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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[D_Fresh]

Fantastic tool, and great work! Thank you @rsingler , @stepfen , @johndiver999 , @kmarks , @Akimbo and the everyone else who contributed.

I really enjoyed geeking out over the numbers. I can confirm that, for me, the numbers came out exactly as I expected and confirmed my ditchable lead for my current setup. Yay!

 

[CDMac]

Reading ScubaBoard, you will discover 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.

Yeah, that seems to be the thing I struggle with the most but I am going to go with BP/W setup to alleviate all the bloating.

I'm moving to Fort Lauderdale (from Pittsburgh, PA) in 2 weeks and I am excited about the diving opportunities in Florida.

I'm looking for an instructor now with whom I can do a pool refresher and my open water dives (have my referral from instructor here in PA).

PA: Not diving until May
PA: Diving in may in dark, cold quarries with 7mm minimum exposure
FL: Diving year round
FL: By May most will have ditched the 5mm and donned the 3mm or rash guard and board shorts

Sign me up!!

 

[Fastmarc]

Fantastic tool, and great work! Thank you @rsingler , @stepfen , @johndiver999 , @kmarks , @Akimbo and the everyone else who contributed.

I really enjoyed geeking out over the numbers. I can confirm that, for me, the numbers came out exactly as I expected and confirmed my ditchable lead for my current setup. Yay!

It really is. It was helpful for me when I was switching over to BP/W.

I've budgeted to go 'red' soon and finding this tool was the final nudge. That someone would take the time to not just put something like this together, but be constantly improving it and then just share it with the community?
This is a hell of a community and this is a prime example of that.

 

[rsingler]

We're getting close, folks!
Thanks to @Fastmarc and @stepfen , we have completed a major upgrade which will allow doubles/sidemount divers, and those who carry ponies, to calculate buoyancy when returning with significant reserve gas weight. You will also get help deciding on your choice of weight in case you are forced to use ALL available gas in an emergency or delayed ascent (down to tank pressures of 300 psi/20 bar).

The spreadsheet is done and now undergoing error checking, and portions of the manual are almost finished being rewritten.

Soon!

 

[rsingler]

Attached to post #1 at the top of this thread is another major upgrade of our tool. Please download the revised User’s Manual along with one of the spreadsheets. Make me believe you have read the disclaimers and the theory, even if you don’t need help with Excel.
In response to your requests, we have added the capability to designate both starting and planned ending tank pressures, for divers that carry a “cave fill”, that carry a small pony that they plan to bring back full, who are diving doubles that will return with 1/3 of their air as a reserve, or are carrying stages that they plan to use to various levels of residual gas weight.

The Quick Results, Lift, Wetsuit and Drysuit tabs have been reformatted to reflect the dilemma you face, now that you can specify returning with a half-full tank: do you compute buoyancy for your planned ending pressure? Or do you plan for an emergency in which you’ve used up almost all your available gas, and need to be able to maintain your last deco/safety stop?

This implementation is fully discussed in ten additional pages in the User’s Manual.
Subtle formula changes have been made based on ongoing experimentation.
A number of spreadsheet computation errors were discovered and corrected.

The tool now allows you to specify:
1) Imperial or metric units
2) Salt or Fresh water
3) Bathing suit, wetsuit (shorty, full or Farmer John), drysuit (Trilaminate, Neoprene, Compressed Neoprene, Crushed Neoprene), and variations for personal diving habits (like a full drysuit, or a wetsuit with an extra vest).
4) Any of more than (EDIT) 200 tanks, or custom tank specifications
5) Starting and/or ending tank pressure(s)

With the addition of tank pressures, your buoyancy status at both planned end dive pressure, and after an emergency that uses up all your gas is spelled out. Capabilities for multiple tank divers are significantly improved.

For the casual user, little has changed. Default values are buried in each of the formulas, so that you are not required to specify tank pressures. If you are diving single tank in a warm water wetsuit, the added capability of this redesign will occasionally mean an extra pound or so of recommended weight to account for added buoyancy in an emergency where you are holding a safety stop with near empty tanks. Otherwise, nothing will have changed. In the Lift tab, you can still customize your desired buoyancy for any stage of your dive, no matter what has been suggested in QuikResults.

Many thanks to @stepfen and @Fastmarc , who have provided invaluable assistance with this latest iteration. This has been a crowdsourced product and there are dozens more SB’ers who have made this a better toy. And thank you again to @johndiver999 whose comment here in 2018 about reaching a point of neutral buoyancy on the way to the surface after ditching some weight, was the genesis for this entire project.

Additional suggestions continue to come in, so expect this to be an evolving tool.
As always please comment, either in a thread post or by Direct Message if you find a formula error, disagree with a recommendation or numerical result, or have a suggestion for a future version.

Dive Safe!

 

[Couv]

The spreadsheet is done and now undergoing error checking, and portions of the manual are almost finished being rewritten.

You ought to consider taking a vacation sometime. ;-)

.....and by extension the concepts of Archimedes' principle.

Yep, getting back to the ABCs of diving physics would be a good thing.

Archimedes
Boyle
Charles
Dalton
take a break for E & F
Gay-Lussac (take another break, it's pretty much the same as Charles)
Henry
Ideal (never mind, B + C = close enough for I)

Now, back to our regularly scheduled program.

 

[T Mogle]

Very impressive excel sheet.

My PADI Instructor got a very simple view. Just add 10% of your body weight with a 5 mm wetsuit and 12l tank.

It might be too simplistic, I got the impression it will work for most.

 

[Doby45]

Very impressive excel sheet.

My PADI Instructor got a very simple view. Just add 10% of your body weight with a 5 mm wetsuit and 12l tank.

It might be too simplistic, I got the impression it will work for most.

In that situation I would be way overweighted. I weight 200lb and with a 5mm and AL80 I use 14lb salt 12lb fresh.

 

[rsingler]

What a pleasure to meet one of my Internet collaborators in person at last! Here is @stepfen and his lovely children in their home town of Chania, Crete.

By sheer coincidence, my wife's and my first anniversary Med cruise had Chania as one of its ports of call.
It was so nice to attach a face to a name that was before, just that of an electronic friend. Albeit one in the best scuba family in the world: ScubaBoard!
Thanks for all your help, @stepfen !

 

[stepfen]

@rsingler Noooo!!!! I'm trying to hide from these crazy people

It was so nice meeting you! Thanks a lot for the gift and the opportunity to chat with you!
All the best!