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Dive without politics
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While not havin a go a peterk.

I want to ask why computers are seen as dangerous? How many people feel the same way as peter? I mean he seems to blame his computer for the bend. After reading this post, and knowing the sites he is talking about, I would say it is more to do with his profile and pre/post dive cross country hike and weight lifting.

I don’t know what type of computer peter has, but I looked at my Aladdin Pro MK11 and according to that on a square profile he would have needed to do 73 min of stops with the first stop at 9 mtrs for 7 min, if his deepest depth had been 36 mtrs. I can’t even get a deco time on ‘88 tables. Of course this is the point of computers, they take into consideration all the time you haven’t spent at the max depth, but that is all it can do. The diver is still in charge of his/her dive profile and conduct.

This is not a wind up i have only used a computer for dive planing since 90, i love them.
 

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Hello Mr Moll,
             I didn't want to go too technical earlier on, purely because that is not my style.
1st dive-max depth 36.8mtrs, I reached 33mtrs after 6mins but bumbled about for a further 2mins till I reached the max depth. After a total of 18mins bottom time I started my ascent. The ascent was square and it took me 16mins to get to my 3mtr deco stops, where i did what my 'pooter told me with a bit added on.
Total dive 36.8 mtr for 42min with 8 min deco at 3 mtr
2 hour 1 min surface interval.
2nd dive
max depth 30.4mtrs reached after 13mins with a square ascent after, the 'pooter did not even register any deco. The nearest it got was 5mins away.
Buhlmanns:
1st dive
2 [email protected]
4 [email protected]
12 [email protected]
I did(following the 'pooter 8 mins at three, this is some discrepency)
2nd dive
max depth 30.4 mtrs
I was in deco after 9 mins according to the tables, my computer showed me hee-haw. What has been written on my profiles says(for a maximum depth of 30.4mtrs I was already -1min when I got there, For a Max time(42min) my max depth should have been 15mtrs. I was way off the Buhllmans. All the Info is posted for anyone who cares to check for themselves. It might not be too clear, but it's here.

Peter

     
 

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It's not the computers fault... It's biology...

The computer is basically just integrating the datum form hundereds of points within the dive to produce the best theoretical limit for DCS for Mr(s) Average - it's essentially just writing a custom dive table which is no more, or less valid than a normal one expect it shows more no-deco time due to taking out unnecessary (here's the flaw) rounding which would otherwise be your safety net.
 

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Dive without politics
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I did not set off to wind you up but you have mentioned some things that I think should be cleared up

</span>
[b said:
Quote[/b] ]Quote: from peter k on 2:03 am on Jan. 24, 2003


1st dive-max depth 36.8mtrs, I reached 33mtrs after 6mins but bumbled about for a further 2mins till I reached the max depth. After a total of 18mins bottom time I started my ascent. The ascent was square and it took me 16mins to get to my 3mtr deco stops, where I did what my 'pooter told me with a bit added on. Total dive 36.8 mtr for 42min with 8 min deco at 3 mtr

My understanding of a square profile says that when you leave your deepest depth you must do a continuous and direct ascent to the surface, if you use '88 tables your dive time starts when you leave the surface and stops when you reach 6 or 9 mtrs on the way to the surface, depending on your deepest stop depth. Using '88 tables you would have been required to do 20 min of stops, 2 @ 9 and 18 @ 6. That I feel is the point, you did not do a 'square profile', it took you 16 mins to ascend from 36.8 meters to 3, so your ascent rate was something like 2 meters per minute, it sounds like you 'chased' the computer to the surface, not good practice. The point of computers is that they take all the time into consideration, and calculate your profile up to 4 times a minute or so, it is supposed to help you dive coz it gives you credit for all the time you have not spent at max depth.   The thing is, did you need your computer to tell you not to yomp over the hill at stallion rock after doing a dive like the one above, peter I have been diving for a few years, all over loch Fyne and I would never walk over the hill like you and your buddy did, its not that I cant, but just imagine if you had surfaced unconscious from that dive what would your buddy have done? Also you are living proof that the rules associated with dive tables/computers are real. Its late and I cant be ars** going throu them but I am sure you know what they are.


