Wing Size in Sidemount: Choosing Proper Lift

What Does Wing Lift Actually Mean?
Start With Your Actual Configuration
Lift Requirement Is Not the Same as Equipment Weight
Don’t Forget Your Exposure Protection
More Cylinders Don’t Automatically Mean You Need a Huge Wing
Wing Size and Wing Shape Are Different Issues
Bigger Isn’t Always Better
Too Small Is a Different Problem
Your Wing Shouldn’t Be Your Trim System
Consider the Worst Reasonable Configuration
Stages Can Change Your Requirements
Don’t Confuse Wing Capacity With How Much Gas You Should Put in It
How Much Reserve Lift Is Enough?
Test Your Configuration in the Water
What About Redundancy?
A Practical Way to Choose Wing Size
Final Thoughts

Choosing the right wing for sidemount diving is not simply a matter of buying the wing with the most lift. A wing that is too small may not provide enough buoyancy when you need it. A wing that is unnecessarily large can create its own problems, particularly in a cave environment where streamlining, control, and minimizing drag matter.

The goal is not maximum lift. The goal is enough lift to comfortably support your actual diving configuration, with appropriate reserve, without carrying unnecessary wing volume. This becomes particularly important as your configuration changes. A diver carrying two aluminum cylinders has very different buoyancy considerations from a diver carrying two large steel cylinders, multiple stages, a drysuit, or a combination of all three.

Let’s look at how to determine what you actually need.

What Does Wing Lift Actually Mean?

Wing lift is normally expressed in pounds or kilograms of buoyancy. A 30 pound/13.6 kilogram wing, for example, is theoretically capable of producing approximately 30 pounds/13.6 kilograms of lift under the conditions specified by the manufacturer. That does not mean a 30 pound/13.6 kilogram wing can lift a 30 pound/13.6 kilogram heavier diving system out of the water under all circumstances.

Wing ratings are a measure of the wing’s buoyant capacity. They don’t tell you exactly how much lift your particular configuration requires. That distinction is important.

Your wing isn’t there to support the entire weight of your equipment. Your equipment is already being supported by the water through its own displacement and buoyancy. The wing is there to compensate for the negative buoyancy of the diving system and to provide enough additional buoyancy to maintain control throughout the dive. That includes changes that occur as gas is consumed and cylinders become lighter.

Start With Your Actual Configuration

Before deciding on wing size, look at the configuration you actually dive.

Consider:

• Primary sidemount cylinders
• Stage and decompression cylinders
• Cylinder material
• Cylinder size
• Gas volume
• Regulator and hardware
• Harness and backplate or butt plate
• Lights and other accessories
• Weights
• Exposure protection
• Drysuit undergarments
• Any additional equipment you regularly carry

This is much more useful than simply looking at the manufacturer’s maximum load recommendation.

A wing that works perfectly for a recreational sidemount configuration may not be appropriate for a technical cave configuration carrying several additional cylinders. Likewise, buying an oversized wing simply because you occasionally carry more equipment isn’t necessarily the best solution.

Your configuration should determine the wing.

Lift Requirement Is Not the Same as Equipment Weight

One of the most common mistakes when thinking about wing size is adding up the weight of all your equipment and assuming the wing needs to support that amount. It doesn’t.

If your complete diving system weighs several hundred pounds, you don’t need a wing capable of producing several hundred pounds of lift. Much of that equipment is already close to neutrally buoyant or has its own displacement in the water.

What matters is the amount of negative buoyancy that must actually be offset by the wing. This is why the relationship between your cylinders, exposure protection, ballast, and wing is more important than the dry weight of your equipment.

Steel and Aluminum Cylinders Change the Equation

Cylinder material is one of the biggest factors affecting sidemount buoyancy.

Aluminum cylinders generally become increasingly positive as gas is consumed. Steel cylinders typically remain more negative and can have a much greater effect on the overall configuration. This difference becomes particularly noticeable when you carry multiple cylinders.

