New Divers -- I need your help...

[alchemist1024]

OK planning your dive is absolutly 100% important no doubt. For me even though I am very new to diving I found this paper very useful. However looking back to OW we had people that were having a hard time with the standard PADI dive charts and figuring their NDL etc... Most of the students when in the water for the first few times were consuming huge amounts of air and I'm not sure that they could even begin to figure out where they fit on the scale. My dive partner had on something like 44+lbs of weight and was uneasy the whole time and consuming way more air than I was. We did cover the rules that at different atmospheric pressures we consumed more air but that was it. When we talked about planning a dive we were told just to use the chart and common sense. If I were to change anything on the paper you posted for myself I would have only included the 80AL figures to keep things simple (we used only 80's in our class). Hopefully a good starting point. Also I would include a chart with all the figures filled out for a specific common air consumption. Doing this for me would allow me to compare my own air consumption to a standard to see if my figures make sense. I'm glad to see someone putting so much thought into teaching. Good luck and I hope this helps!!

 

[gcbryan]

(This is how I would simplify your original)

Basic Gas Management for Dive Planning

Minimum Gas For an Aluminum 80
Minimum Gas at 66 fsw = 25 cu ft or 1,000 psi
Minimum Gas at 99 fsw = 40 cu ft or 1,600 psi

Gas at depth plus Minimum Gas

Example:
Dive planning for a dive to 66 fsw for 25 minutes

Information needed:
1. SAC rate = assume .7 cu ft/minute
2. Planned depth (66 fsw) converted to atmosphere's absolute (ata) = 3 ata (66/33 =2 +1)
3. Planned time at depth in minutes = assume 25 minutes
4. Determine air consumption at depth (SAC * ata * time = .7* 3 * 25 = 52.5 cu ft)
5. Determine if you have enough gas to make the dive = Gas at depth + Min Gas = 52.5 cu ft + 25 cu ft = 77.5 cu ft needed for a safe dive

Notes:
What is "Min Gas?"

This is defined as the amount of gas you need to safely get you AND your buddy to the surface if your buddy goes Out Of Gas assuming 1 minute to get the air share going, SAC rates of 1 for you AND your buddy AND all recommended stops on the way up. Note that the SAC rate goes up when a diver is stressed

What is SAC Rate (Surface Air Consumption)?

This is the volume of air consumed per minute at the surface.
This typically ranges from a low of 0.5 cu ft/minute to 1.0 cu ft/minute and higher.

To determine your SAC rate:

Note the starting and ending tank pressure, determine the average depth and the length of the dive - then calculate the SAC rate.

Example
Determine the total volume of gas used (assume AL80) : assume starting pressure 3000 psi - assume 600 psi ending pressure = 2400 psi.used.
2400 psi/3000 psi =.8 (80% used)
80 cu ft * .8 = 64 cu ft used

Divide cu ft used by minutes and divide by the average ata to get the SAC Rate.
64 cu ft/30 minutes =2.13 cu ft per minute (at depth)
2.13 cu ft / 3 ata = .71 SAC rate

 

[GSDMan]

Long ago I accepted the fact that my brain doesn't work like most peoples'. So I leave it to others to decide if my suggestions make sense.

I'd like to see three sections. Definitions, the Chart, and an Example or two.

• Definitions would contain the information required (Surface Air Consumption(SAC), Minimum Gas, etc.) and any notes on what they are and how they relate to the other terms.
• Then I think the chart would make a lot more sense. (What purpose does the tank factor serve, anyway? It wasn't used anywhere on the page that I could tell, or did I miss it?)
• Lastly, a clear section where a couple examples are worked through. It has a kind of mixed up feel to it right now and I really think separating it like this would help. I'd like to see included here consulting the Recreational Dive Planner(RDP) just to see if the dive will be limited by the No Decompression Limit(NDL) or air supply. (I'm assuming they make you use the RDP for the advancd class, too.)

Just afew more thoughts.

• Determining one's SAC rate doesn't belong here. It is a topic for a one pager all by itself, I would think, and is kind of a prerequisite for this paper. In other words, if I can't already figure out my SAC rate then the rest of this isn't going to help. At the very least, to include it will push you over your "One Pager" goal.
• Avoid using equals signs where you can. It provokes memories of struggling through algebra tests and I think most folks tend to recoil a bit when they see them. I'd rather read, "Multiply this and that together to get the result," than I would, "AxB=C."
• Do NOT use acronyms until after you define them. I don't care if your intended readers know them already, or not. It's just bad writing.
• Also, ditto what Kingpatzer said on the standard abreviations. Had me scratching my head for a while, too.
• And lose the semi-colon on the second page.

Okay, I'm done. I'm a PADI OW graduate (and a pubic school graduate, to boot), so I'm having to pick this up on the street, as it were. You've set yourself a daunting task here and my considerable ignorance of the subject at hand is at your disposal.

Jim

P.S. What the heck does ATA stand for? It's bugging the bunny-stuffing out of me.

 

[Steve R]

P.S. What the heck does ATA stand for? It's bugging the bunny-stuffing out of me.

It's short for ata-boy.

It's the number of pats on the back you give someone after their dive. Basically the deeper they go, the more ata-boy's you give them.

It is directly proportional to the number of bad looks Peter will get from his instructor for trying to "help".




While I commend the effort Peter, since you're not in the driver's seat of the class, you'll quickly realize you're wasting your time.

When you consider that the typical Padi AOW class (I guess your market here?) is all of a couple days long, jammed with a whole lot of nothing but a series of ill-conceived and poorly performed dives, what you hope to achieve is pretty much doomed to fail.