2 hour 1 min surface interval.
2nd dive
max depth 30.4mtrs reached after 13mins with a square ascent after, the 'pooter did not even register any deco. The nearest it got was 5mins away.
Buhlmanns:
1st dive
2 [email protected]
4 [email protected]
12 [email protected]
I did(following the 'pooter 8 mins at three, this is some discrepency)
2nd dive
max depth 30.4 mtrs
I was in deco after 9 mins according to the tables, my computer showed me hee-haw. What has been written on my profiles says(for a maximum depth of 30.4mtrs I was already -1min when I got there, For a Max time(42min) my max depth should have been 15mtrs. I was way off the Buhllmans. All the Info is posted for anyone who cares to check for themselves. It might not be too clear, but it's here.

Peter your second dive was also below 30 meters, with only a two hour SI, what do you expect your computer to do if you have bad practice, you have be in control of the situation and remember all the rules, after such a deep dive you should rest, not go hill climbing. I am not trying to have a go, but it is unrealistic to say ‘puters are bad’, they are a tool and must be used correctly. How many dives a year do you think are done on computers, I would put money on many more than tables. All that said your man at the chamber was probably right when he said bends increased as more people started to use computers, but I tend to think that a lot of that was down to a RTFM problems.



     
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Darthmoll - I'm not convinced on how proficient you are with deco theory from some of those comments.  
 

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Can I remind folk of the basic premise, which we all already know but we sometimes forget 'cos we're only human: a computer is not a substitute for dive planning and it is advisable to carry a slate with your dive plan and contintengies - worked out via your tables of choice - already written.
Chee-az
steve
 

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Dive without politics
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Darthmoll - I'm not convinced on how proficient you are with deco theory from some of those comments.

Show me the mistakes I have made, I always want to learn.

Steve W, I am sorry if I suggested that a computer will replace dive planning, I did not mean to, as far a carrying a dive schedule, that depends o the type of diving you intend to do, I never do deco, I do not think, (it is only my opinion before everyone starts), that recreational divers can have all the safety equipment required to deco dive properly, Peter K did not even have a O2 set with him, but he felt it was safe to dive the profiles that he did.
 

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Just not enough dive time.
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Thats a very good point, given that ALL the diving we do is potentially life threatening we should always carry or have available 02 and the knowledge of how to use it. Maybe if you are doing a recognised quarry you can rely on the site, but remote sites/cave diving etc - we are into the self sufficiency argument again here arent we?
Matt
 

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I don't really wanna get involved here but it this might provide a point to debate.

I always make sure that if I dive to 30 or 40 or plus metres on the first dive the second one - even with a four hour SI will be no more than 25m. I stick to this in blue water abroad and cold water here. Yes it can be a long way to travel but I'd rather do one good dive and have the rest of the day off to offgas.

Just a thought.

BTW Just because my second dive is shallower - I know this will not preclude me from getting bent - but it'll help.
 

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Darth-dude, Isome misunderstanding there, wasn't aiming that comment at you, sorry if you felt I was "having a go" it wasn't my intention, I just wanted to bring everybody back down to earth in that dive computers are a bunch of wires and bit and bobs and can't really compare to the old "grey matter" that evolution has provided us with.

Yes, we can, and do, all get complacent and rely on our computers, I don't worry so much about it if diving up to about 20 or 25 metres, but if I'm going to 30m or over, then I check the tables and have it written down for comparison
Chee-az
Steve
 

