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.

---

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.

---

 

[stepfen]

Insipred by this spreadsheet, I've developed this into a webapp, which is available here:

Scuba buoyancy calculator

There are a few philosophical differences:

• Personal weight: I've added a simplified model based on estimated lung capacity, and estimated body fat %. Input: Weight, height, sex and age. This should be able to give a reasonable, but should you feel the need, you can still either do a body fat estimation/calculation.
• Diving suits are estimated in a pretty similar way, but have a bit of an easier interface on how to approach this.
• I've simplified the list of tanks to more general estimations, but you can add your own, should you feel the need. (Especially the list of US-sizes of tanks can be a bit off/weird, any ideas about that on the other side of the pond?)
• It's both in imperical and metric units, but the imperical units are a bit less tested.
• There's a default list of commonly used stuff, but you can add your own items pretty easily, either by volume and weight, or weight and buoyant weight.
• There's a balanced rig view, where you can easily compare the heaviest scenario and the lightest scenario, and play with the amount of weight you want to take.

Source code is available here: GitHub - arendvw/buoyancy-calculator: A scuba buoyancy calcualtor

Most relevant calculations and their source are contained in this file.

I'm curious what you think! Does it give useful enough results for you?

Wow... Magnificent work! I'd dare to say that this is much more user friendly than the original "Optimal Buoyoancy Computer" by @rsingler. Well done.
The only thing that might be missing is a way to save/export the results.
For example a diver might want to have a "collection" of cases. Say one for traveling/tropical water (eg with shorty, al80), one for medium water (eg with thicker wetsuit) and another one for cold water (drysuit, doubles diving).

 

[BoltSnap]

Wow... Magnificent work! I'd dare to say that this is much more user friendly than the original "Optimal Buoyoancy Computer" by @rsingler. Well done.
The only thing that might be missing is a way to save/export the results.
For example a diver might want to have a "collection" of cases. Say one for traveling/tropical water (eg with shorty, al80), one for medium water (eg with thicker wetsuit) and another one for cold water (drysuit, doubles diving).

What he said plus android app

 

[Pressurehead]

Stops at age 70, that's OK, to be expected, you have done your 3x20+10 years.
Well done.

 

[inquis]

Great work overall! A couple minor issues, but I'll put them in the GitHub. The primary one is that I think "normal exhale" would be the better value to use when totaling up buoyancies. (IIRC, that's also what the spreadsheet also used.)

 

[grantmac]

It tracks with the weight I'm currently using, although maybe a touch negative (or maybe my body fat is up?) although spot on for my body in a pool (can sit at 4m with almost full lungs).
It's possible my drysuit garment is thicker than I'm estimating too.

 

[arendvw]

Stops at age 70, that's OK, to be expected, you have done your 3x20+10 years.
Well done.

Yeah, it's quite non-inclusive. It's when all the common lung volume and fat percentage equations stop having data points, not a recommendation to quit diving though

 

[rsingler]

With it now being 20+ years since Microsoft discontinued the .xls extension in favor of .xlsx, I have deleted the .xls version of the Optimal Buoyancy Computer from the thread.
The .xls version did not have extensive protective formatting, and the potential for seeing erroneous inapplicable data on a page was just too high for comfort.
The .xlsx version remains active, and though somewhat complex compared to the weighting apps which have since been posted, remains a good educational tool for its original purpose: understanding buoyancy at depth, the effect of wetsuit expansion on your safety stop, and assessing partial ditching of weight as a self-rescue technique after multiple gear failures.

 

[undrwater]

OpenDocument - Wikipedia

The above document format does not require proprietary software to be viewed or manipulated.

Microsoft office can open it, but so can many others, including LibreOffice.

 

[DavidFL]

OpenDocument - Wikipedia

The above document format does not require proprietary software to be viewed or manipulated.

Microsoft office can open it, but so can many others, including LibreOffice.

Excel provides the capability to save the .xlsx in .ods format. But the .ods conversion from .xlsx in Excel requires removing the password on any password protected workbooks/worksheets, which means a similar issue that caused @rsingler to remove the .xls version exists if it is converted to .ods. Since it is entirely a volunteer effort, I respect Rob's work and contribution and desire to at least attempt to restrict end-user capability to corrupt the formulas accidentally, and respect his condition of restricting the version that he makes available here to the .xlsx format.

 

[undrwater]

Excel provides the capability to save the .xlsx in .ods format. But .ods doesn't support password protection, which means a similar issue that caused @rsingler to remove the .xls version exists if it is converted to .ods. Since it is entirely a volunteer effort, I respect Rob's work and contribution and desire to at least attempt to restrict end-user capability to corrupt the formulas accidentally, and respect his condition of restricting the version that he makes available here to the .xlsx format.

.ods does provide password protection, but only within the app that created it.

Anyway, my intent was to provide information, not a request to change.