article on rock bottom

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socaljohn

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a couple yrs ago someone directed me a fine article on gas management (included calc SAC and Rock bottom and stuff like that there) and like a dummy I did not bookmark it. I know there are probably many but would appreciate direction.
Thanks,
John
 
NWGratefulDiver.com

I hope that's the one you're looking for, from Bob, aka NWGratefuldiver.
 
... and from Peter Guy ... http://www.tsandm.com/gm/gm.pdf

Note that all of these references are from folks who live and dive in the Puget Sound area ...

... Bob (Grateful Diver)
 
Rock Bottom Calculation Spreadsheet

Since I have just purchased a new tank, I though it would be useful to do the Rock Bottom calculations for it. I was surprised that I did not easily locate a spreadsheet with the necessary calculations so I created one. Hopefully it will be useful to someone other than myself.

While the articles above contributed to my understanding of this subject, the spreadsheet is based on the article by Bob (Grateful Diver) Bailey NWGratefulDiver.com

I have included columns for both divers to show the values unique to each diver, depending on their chosen tank. I chose to calculate the gas used for the entire ascent rather than break it into separate steps and provide cells for users to see what happens if they want to change things such as the length or depth of their safety stop, reserve gas, etc.. My numbers for the 66 foot dive with aluminum 80's are slightly different from the example provided by Grateful Diver. I attribute this to rounding error. I also calculated the gas required as volume since this is independent of tank size. The required PSI is then calculated from this volume combined with the specified reserve. The values at 0 ft assume you are breathing off your regulator at the surface and a safety stop is only calculated if your are deeper than your specified safety stop depth.

I want to encourage anyone who chooses to use this spreadsheet to read the articles so that you understand why you are getting the values you do. Thank you everyone for publishing the articles to help me understand this concept.

Capture.jpg

-Chocula
 

Attachments

  • RockBottomPressure.xlsx
    15.8 KB · Views: 54
Last edited:
Bob -- it is funny that all of the articles are from the PNW and that we all dive/have dived together. What does it say about our community?
 
https://www.shearwater.com/products/perdix-ai/

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