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Re computers vs tables, the following posting by John Bantin on Diverent last May puts the case well, in my opinion:
"No computer manufacturer will guarantee that its product will stop you getting a DCI incident.
However, I believe it is very wrong to say that using a rough table is more safe than using a computer with an algorithm designed to match the sort of diving you are doing.
I have done as many dives as almost anyone. I have dived deeper than it is now recommended to dive using air. I have done six (6) dives a day for periods of up to five days on several ocasions. I have done three and four dives per day for a non-stop period of 20 weeks while dive-guiding. And I have done this now for 22 years and always with the guidance from an in-water diving computer.
In fact, have used a diving computer since the time when other divers used to try to physically tear it off my wrist because they thought it was dangerous. I now use a minimum of two because if I have a failure I do not want to have to stop diving for 24 hours. (I usually use three.)
I may get a DCI tomorrow. However, I have recently had the retinas of my eyes examined for damage and, contrary to expectations, NONE has been found so I have not had a DCI incident yet. I believe that the correct use of the right diving computer has been the single most important contribution to my diving safety.
Computer manufacturers are striving to make them even safer (eg. Suunto RGBM, Uwatec Smart and others).
If you pre-plan your dive using a PC you are using a computer but simply foregoing the opportunity to make changes during the dive. This is all very well if you have the discipline to stick to a strict regime but that is usually out of the question on most leisure-dives (world-wide) because, how can you plan for the effects of an up-current or down-current?
I never had the advantage of youth because I started diving only when I was 33.
I am now an old diver. I never was a bold diver. I am certainly not superman when it comes to fitness.
Use your computer(s) and understand the significance of the information displayed. Understand the concept of continuous decompression. Have perfect control of your buoyancy and always ascend slowly especially through that last couple of metres. Never kid yourself that diving can be without risk."
 

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Just not enough dive time.
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Hmm, I wonder. I like JB's attitude etc and I know how JG dives so I dont want to upset either, BUT.. just because JB hasnt got bent (yet - and hopefully never) doesnt mean any one of us wont, we all have different physiology. However the point being made I suppose is not to trust the computers to be spot-on and just intepret the info and make a judgement call. Am I correct in saying that JB dives mainly warm water, could that be a factor. I am surprised that he hasnt been damaged in some way as statistically the deep dives combined with multi dives and multi days are the ones likely to result in a bend.
Matt
 

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JB dives anywhere and everywhere, on average 30 hours a month. He can probably more than match anybody on this forum or Divernet as regards experience, training and diving in varying conditions, with every possible kind of equipment.
The basic point is that a dive computer is in principle no different from any other computer - it just gives you a heap of information,which you can choose to ignore or use as you wish. It's up to you to use it intelligently. It doesn't mean that you can forget all the fundamental rules that you've learnt, though.
 

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I read the post from Peter K with sympathy and read it again carefully to learn.
I also recall reading on a number of occasions and from a number of sources, that to plan a dive and dive that plan, with or without a computer does NOT mean that you are immune from a DCS hit.
Perhaps people, and Peter and the guts to say it himself, become complacent, perhaps the computer didn't provide the 'perfect' profile. On the other hand the march over the hills could have done the damage.
A friend of mine climbed down to Dotty dived the same profile, stops and all as the others in his party. He got the DCI hit and the chamber others did not.
The thing to learn here is 'There but for the grace of god go I' and modify our practices. That is until we forget
again.
 

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Dive without politics
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Still no answer from ann marie, wot a surprise, what is it they say about empty vessels?
 

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Show me a dive profile on a computer and I'll show you a table that says you 'missed' stops on that dive. It's just the nature of computers v tables. A table will always assume that you descended directly to the maximum depth at the recommended rate, stayed there for the entire duration of the bottom time and then ascended directly to the surface or first stop, again at the correct rate. Even on intact wreck on a perfectly horizontal bottom there will be some time spent shallower than the max depth that the computer will allow for but a table will not.

The point is that millions of dives have been done on computers and AFAIK no-one has ever succesfully sue a manufacturer for product liability after a bend.

FWIW I was bored one day 10 or so years ago so I gathered up the incidents reports for the previous 6 years or so and compared the number of bends. This covered the period when computers became much more affordable and reliable after the Decobrains and Edges. There WAS an increase in the number of bends over the period but it wasn't a huge jump. The increase wasn't significant enough for one single contributory factor to be suggested.

I daresay bends have increased threefold since the mid eighties but since there are many more divers doing lots more dives deeper and longer it is difficult to say whether or not the actual rate has increased or simply the overall number of bends.

(Edited by Stephen H at 9:52 am on Jan. 26, 2003)
 
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