Questions to MHK

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Posted by seahunt on February 22, 2001 at 13:25:54:

In Reply to: Re: Of computers and soap boxes. What I think. And it is long. posted by MHK on February 22, 2001 at 12:01:20:

Well, we finally get to see a description of this deco method
from Terry and we both applauded his essay. It's a good one.
I will mention that you may have misread his post just a
>Terry put out a good post yesterday about varying 10' or 20'
Actually, that was his third case and referred to a dive with NO
signifigant bounce, but as I agreed, it wasn't important.
What is signifigant, is that we finally have some description
of the method that we have been demanding from you to support your
contentions about manual deco. Since it is the first time we have
seen this description, I think it fair to comment on my questions
about it. The post and my response were quite polite.
Having this description, I can see that asking you to describe
your method for a dive profile I offered at Eagles Reef and the
High Spot is not a good test case. Your methodology, stops, is not
all that precise, but they should keep you out of deco under those
conditions with your methods. That doesn't sound that difficult.
As such, I described some other typical dive days that would
present more difficulty for your methodology. I was hoping that,
in light of Terry's post and the new information it provides, you
would comment on the problems I politely mentioned.
If I didn't mis-understand him, then the methodology sounds
exactly like what we used before computers were available and we
had to constantly track our depth and time as accurately as we
could. Since I always use the Navy tables, I expect my manual
calculations were very liberal compared to any present tables.
Still, I got the results I stated.
Just to clarify the profiles I mentioned, I will repost my
reply to his post that you seemed to aprove of. I will mention
that those were very typical profiles for me, especially in the
80's and 90's. I do hope you can follow up on this thread that has
remained very polite since Terry started it below. Correct me if I
made any mis-assumptions or even if you think it was an
un-warrented attack of some sort.
Thanks, seahunt

Repost of my reply to Terry's Post:

Well, that's something...

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.

PS. I'll add that the He comment does not apply to sport divers.

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