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nrembis
07-26-2009, 19:46
My son just finished up his open water class/poolwork thru PADI and they did not go over calculating SAC at all.....

I thought that was odd, I cannot believe that they push computers so much now they neglect an important part of diving, one of the first things we did years ago was start calculating our 10/10 which was NASDS way of getting your SAC, of course we used psi/min(and I still do 20 years later), but still its better than nothing at all if you use the same size tank all the time and do not switch....

seems to me they could have atleast covered this a couple minutes in class :(

navyhmc
07-26-2009, 19:59
I noted that when I was diving amongst some OW students and my buddy and I were discussing SAC and RMV and the students had the deer in the headlights look. No, they didn't even understand psi/min. All they knew was a surface at no less than 800 psi.

I remember doing SAC rates in my OW YMCA class and PADI class.

The problem with pushing a computer on the SAC issue is that the student would have to rely on a AI computer to do it as a safe "Trust Me Dive". And that means more $$$$ up front. I got my first dive computer 2 years ago and still don't fully trust it.

Yea, that is a scary trend.

PTAaron
07-26-2009, 20:21
We didn't talk about SAC in my OW class in May either... they also DIDN'T push computers as a lot of people seem to be reporting. We did a lot of table work, and after the final exam our instructor briefly mentioned how useful computers are.

nrembis
07-26-2009, 20:45
We didn't talk about SAC in my OW class in May either... they also DIDN'T push computers as a lot of people seem to be reporting. We did a lot of table work, and after the final exam our instructor briefly mentioned how useful computers are.


They may not have come right out and PUSHED computers verbally, but they did push computers, as you have no idea how to tell/calculate exactly how long an 80cu ft tank of air filled to 3000 psi would last you at 60ft unless you were using a computer to tell you.......I can tell you for sure that an aluminum 80 filled to 3000psi will last me 70 minutes with my SAC if I stick to my 60ft profile, if I dont go 60ft deep, great I have plenty of air left!, if I go to 70ft no problem, I just lost about 10 minutes time, I can adjust....and I could have have told you this after my first pool dive 20 years ago.

Don't get me wrong, computers are nice and may extend times to an extent, but I have seen them fail...

Rileybri
07-26-2009, 22:10
They did not do much with calculating SAC (http://www.spearfishing.org/bruces_tips/java/sac.html) in my NAUI Scuba Diver (OW equivalent) either. Then again it feels live there is not much more than boosting diving numbers and giving enough info so as not to kill people in OW and even AOW. If a diver wants to "progress" and actually gain useful info they have to find it and learn it on there own.
Another gem I have picked up along the same lines as SAC is Rock Bottom Gas Management (http://www.scriptkiddie.org/diving/rockbottom.html).

happy learning and safe diving!

nrembis
07-26-2009, 23:28
I just think its useful and should be a requirement to know this information during OW training, its not even close to being technical and shouldnt be moved further on down the line in your course of training.

I think SAC is good for pairing single divers up on the boat iif need be....there is no sense in putting a single diver with someone that only gets 40 minutes time with someone that gets 70 minutes on a leasurely recreational dive......but how is anyone to know this if they arent taught from the start?

CompuDude
07-27-2009, 02:54
I just think its useful and should be a requirement to know this information during OW training, its not even close to being technical and shouldnt be moved further on down the line in your course of training.

I think SAC is good for pairing single divers up on the boat iif need be....there is no sense in putting a single diver with someone that only gets 40 minutes time with someone that gets 70 minutes on a leasurely recreational dive......but how is anyone to know this if they arent taught from the start?

That's a very good question, and I wish PADI, NAUI, SSI, SDI, etc. would come up with a satisfactory answer, but the truth is they just don't think it's needed, and they think it's too hard and could cost them students. (income from students, that is... apparently actually losing the students ... once they have their cards and are no longer really students ... is not something they're as worried about.)

mrmccoy
07-27-2009, 03:37
They did not do much with calculating SAC (http://www.spearfishing.org/bruces_tips/java/sac.html) in my NAUI Scuba Diver (OW equivalent) either. Then again it feels live there is not much more than boosting diving numbers and giving enough info so as not to kill people in OW and even AOW. If a diver wants to "progress" and actually gain useful info they have to find it and learn it on there own.
Another gem I have picked up along the same lines as SAC is Rock Bottom Gas Management (http://www.scriptkiddie.org/diving/rockbottom.html).

happy learning and safe diving!


good read thanks Rileybri !

navyhmc
07-27-2009, 03:46
I still can't help but wonder if it is not taught as it's another thing that a new student will be worried about and in the end not have as much fun-if any fun-on their first dives. They do indeed give them enough so that they won't kill themselves and give them "rules" that they should follow IRT air management so that they can indeed dive safe but really only have to worry about NDL's essentially not task overloading them...

mitsuguy
07-27-2009, 05:35
As mentioned, it's one more thing for new divers to think about. Many are task loaded to the max just worrying about buoyancy and remembering to check their air pressure.

I was not taught how to calculate air consumption, and to this date, the only reason I ever have was because it is built in to my dive software - average depth, air pressure used....

Who cares what your SAC rate is??? I mean really... In a recreational setting, is it really that important??? People generally know if they are air hogs, and most are very willing to admit it... Sure, they don't come out with "my SAC rate is 1.5" or anything like it, but they know that they are typically the ones running low on air first out of a group...

