Computers

[And]

<font color='#0000FF'>Hi

This question will come up sooner or later and recently I saw this on Scubaboard from Michael Kane, who is instructing on the DIRF course being run in Capernwray November time. I found it a balanced read and with some useful info. Hope you find it useful.

Andy

Originally Posted by [b

Quote[/b] ]The context with which we approach this issue is from the perspective of efficiency, I'll specifically avoid buzz words like &quot;right&quot; -v- &quot;wrong&quot; and I'll stipulate that either way you approach the issue you aren't likely to die. In other words, the &quot; Do it this way or you'll die&quot; allegation is beyond the scope of this analysis.

That being said, our thinking is that many [not all], but many divers become reliant on a device that could fail. To the extent that device fails then the diver is left without essential diving information. Moreover, as agencies start to move towards eliminating tables from the curriculm in favor of teaching computers it's starts the slippery slope downward. Would you prefer your child never learn basic math in school just because they have the ability to use a calculator??

Secondly, the way we approach a dive is to teach divers to turn their brain on underwater not to turn it off and rely on devices. We try to build in a protocol called situational awareness, which basically is taking 5 minute snap shots of your dive, including max depth, average depth. Furthermore, computers eliminate from many pre-dive planning and the analysis and impact of various mixes and profiles. Many believe that decompression theory is an exact science in terms of depth and time. In other words, many don't recognize the benefits associated with deep stops, or the importance of shaping the ascent profile [or &quot;deco&quot; curve]. These critical pieces of information are accumulated over time when a diver takes note of his dive profile, generally speaking many divers simply look at the pixals on their computer in terms of whether they are in the green, yellow or red and then base the repetitive dive plan on pixals. Obviously, if the computer then fails, the diver will generally lack the wherewithal to continue diving.

Thirdly, many divers are sold on the computer as a way to extend bottom times. That is partially true when the choice is limited to tables -v- computers. However that is only part of the equation. To the extent that the algorithm in the computer is set to a conservative gradient to provide a certain amount of &quot;padding&quot; more often then not you wind up with modest levels added bottom times.. For certain some models allow for the adjustement in gradient factors, but the fact is that many lack sufficient knowledge to understand the impact of the change in gradient factors.. The concept of course is that by the &quot;padding&quot; you reduce the very benefit they purport to give you.

Next, recently you've seen a trend towards RGBM based algorithms, but primarily most in-water computers use a Buhlman based algorithm set to 65% - 80% gradient factor. We refer to Buhlman as a &quot;bend and treat&quot; model. What we mean by that is that it tries to get you shallow as quickly as allowable [60' per minute] when a given tissue group reaches it's M-value, and then keeps you shallow to allow for elimination of accumulated nitrogen.. Buhlman specifically notes in his studies that advent of microbubbles but bases his algorithm strictly on saturation and desaturation of N2, accordingly he ignores bubble formation. As such when you attempt a hybrid of bubble mechanics and free phase ascents, Buhlman will unnecessarily penalize you because you incorporated deep-stops and/or used a 30 fpm ascent rate. This of course will generate longer decompression then actually necessary.

Nothwithstanding the foregoing, as diver's progress into helium based diving few in-water computers provide for gas switches, proper algorithms and are by-in-large cost prohibitive, usually in the $1,000+ range. We feel that money can be better spent elsewhere whether it be on proper equipment or training that will allow a diver to compute these calcualtions without the need for devices that can fail..

[Andy Phillips]

You can not disagree with his fundimental premise that relying on a single piece of technology is foolish, which is why we are all taught to wear a watch with some sort of timer (a rotatable ring) as well as carrying tables. For any agency to abandon this would be utter madness. As we start using computers a lot of people abandon tables, I am no angel in this as my old padi tables are floating around in the red sea somewhere as they blew off the boat about 5 years ago.

However. the piece of kit he is really attacking, very cleverly I admit, is the VR3. It has to be said, I am the eternal skeptic with this bit of kit, but I am going to get myself one. It offers the advantage of real time up date of your dive profile, uses a modified buhlman table and gives deco profiles very similar to the tables I run off prior to each dive. It allows for the fact that although I have planned for a 65M dive my actual depth was probably 57M, this gives a reasonable saving in deco when bottom times are 40 mins. With a deco commitment of well over an hour, 5 mins can seem like an eternity, if it is possible to save this then I for one will take it thank you very much. Having said this, only a raving maniac would rely exclusivly on a single piece of kit, which is why all the people I know who dive a VR3 also carry a dive timer of some sort as well as tables and bail out profiles.

My attitude is simple, technology can be fab, use it wisely and it will give massive advantages. Try to be clever and it will hurt you.

Andrew

[Dominic]

I intend to do the GUE course at some point to find out their &quot;Deco on the fly&quot; method. Then I'll decide whether to use their methods and sell my computer; work out a load of tables on DW and use them, or just get a VR3 and use tables as a backup.

Until then, I reserve judgement. We shall see

Will a computer rot my brain even if it's not Microsoft?

