Basic Math Formula to calculate reserve, safety stop, etc etc

[decompression]

Fascinating, so you teach planned decompression to OW students ?

The point I was attempting to make (obviously to obliquely) was that training for scenarios you shouldn't be in can encourage divers to get into those scenarios.

Wouldn't an OW student be better served to understand what an overhead environment is and taught to avoid it until their skill and training is appropriate?

Hey John, good questions,

I teach min deco to OW students as an ascent strategy. I also teach rock bottom as a gas plan to ensure you and another dive can safely reach the surface. This eliminates the arbitrary return with 500 psi or rough 2/3 of a tank. What those dont account for, amongst others, is the following scenario;

2 divers with 800 psi, at a stop....approached by another diver with OOA. Decision time, do I say no?Do I donate and possibly not have enough gas? Do I donate and Grab from my buddy? Rock bottom avoids this dilemma.

 

[Steve_C]

Worst case you both surface and swim back to shore....

Ahhh, where I dive shore is 18 to 28 miles away. And yes I see pretty new OW students out there. Hopefully they have a better plan than that.

 

[Bob DBF]

Thank you all. Obviously there are some comments that go over my knowledge. Not sure if I am freaking out or not.. But, do you really have to do all those calculations before scuba diving ? Or, what is the simple rule of thumb ? You have to know, how deep you are going to be ? Then based on depth, do you take a 10000 or more psi's with you ? Sorry, sorry for my stupid questions. I am totally new on this.

First, take up your problems in the course with your instructor so you can get the right answer on the test. On Scubaboard there are a number of schools of thought on gas management, and I would suggest getting certified and then checking out the board as the amount and difference of information can be quite confusing.

Accordingly, my simple rule of thumb for turning recreational dives is 1,000psi for my way out, 1,000psi for my way back, and 1,000psi for you. I can calculate that. My buddy can calculate that. My SPG can display that. And if we get back to the exit point and both of us have 1,000psi left... we simply extend the dive.

This method from RJP would work quite well for a new diver out with his buddy until you identify the planning method best for you and your diving as you progress.



Bob
-----------------------------------------
"This is scuba board, where problems are imagined or overstated......and chests get thumped about what some would do about those "problems" "- PullMyFinger

 

[RJP]

Sorry, sorry for my stupid questions. I am totally new on this.

It's not that hard. Think about it this way: The people you are looking to here for advice are mostly idiots... and we've managed to dive without killing ourselves. (So far, anyway.)

 

[namerg]

Thank you, thank you guys. I will let you know how it goes.

 

[Basking Ridge Diver]

Ahhh, where I dive shore is 18 to 28 miles away. And yes I see pretty new OW students out there. Hopefully they have a better plan than that.

That was cute....

The op stated in his question -
I have this question:
My buddy and I are planning a shore dive.

So you must have very good lungs and stamina...

 

[Adobo]

And so your buddy needs some air

And your are coming back and the viz has dropped and it take a few extra minutes to find the anchor line,

And somebody gets a cramp and you need to stop for a few minutues.

And .......

Depends on how you define usable gas I guess

Shrug. You either need to get back to the anchor line or you don't. If you need to get back to the anchor line, you have other considerations other than gas.

The way I was taught to conduct recreational dives is to take the minimum amount of gas I need to get to the surface under stress (that includes gas for my stops) and double that in case I need to exit the dive sharing gas with my buddy. Everything left over after the "min gas" is usable gas.

Most recreational dives, I dive "half usable gas" which with my buddies means, we use half going out, half coming back in. On the rare occasion, I have dives "all usable gas". For example, I did a drift dive in Maui this way. I went down, continued my dive until I was at close to my min gas, then I ended my dive.

It's been a while since I've taken a class so I might be misremembering but the definition of the term "usable gas" that I am using is not one that I made up but rather one that is used by the agency from which I took the class.

 

[rx7diver]

Fascinating, so you teach planned decompression to OW students ?

JohnN,

Many of us here learned how to read a deco schedule (using the US Navy tables), compute the gas requirements for a decompression dive, and conduct (in theory, at least) a deco dive, in our open water course. Not too long ago this was part of the standard open water course curriculum. For example, the "New Science of Skin and Scuba Diving", for years a standard open water textbook, discusses this. Of course, we were all made to swear that we would not attempt a decompression dive until after we had completed a sufficient number of significant non-deco open water dives. None of this stuff is rocket science, imho, though some would have us believe it is.

Safe Diving,

rx7diver

 

[Keith.M]

To the original poster... Welcome to what is... ScubaBoard!

Where even the most mundane question can take off for several pages of either applicable or non applicable chatter.

I am just glad to see you are doing the reading ahead of time and asking questions where you are confused.

It is all an addiction, but well worth it!

 

[namerg]

Thanks Keith.M