Computers and "technical" diving

[Divesherpa]

I have spent many hours thinking about why some members of the board are so anti-computer and some are pro-computer (with appropriate backup, of course). Finally the reasonings began to make sense. If someone is diving a "square" profile with an absolute bottom and very little depth variation (which it seems most of the anti-computer guys are doing), than a computer is a very ignorant tool to be using. A computer does nothing for you here that tables won't do.
The reason I am pro computer is because my typical profiles are nowhere near square. We have cave systems in Florida that have depth variations in excess of 100 feet. The profiles are very up and down. In this scenario, tables are very damaging as the hangs become very long very quickly. Planning a multi-level dive of this magnitude (with no knowledge of how the system depths vary) is not feasible.
For example, in a two hour dive at Ginnie, if you planned for max depth of say 100 feet but spend most of your time between 50-80, your hang would be quite lengthy. With a computer (using tables as redundancy in case of failure), your hang is cut significantly (and SAFELY). Throw in the deep stops that almost everyone advocates and you are good to go.
For the die hard computer haters, I understand why your profiles lend themselves so easily to disliking computers. I use tables on wrecks and have a computer for profiling/BT.
Sometimes you have to appreciate the value of a tool if used properly. :D
Cheers and safe diving

[WreckWriter]

I actually do it backwards to most folks, I use a computer as a backup. Not a backup for lost tables but for a busted plan. An example would be the site being deeper, or shallower, than had been planned for. When the planning is right on I dive the tables generated by Deco Planner or Decoweenie.

I think its important, if one chooses to use a computer, that it be the proper computer for the job which, for tech diving, leaves only a couple options. Mine is a VR3. I hear DiveRite is going to release a mix computer soon based on their Nitek3 design. They're hoping to take VR3's market share by pricing much lower.

Tom

[Waterlover]

I agree with the point that wreckers and computers might not be the thing to do. I use only tables on wrecks but like to bend my computer sometimes. I have cut some special tables for places like Cow Springs to avoid a 30' stop, plus some other assumptions about the dive. I have a 32% mix table for ginnie that a 90 minute dive requires 39 minutes of deco. A table can be cut but it takes some knowledge of the cave and the tables you are using to do it. When using tables I just feel better and in control of the dive. Your right a computer is just a tool. If I use one I prefer to use it to supplement the puter tween the ears, not depend on it to get me out. Just my $.02 :)

[Walter]

I don't understand your opposition to using a computer on wrecks. IMHO, wreck diving is ideally suited to the advantages of computers.

[maddiver]

What is causing you to do 39 min of deco at Devils on 32%? Is that without o2 deco? If you run 32-33 up to 100min at Devils you should require no longer than 20-24min max deco time.

On cow...why would you suggest cutting tables to avoid a 30ft stop (inside the restriction I guess?). Seems to me to be part of the overall safe ascent and there really is no way to 'make up' shallower for blowing off a deeper stop....but there is the possibility of blowing off or shortening shallower stops after doing or lengthening the deeper ones. Old habits and teaching of 'getting out of deep water fast' are hard to break- thank your original ow instructor and agency.

True the knowledge is requisite, hence the value of standard mixes. That way you 'learn' the deco and not simply memorize the tables for a particular depth and time component.

For example- I recently returned from Scapa Flow in the north of Scotland. I did not take a computer not even for the 'recreational depth' dives which most of them were. Merely requested and ran with the mixes/deco that I was used to (many of the profiles approached those that I had run in places like Devil's or lower peacock etc). No cutting tables, no recalcing for contingencies, no altering computer settings between diving.....pure computational freedom and the freedom from having to bring computer, laptop, or pda along. I was free to concentrate on the diving.



Waterlover once bubbled...
I have cut some special tables for places like Cow Springs to avoid a 30' stop, plus some other assumptions about the dive. I have a 32% mix table for ginnie that a 90 minute dive requires 39 minutes of deco. A table can be cut but it takes some knowledge of the cave and the tables you are using to do it. When using tables I just feel better and in control of the dive.