[Mark Chase]

Just reiterating Andrews point realy. Computers can and do fail and only a fool would plan the dive and not cut manual tables before hand. The fact that we often cut these tables on a home computer gets frogoten but what the hell.

I have never knowingly carried out a decompresion with out a minimum of bail out tables and a computer.

Deco on the fly is OK with pre set gas mix diving but it is not suitable for best mix diving.

The fact is that a computer is a useful tool. If working corectly it can and does do a far better job of monitering a dive than the diver can. It can help to releive the stress of a dive where math on the fly might add a few problems. A quick glance at the wrist and you know where you are. BUT you MUST be able to look at the data and say 'hang on thats rubbish'.

I recently looked at two dive profiles and immediatly thaught, they dont look right. On further alalisis I couldent even get the most adventurous modle to accepth the profile. Both divers who did the dive got bent. They got bent because they didnt fulley understand what they were doing and they had no computer to warn them of their error.

I think tables will be like the logeritham books &nbsp;we used at school. In 20 years time when computer modles are more advanced and multi gas computers are the norm we will look back at tables and laugh. It is already the case in leasure &nbsp;/ holiday diving where single mix computer only diving is the norm. It is only the so called Tec diving that still has a pasion for tables and I beleive it is the newness and cost of the computers that is affecting this area.

That said a computer is a tool with no heart and a cold logical brain. It dosent know how fit you are it dosent know what level of hydration you have it dosent know you spent the boat trip out throwing up over the side and it WILL bend you unless you use your knoladge of decompresion and your brain to pad out the basic data to suite the dive and your state of health.

It is possable (see recent posts on profiles) to totaly screw up your tables and set down a plan that will bend you no matter how fit you are. The computer would be screaming a warning at you that you then have to choose to accept or ignore. So the computer adds a safety feature to table dives.
Theoreticly the tables should always be more conservitave than the computer as they are planned at a depth on a square profile. If the computer is giving you more deco than your tables you have to ask why?

I run my computers on 0 safety for this reasion and invariably the tables and the computer are prety close.

To dive on tables and have a computer as back up is fine. To dive on tables and have a computer that is capabale of maping that type of dive (multi gas computer) and not use its capabuilities is IMHO daft.

To rely totaly on a computer for a deco dive with no pre palnning is daft

To rely totaly on one computer only on a no deco dive is daft

To dive without understanding decompresion is daft


So in short there is nothing wrong with a knoladgable diver diving on a computer with adquate contingancy for redundancy.

Why any one should think there is baffeles me.

ATB

Mark Chase

[Mark]

<font color='#000080'>

Originally Posted by [b

Quote[/b] (wetlettuce @ Sep. 05 2003,15:42)]We feel that money can be better spent elsewhere whether it be on proper equipment or training that will allow a diver to compute these calcualtions without the need for devices that can fail..

That really hits the nail on the head. You need the 'right' training to get that kind of a grasp on deco theory and what works (or do a few thousand extreme dives and work it out for yourself).

People just need to be aware that using a VR3 is not the pinnacle of tech/deco/mixed gas diving (by any means) and that there is a much better way of doing things (using your brain).

It's all a question of training and where you get it.

Regards,

Mark.

[Rob Evans]

Originally Posted by [b

Quote[/b] ]People just need to be aware that using a VR3 is not the pinnacle of tech/deco/mixed gas diving (by any means) and that there is a much better way of doing things (using your brain).

This much has already been established judging by the previous replies, though I'd be interested to know just how many mixed gas divers do actually jump into the water and let the pooter handle everything without having planned the dive beforehand. Not that many I suspect.
What I have seen plenty of- and I plead guilty to same - is having a bunch of laminated pre-cut tables on a ring stowed in the dry-suit pocket with a D-timer as a backup to the VR3/Nexus.  Pooter drops out, pull out the tables and go over to the established method.
Reason being, the VR3 invariably gets me out of the water long before my pre-cut tables do for the reasons Chasey's already outlined.

Originally Posted by [b

Quote[/b] ]It's all a question of training and where you get it.

Absolutely.

Originally Posted by [b

Quote[/b] ]To rely totaly on one computer only on a no deco dive is daft

Unfortunately that does pretty much sum up the vast majority of the world's rec divers....

[Mark]

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Originally Posted by [b

Quote[/b] (Rob Evans @ Sep. 06 2003,01:16)]though I'd be interested to know just how many mixed gas divers do actually jump into the water and let the pooter handle everything without having planned the dive beforehand. Not that many I suspect.

A lack of planning is not the issue (unless there is no planning of course)

The deco schedules produced by the computer are basically inferior in shape and effectivenes to what can be produced with a good understanding of deco and what really works. The VR3 will still try to get you up to 6m as quick as possible then keep you there for a very long time (bend and mend). It uses Buhlman ZHL16B does it not? Couple that with 32% and 80% deco gasses and you have what is somewhat less than optimal deco - a no brainer.

The excuse that the VR3 can save you some deco time if you don't hit your planned max depth just shows who really does rely on their computer. A quick mental caluculation or a quick look at the wetnotes is all it should take to re-calculate ones stops.

