Dive computers and 'Bends'

[dapl]

Peter K,
Thanks for the post on your bend. Hopefully you are on the mend now. I am a bit curious about your perception that it was your computer at fault. Did your dive buddies computer miss the same amount of stops as you reckon yours did?

[peter k]

I did NOT miss any computer stops. That's the point. My buddy did less than me to be truthfull, but there was points in the dive where I went wee soiree's(+10mtrs) deeper than him. I have realised that saying it's the 'pooters fault does bring up bones of contention in the fact we all use them and(I did)trust them. I did what I was told!!!! It leaves the questions; Are the computers basicly dangerous or is my body more suited to table diving? I think it is a mixture of the two options. The difference in deco I missed compared to the Buhllmans and my 'pooter was 8mins on dive 1 and dive 2 was off the table. As I said in another thread the lowest my 'pooter got to was a 5min no stop in dive 2. The reason I tend to go with Buhllmans is that Navy tables were designed around fit, healthy Navy divers. Buhllmans, I believe, were not. As an example, the next time you go for a dive, follow your computer then check tables after you get out. I think you might see a big difference in stops.

Peter  

[Gavin Yates]

Pete,

Which pooter were you using and had you got it set for the most conservative setting ... considering it was Winter and cold and shit.

Just a thought .... I have me Vytec set on the most conservative at this time of year ... just to be on the safe side.

[darthmoll]

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Originally Posted by [b

Quote[/b] ]Quote: from peter k on 11:37 pm on Feb. 5, 2003
As an example, the next time you go for a dive, follow your computer then check tables after you get out. I think you might see a big difference in stops.

Peter  

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Without stirring things up, i hope, that is what computers are ment to do, give you an accurate dive schedual based on what you have actually done, tha basic rules must still be followed. Looking at the time you said you spent at depth on the first dive and your ascent time i am still thinking you chased the computer to the surface, only you can tell us that, in its self not best practice, but not the end of the world, if you follow the rules, i mean the computer is a tool not a magic box, i have done hundreds, around 1500 dives on computers and have never had a bend, but i do not expect it to think for me, i always follow all deco rules, it is just a pity to blame such a good tool coz people dont follow the rules.

BTW watch out for my bend report next week.

[dapl]

[quote]Quote: from peter k on 11:37 pm on Feb. 5, 2003
I have realised that saying it's the 'pooters fault does bring up bones of contention in the fact we all use them and(I did)trust them. I did what I was told!!!! It leaves the questions; Are the computers basicly dangerous or is my body more suited to table diving?

Peter, maybe table diving is safer for some people, you included, but have you sought any other professional opinions on which (tables or computer) is best and safest for you? I would guess that you may need to find this out before you decide your diving future.

(Edited by dapl at 8:31 pm on Feb. 6, 2003)

[Rob Evans]

I'm not sure about this talk about pooters.  When reading Peter's report, the very first thing that struck me was the long kitted up surface walks to and from the dive sites.
To my mind, those were the source of the bend from the very word go.
You can dive within tables or computers as much as you like, but if you start the first dive with a real possibility of excess CO2 still hanging around your bloodstream, finish the dive with another long slog and repeat the process for the second dive you're looking for trouble.  It's well known that excessive physical exertion post-dive can have a great effect on the body's ability to off-gas - unfortunately no dive computer anywhere can compensate for this.
I'm quite happy to do long deep dives with - so far - up to 1 hr breathing high PO2 nitrox mixes for decompression and let the pooter handle the whole dive (backup tables in pocket).  What I'm also very careful to do post dive is sit on my fat arse and do nothing until it's time to get into the water again or go home.
Personally - and with absolutely no slight against Peter cos I'll be seeing him on the Mull gig soon and I enjoy having my bollocks exactly where they are thank you very much -  I'm not at all convinced it's the pooter's fault.  Excess exertion, maybe not as fit as he'd like to be and not forgetting the slight possibility of a PFO all look more likely suspects.

