Basic Training + Planning

[TSandM]

Bob, that is an absolutely beautiful post.

When I took Bob's gas management seminar, I couldn't hold a safety stop, and I'd only just been cured from doing my descents on my back. But I was able to understand the concept that one should always reserve enough gas to get two people to the surface, and that gas should be planned according the type of dive one was going to do. In fact, the concepts were so simple, and so clearly presented, that my intiial reaction was, "Why has nobody ever told me this before?"

Deco limits simply hadn't applied to my dives to that time . . . like most new divers, my gas consumption had limited my dives much more than my no-deco limits had. But I had no tools to estimate how long I could spend on descent, bottom time, and ascent, or how to ensure that I got back to the boat with 500 psi, short of ascending when I got close to that limit. Which sometimes wasn't when I was anywhere near the boat!

If you believe that new divers can't learn or understand something, you pretty much guarantee that they won't. And if you spend hours trying to walk your students through dive tables that are complicated, and rarely are going to be relevant to them (since a) they will dive computers, and b) their gas consumption is going to keep them well away from decompression limits) and don't teach them gas management, you set them up for the scenarios that DAN documents as pertaining to many diving fatalities.

 

[Ste Wart]

You're the one who's been insulting ... as you've had a history of doing since joining the board.

I've had a history of being honest. If you find that insulting so be it.

I'm not looking to argue with you ... which would be rather pointless. But when you make comments like you've made previously in this thread, you come across someone who doesn't know what he's talking about.

Yeah nothing. Just 10 years of diving. 6 years of instructing, tech qualified and my job is working as a diving archaeologist. Clearly I'm an amateur.

You made a statement that PADI OW is a rigid set of do's and dont's ... which suggests that you don't comprehend that agency standards (even PADI's) are intended to provide a baseline of skill sets, not a ceiling which provides everything you need to know.

You're not even a PADI instructor so your point is moot from the get go.

Apparently you cannot dive from the PADI manual. Others can. I can, thousands of other PADI divers can. Still without a need to use SAC's for daily planning. (which is the 6 or 7th time I've reiterated that same point). You have identified a hole in the training, or what you perceive to be a hole in the training and endeavour to educate people to say that they are missing this from basic training. I say, SAC's have there place and are not needed with a dive with no ceiling a basic set of 'do's and don'ts' will get you diving, get your practicing how to dive safely. Once you have begun to deal with basic dive planning you can move onto something as wildly fluctuating as SAC's. But there is a fact of diving which you cannot ignore. You need to monitor your SPG whatever plan you use, that is what I teach.

You made a statement that if you exceed your depth by 10 cm you go to Plan B ... which suggests that you don't comprehend the nature of deco, the point of a Plan B, or the fact that 10 cm is 0.01 ATA, which is an essentially meaningless quantity in any consideration of decompression obligation. It suggests that you don't comprehend even the basics of how decompression works. Nor is it even relevent to the conversation we were having here. The only point seems to be an attempt on your part to come across as some sort of impressively skilled diver.

Ah my dear boy, nobody really understands the nature of deco that is why it is called a theory. As I've said I primarily use decoplanner for my technical dives. Now if you've ever utilised said program, judging from your post, you haven't. Decoplanner allows for a multitude of factors beyond the standard. If I choose to go aggressive on my GF's and then I drop below my plan A even for a few moments I will of course switch straight to plan B. As I posted above it may not really matter in terms of deco obligation. But on that day, on that time, with levels of hydration, GF's and however much coffee I've drunk pre-dive will elicit that I err on the side of safety and switch to plan B. It is a matter of conservatism, and shows that my skill level likes me getting back to the surface, that is the kind if diver I am.

You made a statement that you can't safely push the limits, othewise they aren't limits ... which suggests that you don't understand that there is no "line" upon which one side is safe and the other is not. The nature of diving ... whether you're talking deco obligation, gas management, or any number of factors ... is that there are an interconnected set of risk factors associated with your dive plan. "Safe" is a relative term, based on a continnum of risk factors. You base your decisions on a fundamental understanding of what those factors are, and how much risk you find acceptable ... and then you factor a certain amount of mitigation into your limits. Exceeding those limits doesn't necessarily make you any less safe ... it simply increases the odds that it might. For example, the classic "end the dive with 500 psi". So how much less safe are you if you end your dive with 400 psi? ... or 350? Another example ... take two dive computers of different manufacture and strap them side-by-side on your wrist ... take them diving ... and notice the variance in NDL. Why does that variance exist? What does it mean? How does that affect you as an individual diver? Which one will you follow? And why?