[maddiver]

Walter once bubbled...
I don't understand your opposition to using a computer on wrecks. IMHO, wreck diving is ideally suited to the advantages of computers.

At first this seems quite logical. Upon further inspection, what happens if your computer fails...what then? You will say to just ascend....Ok...to where..what depth and why? 15ft 20ft 30ft? What happens if it craps out when you have a manditory deco ceiling or malfunctions? The key to the arguements surrounding the nonreliance on computers as 'computational devices' are pretty simple. If any piece of equipment fails, you want to minimize the effect of the failure..right? Well if your computer fails you lose your bottom timer and your ascent indicator (deco obligation or nostop time). Would you not benefit from securing this info in your own brain that if it fails...then you have a much bigger problem than the deco ceiling above you.

Your buddy has a computer right? Great that's your back up....or did he really have the same profile and is it the same computer and settings as yours with the same repetitive dive info? If you used your 'grey matter tables' you merely use his depth indicator and timer and have him accompany you throughout the most 'conservative' of the two ascents either of you would be required to do.

[Divesherpa]

Hey Waterlover,
Do you actually use this profile at Ginnie? Typically, a 90 minute dive in Ginnie will net maybe 17 minutes (O2) plus the stop at the rock at 40 for a few and then in the bowl at the eye for a few. We do this dive a few times a week, give or take a few minutes (or an hour). I am thankful for the additional tool on dives like these.

I've done several dives in Cow as well. Where are you going in Cow to mandate doing deco in a restriction?
We do stops in the hole in the ceiling prior to the second restriction "Sandy", and avoid this spot all together.

Thanks for the input as I enjoy learning from others.

Cheers

[Divesherpa]

Hey Mad,
Where did you get the devil? That's funny!

[Walter]

Those arguments are not wreck specific, they apply to any dive.

For a back up, I use my other computer.

[maddiver]

Divesherpa once bubbled...
Hey Mad,
Where did you get the devil? That's funny!


He was just waiting there and somehow he seemed appropriate- although I'll have you know he's a 'DecoWeenie'.

[maddiver]

Far fetched but probably as statistically valid as a first stage failure....

Do you employ special battery changing/servicing regiments to fend off this possibility? And should the 'unthinkable' happen, what would be your plan of attack? Lets say you were diving the HydroAtlantic in your own Sunshine State and incurred a deco obligation....you set the parameters and help us understand the logic of why two computers would be more appropriate than tables and your mind.

I certainly hope everyone doesn't still believe that old wives' tale that 'computers get you out of the water faster and safer'.....most of the time the computer guys leave me deep and I'm out of the water and dry by the time they finish their 20 (and I'll argue my 'profile' was safer and less 'symptomatic'. Go over and visit the 'Ask Dr Deco' section when Wenkie is there...he'll help you with computers vs tables argument.



Walter once bubbled...
Those arguments are not wreck specific, they apply to any dive.

For a back up, I use my other computer.

[Divesherpa]

I was a big fan of using another computer as back up at one time also, but fortunately, no longer. There is a device used to pinpoint locations in a cave in reference to the surface. Hell of a surprise when it started and the computers went kaput. I will never get in the water without tables again.
Cheers and remember that electronic things break.

[Waterlover]

The Ginnie dive is without O2. The Cow dive is done to avoid blocking the restriction doing a 30' stop. A 125 runtime back to the entrance to the restriction results in a 11 minute stop @ 40 ft then 19 total @ 20 and 10. This tables assumes I spend between 20-80 minutes at 105ft I have runtimes from 50 -125 minutes on the table. I also consider my tables to be very conservative and can still get out of the water before most computers.