The one thing we do emphasize in an OW course is to plan a dive, dive the plan, which includes making sure there is enough air to surface safely, and have some air in reserve. This doesn't include any calculations, but we do show how air consumption doubles, triples, quadruples, etc. due to depth, and that these things should be taken into consideration when planning a dive...

rongoodman
07-27-2009, 05:39
As far as I know, there is no gas planning taught in any PADI course, and what little there is in the DSAT courses is rudimentary at best. Go figure.

navyhmc
07-27-2009, 05:53
PADI actually sets a foundation for it in the Deep Diver Course. However instead of cuft/L per min, they talk in PSI/Bar per min. But they at least they have some exposure to it.

rayaa3
07-27-2009, 09:40
I don't think the lack of SAC is a 'computer pushing' issue. Most people who I dive with who use computers aren't using AI (still too expensive for most I suppose). We did my OW, PADI, using nothing but tables. I considered my OW to be a little light on instruction (in hind sight) and really just a push to get students certified in as little time as possible. I don't necessarily think this reflected on PADI, as it did the individual instructor/shop that I chose. However, he didn't push computers that hard, not until he detected that you might buy one anyway ;)

As far as the the need for SAC training in OW issue...hmmm...most recreational divers, certified in the US will dive a couple of times a year, from a guided dive boat using table caculated bottom times (or bottom times calculated by the demands of the dive boat schedule for the day, meaning that the boat needs to be back at the shop by 1pm, so dives are 30 minutes). I do think that it is an interesting idea to teach it in AOW, but I don't think it's a skill that most divers with less than 20 dives needs to begin to think about. I'm happy if new divers can simply not bump into coral, or ME, manage to keep an eye on their gas, and try not to get away from the group, or their buddy.

I realize that their are certain geographical areas where divers tend to get more unguided/unsupervised dive time in the ocean (if you live near the coastal areas like florida, if you dive primarily in the US) but the majority of divers I have met don't fit that profile. They don't live near the ocean, they don't do quarry dives, and they MIGHT dive 8 dives a year from a cattle boat in Mexico. Those guys need more time with basic skills, not SAC calculations. Now - the majority of the divers on this forum, probobaly do NOT fit that profile. As far as I can tell we are all afflicted with the same addiction which makes us seek every dive we can, even in slimey mudholes where you can do a night dive in 30ft of water, at 3pm in the afternoon on a sunny day in july :)

incidentally - SAC didn't come up much in my AOW either (still padi, different shop and instructor) - though I think it would have been a good addition because by the time I took my AOW I was ready to start PLANNING my dives a little more, rather than just 'not bumping into crap' and enjoying the scenery.

obrules15
07-27-2009, 09:50
I think SAC is good for pairing single divers up on the boat iif need be....there is no sense in putting a single diver with someone that only gets 40 minutes time with someone that gets 70 minutes on a leasurely recreational dive......but how is anyone to know this if they arent taught from the start?

:smiley31:I would have loved to have this info on past trips as a few insta buddies have decimated my dives due to their SAC. But I wasn't taught it in my PADI OW in '99 nor my NASE AOW in '01

Damselfish
07-27-2009, 10:40
We didn't do SAC in my PADI OW in 1990, even.

(Though honestly, even though I know what it is now and have figured it out, it's actually something I've never needed in my diving. I have a good intuitive handle on my air use, which is low compared to everyone I dive with it just doesn't matter anyway.)

There seem to be lots of classes that don't cover what they should well enough. But there is always more to learn, and also sometimes arguments for not possibly overwhelming some people at first. And I'm really not so sure a bunch of people on a boat comparing SACs as a practical way of pairing people up, for many reasons.

cummings66
07-27-2009, 11:25
The one thing we do emphasize in an OW course is to plan a dive, dive the plan, which includes making sure there is enough air to surface safely, and have some air in reserve. This doesn't include any calculations, but we do show how air consumption doubles, triples, quadruples, etc. due to depth, and that these things should be taken into consideration when planning a dive...

There is the rub. Plan the dive, dive the plan, but don't bother to show them how to plan. That's what annoys me. I didn't get taught it either, and I consider it to be valuable.

It is not that much extra work, I know many agencies say that the students can't handle one more thing or their little brains will explode, but I don't think that is true. It's not anything they don't already have the skills to do. They're either in school or have graduated from high school and they should have enough basic math to handle it in either case. You are not teaching math here because they already know math.

You can dumb it down even. Take them to 33 feet (or any depth) and have them set there for 5 minutes watching how the psi drops. Have them write that number down. Now show them that if they used X at 1 ATA they would use X more at 2 ATA. You're already giving them the basics in explaining how you use more air at depth. Just show them how to determine their SAC which every single one of them can handle and then how that number goes up or down as you go up or down. You can even do that in the classroom if you liked and then relate that to the ATA which you do teach.

Now they know if they use 500 psi a minute at depth they can only be there so long until they run out. Easy as pie and I bet they all handled it easily. Don't bother showing them how to convert to cf, just make sure they know it's different for each size cylinder and you've given them all the tools they need.

What did that take? 5 minutes of your time is all it took under water, 2 minutes above water. So for less than 10 minutes you could give them the tools to plan the dive. Or it could have all been done in the classroom.

You doesn't mean you, it's really meant to be a reference to the dive agencies.

