I'm not quite sure who you're referring to here. You really do appear to be trolling for an argument. Not gonna waste my time.
You're failing to see the irony in replying to my every post.
That is not the rule of thirds ... and if you're shore diving, your return IS your ascent.
It's rare to see someone argue so vehemently in favor of ignorance ...
To be honest this is my view of yourself. I freely admit to using both SAC's and basic dive planning in my diving. Whereas you are arguing that there is only one way to dive. That is ignorance. I accept the use of other methods you are not.
My example stands for the shore dive, if you missed you turn point you would ascend directly earlier than planned, i.e not in the shallows at the shoreline. And look at my profile to see where I dive. I dive in areas that have steep drop offs straight from the shore.
Your logic for SAC's breaks down outside of a square of profile. Show me how you would work a multilevel wall dive at a unknown site and I will accept your logic.
---------- Post added February 10th, 2013 at 10:43 AM ----------
If I work with an AL80, 3000PSI and be a "good student" trying to return with 500PSI I then have 2500PSI for my dive. If I agree to using thirds, based on my 2500PSI model of air I really should be using that means 833.3_ is available (lets be conservative, round down to 800). Mathematically from what I understand, that's 800 descent, 800 bottom, 800 ascent (this is probably wrong so please correct me but, it will work for my point however). I don't actually feasibly know if I can safely get down to that depth that I've planned and stay there for the time I planned, thus it will result in me turning early (according to dive plan) to end the dive, based on my pressure gauge or doing something I'd personally never do, and be reckless and keep the dive going. This isn't including halving the entire formula for diving with a buddy.
Not quite. The first 1/3rd of the tank is descent and bottom time, the 2nd is for returning to the ascent/descent point use the final 1/3rd to ascend. This is not the rule of thirds, this is splitting the tank into 3 sections of the dive.
1: Down and out
2: Return
3: Up
The key thing is when you reach any point in the tank, you adjust the plan. It won't fit exactly to the dive site, but it will be a model of best fit.
This plan works for anybody, I use it for students and for guided diving, where you are constantly presented with the unknown. Imagine a scenario where you are given an instabuddy on a dive trip who knows nothing of SAC's. How do you plan the dive together? Do you guess an arbitrary SAC based on a few minutes talking or simple set a basic dive plan which can be followed by checking each others air periodically.
I guess that's my motivation to want to learn what I consume so that I can try and plan dives early on that are realistic and feasible to gain confidence in that skill (dive planning). Given that I love water it isn't a huge deal to swim around at different depths to get a feel for what I consume via PSI so that I can eventually plan closer to what I will be able to dive. Until then I literally do have to wing it and possibly not accomplish anything closer to the deeper end of things based on just trusting my eye on the SPG rather than enjoying the dive and glancing at it maybe less often because I know that what I've planned will be feasible. The way I'm understanding a SPG at this point is that it's there to really monitor air and make sure you'll have enough to dive your plan, not to specifically plan your dive. I just don't feel I have enough experience as of yet other than to create a turning point I'm comfortable with as is my buddy and follow that during a planned dive that had a goal to see something at a specific depth for a planned time.
Zack as newbie diver you will be paying attention to your gauge with an almost OCD like compulsion. It's a natural evolution until your SAC starts to drop. There's nothing wrong in this, we've all done it
Your Gauge is not there to tell you you have enough air to dive your plan. Your gauge is there to tell you if you have reached your Air turning point before your time turning point. The point of dive planning is to set both, otherwise there will be an accident.
You are not trying to complete the dive plan at all costs. If I plan a 50 minute dive to 18metres, it doesn't mean I'm going to necessarily dive to 18m, it means the maximum depth will be 18 metres. Similarly with time, I may decide to only do 40 minutes. The key thing Is I planned a dive to remain to within the NDL and I didn't exceed the plan.
I think the only solace in feeling so ignorant right now is I have yet to learn this sort of dive planning and get a true feel for what my pressure gauge is doing while I dive. At this point I have to truly trust those around me with experience and follow them blindly and depend on myself only to call it quits based on what I need to make it to the surface in an emergency.
Your instructor has no doubt taught you hand signals and how to communicate your tank contents by now? He/She will help you plan the dives. In PADI OW courses students are not required to have timing devices, so your instructor could be the only one timing the dive. In this instance you are forced to reference your gauge as there is not point trying to count seconds in your head. Respond to what you SPG is telling, tell your instructor. They want to see that you are paying attention and not just looking at the fish. They are evaluating to see if you are safe to dive under your own steam. If you allow yourself to run out of air waiting for the instructor to tell you to turn, have you achieved this?
Whatever failings PADI courses may have around the world, their modular instruction methods is not one of them. Yes SAC dive planning is not included in the PADI rec courses, and only briefly discussed in the Deep Dive Specialty. Is PADI wrong in the approach. I'd say no, I agree with the teaching system. It may not be taught properly by some people, but that is not because the materials are lacking. SAC dive planning is in the PADI model and at a higher level, and I'm happy with it's position.
I am grateful for your assistance!
