Logging multilevel dives with tables

[redacted]

awap,

You are right, 24 hours is somewhat a "stock" answer but it meets training organizations' recommendations and most computer manufacturers' recommendations as well. The best place for the answer is in the computer's manual as I have said in my post.

I am not sure of how you can make an informed decision otherwise by not following "industry" or computer manufacturer recommendations. I look at it this way, I'd rather stay dry for 24 hours (or even longer) than suffer DCS. This is not something to toy with or take lightly. Again, if diving is that important and staying wet is crucial, why not use two dive computers?? I do (sometimes I have 3 on my).

In the worst case, I put myself in PG Z, do a 2.5 hr SI, and plan my next dive on tables starting in PG B. I then stay a bit on the conservative side while I spend a day loading up my backup computer. I also use my buddy's computer info as we stay pretty close.

If the failure occurred in a place like Cozumel I'd adjust my PG based on actual max depths of previous 24 hrs dives and go from there, still on the conservative side.

If the diving were fairly conservative anyway, like Bonaire (32% and 40 ft max) I would not even worry about it. Just finish the tank(s) on buddy"s computer (for depth/time info) and switch out computers when we exchange tanks.

Sure, there is no data supporting my method. Just reasoning and a willingness to accept a little risk to go diving.

 

[Paladin]

To be fair, it doesn't seem to me that you're switching from a computer to tables. Seems that you're diving planned table dives and using a computer to monitor depth and time. In my mind, those are two different things.

Unless I'm reading too much into that bolded bit and you're just running your actual profile with 0 SIT through the table after each dive.

I'd call that profile 60 feet for 40 minutes which gives me the same pressure group on the PADI table as your method. Ever thought about using average depth instead of stacked 0 SIT square dives?

Actually, it comes out as a melding of the two methods, if that makes any sense to you. That way, if the computer should die on me, I already have a backup plan to follow to save the dive. I just don't like relying completely on the computer and like to have "a way out."

I am afraid I must confess my abject ignorance of the "average depth" method. I'd never even heard of it before joining SB. The tables were all I'd ever used. If the formula isn't too complicated for this thread, would you mind laying it on me?

 

[Blackwood]

Actually, it comes out as a melding of the two methods, if that makes any sense to you. That way, if the computer should die on me, I already have a backup plan to follow to save the dive. I just don't like relying completely on the computer and like to have "a way out."

Makes sense to me, yes.

I am afraid I must confess my abject ignorance of the "average depth" method. I'd never even heard of it before joining SB. The tables were all I'd ever used. If the formula isn't too complicated for this thread, would you mind laying it on me?

It's pretty simple and easy provided you don't bounce around dramatically throughout the dive.

Take your first example:

90 feet, 10 minutes.
70 feet, 10 minutes.
40 feet, 20 minutes.

90 for 10 followed by 70 for 10. Okay, that's 80 (i.e. halfway between 70 and 90) for 20.
80 for 20 followed by 40 for 20. Okay, that's 60 (i.e. halfway between 80 and 40) for 40.

There are of course limits, and you gotta use some (perhaps un-)common sense. I wouldn't go dive a wreck at 170 feet and then try to average it out with an adjacent reef at 20.

But a wreck in the sand at 100 feet with 40 feet of relief, absolutely passes my giggle test.

 

[Paladin]

F.Y.I. My instructor who is still alive and is in his 80's is still diving and using a dive computer, BCD, drysuit but insists on using his old Nikon IV and really old round high volume mask. He claims that his nose is so big that only that mask would fit without causing him pain.

I prefer the old oval style masks, too. I've tried many different masks of more modern design, but none really work for me. I keep going back to the old tried and true. If he should need a new one, Vintage Scuba Supply sells them for a good price.

 

[Paladin]

Makes sense to me, yes.



It's pretty simple and easy provided you don't bounce around dramatically throughout the dive.

Take your first example:

90 feet, 10 minutes.
70 feet, 10 minutes.
40 feet, 20 minutes.

90 for 10 followed by 70 for 10. Okay, that's 80 (i.e. halfway between 70 and 90) for 20.
80 for 20 followed by 40 for 20. Okay, that's 60 (i.e. halfway between 80 and 40) for 40.

There are of course limits, and you gotta use some (perhaps un-)common sense. I wouldn't go dive a wreck at 170 feet and then try to average it out with an adjacent reef at 20.

But a wreck in the sand at 100 feet with 40 feet of relief, absolutely passes my giggle test.

Thanks. That makes sense. I'll play with it until I get it internalized. It just might save a dive someday.