Rule of Thirds & Shallow Rec diving

[gcarter]

I have lost my taste for the bait, personally. I am reverting to this mode.

 

[GCullen94]

Foxfish when I say cross referenced I mean I did the metric calculation and then used a conversion factor to CHECK my metric calculation from the imperial one and yes it was slightly different (to be expected) Storker used a faster time to surface than I did, causing his calculation to equal EXACTLY 80B, mine was a slightly more conservative ascent rate and caused it to be 86B, because you cant read 86B on a gauge I rounded up. Again they make a difference of making the surface or not making the surface before running out of gas, your choice. I'd prefer to come home without running out of gas in an emergency, I'd also like to use a gas plan where tank choice doesn't matter in determining pressure. I can see that you're going to stick to your ways and I just hope that some people reading this thread got something out of it and saw or learned that minimum gas calculations are useful.

With that, unless there is a huge need to, I am done posting in this thread. I hope some people are now using min gas laws, foxfish I can see you never will so good luck diving to you. You're gonna need it.

 

[Foxfish]

Afraid the prey has slipped the hook, the wily fisherman gives the line a quick set of jerks.

Or would that be 'getting caught in your own web of deception"?

 

[gcarter]

Foxfish when I say cross referenced I mean I did the metric calculation and then used a conversion factor to CHECK my metric calculation from the imperial one and yes it was slightly different (to be expected) Storker used a faster time to surface than I did, causing his calculation to equal EXACTLY 80B, mine was a slightly more conservative ascent rate and caused it to be 86B, because you cant read 86B on a gauge I rounded up. Again they make a difference of making the surface or not making the surface before running out of gas, your choice. I'd prefer to come home without running out of gas in an emergency, I'd also like to use a gas plan where tank choice doesn't matter in determining pressure. I can see that you're going to stick to your ways and I just hope that some people reading this thread got something out of it and saw or learned that minimum gas calculations are useful.

With that, unless there is a huge need to, I am done posting in this thread. I hope some people are now using min gas laws, foxfish I can see you never will so good luck diving to you. You're gonna need it.

I think you need some of this too

 

[Storker]

Afraid the prey has slipped the hook, the wily fisherman gives the line a quick set of jerks.

I imagine this being said in the voice of Robb Webb. I'm not sure if it should be like this or like this, though

---------- Post added December 11th, 2013 at 07:44 AM ----------

I think you need some of this too

View attachment 173125

I'd like some, if you don't mind.

 

[Foxfish]

quod erat demonstrandum

 

[tattooedjeeper]

Foxfish, I've honestly never seen a grown person more hard headed and argumentative in my life. It seems you cannot resist having to be right and get the last word in. I'd imagine working with or being around you in person to be an "interesting" experience... I'm not going to argue the math or the validity of gas planning with you... you have your way, I now have mine. I do want to say once more to all that have helped here, thanks. I've learned something valuable from this and, even though this thread has taken a definite turn for the worse and towards the end it got diluted and argumentative, I'm sure many others have learned something as well. And now.... I beg of you all, stop feeding the fish. I sure I'm not the only one that feels this has gone on long enough

 

[victorzamora]

I estimated that using the 50 b method, you'd need to start an ascent at around 80 b for a 12 L tank from 30 m

You are LITERALLY wrong on every level with this statement. You didn't "estimate" a thing. You guessed. This is what we're trying to avoid using basic arithmetic.

Foxfish, I've honestly never seen a grown person more hard headed and argumentative in my life.

THIS is the only reason I'm insisting. You weren't aware of any of this. You're a new diver. You see the logic, and you've added a tool to your arsenal. Even if you're the only diver introduced to something new by this thread, and you never really use it to its full extent, you've been made aware and this whole thread has been worth it. Also, you're right. This is my last post in this thread. Everything has been said that there is to be said, and then some. I just hope other new divers can see that this isn't advanced stuff we're talking about, but their safety.

Speaking of which, I've made an Excel spreadsheet calculating RB/MG in imperial with a bunch of variables allowed to be changed. I'm tempted to add two different ascent rates, to allow for 60ft/min below 30ft and 60ft/min above 30ft if you choose to. I'm also about to add flexibility to add different tanks, and doubles/SM tanks. Let me know if you want it.

 

[tattooedjeeper]

Victor,
The spread sheet sounds awesome! I sent you a p.m.
-Mark

 

[shoredivr]

Scott, here's what I found when I dug out the Adventures in Diving Advanced Training for Open Water Divers, published 1991 by PADI.
Page 69 has an air consumption calculation with conversion factors for depth:
Psi used divided by actual bottom time * conversion factor = surface air comsumption rate.
While you are right that there are simple calculations, the objective stated on that page is "to tell how long a tank of air will last at a given depth if you've never been that deep before". Yeah, the page does also give you verbal warnings about added excitement, activity and cold increasing air consumption, "so you should allow room for error in your dive planning" without suggesting how to do this. Absent is any concept of planning how much gas for you and your buddy to ascend from depth, or how to calculate how much is needed to ascend.

It's there a little bit, but not enough IMO.

At the bottom of pg 69 is the following "if you must stop and maintain contact with the bottom, find a spot away from the reference line (so others won't descend on top of you) and free of aquatic life and sharp objects. Allow yourself to settle there gently on your knees." Advice that seems a bit out of favor now....

There fixed it for you.

While the recent changes in the course lays it out for the instructor, many will be learning for the first time, it was taught in my IDC in the early 90's. Not RB and the calculations that are being discussed here but a 'simpler' version but still more complex than be back with 500 psi.