500 psi for two divers?

[TatianaSilva]

i think people doing the OW dont really think about tech things like this and there isnt enough time for this type of information, its only 3 / 4 days to do the OW so you dont really expect to know everything. The person who liked it and knows the basic etc will continue asking and getting information from more experienced divers. All the things i learnt were basically from me searching, reading, etc. It depends on how much you are into diving.

im obviously not prepared to dive on my own and my buddy and will be a long time before i can actually be more independent and not rely so much on the DM

---------- Post added August 21st, 2014 at 08:22 PM ----------

So you have zero concept of what your NDLs are, no PDC and just dive until you run low on air then come up? PLEASE, PLEASE read the links provided. If you don't understand them, find someone to help you learn because it is essential information. Please also spend some time looking online for how to plan a dive, how to use dive tables, and download a set of air diving tables.

Just randomly swimming around underwater is going to get you or a buddy hurt.

i havent planned any dive with my buddy yet and im not doing it either in following dives ... like i said, i only have the OW two months ago so right now, im relying on the DM who will come with me and my buddy in the next dives and start learning how to do everything on my own =)

 

[boulderjohn]

I feel very strongly that a proper ascent strategy should be taught in OW. Rock bottom and min deco are concepts that a diver should know. There are agencies that teach these, I wish more did.

Yes, I know there are agencies that teach those concepts. I believe 2 of the 145 listed agencies do that. I was trained by 1 of them. Those two agencies are primarily technical diving agencies that teach very, very few new open water divers each year. In fact, the dive operation that invented the concepts and which is the home of one of those agencies primarily teaches OW students through PADI.

There are different ways to plan ascents. I fully agree that the standard OW class does not do enough in this regard, and I do more with my own students. You are entitled to feel your rage because 143 out of 145 agencies do not teach this one specific concept, but that is the topic for another thread in another forum.

---------- Post added August 21st, 2014 at 01:33 PM ----------

i think people doing the OW dont really think about tech things like this and there isnt enough time for this type of information, its only 3 / 4 days to do the OW so you dont really expect to know everything. The person who liked it and knows the basic etc will continue asking and getting information from more experienced divers. All the things i learnt were basically from me searching, reading, etc. It depends on how much you are into diving.

im obviously not prepared to dive on my own and my buddy and will be a long time before i can actually be more independent and not rely so much on the DM.

i havent planned any dive with my buddy yet and im not doing it either in following dives ... like i said, i only have the OW two months ago so right now, im relying on the DM who will come with me and my buddy in the next dives and start learning how to do everything on my own =)

I am sorry you feel this way. Your OW class is supposed to prepare you to do dives independently, and if you are not prepared to do so, then I believe something is wrong. Perhaps you should go back to your instructor and tell him you feel this way.

When I teach the required dive planning content to my students, I have several times had students tell me that their friends who are already certified told them that they only have to do that stuff for class--in the "real world," DMs do all that for you. The unfortunate thing is that in many parts of the world, the DM does do it for you. Divers who do those kinds of dives a lot become dependent upon them and forget what they were taught. You should know everything you need to know to plan a dive with a buddy in the same kind of location and conditions in which you were trained. If not, ask your instructor for either a refresher or an explanation.

 

[TN-Steve]

i think people doing the OW dont really think about tech things like this and there isnt enough time for this type of information, its only 3 / 4 days to do the OW so you dont really expect to know everything. The person who liked it and knows the basic etc will continue asking and getting information from more experienced divers. All the things i learnt were basically from me searching, reading, etc. It depends on how much you are into diving.

im obviously not prepared to dive on my own and my buddy and will be a long time before i can actually be more independent and not rely so much on the DM

---
i havent planned any dive with my buddy yet and im not doing it either in following dives ... like i said, i only have the OW two months ago so right now, im relying on the DM who will come with me and my buddy in the next dives and start learning how to do everything on my own =)

I KNOW that the dive tables are taught in OW... if you don't have a copy, here are some great links on how to use them. Marcos does a great job explaining them

Dive Tables 101 - Introduction

Dive Tables 102 - Max Allowable Bottom Time

Dive Tables 103 - Minimum Surface Interval

Dive Tables 104 - Recap

If you don't have a copy of the tables, I bet a minute on the google for PADI Dive TABLES PDF will find you a copy.

Steve

 

[boulderjohn]

I KNOW that the dive tables are taught in OW... i

Actually, lots of OW classes from a number of agencies do not necessarily include tables any more.