I feel justified in said statement. It is not meant to be quantifiable, pushing the limits is exactly that.

These aren't difficult questions to answer ... and yet you've not attempted to answer ANY of them. I suspect it's because you can't ... which is why you're so quick to dismiss the ideas of those of us who can.

If that statement has an more irony I'd need a magnet

Diving's NOT an exact science. You ... an individual ... will present varying levels of risk into your dive every time you go diving. Those risk factors will depend on a great many things about you that change on a daily basis. Your dive computer ... or the tables you used to plan your dive ... don't know a thing about you, or what you did within the last 24 hours that might impact those risk factors. So how can you determine that 10 cm difference in depth will have ANY impact on your safety whatsoever? Again, how can you even tell?? In case you're not aware, the pressure sensor in your computer doesn't even function to within those tolerances. Hell ... even moving your arm to look at your gauge is going to change the depth reading by more than 10 cm in some cases ... and doing things like a bottle switch CERTAINLY will. So while that might make you ... in your own eyes ... look like some sort of impressive diver ... it's MEANINGLESS!

You focus on my conservatism and claim it is a bad thing.

When you make statements like that, you deserve to be called out as someone who's either trolling or doesn't know what he's talking about.

Of course. So I put my PADI number in my sig for all to check and my work website? Clearly the actions of a troll. More likely the actions of a guy who actually dives more than he posts.

Think about what you post ... and try giving some meaningful rationalization for why you take that position. Otherwise, you're just regurgitating something you read or were told without really understanding it.

... Bob (Grateful Diver)

I can only wonder why you think your knowledge outweighs mine simply because I believe that diving is a simple affair.

My safety record and amount of dives speaks for itself. As I've said above I work as a diver, not an instructor any more, a diver. I am governed by the rules and regulations of the country I work in (and the UK is pretty stringent). Kindly think on that when you accuse me of phoning it in. I am responsible for a team of divers, where as you are not. I have liability and risk assessment to consider in all dives to ensure the safety of said team.

I'm sure that if I was grossly negligent as you keep trying to suggest this would have been flagged up at work. Oddly it hasn't.

The reason.

I know what I'm talking about.


EDIT: http://www.hse.gov.uk/pubns/priced/l107.pdf Diving Regulations I work under.


I look forward to your response

 

[dbulmer]

Stu,

I agree with you that planning a dive can be very simple and does not need to be complicated. I think Bob would agree with that too.

The issue from a training perspective is a very simple one.

Joe or Joanna Blogs at work asks you: How long can stay you down in the water? A very reasonable question I think and one I would not have been able to answer when I first started diving and I bet I'm not the only one.

If an instructor can show a student how to calculate the SAC rate and use it to determine how long the diver can stay down at a set depth, surely that helps the new student?

Both looking at the SPG and having a method to calculate a realistic reserve for both the individual diver AND buddy if things go tits up is pretty basic stuff and is valuable to every diver no matter the skill level.

As for tides, beach and your sort of diving do require a little bit more planning but for boats a brief chat to a skipper is often all it takes. Even then, the weather can change all of that.

You can use SAC rate in any sort of diving but knowledge of tides is going to differ from location to location. Leave the tide stuff to local flavours of training but add the SAC stuff to basic training is my view.

None of this is rocket science is it?

 

[Kevrumbo]

(It isn't Rocket Science . . .just Middle School Mathematics)

Vindictively incredulous & bombastic rhetoric with no objective, contributory or redeeming value whatsoever. . .

Excuse yourself Wart the Master Instructor . . .your "Scatology" is not relevant nor appreciated.

 

[Ste Wart]

Stu,

I like it when people work out why I'm called Wart

The issue from a training perspective is a very simple one.

Joe or Joanna Blogs at work asks you: How long can stay you down in the water? A very reasonable question I think and one I would not have been able to answer when I first started diving and I bet I'm not the only one.

Pretty sure I asked that as well. And I think I used the 'if a tank lasts X on the surface how long will it last at 4 atm' to explain it to my students. This works in a representative way, but doesn't mean much in practice to students without dive experience. Part of why I get students to call out when they hit certain pressures during the training dives, usually 120, 100 and 70 bar (and 50 of course). They see air consumption in real time and alter the basic dive plan accordingly.

Neither system will work, what I or Bob proscribe without active checking of the gauge.

If an instructor can show a student how to calculate the SAC rate and use it to determine how long the diver can stay down at a set depth, surely that helps the new student?

