how to pressure group / deep dive

I just completed my AOW training on Maui and for our deep dive, we went to 110 feet (BTW great visibility at Molokini even at depth). Our total time in the water was 31 minutes. Obviously, this was not all at 110 feet as we swam around quite a bit.

We then had a surface interval about 1:20 minutes followed by 32 minutes in the water at maximum dept of 82 feet.

My question is: How do I log the pressure group for these dives in my log book. I won't be diving today, so I guess I'm back to using tables, but I hate to have blank spaces in my log book.

Thanks.

adjuster-jd once bubbled...
I just completed my AOW training on Maui and for our deep dive, we went to 110 feet (BTW great visibility at Molokini even at depth). Our total time in the water was 31 minutes. Obviously, this was not all at 110 feet as we swam around quite a bit.

We then had a surface interval about 1:20 minutes followed by 32 minutes in the water at maximum dept of 82 feet.

My question is: How do I log the pressure group for these dives in my log book. I won't be diving today, so I guess I'm back to using tables, but I hate to have blank spaces in my log book.

Thanks.

Click to expand...

1) Were you using a computer or tables in Maui? 2) Was this on air?

If it was on air and you were not using a computer, you blew through the NDL pretty badly on both dives.

Can't help ya a bit on those pressure groups as I depend on my computers but I just wanted to say howdy. That backwall is pretty cool isn't it?

Is the embassy treating you right? If you are staying in 841 let me apologize for all the sand in the tub but those huge tubs are great for soaking the gear after a dive

I guess I have more blank spaces in my logbook than in my gray matter=-)

Since this was a training dive, I was with an instructor who was using a computer. (I guess I forgot to say that in the original post). We were breathing air.

When I went to log the dive using tables later, I looked at 110 feet and 32 minutes and KNEW that couldn't be right.
Perhaps the solution is using a wheel, which I don't have or know how to use, so I'm just trying to figure out what pressure group I was actually in.

Does this clarify it?

Thanks.

adjuster-jd once bubbled...
Since this was a training dive, I was with an instructor who was using a computer. (I guess I forgot to say that in the original post). We were breathing air.

When I went to log the dive using tables later, I looked at 110 feet and 32 minutes and KNEW that couldn't be right.
Perhaps the solution is using a wheel, which I don't have or know how to use, so I'm just trying to figure out what pressure group I was actually in.

Does this clarify it?

Thanks.

Click to expand...

It, unfortunately, makes total sense. Its good to see that you trust your instructor.

I realize you already said that, but it's the answer you're looking for. Was this the official Deep Dive for your AOW? If it was did your instructor not make you do a plan for this dive?

Rachel

adjuster-jd once bubbled...
Since this was a training dive, I was with an instructor who was using a computer. (I guess I forgot to say that in the original post). We were breathing air.

When I went to log the dive using tables later, I looked at 110 feet and 32 minutes and KNEW that couldn't be right.
Perhaps the solution is using a wheel, which I don't have or know how to use, so I'm just trying to figure out what pressure group I was actually in.

Does this clarify it?

Thanks.

Click to expand...

Not to be critical, but one of the first things they teach you is not to share computers. I am a little surprised that went down in a class, but I guess I shouldn't be given the state of instruction (especially in vacation locales).

There is no way for you to log it unless you know what times you spent at various depths. In order to log it using tables or the wheel, you would have to have planned a multilevel dive, stuck to your plan, and then computed your NDL and then repetitive dive info. As it stands, there is no way to get that information unless you remember exactly what times you spent at each depth.

Hello Biscuit;
Well, we did plan for the dive, but this was the deep dive for AOW and not the multilevel dive, so the plan was we would go deep to 100-110 feet and try the math problem, etc. The book does not list multilevel planning as part of the deep dive, so we didn't do that.
Ok, well, I guess the pressure group stays blank. No big deal. I discussed that with the instructor and thats essentially what he said is that with using the computer the pressure group would stay blank.

Al,
We're in room 617 so I didnt find your sand here.....
Thanks for all the advice. We didnt do the back wall, we went over to the right hand side of the reef (reef's end??)
I'm looking for suggestions for other interesting boat dives here though. Any suggestions Al?

I'm not sure where the confusion lies. If you are computing your groups with tables, then generally speaking you dive square profiles. On a set of PADI dive tables lying on my desk, a dive to 110' for 30 minutes puts you in the J group with 7 minutes deco due at a 10' stop. Adding the other minute (31 minutes total bottom time) theoretically would put you in the K group. The fact that you were not actually at that depth for the entire period does not matter, if you are using tables to calculate your dive (and no computer data).

For the second dive, using J group as a starting point, with a surface interval of 1:20 you entered the water as a G diver. Because you descended below 80', you would use 90' on the tables. You had 29 minutes of residual nitrogen time. Adding your RNT to your 32 minutes of actual bottom time gave you a total bottom time of 61 minutes at 90', for calculations with the tables. Even rounding down to 60 minutes puts you in the M group, with a 25 minute deco obligation.

O-ring is spot on. You do not mention computers, safety stops, awareness of or execution of decompression times, or nitrox. Unless you spent the majority of your bottom time at very shallow depths, you blew your NDLs - calculating your dives using PADI air tables.

Some people would suggest, based on the data you indicated, that you were not diving cautiously.

Regards,

Doc

Ok, well, I guess the pressure group stays blank. No big deal. I discussed that with the instructor and thats essentially what he said is that with using the computer the pressure group would stay blank.

Click to expand...

If you dive with a computer you will often find that you cannot compute pressure groups using standard tables. The nature of the multilevel dives makes them impossible to translate to square profile tables to derive pressure groups.