Bendy computers

[darthmoll]

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.

[peter k]

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 mins@9
4 mins@6
12 mins@3
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

     

[Driftwood]

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.

[darthmoll]

I did not set off to wind you up but you have mentioned some things that I think should be cleared up

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Originally Posted by [b

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. &nbsp; 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 mins@9
4 mins@6
12 mins@3
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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[Ammers]

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

[Dr Stevil]

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

[darthmoll]

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.

[MATTBIN]

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

[Gavin Yates]

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.

[Dr Stevil]

Darth-dude, Isome misunderstanding there, wasn't aiming that comment at you, sorry if you felt I was &quot;having a go&quot; 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 &quot;grey matter&quot; 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