 

[Dirty-Dog]

i think people doing the OW dont really think about tech things like this and there isnt enough time for this type of information, its only 3 / 4 days to do the OW so you dont really expect to know everything. The person who liked it and knows the basic etc will continue asking and getting information from more experienced divers. All the things i learnt were basically from me searching, reading, etc. It depends on how much you are into diving.

im obviously not prepared to dive on my own and my buddy and will be a long time before i can actually be more independent and not rely so much on the DM

i havent planned any dive with my buddy yet and im not doing it either in following dives ... like i said, i only have the OW two months ago so right now, im relying on the DM who will come with me and my buddy in the next dives and start learning how to do everything on my own =)

If you are not prepared to dive on your own, then you should not have been certified. The very definition of a certified diver is one who can plan and execute a dive within the level of their training and experience.
I am saddened by your willingness to trust your life to some random, unknown DM.
I am the product of a PADI OW course, and after that course (which was done online, followed by a 4 hour pool session and 4 open water dives) I was capable of planning and executing a simple, shallow open water dive in mild conditions. I understood the concept of NDLs. I understood how to plan a dive with tables or a computer. I had a basic understanding of gas management. I understood why a safety stop was a good idea, and why it might be OK to skip it. I understood the concepts of buoyancy and trim (although as with any physical skill, these require extensive practice to master).
No, you don't "know everything" after this course. That is why there are additional courses for deeper diving, mixed gas diving, wreck diving, cave diving, etc etc etc.

I recommend you tear up your certification card, go find a good instructor, and get proper OW training.

OK, that may be a little extreme, but the point is that you did NOT get the training you paid for, and you should take steps to correct the deficit. YOU are responsible for your life and your safety, not someone else. And if you actually read the course materials for your OW program, I'm quite certain you will see that you are, in fact, expected to be competent to plan and execute a dive. If you cannot, you should not be certified.

---------- Post added August 21st, 2014 at 01:55 PM ----------

Actually, lots of OW classes from a number of agencies do not necessarily include tables any more.

This is true, and not a big loss given that the vast majority of dives are done with a computer.
However, every OW class DOES teach dive planning, and if you cannot plan a dive, you aren't supposed to pass, as I'm sure you'll agree.

 

[flots am]

i just cant figure out how long 500 psi would last and i think is useful to know in case i get to that situation.

You have the question backwards. It isn't "how long will 500PSI last", it's "How much air do I need to reserve for an emergency?"

500PSI is just an easy number that takes into account that mechanical SPGs aren't very accurate, and divers aren't always paying attention and regs won't usually breathe down to 0 PSI.

It's not guaranteed to be enough to get anybody back from anywhere.

The answer to "How much air do I need to reserve for an emergency?" is on the website rivers linked to.

flots.

 

[eelnoraa]

I don't find it presumptuous that someone doesn't know what they aren't taught, but I still find it sad how low the dive curriculum is and how few instructors teach beyond that bare minimum. Teaching rock-bottom isn't rocket-surgery, but new divers should come out with at least the concepts of tank volume to pressure relationship and what their SAC is for different activities.

I am with you. But I think the bigger issue is that how few instructors actually understand rock bottom concept. I believe those who understand it and understand the importance of it will teach it in their class.

---------- Post added August 21st, 2014 at 12:59 PM ----------

..... they have a very good "rule of thumb" formula. For a 80CF 3000 PSI tank, your "Rock Bottom" pressure (Air to get you and your buddy safely to surface with stop) is (depth (in feet) X 10) + 300. This is assuming a high consumption rate for the both of you, probably realistic for most divers (I suspect it would be for me) It varies a bit for other tanks. So, if you're at 60 feet, the ROCK BOTTOM is 900 PSI. That would get you and your buddy safe to the surface. You don't have to END your dive then, if you're on reef or any other situation where there are levels, you can just move up to shallower depth for a while.

This one article made it the most understandable for me, and I like the quick rule-of-thumb method he gives, it's easy, I can remember it, and do it in my head. FWIW, at 100 feet with an 80 AL tank, your rock bottom would be 1300 PSI.

At 60ft, this formula works. But for 100ft, it becomes quite aggressive. When you are deeper, you get double penalized. You are breathing denser gas, and you will taking longer to surface. So relationship between min reserve gas and depth is NOT on linear scale

 

[TN-Steve]

Actually, lots of OW classes from a number of agencies do not necessarily include tables any more.