It's important because if all they know is they use air faster at depth and they have 1000 psi at 60 feet, it would surely be nice if they could plan how long to stay at 60 feet by something other than tables which are not the limiting things for a new diver. Air consumption is. I've seen far too many divers run low or out of air because they were not given the tools to plan a dive properly.

PS, that doesn't mean they need to do it on every single dive, but for some dives I think it's helpful.

scubadiver888
07-27-2009, 12:54
I had my original training with a personal OWSI. It was just me and him so I didn't get to see how other students learned.

After OW I've been taking classes with a group of people. I find most the people REALLY hate the theory. Just doing the Nitrox math seemed to be a lot of memorize the material rather than really understand it. The instructors tried to make sure the students understood the material but after the class it seemed like the students believed, "The knowledge review and testing was a punishment I had to endure to get my card. Now that I have my card I can forget the material." My wife was an examiner for driver's licenses and saw the same sort of behaviour. People felt the testing was a punishment they had to endure to get their license and not a test to ensure they knew what they were doing.

The people who seek out more knowledge and end up on boards like this are not the people PADI and other dive agencies are catering to. They are running a business. They want to make money. They try to put things in place to reduce risk and maximize clientèle.

As someone who is now working towards PADI Dive Master, I can see in the material that they want to dumb it down. They had very little when I went diving the first time (1998). Now they seem to encourage DMs/OWSI/etc. to start people with Discover Scuba. Keep the depths so shallow you shouldn't have to worry about gas management. If you are a REAL air hog you can always CESA as a last resort. Now they have another certification were you can only go to 40' and it is assumed you will go on DM lead tours. Finally there is a the OW. But even with the OW they encourage you to push refresher courses every so often. When pushing the refresher course you might want to introduce Peak Performance Buoyancy.

I'm still going through the material but it seems they want to attract as many people as possible and it will be my job to teach them the bare minimum but encourage them to come back again and again. Each time teach them a little more.

Bottom line, people like us will go for their DM, we will get GUE/DIR training, we will find a good mentor, etc. At that point, we are not the people PADI is catering to.

Additionally, PADI emphasizes that the requirements are minimums. We, as DM, are expected to use our best judgement. For colder water, low viz, current, etc. the minimums might not be correct. You might want to add 10' to your depth as a safety or reduce the number of students to OWSI if viz is poor. Most the safety standards are based on liability. If the lawyers are okay with it, it is good enough. Do we need a SAC rate to dive safely? For recreational diving it should be okay to not know your SAC rate.

cummings66
07-27-2009, 14:47
I agree that for many dives you don't need to know your SAC rate, heck, I can do a solo dive to almost any depth you want in the recreation arena and I'm fine without knowing anything other than how much air I have left. Why? Because I have dove enough that I know how much air I'll need to get back to the surface and still have a safe margin.

But, how many recreational divers have you seen at 100 feet with 700 psi of air left? Me, I've come across a couple that I ended up aiding because they and their buddy neither one had enough air to support the other. They were lucky I chanced upon them. For what it's worth, one was SSI and the other Padi.

Is it necessary to know the numbers, absolutly not. My VT3 will tell me based on my current air consumption how much time I have left before I run out of air, it'll tell me my NDL at all times, how much deco time I have. Should I then rely on it for all my dive needs?

Nope, here's why. What if it goes crazy and I'm blindly following it's advice? I can end up in trouble. I should be able to on my own tell if what it's saying is in the ballpark or not. By knowing my air consumption I can tell if it's sane or not, by knowing the tables I can tell if it's sane or not. The methods behind the diving help me to know if the computer on my wrist is telling me a fib or if it's telling the the straight scoop.

Tell me though, what's wrong with figuring out how much psi you use in 5 minutes in the classroom, then relating it to the ATA and how much psi you would use at that depth? You go through so much effort to tell them the effects of ATA and fall short when it comes to real life examples. You are 99% of the way there, what's wrong with finishing up?

See, to be honest, what theory do you need to teach a diver to be safe? Bare essentials only? How about don't hold your breath and add air to the bc going down, release air going up, and clearing a mask. Look at the SPG, keep it above 500 psi and turn em loose. Do you really need to spend hours upon hours in a classroom teaching them about wetsuits, regulators, bc's, charles law, etc? No, not if all you're doing is turning out a diver who you want to be safe. What do they need to know about a wetsuit other than the thicker it is the warmer it is? I was told about how it works, who cares? Does it affect me as a diver to know how it works. A simple get the thickest you can afford for diving in the local lakes would have been fine, or get a drysuit for all season diving. Why do I need to know how a regulator works? Who cares that it takes the HP cylinder air and reduces it's pressure and all that trivia. Why bother to teach that garbage and then skip something of value? Does teaching me how a wetsuit works make me safer? No. Can teaching me about SAC make me safer? Yes. Do I need to know about SAC for many dives? No, for some yes. Get my point, what they teach is not just the bare essentials, some of it is garbage that has no value at all.

obrules15
07-27-2009, 15:06
I agree that for many dives you don't need to know your SAC rate, heck, I can do a solo dive to almost any depth you want in the recreation arena and I'm fine without knowing anything other than how much air I have left. Why? Because I have dove enough that I know how much air I'll need to get back to the surface and still have a safe margin.

