and it has a glitch, this would be replicated in both run schedules.


I fully assume my computer will fail. I fully assume my knife will fail. I fully assume my primary reg will fail. I fully assume my X will fail. I have ATLEAST one quick simple solution to each. That being said, I will not use my redundent bladder if my primary does not fail. I also will not use my backup light if my primary does not fail. I also will not use all three knifes if the first one does the job.

I really enjoy discussions a long these lines because we are all logical people who value our lives, and yet we all have different conclutions on the best way to protect ourselves. I loving hear the rational of others and presenting my own. I am happy to change my practice and policies and have done so in the past when I had not understood the rational behind decissions. So please do not interperate my discussions and questions as attack or flaming you. Only through open discussions will we advance our sport.

jimmy