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On Fri, 17 Feb 1995, Ken Sallot wrote: > I have a question, which maybe someone can answer for me. > Two weeks ago, after a rather lengthy dive, I noticed a friends > Solution wanted to keep him in the water 10 minutes longer then my > Sherwood Source on the same dive profile. I got to wondering about > this, and put on my investigators hat. What I found out was that the > schedule for the dive we did on the Navy tables would have had us out > of the water about 20 minutes before we got out and my computer was > ready to pull us out 10 minutes before my friends Solution. > Last night we dive which we decided to test the theory that Navy > tables pull you out of the water quicker. We were a three person > team, myself diving my Source, my friend Kevin diving his Suunto, and > another friend (Todd) diving the tables. > > The profile was 98' for 57 minutes. Average depth was about 95'. > > The schedule for the Navy tables was 20'-9m, 10'-28m (tbt=37m). Todd > added 5 minutes as an added safety stop and got out 42 minutes after > deco started. > > My Sherwood kept me at 20' for 10 minutes, then 10' for 45 minutes. I > got out of the water 55 minutes after deco started. When I left, > Kevin still had 15 minutes to go, even though at the start of deco > his computer said he only had 39 minutes total deco time. He decided > to violate his computer (I will not get into a debate condoning or > condemning his action) when I left based on the tables and my > computer. > > So the question(s) are: > > 1) Why? I realize that the advantage of a computer is for multilevel > diving, and the majority of that dive was a square profile, but we > were not pushing the tables totally to the edge (depth wise). > > 2) I have noticed that it only happens on very long relatively square > deco dives (we were staging and wearing doubles). Has anyone else > seen this same thing happen? > It's been my experience that the Navy tables are faster (less deco) than almost any computer when you are comparing apples to apples (i.e. square dives on both). So why use a computer? Most dives aren't square dives, the computer woun't round 123 feet to 130, you get charged "exactly" for the time and depth of the dive. Why use tables then? With air computers your entire dive profile is figured as if you were on air. You would not get out of the water any faster by using ntrox and O2 to deco. Now if you'll look at a table of an air dive to 200 feet for 30 minutes using nitrox and O2 for deco and compare it to an Aladdin Pro on the same dive there is a BIG difference. What to do? I use my Aladdin Pro on any air dive where I only use O2 for deco and saty the time. That way I get a big deco "cushion". If it's a trimix dive or a double gas deco I run tables and use them with a cushion added in of course. r.b.
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