Getting out of the water in record time is not what we should be aiming for either. Doing an effective deco is far more important.


Regards,

Mark  

[Rob Evans]

OK - so what you're really getting at is your understanding of deco versus Buhlman then isn't it?

As the software packages that most of us use are based around ZHL16B using either GFs or Pyle stops, how does that preclude the VR3, which does enforce Pyle stops?
Admittedly Pyle stops are less optimal than GFs or RGBM in terms of bend and mend, but I can assure you the thing isn't all about getting up to 6m ASAP. &nbsp;It also allows 99% deco gas, but more importantly (to me anyway) constant PO2 with the option of switching to 99% when I do hit 6m.

It's not an excuse that the VR3 saves me deco time, just a statement of fact. &nbsp;Most of the wrecks I dive nowadays are unknowns. &nbsp;We know the max depth, so plan for that. &nbsp;However looking at a typical profile for one of these dives - over the course of 40-odd minutes at or around 70m I'm very seldom at the same depth for more than a few minutes - time on the bed, time on the hull, time in the hull. The variance will frequently be up to 10m. The pooter adjusts for that on the fly, and will typically take 10min off what I'd calculated on the surface

I'm all for doing an effective deco, but given that nobody's interested in spending more time in the water than they have to it works just fine for me.

[Mark Chase]

Originally Posted by [b

Quote[/b] (Mark @ Sep. 06 2003,07:28)]

Originally Posted by [b

Quote[/b] ]The deco schedules produced by the computer are basically inferior in shape and effectivenes to what can be produced with a good understanding of deco and what really works. The VR3 will still try to get you up to 6m as quick as possible then keep you there for a very long time (bend and mend). It uses Buhlman ZHL16B does it not? Couple that with 32% and 80% deco gasses and you have what is somewhat less than optimal deco - a no brainer.

The other thing that uses Buhlman ZHL16B is DIR's computer package Decoplanner. It uses exactly the same softwhere as Proplanner which is a system in popular use by tec divers arround the world.

The VR3 rather like the Decoplanner uses a MODIFIED ZHL16 system to include Microbubble stops (deep stops) in the profile.

When I dived the Illinoys it gave me a first stop depth of 42m

The VR3 is dived by thousands of divers all over the world. It is also a pro active computer that can be upgraded every year with the latest development softwhere. IT IS NOT A NO BRAINER and frankley neither are tables.

Look at the profiles and the Viper print out of the DIR dives where the divers got bent. They screwd up they got their deco profiles wrong. They were aledgedly trained by the best. So it hapens on computers and it hapens on tables.

Originally Posted by [b

Quote[/b] ]The excuse that the VR3 can save you some deco time if you don't hit your planned max depth just shows who really does rely on their computer. A quick mental caluculation or a quick look at the wetnotes is all it should take to re-calculate ones stops.

Mental calculations can be wrong.

Diving the VR3 on a new wreck planed 5m deeper than the actual dive turns out to be and looking at the computer saying OK it has reduced my deco by 10mins against my planned tables but I remember doing aproxamatly that deco on the dive of similar profile I did three weeks ago and being fine. Is not gung ho it's the act of an experianced diver taking a logical decision. First time it hapened to Andrew and I we ignored the VR3 and followed the tables any way as we had no point of referance fro the dive profile. When I got home and down loaded the dive profile and ran the profile through deco planner it turned out the VR3 was right all allong.

ATB

Mark Chase

[Mark]

<font color='#000080'>

Originally Posted by [b

Quote[/b] ]The other thing that uses Buhlman ZHL16B is DIR's computer package Decoplanner. It uses exactly the same softwhere as Proplanner which is a system in popular use by tec divers arround the world.

As I have said before, DecoPlanner does not produce DIR deco schedules straight out of the box. You need to know how to shape a deco curve and modify what it produces. You can happily dive the standard profiles (as you do) but they are not DIR and don't claim to be.

Originally Posted by [b

Quote[/b] ]The VR3 rather like the Decoplanner uses a MODIFIED ZHL16 system to include Microbubble stops (deep stops) in the profile.

When I dived the Illinoys it gave me a first stop depth of 42m

If your max depth was 65m then you blew your deep stop if you did it at 42m.  

Originally Posted by [b

Quote[/b] ]The VR3 is dived by thousands of divers all over the world. It is also a pro active computer that can be upgraded every year with the latest development softwhere. IT IS NOT A NO BRAINER

Oh yes it is........ It does not encourage you to use your brain or learn. In fact it is probably designed to fool you into thinking that deco is a super-technical-science that needs a fancy bit of hardware to work out for you (££kerr-ching££). &nbsp;

Originally Posted by [b

Quote[/b] ]Look at the profiles and the Viper print out of the DIR dives where the divers got bent. They screwd up they got their deco profiles wrong. They were aledgedly trained by the best. So it hapens on computers and it hapens on tables.

They were not GUE trained actually. They did screw up a little in the deco but more importantly with what they did after the dive. They did post dive activities which are supposed to be avoided.

Regards,

Mark.