But, how many recreational divers have you seen at 100 feet with 700 psi of air left? Me, I've come across a couple that I ended up aiding because they and their buddy neither one had enough air to support the other. They were lucky I chanced upon them. For what it's worth, one was SSI and the other Padi.

Is it necessary to know the numbers, absolutly not. My VT3 will tell me based on my current air consumption how much time I have left before I run out of air, it'll tell me my NDL at all times, how much deco time I have. Should I then rely on it for all my dive needs?

Nope, here's why. What if it goes crazy and I'm blindly following it's advice? I can end up in trouble. I should be able to on my own tell if what it's saying is in the ballpark or not. By knowing my air consumption I can tell if it's sane or not, by knowing the tables I can tell if it's sane or not. The methods behind the diving help me to know if the computer on my wrist is telling me a fib or if it's telling the the straight scoop.

Tell me though, what's wrong with figuring out how much psi you use in 5 minutes in the classroom, then relating it to the ATA and how much psi you would use at that depth? You go through so much effort to tell them the effects of ATA and fall short when it comes to real life examples. You are 99% of the way there, what's wrong with finishing up?

See, to be honest, what theory do you need to teach a diver to be safe? Bare essentials only? How about don't hold your breath and add air to the bc going down, release air going up, and clearing a mask. Look at the SPG, keep it above 500 psi and turn em loose. Do you really need to spend hours upon hours in a classroom teaching them about wetsuits, regulators, bc's, charles law, etc? No, not if all you're doing is turning out a diver who you want to be safe. What do they need to know about a wetsuit other than the thicker it is the warmer it is? I was told about how it works, who cares? Does it affect me as a diver to know how it works. A simple get the thickest you can afford for diving in the local lakes would have been fine, or get a drysuit for all season diving. Why do I need to know how a regulator works? Who cares that it takes the HP cylinder air and reduces it's pressure and all that trivia. Why bother to teach that garbage and then skip something of value? Does teaching me how a wetsuit works make me safer? No. Can teaching me about SAC make me safer? Yes. Do I need to know about SAC for many dives? No, for some yes. Get my point, what they teach is not just the bare essentials, some of it is garbage that has no value at all.

I think the thing that frustrates me the most is that those same people who run out of air at 100ft not knowing their SAC will run out of air at 100ft knowing their SAC. I just think they are sloppy divers. Though I think SAC is a good thing and knowing it wouldn't be difficult or bad, is it really that hard to look at your freakin' gauge? They won't calculate and they won't look.

mitsuguy
07-27-2009, 18:50
I think the thing that frustrates me the most is that those same people who run out of air at 100ft not knowing their SAC will run out of air at 100ft knowing their SAC. I just think they are sloppy divers. Though I think SAC is a good thing and knowing it wouldn't be difficult or bad, is it really that hard to look at your freakin' gauge? They won't calculate and they won't look.

You have a very good point there that I'm surprised I didn't bring up earlier...

So, obviously, I lead many certified divers on dives all over the place... I keep it conservative as I'd like everyone to get as much dive time for the location as possible... we don't limit time in the water other than to be somewhat respectful for those already getting out of the water...

that being said, the way we typically lead a dive is to head out at 70 feet or so along the wall, at 20 minutes, or the first person hits a half tank (1500 psi), turn the dive around, ascend to the top of the wall, 30 feet (everyones air consumption should drop by a little more than 1/3), and, so long as we did a good job of getting the current right, have everyone back under the boat with 700 psi, just in time to do a safety stop and ascend for those low on air - those that have air remaining are free to explore around under the boat until they get to 700-800 psi, they are then encouraged to do their safety stop and ascend to the boat...

the problem with this, is that I rarely EVER get the half tank sign from anyone... I brief it every single time, but hardly anyone ever gives me the half tank sign... I make it a point that when someone is getting their gear on, that I turn their SPG so that I can see it... sad thing is, most of the time 3/4 of way through the dive, it hasn't been touched and I can still read it from in front of them just fine... my favorite is getting the half tank sign when they are clearly at or under 1000 psi... I brief it this way every single time and it never ever seems to work out except for my Discover Scuba participants and my actual students - those guys are spot on with telling me their air pressure...

As far as teaching air consumption and such... I'd be happy if I could find students who could truly learn the tables... I teach it and teach it and have them work practice problems above and beyond what the book says, but they still rarely understand it completely... They pass the tests, but just days later, when I have them plan their dives, they are always asking questions about minimum surface interval... or, when they log their dives afterwards, always about residual nitrogen time...

scubadiver888
07-27-2009, 19:30
I agree that for many dives you don't need to know your SAC rate, heck, I can do a solo dive to almost any depth you want in the recreation arena and I'm fine without knowing anything other than how much air I have left. Why? Because I have dove enough that I know how much air I'll need to get back to the surface and still have a safe margin.


PADI is diving for the masses. Does it hurt to know how to calculate your SAC rate and have a better understanding of gas management? No. Is everyone willing and capable of understanding it? No. Some people are overwhelmed by the amount of information they get their OW.

PADI wants to get as many people diving as they can. Their literature is all about getting people diving, keeping people diving, encouraging them to continue.

Most people will never progress beyond OW and don't really need to learn proper gas management for the type of dives they do. So you don't want to introduce this topic in OW. Could it be an Adventure Dive (like Deep, Wreck, Navigation, etc.)? Absolutely. Once I'm a certified dive professional I'll talk to my agency about this.