Two large steel sidemount cylinders create a very different buoyancy problem from two aluminum cylinders. Add two or three stages and the difference becomes even more significant.

This doesn’t automatically mean that a steel-cylinder diver needs an enormous wing. It means the wing should be selected based on the configuration’s actual buoyancy characteristics. And remember that the cylinders are changing throughout the dive. The configuration at the beginning of the dive isn’t necessarily the configuration at the end.

Don’t Forget Your Exposure Protection

Your exposure protection also affects the calculation. A wetsuit can provide significant buoyancy, particularly when new and at the surface. A drysuit provides another variable because the diver uses gas within the suit for insulation and buoyancy management. This is one reason there isn’t a single wing size that is automatically correct for every sidemount diver.

A diver in a thin wetsuit carrying two aluminum cylinders may have very different requirements from a diver wearing a drysuit with substantial undergarments and carrying multiple steel cylinders. Your wing is only one part of the buoyancy system.

More Cylinders Don’t Automatically Mean You Need a Huge Wing

Technical sidemount divers sometimes assume that adding stages means they need to move to the largest wing available. That’s not necessarily true. Additional cylinders can increase the amount of negative buoyancy in the system, but their buoyancy characteristics also change as gas is consumed.

The way those cylinders are carried matters as well. A configuration with multiple stages can experience significant buoyancy changes throughout a dive as cylinders are breathed down, rotated, staged, and eventually removed from the diver’s configuration. This is especially important in cave diving. You aren’t simply carrying a fixed amount of weight from the beginning of the dive to the end. Your configuration is changing.

Wing Size and Wing Shape Are Different Issues

Lift capacity isn’t the only consideration. Two wings can have similar lift ratings but behave very differently underwater because of their shape and construction.

A sidemount wing should work with the way your cylinders are positioned. You want the wing to provide the required buoyancy without creating unnecessary bulk around your body. In a cave, this matters. The larger and more cumbersome the wing becomes, the more attention you may have to pay to how it sits around your cylinders and body.

A streamlined wing that provides adequate lift can be preferable to a much larger wing that creates unnecessary drag or makes cylinder positioning more difficult. This is one reason simply choosing the largest wing available isn’t a good approach.

Bigger Isn’t Always Better

There is an understandable temptation to buy more lift than you need. After all, having extra capacity sounds like a good safety margin. But there is a difference between reasonable reserve capacity and carrying a wing that is substantially larger than your configuration requires.

An oversized wing can:

• Add unnecessary bulk
• Increase drag
• Make gas management within the wing more difficult
• Change how the wing interacts with your cylinders
• Make buoyancy adjustments less precise
• Potentially complicate positioning in restrictions

For open-water recreational diving, some of these considerations may be relatively minor. For cave diving, they become much more important. You spend a significant amount of time moving through environments where equipment profile matters.

Too Small Is a Different Problem

At the other end of the spectrum, a wing that is too small can leave you without enough buoyancy reserve. This becomes particularly important when the configuration is heavily negative.

Imagine reaching the end of a dive with:

• Nearly empty cylinders
• Stages that remain in the configuration
• Significant ballast
• A drysuit configuration
• Equipment that is negatively buoyant

If your wing is already near its practical capacity, you have little room left to compensate for additional changes. You shouldn’t be operating at the absolute limit of your wing’s capability during normal diving. The wing should have sufficient capacity to handle the configuration without requiring you to completely fill it.

Your Wing Shouldn’t Be Your Trim System

This is where wing size connects directly to proper sidemount configuration. A wing is a buoyancy device. It should not be used as a substitute for proper weighting or cylinder positioning. If you have to put a large amount of gas into one part of the wing because your body wants to sit at an angle, the problem may not be wing size.

It may be:

• Weight placement
• Cylinder positioning
• Harness geometry
• Cylinder rigging
• