Info Optimal Buoyancy Computer

The Optimal Buoyancy Computer
A tool to help nail buoyancy and improve safety, before you splash​

1) How much lead should I carry with my new wetsuit?
2) How big a wing should I buy?
3) Will my BCD support my lead, both at the surface and when my wetsuit is compressed at depth?
4) Will my BCD support my rig without the help of my wetsuit/drysuit, if I doff it at the surface in an emergency, or underwater due to an entanglement?
5) How do I balance my rig?
6) How might partial weight ditching help me deal with an emergency? Will it really result in a runaway ascent?
7) How does the neutral buoyancy check change with thick neoprene?

I’m excited to announce the release of the Optimal Buoyancy Computer.
Designed to answer a variety of buoyancy questions, it provides accuracy directly proportional to the precision of your data input. Starting with as little as your height, weight and suit thickness, you can get ballpark weight requirements quickly. With additional information, you can compare equipment configurations, and plan for self-rescue after hypothetical equipment failures.

This tool is an Excel spreadsheet, and is a revision of a tool originally released in Buoyancy, Balanced Rigs, Failures and Ditching – a comprehensive tool , which was itself a revision of a toy spreadsheet first introduced in this thread: Advice on lift capacity for BP&W in April, 2018. After months of user suggestions, this new tool uses a simpler, modified data input system, and produces both simple and complex analyses of buoyancy. It works in both metric and Imperial units, salt and fresh water, and with both U.S. and European tanks.

Included is a 50-page user’s manual to lead you through the more complex parts of the tool, and a Quick Start section to get you going with minimal familiarity with spreadsheets. Additionally, the manual discusses the theory behind the more complex buoyancy calculations, whether you need help with Excel or not. If you are not facile with Microsoft Excel, the manual will take you through it all, step by step.
Here's the Table of Contents:

Download the .xlsx file for current versions of Excel. Use the .xls file for Excel 97-2003. Other spreadsheet programs may or may not recognize the internal links, but trial versions of Excel are available for free. You will see a generic Excel warning about possible viruses - don't worry, there are none! Click "Enable Editing", and save a copy. After saving, you will be able to edit the data fields for your use.

Many thanks to @stepfen , @johndiver999 , @kmarks , @Akimbo and the many others who have made suggestions and comments along the way.

NOTE: If you are using Excel 2003 and download the .xls file, extensive protective formatting is not functional. Thus, when you are diving a wetsuit (for example), you may be able to see drysuit "data" on the same page. The data for the "other" suit is NOT accurate under those conditions and should be ignored. With current versions of Excel, this information is blanked out for safety.

As each new version is uploaded, the count of downloads returns to zero. We are currently at over 2000 downloads of the tool, counting repeat customers! Thank you for your interest!

WARNING: These spreadsheets are experimental tools using formulas created by amateur divers for educational use only. Numerous assumptions regarding buoyancy have been made based upon only partially tested equipment configurations. The information herein is for your personal educational use and should not be relied upon to determine the adequacy of a given equipment configuration. Consultation with a dive professional regarding equipment, weighting and performing a neutral buoyancy check should all be strongly considered before diving a new equipment configuration. Note specifically that the practice of ditching weight at depth is a controversial one, and the theoretical data in this spreadsheet should not be considered a recommendation of that practice.

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Selected for the ScubaBoard Knowledge Base.

This thread was selected for the ScubaBoard Knowledge Base on 22 November 2021. Special rules discouraging off-topic and counterproductive replies apply after this date.

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[rsingler]

Thanks, @Compressor !
There's more to come! A great suggestion was received from @Fastmarc just before we closed out the old thread with the previous version, who noted the need to provide better estimates for folks who dive with a pony and come back with a full bottle, and for the doubles/sidemount crew who come back with thirds instead of 500 psi. So there's another edition slowly taking shape that will offer better output for that group.

As has been made clear with our struggles with the first version, we need to keep layout simple enough that the results are obvious, without having to go consult the User's Manual. Stand by! Yet another version will get here one of these weeks...