Once you start getting into the professional levels (DM or higher) you start learning a LOT more. This is understandable. It is a career. Could I program in high school? Sure. Did I understand enough to write good programs? No. When I became a professional programmer I was expected to learn source control, IDEs, design patterns, etc. Could I have been a better programmer if I knew this in high school? Yes. Would I have been able to absorb it and use it properly? No.

PADI is for Bob, the VP of Accounting. Bob goes to the Caribbean twice a year for two week vacations. During that time he'll go diving two or three times. Bob will never dive in Lake Ontario. He will half enough gas if he turns at 1500 PSI.

PADI's only responsibility is to make sure Bob understands that scuba diving is dangerous and to give him ENOUGH knowledge to reasonably prevent an accident.



But, how many recreational divers have you seen at 100 feet with 700 psi of air left? Me, I've come across a couple that I ended up aiding because they and their buddy neither one had enough air to support the other. They were lucky I chanced upon them. For what it's worth, one was SSI and the other Padi.


The only time I see people at 100 feet with 700 PSI left is because they aren't following everything they were taught. The methods used for PADI divers work. If they followed what they were taught this would not happen. If they were taught how to calculate their SAC rate it would make no difference.

Knowing your SAC rate will let you do better gas management. PADI teaches to be more conservative. They encourage you to put in more margin of safety. PADI assumes you aren't capable of ROCK BOTTOM gas management so they restrict new divers to ranges they really don't need gas management. When you get to AOW they teach BIG SAFETY MARGIN gas management.

You might think if you are going for AOW you are serious enough to want to learn rock bottom gas management but this is not necessarily true. Many divers just know some dives require AOW so they get AOW immediately after OW.

Maybe it shouldn't be more information for the diver but require more experience before moving to a level that requires better gas management? I don't know.



Is it necessary to know the numbers, absolutly not. My VT3 will tell me based on my current air consumption how much time I have left before I run out of air, it'll tell me my NDL at all times, how much deco time I have. Should I then rely on it for all my dive needs?

Nope, here's why. What if it goes crazy and I'm blindly following it's advice? I can end up in trouble. I should be able to on my own tell if what it's saying is in the ballpark or not. By knowing my air consumption I can tell if it's sane or not, by knowing the tables I can tell if it's sane or not. The methods behind the diving help me to know if the computer on my wrist is telling me a fib or if it's telling the the straight scoop.


This is something completely different. You don't need to know SAC rate to notice your dive computer has gone crazy.



Tell me though, what's wrong with figuring out how much psi you use in 5 minutes in the classroom, then relating it to the ATA and how much psi you would use at that depth? You go through so much effort to tell them the effects of ATA and fall short when it comes to real life examples. You are 99% of the way there, what's wrong with finishing up?


For you and me (and I suspect all the people on this board), learning SAC rate and the basics of proper gas management is no problem. For many people who have been diving for years and enjoying OW dives lead by a DM in crystal clear water, this is asking too much.



See, to be honest, what theory do you need to teach a diver to be safe? Bare essentials only? How about don't hold your breath and add air to the bc going down, release air going up, and clearing a mask. Look at the SPG, keep it above 500 psi and turn em loose. Do you really need to spend hours upon hours in a classroom teaching them about wetsuits, regulators, bc's, charles law, etc? No, not if all you're doing is turning out a diver who you want to be safe. What do they need to know about a wetsuit other than the thicker it is the warmer it is? I was told about how it works, who cares? Does it affect me as a diver to know how it works. A simple get the thickest you can afford for diving in the local lakes would have been fine, or get a drysuit for all season diving. Why do I need to know how a regulator works? Who cares that it takes the HP cylinder air and reduces it's pressure and all that trivia. Why bother to teach that garbage and then skip something of value? Does teaching me how a wetsuit works make me safer? No. Can teaching me about SAC make me safer? Yes. Do I need to know about SAC for many dives? No, for some yes. Get my point, what they teach is not just the bare essentials, some of it is garbage that has no value at all.

When I took a refresher course, it was with an OW class. All the OW students wanted to learn about equipment. They expected the class to teach them how to buy the equipment after they were certified.

You need to know how a regulator works so you can understand things like, if you lose your mask and breath in your nose, you can spit the water into the regulator and breath in. You should get air and not the water you just spit out.

Bottom line, not everything you are taught has to make you safer. Some people want to know about this stuff. Some people do not care about their SAC rate. Some of it is garbage that has no value at all TO YOU.

Additionally, go back and re-read your OW manual. I just started doing it again (part of being a DM). Someone recently asked why they don't teach more than one method of clearing your ears in OW class. My manual has three methods for clearing your ears.

I re-read programming manuals after years of programming. As I re-read them I realized there was a lot I missed the first time I read them. I suspect this is true for my dive manuals as well.

scubadiver888
07-27-2009, 19:39
I think the thing that frustrates me the most is that those same people who run out of air at 100ft not knowing their SAC will run out of air at 100ft knowing their SAC. I just think they are sloppy divers. Though I think SAC is a good thing and knowing it wouldn't be difficult or bad, is it really that hard to look at your freakin' gauge? They won't calculate and they won't look.

You have a very good point there that I'm surprised I didn't bring up earlier...

