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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[Darcimus]

I have no idea how to find the buoyancy specs for my Fusion Bullet. The website says lycra stretches, but there's neoprene pads there. How do I account for this?

 

[Saboteur]

Great tool. You must have spent days on this. Thanks for creating and sharing.

 

[rsingler]

I have no idea how to find the buoyancy specs for my Fusion Bullet. The website says lycra stretches, but there's neoprene pads there. How do I account for this?

From the Fusion Manual, I don't see a specification of Neoprene foam pads. I'm guessing they're open cell, which means they'll trap air and be buoyant at the beginning of the dive but will probably be neutral by the end. The bladders are listed as 35#/16liter for Small, 38#/17 l for Med, and 45#/20 l for Large.
I'd guess that 0# would be a good starting place for that bcd's buoyancy. If you're sure that the pads are closed cell foam, then try to estimate their cumulative volume and convert that to positive buoyancy at ~1lb for a 5" x 5" x 1" pile of foam.

 

[Compressor]

Thanks @rsingler for the spreadsheets.

 

[johndiver999]

column H on quick results needs to be wider to show a triple digit depth.

 

[happy-diver]

Very impressive rsingler

You are a Superstar Tinkerer in Brass

Just noticed that less than half of you are downloading the User's Manual with the tool.

 

[rsingler]

column H on quick results needs to be wider to show a triple digit depth.

I'll fix that, thanks!

EDIT: Column H widened on QuikResults.
Version 44 loaded in post #1.
Thanks @johndiver999 , again!

 

[rsingler]

User's Manual reloaded (v15) after correction of scattered typo's.
No substantive changes.

 

[Compressor]

Now I've had some time too look at this great work in detail and really appreciate it. Thank you @rsingler.