 

[Mike1967]

Does this not work on an iPad,only a computer?

 

[rsingler]

Does this not work on an iPad,only a computer?

It works on my phone, and on my Samsung Tab. But both have Excel loaded. I'm not an Apple guy, but I'd guess that if you have Excel loaded, it should work fine. I don't know about other spreadsheet programs. Not all will recognize the links between the tabs.

 

[Mike1967]

Excel

Ok I got Excel and that gives me the drop down menus now, I just can't change anything. It says read only so I'm guessing that's got something to do with it?

Edit: had to save a copy and now it works...Yay!
Thanks rsingler.

 

[rsingler]

had to save a copy and now it works...Yay!

As @Mike1967 's post implied, whenever you first open an Excel file from an outside source, Excel warns you at the top of the page, and won't let you change anything (trying to protect you from malicious code).
Once you save a copy, it's open to data entry and additional saves.
That's why the functionality of this tool is slightly less polished than it might otherwise be: if I included macros to pre-populate data fields or automate certain tasks (which I really wanted to do), I'm sure there is a percentage of tech-savvy SB'ers who would never open the file, worried that a malicious macro might execute. That means slightly more work for you, but slightly more reassurance that there's nothing untoward going on.
If you are experimenting, I'd advise saving different copies with your various configurations (appropriately titled to help you remember). That'll save you from starting from scratch re:data input when experimenting with your favorite doubles rig vs. your vacation rash guard setup.

 

[Rollin Bonz]

Wow! Amazing tool. All that work, and to share like this... Hats off to you @rsingler !

 

[rsingler]

Wow! Amazing tool. All that work, and to share like this... Hats off to you @rsingler !

Thank you, but this is by no means a one-person effort. I must also thank the countless Scubaboard members who have contributed with suggestions, criticism, and error tracking. Just for grins, I was looking at version 8 last week and had to laugh. This tool has morphed quite out of control for any one person to monitor. It used to fit on two sheets!
I need all of your help to check for mistakes, and to make sure it's useful to you. If what the tool recommends does not match the way you dive, please comment! There's probably a hidden formula error somewhere.
The formulas that we use have been tested, but there is no way to encompass all of the neoprene and drysuits out there. If there are changes we need to make to the mathematics, I depend on all of you for your input. Thank you again! I hope the tool continues to improve in the months to come.

 

[CDMac]

@rsingler - This is fantastic. I bookmarked this earlier and am now getting the chance to play around with it.

I am a new (not even certified yet) diver but am a numbers geek so this is a fun exercise.

Is there anything like this out on the web and have you any thoughts about putting this into a webapp or mobile app?

 

[rsingler]

Is there anything like this out on the web and have you any thoughts about putting this into a webapp or mobile app?

I've not seen anything that approaches the current level of functionality out there. My son strongly urged me to make it an App, but frankly, some of the things we're talking about are well past the average recreational diver. Partial weight ditching, balanced rigs, and emergency scenarios just don't make it into OW training.
I'm a little concerned about liability, unless I could get funding and time off for significantly more testing. Here, ScubaBoard is a fairly tight knit community that accepts the risks and understands the disclaimers. Not sure that would fly out in the world.
But yeah. It's kind of tailor made for an app, isn't it? For the record, it fits on my Samsung Galaxy in Excel and works fine. But it really needs significant retooling for app format. At least that would streamline updates!

No copyright! No guarantees!

 

[Akimbo]

I am a new (not even certified yet) diver but am a numbers geek so this is a fun exercise.

Reading ScubaBoard, you will discover the importance of mastering buoyancy control -- and by extension the concepts of Archimedes' principle. Sadly, far too many open water instructors do a poor job in this department. Is it critical to Scuba dive safely? Not essential. Is it critical to Scuba dive well? Heck yes!

Looking for an instructor that emphasizes good buoyancy control will be well worth your time.