So, obviously, I lead many certified divers on dives all over the place... I keep it conservative as I'd like everyone to get as much dive time for the location as possible... we don't limit time in the water other than to be somewhat respectful for those already getting out of the water...

that being said, the way we typically lead a dive is to head out at 70 feet or so along the wall, at 20 minutes, or the first person hits a half tank (1500 psi), turn the dive around, ascend to the top of the wall, 30 feet (everyones air consumption should drop by a little more than 1/3), and, so long as we did a good job of getting the current right, have everyone back under the boat with 700 psi, just in time to do a safety stop and ascend for those low on air - those that have air remaining are free to explore around under the boat until they get to 700-800 psi, they are then encouraged to do their safety stop and ascend to the boat...

the problem with this, is that I rarely EVER get the half tank sign from anyone... I brief it every single time, but hardly anyone ever gives me the half tank sign... I make it a point that when someone is getting their gear on, that I turn their SPG so that I can see it... sad thing is, most of the time 3/4 of way through the dive, it hasn't been touched and I can still read it from in front of them just fine... my favorite is getting the half tank sign when they are clearly at or under 1000 psi... I brief it this way every single time and it never ever seems to work out except for my Discover Scuba participants and my actual students - those guys are spot on with telling me their air pressure...

As far as teaching air consumption and such... I'd be happy if I could find students who could truly learn the tables... I teach it and teach it and have them work practice problems above and beyond what the book says, but they still rarely understand it completely... They pass the tests, but just days later, when I have them plan their dives, they are always asking questions about minimum surface interval... or, when they log their dives afterwards, always about residual nitrogen time...

Mitsuguy,

Do you have many certified divers who bring their own equipment but have you take them on guided tours? When I go on cruise ships with my wife (she doesn't dive), I'll take the shore excursions at every port. EVERY dive the DM tells us to tell him when we are at half tank. Most the people have their own computers. By default the computer beeps at half tank (assumes AL80). I can hear computers beeping when I'm at 2000+ PSI. No one signals half tank. I get to 1500 PSI and the DM turns the dive immediately. I get back on the boat with 1000+ PSI. Many of the divers have 200 PSI. I think the lowest I saw was 160 PSI.

I think the DM knows when he hears the beeping, someone is at half tank. He keeps us out long enough that someone like me won't feel I got a REALLY short dive but short enough no one drains the tank.

You are working with the people PADI is catering to. This is their bread and butter.

mitsuguy
07-27-2009, 19:57
Mitsuguy,

Do you have many certified divers who bring their own equipment but have you take them on guided tours? When I go on cruise ships with my wife (she doesn't dive), I'll take the shore excursions at every port. EVERY dive the DM tells us to tell him when we are at half tank. Most the people have their own computers. By default the computer beeps at half tank (assumes AL80). I can hear computers beeping when I'm at 2000+ PSI. No one signals half tank. I get to 1500 PSI and the DM turns the dive immediately. I get back on the boat with 1000+ PSI. Many of the divers have 200 PSI. I think the lowest I saw was 160 PSI.

I think the DM knows when he hears the beeping, someone is at half tank. He keeps us out long enough that someone like me won't feel I got a REALLY short dive but short enough no one drains the tank.

You are working with the people PADI is catering to. This is their bread and butter.

When we deal with cruise ship passengers, rarely do more than a couple have anything more than mask / fins... Certified divers that are on vacation on St. Croix, I'd say 60% have their own gear... So, yah, a lot of this is with divers on their own gear...

We know (for the most part) the whole time when someone is low on air, or where they are... We definitely try our best to cater to everyone, and you are definitely right - we walk a line of keeping people safe, and making everyone happy too...

I really like it when small groups come to dive with us... not long ago, I took a family of 5 out... 10 dives later, we had all logged a little over 11 hours in the water together... all of our dives were an hour plus, it was awesome... problem is, its hard to get that lucky all the time... with those guys, by the second dive, I knew where everyone was at the end of the dive air wise without even looking...

CompuDude
07-27-2009, 19:59
You are working with the people PADI is catering to. This is their bread and butter.

I love it when companies pander to the lowest common denominator. :smiley11:

scubadiver888
07-28-2009, 07:03
You are working with the people PADI is catering to. This is their bread and butter.

I love it when companies pander to the lowest common denominator. :smiley11:

If there is a dollar to be made, someone is going to go for it. The only thing I ask is they keep them away from the nice dive locations. :smiley2:

scubadiver888
07-28-2009, 07:27
When we deal with cruise ship passengers, rarely do more than a couple have anything more than mask / fins... Certified divers that are on vacation on St. Croix, I'd say 60% have their own gear... So, yah, a lot of this is with divers on their own gear...


We typically sail on Princess cruises. They have two or three itineraries which hit 12 ports in 14 days (very few 'at sea' days) and 10 of those ports have good diving. So I can get in 20 good dives. Maybe it is because the itinerary is good for someone who wants to go diving but maybe ten to twelve people (out of twenty) bring their own dive gear.

Mind you, just because they bring their own gear doesn't mean they are good divers. These are the guys who you can hear their half tank warning yet they don't inform the DM.

Last time I went, one person realized as she was focused on her $10,000 video camera system she would often float off. Her solution: wear 20 lbs of weight (no wetsuit; I'm pretty buoyant and I wear 12 lb with 3mm). She could then let all the air out of her bcd and STAND ON THE CORAL.