[Divesherpa]

Hey Waterlover,
First, let me thank you for not blocking the restriction. Second, let me recommend O2. Whoever you decompression instructor was should have informed you that doing back gas deco is not the best thing to do. Do you have contingency gas in the water for a wtf? If not, you may want to speak with someone next time you are in Fl as I would hate for you to get bent due to gas problems.
2 hours is an eternity in Cow. You are sidemount? Lining out all of the tunnels passable in backmount doesn't take much longer than this.
Cheers and safe diving.

[AquaTec]

your question seems to be on which computer to use.

for technical diving there is only one. VR3 it will change the way you dive.
The reason i say the only one, is because it is helium friendly, uses hetox for deco profiles, can change gasses etc underwater, ++++

only those who use it really understand how benificial it can be. for instance you dive is now decided on how much deco you want to do. so say you know you have enough gas to do 1 hours deco.

bottom time becomes less important, you simply watch your deco time, [and of course your gas consumption,] especialy in caves or wrecks as you are diving a saw tooth profile. you will find that your run times are extended. and for those square patterns like in open ocean dives you will be out of the water well before the rest of the team. [or at least you will know that you are doing that "extra" deco

as for redundency, it is like every other piece of gear. have two or more. I personaly use two VR3's and cary tables in my pouch.
I have had the computers fail before, but it doesn't prevent me from using them. I have had regs fail too but i still use a regs. the same with almost every piece of gear

[techdiver2us]

For a "technical" dive there's only one thing I count on - tables. Dive with 2 computers and a bottom timer. Having had computers turn to pumpkins too often, tables are my plan, computers are for verification only.

[AquaTec]

techdiver2us once bubbled...
For a "technical" dive there's only one thing I count on - tables. Dive with 2 computers and a bottom timer. Having had computers turn to pumpkins too often, tables are my plan, computers are for verification only.

why spend the money on computers then, just use a bottom timer and tables. the dark ages embase you

[Waterlover]

Sherp,
next time I talk to Barb I'll scold her for not reenforcing the O2 deco enough......:):).

[DocRCH]

I'll throw in my 2 cents... I usually use a computer on wreck dives where I do not plan to do a gas switch during deco. I also have a bottom timer so if the computer craps out I have a clue about where I am in the dive. If I am doing a deeper dive where I switch to 50/50 then O2, I usually have two bottom timers along with the slate and the dive plan.

The computer is a good tool for diving. It is not perfect and not infallible.

Robert :doctor:

[Divesherpa]

Hey Waterlover,
I forgot about that tie.
You may want to seek some additional training if she was your last instructor. Great new information has come out in the last few years.
My "training" was cutting edge once. The deco methods that we are using on a quazi-daily base now are very different than what I was taught.
Cheers, and don't forget the O2.

As a side note, your "instructor" uses computers exclusively unless running tables from memory.

[techdiver2us]

AquaTec once bubbled...


why spend the money on computers then, just use a bottom timer and tables. the dark ages embase you Because not all my dives are technical and a verification of sorts. I like the Matrix to at least clear RED no matter what and the Cochran only handles 2 gases. By the time I got to mix I refused to buy more computers since they really are problematic, especially if you try and depend on them.

[AquaTec]

it seems so many peple are afraid of computers, or at least don't trust them.
Who has acualy had a problem with their computer, that wasn't a result of not changing the battery when they should.

If you don;t trust your computer for deco "technical" dives, then how can you trust it to keep you out of deco, how do you know that you are on a no deco dive. or what if you are on a computer dive and then it fails. do you go to tables, and use you max depth and time to evaluate all the deco you are obligated to.

[techdiver2us]

AquaTec once bubbled...
it seems so many peple are afraid of computers, or at least don't trust them.
Who has acualy had a problem with their computer, that wasn't a result of not changing the battery when they should.

If you don;t trust your computer for deco "technical" dives, then how can you trust it to keep you out of deco, how do you know that you are on a no deco dive. or what if you are on a computer dive and then it fails. do you go to tables, and use you max depth and time to evaluate all the deco you are obligated to. Because I don't trust computers for deco. They're great for NDL dives and mild deco scenarios that may pop up. But a planned deco dive is best run with tables. Any time you spend shallower than your planned depth is an added safety bonus. Learned a lesson early that still holds true - Murphy's Law comes heavily into play at about 150'.