From that point of view that a new students SAC will be a static affair, then yes it can be helpful. However at the start of training a new divers SAC will normally be... well.. rather high, and will then fall after a period of dive experience. So why teach at this stage? Better to teach the student to monitor the SPG, set basic dive times and turn pressures and gain a knowledge of diving. From there move to SAC's when the dive demands it.

Both looking at the SPG and having a method to calculate a realistic reserve for both the individual diver AND buddy if things go tits up is pretty basic stuff and is valuable to every diver no matter the skill level.

Agreed. I don't debate it as a value. I say diving can continue with or without it safely, with a basic dive plan. And it is very basic.

As for tides, beach and your sort of diving do require a little bit more planning but for boats a brief chat to a skipper is often all it takes. Even then, the weather can change all of that.

Agreed. But this is skipped over a lot in basic training. Conducting your own dives can be heavily dependent on tides depending on where your dive. For those in the Mediterranean, not so much of a problem, where I live it makes all the difference.

But tides do not change with dive experience SAC's do. Learn the dive conditions of your local area soon, know your SAC when it has stabilised and you are moving beyond basic dive plans.

You can use SAC rate in any sort of diving but knowledge of tides is going to differ from location to location. Leave the tide stuff to local flavours of training but add the SAC stuff to basic training is my view.

Fair play. Come down for a splash some time, although the local skipper is bit testy (it's me)

Excuse yourself Wart the Master Instructor . . .your "Scatology" is not relevant nor appreciated.

Like it or not, it works.

Scatology would be the study of sh*t. If you believe my studies are sh*t then it would be your scatology :cool2:

 

[261311]

I don't mean to really step in and be the jerkoff who takes a side but from what I've been reading under Bobs website for SAC is that you don't just "pick" a SAC value based on 1-2 dives, it's a constantly changing average that you monitor over time. From what I gather from that, or at least what I take in value is that you constantly monitor it as you grow as a diver. From what I've read* personally I think I'd feel comfortable with the extra bit of planning because as a noob, I could see myself planning an overambitious dive to say 50 feet for x time, burning through all my gas that I've agreed on turning on for safety and not even getting to my planned depth because of my consumption. It sounds safer knowing what you conservatively consume rather than planning a dive to a set depth and not knowing that you can't make it, and being either disappointed by turning or reckless by continuing, pushing your volume and not having that safety barrier that all the extended planning would allow for.

Everyone has valuable points I can take from this really, learn to love ladies and gents.

 

[Ste Wart]

I don't mean to really step in and be the jerkoff who takes a side but

This is what the internet is here for

from what I've been reading under Bobs website for SAC is that you don't just "pick" a SAC value based on 1-2 dives, it's a constantly changing average that you monitor over time. From what I gather from that, or at least what I take in value is that you constantly monitor it as you grow as a diver.

Sort of.

Your SAC will drop from what you experience on your OW course. A few dozens dives in it will level out and you won't see much improvement after that. Once you find your rhythm as a diver your SAC becomes almost static.

But

I learnt SAC's through my tech training and this is only time I use SAC for planning. A few years after my Trimix course I discovered that with a single tank and lovely warm water I can average a 9lpm SAC, pretty damn low (and yes I am proud of it!). Later still I learned that my body responds badly to thermal stress, i.e I get cold and my SAC will start to spike. Over the course of a dive I find that I can lose 20BAR over my average surfacing pressure if I'm shivering. So I find that gas monitoring and a simple dive plan with in water updates can be far more effective than anything worked out on land for rec diving.

From what I've read* personally I think I'd feel comfortable with the extra bit of planning because as a noob, I could see myself planning an overambitious dive to say 50 feet for x time, burning through all my gas that I've agreed on turning on for safety and not even getting to my planned depth because of my consumption. It sounds safer knowing what you conservatively consume rather than planning a dive to a set depth and not knowing that you can't make it, and being either disappointed by turning or reckless by continuing, pushing your volume and not having that safety barrier that all the extended planning would allow for.

You can only do this by not monitoring your SPG. Referencing your SPG will give an in water update of what is going on in your dive and allow you to make adjustments to your dive. If you miss a turn point either with using an SAC rate calc or simply using a rule of thirds like I advocate then you'll be surfacing earlier than planned, so do check that SPG. However this is rec diving, you should really not be in any situation where you cannot ascend safely. So even if your dive plan was to go from the beach shore and back, and you miss you turn point, you still turn, but ascend when planned and swim the remaining distance on the surface. Next time monitor your gauge (Bascially Chapter 3 in the PADI manual)

Everyone has valuable points I can take from this really, learn to love ladies and gents.