My favourite place to go is St. Lucia Anse Chastanet Marine Park or Bonaire. They require you to do a checkout dive at each location. The checkout is typically, hover, remove mask, replace mask, lose regulator, recover regulator. Once everyone has done that with ZERO issues, we are off for a shore dive. None of the typical cruise ship divers show up to those. They act all indignit and refuse to go.



We know (for the most part) the whole time when someone is low on air, or where they are... We definitely try our best to cater to everyone, and you are definitely right - we walk a line of keeping people safe, and making everyone happy too...


This is the one thing that worries me about going pro. I have to be pleasant to people I would normally want to smack. For now I'm going to be a DM in Lake Ontario. There are very few people who I want to smack here and none of them are at my LDS. So I can avoid them.

I'll have to develop a certain level of tolerance if I decide to work in the Caribbean. :smiley13:



I really like it when small groups come to dive with us... not long ago, I took a family of 5 out... 10 dives later, we had all logged a little over 11 hours in the water together... all of our dives were an hour plus, it was awesome... problem is, its hard to get that lucky all the time... with those guys, by the second dive, I knew where everyone was at the end of the dive air wise without even looking...

That sounds nice. As a single diver I find it rare to be with a small group of good divers. I often end up on the cattle boats with a few guys who go through an AL80 at 60' in 30 minutes. It used to be amusing watching them swim through the water with their hands. The novelty has worn off however.

I've learned to pick a young, fit, new diver for buddy, mentor him on buoyancy control, be the first person in the water, last person out, stay at the back of the group and do my own thing. This worked for me most the time.

Only once did the group lose the DM (being at the back of 20 people I never see the DM). Viz got down to 30' and they lost him. Fortunately, no one panicked but there were a lot of wide eyes.

cummings66
07-28-2009, 07:51
Viz got down to 30 feet, around here I'd say the viz got up to 30 feet, that's awesome viz and one we don't see often. Normally 5 to 15 feet is common around here. Table rock is 5 feet to about 30 feet and then opens up to 20 - 30 feet below 40 feet deep.

We hardly ever lose buddies in those conditions, but it's all what you're used to I guess.

Rileybri
07-28-2009, 08:23
You all sound like a bunch of grumpy old men complaning that slide rules are not used in highschool math class any more! :smilie39:

WHo need to figure that dive math stuff out for them selves when their computer will do it for them????


:smilie40:

scubadiver888
07-28-2009, 12:22
Viz got down to 30 feet, around here I'd say the viz got up to 30 feet, that's awesome viz and one we don't see often. Normally 5 to 15 feet is common around here. Table rock is 5 feet to about 30 feet and then opens up to 20 - 30 feet below 40 feet deep.

We hardly ever lose buddies in those conditions, but it's all what you're used to I guess.

You don't going diving in the Caribbean? Viz in some places is 60 to 100 feet.

Viz here at home is 5 to 10 feet. On a good day it might open up to 20 or 30 feet. This is why I like to get to the Caribbean once or twice a year.

scubadiver888
07-28-2009, 12:23
You all sound like a bunch of grumpy old men complaning that slide rules are not used in highschool math class any more! :smilie39:

WHo need to figure that dive math stuff out for them selves when their computer will do it for them????


:smilie40:

:smilie40:

Flatliner
07-28-2009, 13:10
I taught my son how to calculate RMV and SAC as well as his rock bottom pressure. I also used Joe's table tutor to drill tables into him. I kid you not, in his class they only worked 2 dive table problems. They were too busy selling gear and promoting a computer to spend time on tables let alone RMV, SAC, and RBP! That may not be the norm but it IS what I recall from his class.

scubadiver888
07-28-2009, 13:25
I taught my son how to calculate RMV and SAC as well as his rock bottom pressure. I also used Joe's table tutor to drill tables into him. I kid you not, in his class they only worked 2 dive table problems. They were too busy selling gear and promoting a computer to spend time on tables let alone RMV, SAC, and RBP! That may not be the norm but it IS what I recall from his class.

Yeah, I drive an hour to go to a good dive shop. There is a place a lot closer (10 minutes) but they just seem interested in selling gear.

The sad thing is the good dive shop hasn't made a profit in 5 years and might close shop. :smiley19: I tried to help her out as much as time allows.

chinacat46
07-28-2009, 13:35
I taught my son how to calculate RMV and SAC as well as his rock bottom pressure. I also used Joe's table tutor to drill tables into him. I kid you not, in his class they only worked 2 dive table problems. They were too busy selling gear and promoting a computer to spend time on tables let alone RMV, SAC, and RBP! That may not be the norm but it IS what I recall from his class.

What agency was this?

gNats
07-28-2009, 13:41
Okay everyone. For the noobs on the site. Why is SAC rate so important?

Here are my stats:

Cold water (<47 degrees), moderate low vis (< 20 ft). Average depth around 50'. Deepest depth 80-100'. HP Steel 80. SS bp/w with drysuit and other typical exposure gear.

My SAC rate is typically .43 - .47 for these types of dives.

So what? What does that tell you? If someone with very limited diving experience is reading this thread, what does my SAC rate of .43 mean to him or her?

What if my dive buddy's SAC rate is .68 but he is diving doubles and a pony?

