Observations during gf's cert. class

[dburg30]

I am a very new diver myself, just did my 10th dive this weekend, in 50 degree water...

In the 6 dives I've done since certification, all but one of them, an 11 minute equipment check dive, have been "off the charts" with respect to the tables being at all useful. Go to 63' for 62 minutes and you're at a decompression dive with the tables. 71 feet for 51 minutes Saturday as I touched bottom at a wreck site in a Quarry with a very experienced friend & dive buddy. Average depth for the dive was 35', but touching at 71' and 51 minutes, the charts tell me I'm in the red and done for the day.

It's funny, as a pilot and engineer, I want to do the charts for every dive, but it's becoming clear to me that it's almost useless as every dive I do is over-limit according to them. The $400 I spent on a computer has been the best money I put into diving, definitely.

Cheers,
PittCaleb

I havent done it, but cant you learn the wheel and/or learn to do multilevel diving on the wheel that gives you a bit more accurate reading then showing deco because you were at a certain depth? That would give you a backup when your computer floods or battery dies? Am also curious as to what your computer showed as your nitrogen loading on the dives you did for 63' for 62 min or 71' for 51 minutes since I dont have that much experience using a computer, and know I couldnt get 62 minutes out of a 63' dive on my al80 lol

 

[DBailey]

I compare this part to my flight training years ago and how they do it now.
Imagine being trained to fly by GPS only and one day at the airport they cancel the flight because the GPS isn't working and your pilot can't read an aeronautical map so he can't fly from VOR to VOR.

Dive computer dies = Dive cancelled.

I like that ananlogy.

On the flip side, I would rather my students know how to properly plan a dive using a dive computer. If the diver's computer dies, he/she has a greater chance of success of borrowing another computer for planning purposes (and track with a depth gauge and watch) versus finding a dive table on the boat.

Based on what I have experience, the vast minority of people will travel with a copy of the dive tables, but nearly everyone will have a computer (owned or rented).

Now, if the diver doesn't have a depth gauge and watch, he/she will be SOL no matter what if the computer dies or using the tables.

 

[RedCash02]

I like that ananlogy.

On the flip side, I would rather my students know how to properly plan a dive using a dive computer. If the diver's computer dies, he/she has a greater chance of success of borrowing another computer for planning purposes (and track with a depth gauge and watch) versus finding a dive table on the boat.

Based on what I have experience, the vast minority of people will travel with a copy of the dive tables, but nearly everyone will have a computer (owned or rented).

Now, if the diver doesn't have a depth gauge and watch, he/she will be SOL no matter what if the computer dies or using the tables.

I realize none of this will really apply to the vacation diver that only does guided tours, but planning a series of dives using a dive computer is so tedious compared to the tables. I first have to put the computer in simulate mode; punch in depth and time using 1 or 2 slow buttons; then type in the surface interval; and so on. It's nearly impossible to consider all the permutations on those tiny screens showing one depth at a time, like how will my RNT change for my 3rd dive if i limit my 2nd dive to above 50ft. And this is all assuming the computer even has a multi-dive simulation mode. Not to mention when you rent a computer you aren't usually given the instruction manual or told how to operate an advanced feature like multi-dive simulations.

But you're right the majority of people won't have a table with them thanks in part to new students not being given one. The things are waterproof for a reason; if you own one there's no reason not to have it your gear bag. I always have the navy tables and TDI nitrox chart in my regulator bag.

Depth gauge and watch or backup computer is always a good thing. I'll be the first to admit I don't always have my backup with me.

 

[Blackwood]

It's nearly impossible to consider all the permutations on those tiny screens showing one depth at a time, like how will my RNT change for my 3rd dive if i limit my 2nd dive to above 50ft.

But if you're using a computer to plan the dive, why would you care how your RNT changes based on repet depth? RNT is an intermediate step, not an independently useful quantity.

 

[tracydr]

chance of success of borrowing another computer for planning purposes (and track with a depth gauge and watch) versus finding a dive table on the boat.

Based on what I have experience, the vast minority of people will travel with a copy of the dive tables, but nearly everyone will have a computer (owned or rented).

