Well, that's something...

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Posted by seahunt on February 21, 2001 at 21:40:19:

In Reply to: Re: Aha! posted by tleemay on February 21, 2001 at 15:26:59:

Thank you for a reply with some substance.
Truthfully, it's a long post, so to respond, I have to figure out what you are saying.
Your first description of bounce between depth ranges of say 100 to 40 feet sounds realistic, as opposed to the extremes you mention (though Lem does those extremes regularly at the rock quarry).
What you describe sounds like standard table diving like I was taught many years ago. You seem to calculate using max depth (benchmark) times bottom time. That sounds standard and means that any fluctuations above benchmark can be ignored and even maybe some small fluctuation below (though you aren't supposed to according to the designers of most tables).
You might reply if that part is wrong at any point...
Well, that sounds fine, but doing that, even without major bounces always costs me at least a tank. Don't tell me about careless time or depth keeping. Remember, I was diving long before computers and got one late. We used to keep as close a watch on time and depth as we possibly could... to MAX our bottom time. You come to hate that tables only come in 5 (or so) minute increments. When I got a computer, I still did comparissons to manual deco (oh, by the way, I hate computers on GP cuz I'm good at math) and always came out way better with the computer... and that was using navy tables.
I finally got computer, cuz I was always diving the Badlands at the West end of Nic. Depths are 70 to 85 feet all day. Tables allow 3 (104 LP steel) tanks for out of water by 1 pm. Computers allow 4. I've done 7 tanks there on all my 2 day trips (but one and that's a lot of trips) with a computer, when using single tanks. My double 90's were another story.
I did 7 tanks at Cortes the first day. Max depth 129 feet... All dives had a max logged depth of at least 69 feet. That's a steel 104 again and I don't do thirds.
Since you have carefully written this post, I hope my response has been polite, but I do not think that there is any way that you could match a computer for BT under these conditions, which were not even heavy saw tooths. I sure couldn't and that is with extremely careful, praticed time and depth records on a Navy table, usually diving more than one day a week.
In a sense, I'll just stop this post here, though there are comments following, because this is all the answer needed to respond to my best understanding of what you wrote. If I am wrong at any point please correct me. if there is more to know, please post it. Under these circumstances of near deco diving, a computer always gave me at least one more tank on just single day trips, let alone multi day trips... That is with extremely careful time/depth tracking and liberal Navy tables (Are the tables you use more liberal than those??). All of these dives are chronicled, in detail, on my web site.
Enjoy the diving, seahunt
By the way, I never parse words or do verbal gymnastics.

Both you and Michael talk about working your way up to shallow towards the end of the dive. That's fine too, early in the dive day. Still, after about 4 tanks at most, without a computer, I'm gonna get nervous... Then I have to sit out a tank. I don't with a computer.

>With a firm plan and associated safety margins built in
A firm plan? I don't generally attempt to make those (normally can't be done) and I propose that at the Catalina pinnacles, San Miguel Island, Beg Rock, Cortez Banks, the Buchon Sea Mounts and many other places, it is quite impossible. You cannot possibly predict where you will be. A computer works great.
You say that you do this and that and a saw tooth and the computer will penalize you. Still, anytime I compare manual calculations to my computer, I get at least one extra tank with the computer and also imeasurable peace of mind. That doesn't seem like a penalty.
Same thing with computers not accounting for deep stops. The penalty never occured.
Just of note, these far increased bottom times were without pushing the computer to the limit. Only once have I pushed the computer to the limit and that was with the double 90's. All other times, I got the extra tank with a margin left over.
You state time, depth, and workload. Well, the computer doesn't consider workload. Since I am at a full sprint when hunting lobster, then your manual deco would further penalize me.
You also mention that this works because you are out diving every weekend. Well, that disqualifies 95% of the divers out there.
A computer is not a recess monitor. It is a fantastic safety device and convenience that makes diving more pleasurable and allows more bottom time. If I did those dives without it, I would be scared silly.

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