Personally, I follow the philosophy that SAC rates are good conversational pieces and bragging rights.

My dive instructor went through gas consumption at different depths thoroughly. But we didn't talk about SAC rate. He explained how different conditions will / can cause me to breathe heavier and reduce my air supply faster. He also taught me to plan my dive in thirds and not worry about how much time I can spend under the water.

He also said, that more experience, confidence, and gear fine-tuning will improve my ability to manage my air supply better.

I will, however, look through my dive log and my SAC rate and see the improvement in my gas consumption. It is pretty consistent with my comfort diving and fine-tuning my gear setup.

Should new OW divers be worrying about the amount of time they can spend uw, or that they are diving in thirds and always have a safe reserve of air in their tanks?

:smilie40:

gNats
07-28-2009, 13:49
[quote=cummings66;318167]Additionally, go back and re-read your OW manual. I just started doing it again (part of being a DM). Someone recently asked why they don't teach more than one method of clearing your ears in OW class. My manual has three methods for clearing your ears.

I re-read programming manuals after years of programming. As I re-read them I realized there was a lot I missed the first time I read them. I suspect this is true for my dive manuals as well.

This was a really good point, thank you. Many people read by glossing over the information to find the answer for the knowledge review question.

I would imagine that very few people actually LEARNED what was in their OW books, but instead found a way to answer the questions as efficiently as possible.

You made other good points also. People can be taught anything, but you still have to rely on them to behave in a manner consistent with what they were taught.

For example, What the HELL is an OW diver doing at 100'??? Who cares that he or she is at 700 psi. What were they doing down there to begin with?

Teaching SAC rate to OW students will not make them better or safer divers. OW students should be diving within the limitations of that certification - which is recreational diving. Less than 60' and using conservative gas management planning techniques.

cummings66
07-28-2009, 18:18
I know why the ones I seen were, the DM took them there. That's far too common, the attitude is that they can take care of themselves because they're adults.

I think there's an argument for each method of diving you can find, in certain conditions they are all right, and also all wrong.

A simple thing, not that it happens in real life but lets dive thirds. Say in your example one has a .4 and the other a .8 SAC rate. The .8 guy (always a guy cause women are better) dives a 100 cf cylinder the .43 an AL80. The woman waits until the guy gets to 1100 psi and she has also 1000 psi and they both start up to the surface. (Note both are slightly under the third but the SPG doesn't make exact pressures easy to read)

Would this be a safe situation under the following conditions.

1 - Normal dive, no problems encountered.
2 - The woman's cylinder loses an O ring on the ascent.
3 - The mans cylinder loses an O ring on the ascent.

Remember the big guy has a bigger cylinder so he can stay down as long as the woman with the smaller cylinder. Rule of thirds was used and they have no knowledge of each others air usage other than they turn when the first one hits the third. Under 2 & 3 can they make the surface and still have air, or will they run out before reaching it. Can they do a safety stop or should they skip it?

I know what I'd do and it varies per the situation I'm in. I also know from real life experiences the answers to each question. No number crunching needed.

mitsuguy
07-28-2009, 18:55
I know what I'd do and it varies per the situation I'm in. I also know from real life experiences the answers to each question. No number crunching needed.

I know what I'd do as well without even looking at numbers as well...

I'd share air up until and including as much of a safety stop as possible, then ascend to the surface...

If there wasn't enough air to do a safety stop, I'd bypass it completely.

Remember, all recreational diving is no stop diving... Granted from depth, it may still take a minute or two to safely ascend (60 fpm ascent rate), but the stop itself is not required and can be omitted, unless according to tables, that you are at the limits, or were deeper than 100 feet. Even then, it's not completely required, as again, all recreational diving is no stop diving.

Once it becomes mandatory to do stops, then gas planning should definitely be rethought for the above mentioned buddy team...

mitsuguy
07-28-2009, 19:00
I know why the ones I seen were, the DM took them there. That's far too common, the attitude is that they can take care of themselves because they're adults.

Unless we are doing an advanced dive with more advanced divers, then we typically (at our shop), stay between 60 and 70 feet as a maximum depth. Everyone is free to plan their own dive, or follow the divemaster. I have had people whom I knew were not super experienced divers deeper than myself by 40-60 feet...

PTAaron
07-28-2009, 20:16
[quote=cummings66;318167]Additionally, go back and re-read your OW manual. I just started doing it again (part of being a DM). Someone recently asked why they don't teach more than one method of clearing your ears in OW class. My manual has three methods for clearing your ears.

I re-read programming manuals after years of programming. As I re-read them I realized there was a lot I missed the first time I read them. I suspect this is true for my dive manuals as well.

This was a really good point, thank you. Many people read by glossing over the information to find the answer for the knowledge review question.

I would imagine that very few people actually LEARNED what was in their OW books, but instead found a way to answer the questions as efficiently as possible.

You made other good points also. People can be taught anything, but you still have to rely on them to behave in a manner consistent with what they were taught.


Great point.
I know I personally have read my OW manual cover to cover 2 or 3 times... and every time I pick up on something I missed the time before.
Big difference between "learning for the test" and "learning because your life may depend on it".

cummings66
07-29-2009, 07:56
I think no matter how many times you read and reread books that you learn something new.

In fact, I know an author of an adventure series book I read and he learns new things from reading his own series. So if the author can learn new things, then I'm certain the users can.