[Andy G]

I remember a wise Oldish :sofa: man once saying that the problem with computers is that they are Silicon and we are Carbon.
Now I am a 6'2'' 17 something stone:burgereater:, beer drinking:klo:, smoker and whatever my computer tells me I always do at least 5mins more if normal diving and double that if deco. diving. My view is simple whats 5-10 more minutes in the water compared to 4+ hours in a pot...and the slagging that I would definetly get should the pot happen to be local:thumb:.
Yes I like computers as a guide but would I bet my health on one .....NO.  

[peter k]

Just to try and answer some of the above questions;

Gav, I was using a borrowed Aladin Sport. Yes, I know, not the best deco computer about but my own computer is broke, hence the borrowed one.
DarthVader, As far as I know computers algorithms were figured out in chambers with most of the basics working off Buhllmanns. This would not take int account temp, workload, etc. These things were added on at a guess factor into the algorithms. All instruction books for them tell you not to use them solely for deco info and the Suunto Stinger tells you on page 1 that if you use it for deco you WILL suffer a DCI. I'm not saying that they're a bad thing, just that they should be complimented by the best dive computer you've got, your brain. Instead everyone seems to have follow them like lemmings. What I say is take Buhllmans down with you and if their is a big difference in them to what your computer is telling you, follow the Buhllmans. After all, we're all told to follow the most conservative, aren't we?

Rob, I know about the walks, but, these two dives are dives I have done many times before and in the same way. I think it was just my day for the lightening bolt.

Andy G, Wise man!!!! &nbsp;

[Mark Chase]

There is no doubt in my mind that the computer had a fault or that it was mis read during the dive as it was a strange bit of kit.

I ran the profile on my Vytec

37m for 42mins allowing for ascent and 8min stop is aproxamatly a 30min bottom time;

On air thats 37mins deco
No Nitrox 30 running a PP02 of 1.4 thats 22mins deco

Surface intervall of 2 hours

31m for 40 asuming deco and ascent time again bottom time
30mins

31m 30mins on air 53mins deco
31m 30mins on 30% Nitrox 19mins deco

Running the profile on Deco planner using 35 80 gradiant factors gave 24min and 19min on Nitrox 30 and runing it on air came up with 49min and 42min deco

All in all the profile dosent make sence. I can only asume that it was a multy level dive with the vast majority of the dive at a much shalower depth. I ran a few profiles and to get 8 mins deco on air for the first dive &nbsp;you coud do 5 at 37, 5 at 30, 10 at 25, 10 at 20, On a 30 85 that came up as 9mins of stops.

Please note that was Normal settings and safety off

I would be a bit more conservitave given the conditions surounding this dive.

This is NOT a slag off. This is just pointing out that the figurs dont add up so there must be more to the profile than I have read or the computer is buggered.

Now I dont normaly cut tables for a no deco dive BUT I do check out the dive plan on the PC before the trip so I dont sudenly find that my planned bottom time is going to be well into deco. I also carey INTD bail out tables so even if my computer gos tits up I have some form of get home plan. I offten dive the computer even on serious multi gas dives but I always have a mentle picture of the profile in my mind before the dive so when my computer shows me garbage I will / should notice it.

If I am over seas I dive two computers if I cant get to a PC to plan the dive and do a rough profile on the IANTD tables.

Computers are good but they have to be monitered cairfulley coz all things electrical are the acursed spawn of the devil.

Mark Chase &nbsp;

&nbsp; &nbsp;

[Phil Ennis]

Peter K,
How are you doing?
Just a point with your comments above. After reading I dug out my Stinger handbook but mine states nothing of the sort. It advises against commercial or professional use. In the dive mags it is advertised as having 'Full Decompression Capability'. You either have a different manual, or you have been taking lessons from Bren in 'Poetic embellishment'.
Only joking Bren !!!! and Peter..