You're right. I should have put "Teach Tables OR Computer Diving". (I'm presuming, without facts in supporting evidence, that the OP is PADI). My mistake.

FWIW, I think learning tables at the start is very useful, it lets you understand WHAT'S going on. (at least if they are taught right, but that's a whole number of other threads)

Steve

 

[TatianaSilva]

Yes, I know there are agencies that teach those concepts. I believe 2 of the 145 listed agencies do that. I was trained by 1 of them. Those two agencies are primarily technical diving agencies that teach very, very few new open water divers each year. In fact, the dive operation that invented the concepts and which is the home of one of those agencies primarily teaches OW students through PADI.

There are different ways to plan ascents. I fully agree that the standard OW class does not do enough in this regard, and I do more with my own students. You are entitled to feel your rage because 143 out of 145 agencies do not teach this one specific concept, but that is the topic for another thread in another forum.

---------- Post added August 21st, 2014 at 01:33 PM ----------



I am sorry you feel this way. Your OW class is supposed to prepare you to do dives independently, and if you are not prepared to do so, then I believe something is wrong. Perhaps you should go back to your instructor and tell him you feel this way.

When I teach the required dive planning content to my students, I have several times had students tell me that their friends who are already certified told them that they only have to do that stuff for class--in the "real world," DMs do all that for you. The unfortunate thing is that in many parts of the world, the DM does do it for you. Divers who do those kinds of dives a lot become dependent upon them and forget what they were taught. You should know everything you need to know to plan a dive with a buddy in the same kind of location and conditions in which you were trained. If not, ask your instructor for either a refresher or an explanation.

to be honest with you, even if they have taught me all these things in the course i still would not have enough courage to do dives independently

---------- Post added August 21st, 2014 at 09:08 PM ----------

Actually, lots of OW classes from a number of agencies do not necessarily include tables any more.

i actually only saw tables in the elearning from padi, not in the OW

 

[boulderjohn]

i actually only saw tables in the elearning from padi, not in the OW

So how were your OW dives planned and recorded? Did you use a computer?

---------- Post added August 21st, 2014 at 03:13 PM ----------

I am with you. But I think the bigger issue is that how few instructors actually understand rock bottom concept. I believe those who understand it and understand the importance of it will teach it in their class.

Let's look at a hypothetical case. A diver goes through every single recreational offered by whatever recreational dive agency he or she is in, experiences thousands of dives, and becomes an instructor. Not satisfied, he or she goes into technical diving with one or more of the biggest technical diving agencies in the world, going all the way through advanced trimx. Cave diving from one of the biggest cave diving agencies in the world comes next, and he or she becomes not only a cave diver but a cave diving instructor. This diver becomes recognized as one of the premier instructors in the land. There is still a very good chance this person will not know what you are talking about if you use the phrase "rock bottom."

I was an experienced instructor when I started technical dive training. I had never heard of the term until then. I learned through my training with UTD, one of the 2 agencies I know use the term as an official part of training, and it was thoroughly drilled into my head and my diving practices. Then I got my cave training. My instructor, a long term veteran with credentials to teach all kinds of tech classes from several agencies, had no idea what I was talking about with that term. I have further cave training from a guy with a wall filled with plaques honoring him for his achievements in both diving and instruction, and when we dived we never discussed the term. I did four dives with one of the most well known cave divers in the world not long ago. We planned dives carefully, and we never used the term.

I left the agency that taught me rock bottom and renewed my deep tech training with one of the largest tech agencies in the world. When we started and I explained my background, I had to give the history of UTD--my tech instrucor had never heard of it, and he had no idea what level of training I had. When we discussed ascent profiles, I mentioned rock bottom. He had never heard of it. When I explained it, he dismissed it and said we would do it the way his agency teaches ascents. During my training, I interacted with a lot of other technical divers, instructors, and store employees, where I showed my UTD certification card in order to qualify for fills. I met one person in that entire time who knew that agency name. In our discussions in general, I found some who knew the name GUE (the other agency that teaches rock bottom), but most didn't. Some knew the term DIR but really didn't know or care much about it. None used rock bottom as a way to plan a dive.

If you are yourself surrounded by like-minded divers who use that technique, you will no doubt know it well and think it works great. (I prefer it myself.) You may not realize, though, what a tiny, tiny percentage of the world's diving population knows and uses that term.