Now, if the diver doesn't have a depth gauge and watch, he/she will be SOL no matter what if the computer dies or using the tables.[/QUOTE]

Interesting. I keep my plastic dive tables and nitrox tables in the back pocket of my dive bag. It's always there. Easy. Much cheaper and lighter than a spare computer. Safer and easier than extra batteries.

 

[RedCash02]

But if you're using a computer to plan the dive, why would you care how your RNT changes based on repet depth? RNT is an intermediate step, not an independently useful quantity.

Not quite sure I understand what you mean. How do you plan your day based on the computer?

Tables allow you to get a quick sense of which sites you'll be able to visit that day. Individual dive sites could easily be an hour apart on a boat or more. I'd rather be pleasantly surprised on my 2nd or 3rd dive by the amount of time until the NDL, than have to thumb the dive with 2200 psi because of my residual nitrogen.

There's plenty of circumstances where just jumping in the water is ok -- some people will have every dive planned for them. But not giving the students the proper tools to plan a multiple-dive day, unless they are very competent with advanced features on a particular computer, is unacceptable IMO. My gf said they didn't do any dive planning like that with the computers. They were simply shown how to look at the depth and NDL times after each dive was already completed. I asked her if she'd plan our first weekend of shore dives together and she said, "I wouldn't know where to begin."

 

[skatermegs]

Getting back to the original subject of this thread...

GF had her checkout dives this weekend. The conditions weren't great: 5-10 ft vis, some current, and an average surf entry/exit. All the instructors were anchoring floats and running out lines. Max depth was about 25ft with a temp of 56F. I was in the water one of the days and can attest the conditions were pretty sub-par.

Me= Jealous! Our checkout dive conditions were the same...along with thunder, lightening and hail on the second day. That said, the vis was pretty standard for where we dive (PNW) and we still did a full tour underwater, and didn't hold a line. It is so interesting how much conditions differ from place to place! Tell her congrats, and even moreso for getting her own gear! And since you were shocked at her not learning tables-why don't you just run her through them? I try to do them everytime, even though most dives really are off the table (using a computer now). But it is still worth it to know! My tables live in my logbook, so I always have them along.
~
Megan

 

[Blackwood]

Not quite sure I understand what you mean. How do you plan your day based on the computer?

What I mean is that the RNT values on a table facilitate determining repet NDL. If you have a method to read NDL directly, RNT is irrelevant. I believe that with a computer you enable planning mode, enter a depth, and it returns an associated NDL. No need to go through the intermediate step of RNT.


Take this with a grain of salt since I don't use computers to plan my dives. It's entirely possible that not all computers have planning modes. Both of mine do, but they're set to gauge mode so planning is disabled.

 

[RedCash02]

Me= Jealous! Our checkout dive conditions were the same...along with thunder, lightening and hail on the second day. That said, the vis was pretty standard for where we dive (PNW) and we still did a full tour underwater, and didn't hold a line. It is so interesting how much conditions differ from place to place! Tell her congrats, and even moreso for getting her own gear! And since you were shocked at her not learning tables-why don't you just run her through them? I try to do them everytime, even though most dives really are off the table (using a computer now). But it is still worth it to know! My tables live in my logbook, so I always have them along.
~
Megan

Yeah, wait until you dive somewhere with nearly perfect visibility, if you haven't already. It's quite shocking after you become accustomed to having such a small field of vision. It can actually be disorienting and make it easy to go too deep. I can still remember one time when I was in the sand at 120ft , I looked up and could see read the name on the bottom of the dive boat and could recognize the captain. Next time I was at that same dive site there was an algae bloom; the water was forest green with about 15 ft of vis.

Luckily I already own two sets of tables. She figured it out on her own by looking at it. She also figured out my TDI nitrox depth and mix chart by looking at it, so I guess when she decides to take a nitrox class she won't really need to study much.

 

[bs63366]

I was surprized at the fact of the lack of learning the dive tables but my friend that just went through knew the tables by the end of the class. I helped get them down because I think that they are a big part of diving and making a plan. On top of that I also noticed that when they did their dives the instructor never really explained the computer to them about how it worked or what to watch out for. I was certified in 2007 but I could tell a huge difference between the course content of then and of now. She also did the e-learning option.