If the instructor is not on board and actually teaching this, then they would be your typical Padi instructor...good for shi-tte I mean. They would see you as an impediment.

If he/she was worth anything, then this would already be part of their individual class, which by standard is NOT a typical Padi AOW class, but it at least would mean what you're trying to achieve would not be required from you.

Good luck dude, but you're pissing into the wind.

 

[ClayJar]

What the heck does ATA stand for? It's bugging the bunny-stuffing out of me.

Atmospheres, absolute. Atm would be atmospheres of pressure, and to specify absolute pressure, you change the 'm' to an 'a'.

Strangely enough, when speaking in psi, you just add the 'a' on the end. Pounds per square inch, absolute, would be "psia", and if you want to explicitly specify gauge pressure, that's "psig".

(There is no "atg" or "atmg" anywhere I've ever read, and that's quite a few chemisty, physics, and chemical engineering texts.)

 

[jbmooney]

OK, pdf gremlin located and slain (sorry about that)!

I salute the effort, but for an AOW class, I agree with GSDMan that separating the definitions, the general procedures for making the calculations, and the specific examples would be way more useful (I also can’t stop chortling about his offer to put his “considerable ignorance … at your disposal” – it’s a pitch one doesn’t hear often, and I’ll be stealing it soon! ) A couple of thoughts:

• Changing “Min Gas” to “Safety Reserve” is a good idea – it’s a much more descriptive term.
• I agree that “Tank Factor” is confusing, at least without some explanation of why it’s useful.
• I’d leave out the phrase “Scuba Math”, or be more explicit that rounding to more conservative values is all you mean by that. As it is, I’m wondering what else I don’t know that I should about “Scuba Math” (and groaning about having to learn another math – the first one was hard enough!)
• In the discussion of SAC rate (which I agree should be expanded – it’s worthy of more coverage), you should make some suggestions about how to be conservative about calculating “average depth” for those of us whose computers don’t produce an average depth figure (mine produces only a max depth number) – overly deep average depth assumptions could be dangerous here, as they will produce lower SAC rates and overly optimistic dive plans.

I agree with the suggestion that you should break this down into two sections, only one of which should be compressed enough to put into a logbook. Include the definitions, general calculation procedures, and simplified tables on that one. If you really want to provide your students with a useful logbook insert, give them formulae with blanks above to fill in, and format it so that it can be printed on 5½ x 8” card stock, laminated, and written on (filling in the blanks) with a butcher’s pencil. You could put short definitions and tables on the back side of the card as reminders.

If you break it down that way, you can relax about how much space you use for the other stuff, and can include expanded definitions, more thorough treatment of the principles involved, and a series of sample problems (I don’t think one is enough to know if I have the principles down or just got lucky). I think an AOW student should be far enough along not to be overwhelmed by that increased amount of information, and it would be a great resource.

In fact, I think creating an AOW workbook full of such sample problems would be a great service to newbies like me (I haven’t seen one yet), and an interesting collaborative project – if I had the expertise, I’d write one, because I’d sure like to have one to use. I can understand why you mightn’t want to devote your time to doing that, but half a dozen examples and answers explained would be much better than a quick run-through on one plan.

With due respect to Steve R, I don’t think your effort is wasted at all, and as a recent AOW student, I’m grateful that you’re trying to work on a problem we all recognize, instead of giving up and declaring it hopeless. He may be right that you’ll see some resistance from the PADI instructors you work with, but you may not (I can think of one you won’t get any resistance from, though he does have his own gas management handout that’s pretty damn good already), and it’s worth trying anyway.

 

[miketsp]

Reading this thread it's easy to see why the metric system caught on...

All this is so much easier in liters/min and bar.

 

[Blackwood]

Peter -

Allow me to share with you part of a planning reference I made a while back. This is part of my "what I think should be shown" reply.

Maybe I have a more optimistic view about people than others in this thread, but I think it's presented in a reasonable enough manner that a new diver or a non-diver could be taught how to use the information. I make no attempts to show how to obtain it.

Note that the right column only applies to NDL dives, and that I'm fairly conservative with my ascents. Also note that I don't endorse going past 100' with 32% oxygen. Planning gas for 'mandatory deco' is more involved and I've stripped that stuff out of the spreadsheet (except for the 'deep' gas consumption figures which I didn't remove for formatting reasons).

The tank configurations in the first column represent my tanks and those of my most common buddies. Double any of the consumption figures in top two sets for singles. In my mind, the bottom portion (Al80 singles) represents stage bottles, but it will work just fine for your purposes as back gas. Halve any of the consumption figures for an Al40.

 

[Blackwood]

you should make some suggestions about how to be conservative about calculating “average depth” for those of us whose computers don’t produce an average depth figure .

As someone else mentioned above, go down, note your gas, swim around at a constant depth for 10 or 15 minutes, note your gas.

 

[Steve R]

With due respect to Steve R, I don’t think your effort is wasted at all, and as a recent AOW student, I’m grateful that you’re trying to work on a problem we all recognize, instead of giving up and declaring it hopeless. .....

Well now I almost feel bad :blinking:

Giving up and packing it in and declaring it universally hopeless is exactly what I've done. Sure you're going to help the odd person, but you can do that without aiding the w4ore-house operators.

Now I'm fairly content pounding publicly on the clowns at HQ for stuff they know darn well they need to fix but make a concerted effort to ignore. Of course these hero's of dive instruction seem to have no problem BS'ing the public whilst taking their money, as is evident daily here. That's where I'm more than happy to step in and say something. After all, I've tried it their way and have the written correspondence to prove it, and am more than willing to discuss it with them here on S/Brd, publicly only of course. No sock-puppets required either. Full name, Addy and phone # is well known.