Posted by TDI_2 on May 21, 2002 at 09:18:42:
In Reply to: Logging Computer Assisted Dives in Your Log Book posted by Art on May 20, 2002 at 21:08:34:
Welcome to the modern world of computer diving!
Logging your dives is useful because:
1) Next time you do a similar dive with similar gear and similar conditions, your logbook will tell you what gear and weighting you used last time;
2) Next time you dive the same dive site, your logbook will tell you exactly what gear and weighting;
3) When you go on a dive boat, they usually ask you when was your last dive, and sometimes they will want to see your logbook;
4) When you sign on to a diving charter, they often ask to see your logbook;
5) When you sign up for additional dive training, you will have to prove how many and what kind of dives you did in the past;
6) If you want to certify as a divemaster or instructor, you have to prove a certain amount of logged dives;
7) If you are NAUI certified and they have another fire and you lose your C-card, then your logbook becomes a valid voucher that you are actually certified. :)
Thats the "why" of it. Then the answer to your question becomes easier to explain.
What you log is not necessarily any different when you dive with your computer than it is when you are diving with charts, whether the charts are PADI charts or Navy charts or custom charts.
You should log this, at a minimum:
date of the dive
time of the dive
type of gas used [air, nitrox, etc]
deepest depth of the dive
type of exposure suit [drysuit, wetsuit, etc]
amount of lead weight and type of weights
+ or OK or - if you weighting seemed light or ok or heavy for the dive
water temp [from your computer]
signature of your buddy or divemaster or instructor.
In addition to the above minimums, I also record:
azimuth out to sea for the dive & azimuth back to shore for the dive site
beginning and ending cold tank pressures
size of the tank(s) on the dive
average depth for the dive [from my computer]
RMV calculation for the dive [respiratory minute volume] in cubic feet per minute
actual bottom time for the dive [time elasped from submersion to beginning of final ascent]
interesting things that I saw [fish, invertibrates, type of kelp etc]
hazards if any at this dive site [rip, surge, current, surf etc].
Note, I dont fill out the R-A-T info since I always dive with a computer, like most people.
But if for whatever unearthly reason I am using charts to determine my nitrogen and oxygen saturation [which is almost never], then I would fill out the R-A-T info [residual nitrogen, actual nitrogen uptake, total accumulated nitrogen etc].
With a computer, it does that for you, and you dont really NEED to fill out the R-A-T data. You can if you want, as a backup measure. Its totally up to you because YOU are a certified diver, now.
The PADI charts assume that you limited your dives to 130 fsw and all NDL, and for that assumption they assume a 6 hour off-gassing window. Another PADI assumption is that you did not dive deeper than 100 fsw twice in one day, and that none of your dives were reverse profiles [subsequent dives deeper than earlier dives].
We know from advanced scientific research that it takes more than 6 hours to totally off-gas all nitrogen. In reality, it takes several days.
So if using the PADI tables, you are taught to take a day off from diving every fourth day.
Your computer may or may not have a similar feature built into it, so you have to remember to take a day off from diving, according to some convention, to avoid DCS risk. [1000 geeks on this BBS will probably flame me now for that blanket statement. Flame on boys!]
In other words, no charts and no computer are foolproof against preventing DCS since people are so different and since DCS is not a completely understood science. So be careful with that new computer. And welcome again to the world of modern computer diving!
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