Enjoy your diving Zack.

 

[MXGratefulDiver]

First off, there's more to gas management than just knowing your air consumption rate ... what some in here are calling "SAC". That's just a "miles per gallon" for divers, and a good starting point ... but as noted by the new guy (correctly), it's variable. Yes, it will generally go down as you gain experience and improve your technique ... logically, since improved technique means you're putting less effort into moving yourself through the water. But there's more to gas consumption than that, unless you dive in a static environment.

An analogy first ... you're at home, sitting on the sofa watching TV ... and you're breathing at a certain rate. Noticing it's a nice day, you decide to get out and go for a walk. As you walk, your breathing rate changes. Feeling pretty good, you pick up the pace and start to jog. Once again your breathing rate changes. You round a corner and a dog comes charging out of a driveway, barking and growling ... your breathing rate changes yet again.

Diving's like that. How much air you use on a dive is going to depend on a few factors that are going to affect how much effort you're putting into the dive at a given moment. It constantly changes, and you're looking at averages. If you sit down and do the math after every dive ... total gas consumed x average depth in ATA / total minutes ... you'll come up with a number. Track that number over a period of a dozen or so dives and you'll notice fluctuations. How big or small those are will depend on the variance of dive conditions you dived in, dive profiles (because things like narcosis can affect gas consumption), how you felt on a given day (because things like stress and fatigue can affect gas consumption), what happened during the dive (because something as mundane as an annoying dive buddy or as spectacular as a sea lion in your face will affect your gas consumption) and equipment (because adding a new piece of gear or changing from a singles to doubles rig can affect gas consumption). If you have a dive computer that tracks average depth over the course of a dive, obtaining your SAC for a given dive takes about 30 seconds and uses arithmetic that most of us learned by the time we were in the 5th grade. It's just not that hard.

So the relevent question is why would you want to know this? Well, at the basic recreational level it's because at some point ... often fairly early on ... a diver is going to want to start doing deeper dives. It's not that uncommon for someone new to deeper diving to get taken by surprise at how quickly their gauge goes down at depth ... due to the increased pressure, the effects of narcosis, and the thermal effects often caused by pressure squeezing on your wetsuit and making it less effective at keeping you warm. It adds up ... and even though you were told in class this would happen, it's one thing to "know" something and another altogether to experience it ... and divers do get taken by surprise.

So why wouldn't you want to give some thought to all of that beforehand, and assure yourself you've got adequate gas before beginning the dive? Why wouldn't you want to have a number in your head ... before beginning the dive ... that tells you when it's time to turn around or begin your ascent?

Monitoring your gauge is all well and good ... but remember, you're diving with a buddy for a reason ... part of your gas belongs to them. How will you know you've got adequate reserves if they swim up to you at depth and slash their hand across their throat? More importantly ... how will you know that they have adequate reserves if the person doing that is you?

Think about this for a moment ... if you and your buddy are both diving the same size tank ... have roughly similar consumption rates ... and you run out of or dangerously low on air ... how much do you suppose your buddy wil have? Enough to get you both to the surface??

How will you know?

Why wouldn't you want to? And when do you think would be the best time to be thinking about the answers to those questions?

I don't need to thump my chest, brag about my skills, or insult other people to make a point. This isn't about me ... it's about you. It's about every diver who's reading this thread ... particularly the newer ones.

Give some thought to those questions, and decide for yourself what you would prefer to do ... because, ultimately, each one of us has to decide for ourselves how much risk we're willing to take ... and how much thought we want to put into our dive plan before we hit the water.

... Bob (Grateful Diver)

 

[Ste Wart]

Think about this for a moment ... if you and your buddy are both diving the same size tank ... have roughly similar consumption rates ... and you run out of or dangerously low on air ... how much do you suppose your buddy wil have? Enough to get you both to the surface??

Gee. If we had roughly similar consumption rates we would both be out of air :cool2:


I would have set a basic turn pressure based on a 1/3rd of the tank. Maybe like I've been suggesting for 4 pages now. 1,2,3 I think that would be first grade maths, no?

 

[MXGratefulDiver]

Gee. If we had roughly similar consumption rates we would both be out of air :cool2:

... thank you Captain Obvious ... that's exactly the point. So why risk putting oneself into that situation?

Diving thirds works, if you don't mind ending the dive with a third of a tank. Not the optimal approach ... and normally intended for overhead diving.

But when all you have is a hammer, everything looks like a nail ...

... Bob (Grateful Diver)