[AquaTec]

techdiver2us once bubbled...
Because I don't trust computers for deco. They're great for NDL dives and mild deco scenarios that may pop up. But a planned deco dive is best run with tables. Any time you spend shallower than your planned depth is an added safety bonus. Learned a lesson early that still holds true - Murphy's Law comes heavily into play at about 150'.

which by defalt means that you trust them to keep you from going into deco. constantly moving shallower and shallower to keep out of deco.

if you don;t trust it to do deco dives, then you must plan for a failure at the end of a long no deco dive.

for example say you are at 100 for 20 then come up to 70 for 10 then up to 50 for 20. your computer sees this as a no deco dive.
your current run time is 50 minutes. no what we know is possible [according to you] the computer fails.

thats cool cause you got back up tables.
so i guess that would be 100 feet for 50 minutes now what.


so my point here is you are allready completly trusting your computer on deco dives, so whats the difference.

[Uncle Pug]

AquaTec once bubbled...
so i guess that would be 100 feet for 50 minutes now what.

That would be a censored profile and we would do the censored and climb out happy.

Besides... since we are DIR we would be using EAN32. :D

[AquaTec]

Uncle Pug once bubbled...

That would be a censored profile and we would do the censored and climb out happy.

Besides... since we are DIR we would be using EAN32. :D


explain a censored profile

I don't care what gas you are using, the point is if you don't trust a computer on a deco dive how can you trust it to keep you out of deco.

[Uncle Pug]

AquaTec once bubbled...
explain a censored profile

I don't care what gas you are using, the point is if you don't trust a computer on a deco dive how can you trust it to keep you out of deco.
Can't tell you.... this is your travel year:D

But I will say that I whole heartedly agree with your last statement there. Course I don't trust them for either.

[AquaTec]

PUG it is nice that we agree on something.

just because i spent all my money traveling doesn't mean i don't want to learn anything this year. it just means i won't be taking any courses....probably

[spiro]

I spent quite a few years working in a deco chamber with divers bent to varying degrees who blamed their computer for their predicament and we at the chamber made the required sympathetic noises and for the sake of patient peace of mind said "really?" Evil device.

The computer for it's own defense said nothing. This was circa 1990 when the basic Alladin was new to the market. Then came the Alladin Pro which had a rate of ascent violation recorded in its log. But it was very easily and reasonably overruled by the defense that the victim of it's predations had merely gone from, for example 120' to 110' in a normal fashion and stuck a rate of ascent arrow into the log. Fair enough. Guilty as charged.

Then one nice bank holiday weekend a couple of years later I got a call to come to the chamber and there was another victim of computer induced DCS. After the usual discussion about the profile and which usually went" I was within the limits" and for reasons that can only be explained by the vindictive computer "I got bent" the patient was put into the chamber to be cooked for 6 hours.

Nice computer, be careful though, it's owner claims it's a killer. Don't get too fond of it.
So computer, anything to say in your defense? "Not guilty by reason of owner screwup, he's trying to frame me and I can prove it. Plug me into a PC and let me show you"

In this case the diver in question spent 18 minutes at 90' just short of mandatory deco. Running a bit low on air he went from 90' to 10' in 45 seconds and did a 3 minute stop sucking the rust from his tank thinking that he was now excluded from the risk of DCS.

Since the advent of computers that can download their profile no further computers of that brand have been been implicated in DCS with patients at that chamber. The previous ones had their sentences quashed.

Since then we've ran computers in the chamber for fun and curiosity and have never had a DCS event when it was used as it was meant to be.

Computers are safe and efficient when used properly but you must understand the theory behind them. If you don't understand the theory and have a solid grasp on decompression whether or not you do mandatory deco stop dives stick to walking in the rain.