Scuba Time Calculator (time wheel)

[primalchaos]

Hello all,

I'm pretty new, I am getting my open water test at Bonn Terre next weekend. In the process of accumulating things, I bought a slate, and on it is a air consumption calculator. I am unsure as how to use it, but it looks like it might be quicker than the formulas in the book if I can learn how to use it. I'm attaching a digital picture of it.

Thank you to everyone that can assist

 

[Arnaud]

This is an SSI slate. Is it your agency?

 

[primalchaos]

This is an SSI slate. Is it your agency?

Yes, I am learning through their program, but we didn't go over the slate in the open water class, just the normal stuff and formulas.

Leon

 

[Arnaud]

Let's try to get an SSI guy in here.

 

[primalchaos]

Let's try to get an SSI guy in here.

Sounds good

 

[Mo2vation]

Let's try to get an SSI guy in here.

What are you trying to do? You can calc SCR with that wheel.

K

 

[primalchaos]

What are you trying to do? You can calc SCR with that wheel.

K

Yes, but I can't for the life of me figure out how it works exactly. I understand lining up the psi left, depth, and time, but not what I'm supposed to see then? Maybe I'm missing a step or part of the concept?

Thanks,
Leon

 

[Mo2vation]

Yes, but I can't for the life of me figure out how it works exactly. I understand lining up the psi left, depth, and time, but not what I'm supposed to see then? Maybe I'm missing a step or part of the concept?

Thanks,
Leon

PM sent to you.

K

 

[primalchaos]

Very cool. Now I think I know what I was missing. I do want to start tracking as I go along, to make sure I have a good idea of where I am with it, so I have a good idea on what a dive will take.

Thanks again

Leon

 

[DA Aquamaster]

With a SAC rate calculator you should do a timed swim at a constant depth and measure the total psi of air used. Then input the numbers on the SAC rate calculator to get a surface air consumption rate in psi per minute.

That number (your SAC Rate) is then used to figure the psi that will be used at specified depths and will allow you to plan how much air you will use on a dive and how long you can stay at a given depth.

SAC rate is not real popular anymore as people more commonly use RMV and work in cu ft per minute. But if you know the volume of the tank that you used during your sac test, then you can use a simple ratio to convert your SAC rate in psi/min to cu ft/min. For example an AL 80 hold 77.1 cu ft at 3000 psi and a steel 72 holds 71.2 cu ft at 2475.

So a SAC rate of 17 psi/min on a steel 72 converts to .49 cu ft/min.
(17 psi per min X 71.2 cu ft) / 2475 = .489 cu ft.

I use a SAC rate calculator that is similar but a little larger. Both are essentially circular slide rules dedicated to SAC rate.