Deep Diving Specialty

[jeckyll]

Would people classify the Deep diver Adventure Dive as a "Trust Me" dive?

Would you?

 

[Blackwood]

Would people classify the Deep diver Adventure Dive as a "Trust Me" dive?

Certainly. IMO, very few certification dives are NOT trust-mes.

 

[Toolbox-13]

I'm with KMD on this.


If you went right down to 40 meters and stayed only 2 mins before doing a slow ascent, what do you think your "bottom time" was?

depending on your descent (if it was 3 min) your BT was 5 min. guess you didn't have much time for sightseeing...

 

[rsdancey]

The short answer is that tables are for square profiles; multi-level dive planning works for fairly simple stairstepped dives, but anything beyond that either requires a computer or some deeper understanding.

For no deco dives from 3-4 ATA (i.e. from 66 to 100fsw) which is where we do 90% of our dives, I use this function:

Start planned ascent before (120 - Max Depth = dive time)

Example:

5min: 40fsw (40fsw + 75min = ascent)
10min: 80fsw (80fsw + 30min = ascent)
15min: 100fsw (100fw + 5 min = ascent)
20min: 100fsw (begin ascent)

(This would be a typical I-Beam dive for us, for example, with an estimated time on the I-Beams which average about 100fsw of about 7-10 minutes depending on how long it took us to go from 80fsw to the I-Beams).

When the whole team is on EAN32, and we have ample gas reserves, and we agree ahead of time, we can add 10 minutes to bottom time, trading safety margin for bottom time. Of course, gas management limits always trump.

Ascents are always 30fpm, ending with min deco (or 1 min stops from 30fsw to 5fsw in 5 foot increments, per pre-arranged dive plan). I like to do a deep stop at 50fsw for 1 minute as well for dives deeper than 80fsw.

 

[TSandM]

That works great if you're spending 20 minutes at 100 fsw; if you're going down to 100 fsw for a couple of minutes, then ten or so at 80, then 15 at 70, then spend ten minutes getting up to 40 . . . That kind of Cove 2 profile just doesn't lend itself very well to any quick algorithm.

 

[3-Ring Octopus]

Ahh...Cove 2.. . (I wish we had that kind of "office" around here...ours is the Florence North Jetty...it's a rough place at the best of times..but I digress..) Computers (while not a full-on replacement for at least a cursory working knowledge of nitrogen-loading and dive profiles) are a savior for deep dives. The variables of time and depth on such multi-level dives are way too complex for all but the mathematicians among us to run in their heads. (or on paper for that matter... lol) If you're going to insist on diving by the tables for such dives, you're invariably going to be doing an "ultraconservative" dive profile...which is fine...but it certainly isn't overly enjoyable. It kind of takes all the fun out of going deep in the first place if you're only down there for 2 minutes. (note: For training dive purposes, where you have an instructor having to gas-manage an entire group of students, the 2 minute bottom-time is par for the course...as the instructor SO has told me on many occassions..."get them down there FAST..no sight-seeing...demo skills...then give them time to sight-see on the way back up the gradient...")

Bottom line...if you're planning on diving deep (by rec standards) often...invest in a computer.

Cheers,
Austin

 

[jeckyll]

...Computers ...are a savior for deep dives. The variables of time and depth on such multi-level dives are way too complex for all but the mathematicians among us to run in their heads. ...

Bottom line...if you're planning on diving deep (by rec standards) often...invest in a computer.

Cheers,
Austin

Austin: What if there was another way? One that you didn't _require_ a computer for? And that didn't require you to put so much trust into a piece of electronics?

 

[fisherdvm]

Austin: What if there was another way? One that you didn't _require_ a computer for? And that didn't require you to put so much trust into a piece of electronics?

I don't know. I think the computer can help that slow brain I have. I think in deep dives, you want to milk every minute and every ounces of nitrogen free tissue in your body - and there is no better way to do that than with a dive computer. I think with repeated dives, I would push my NDL before I run out of air.... It is nice to have a computer to remind you when you start your ascend.

Nitrogen narcosis does affect my little slow brain, and hopefully, my buddy or my computer when tell me when I am close to my NDL bottom time.

 

[jeckyll]

fisherdvm: The computer doesn't know how you slept, how hydrated you are, how warm / cold you are, if your drysuit sprung a leak and you're not in a puddle of 40 degree water...

I _never_ try to "milk every minute" out of my computer. But on certain dives I've actually made it unhappy, on purpose, because I was following a different plan. One carefully layed out beforehand.

On other dives, even deep ones, I only glance at it to check the time. We plan our deep dives, even multi profile ones, up front, and strangely it's always happy by the time I get out of the water.

Hopefully if you are doing deep dives you've planned the dive enough and are careful enough in following your plan, to not get hurt. Having a computer "remind you" sounds very scary to me. As does 'milking it' because there is _nothing_ a computer can _give_ you except for a very rough point on a shifty probability curve...

 

[fisherdvm]

You are absolutely correct, we should never trust a computer. But on a few "follow the DM" dives, when someone else does the planning - we pushed our NDL limit. It was nice to see the computer reminding me on how far I was, and how important the safety stop would be....

It could be that the DM had a more liberal computer, or that he just simply did not have one. But for an average recreational diver, it is a good tool to remind you how much nitrogen you accumulated.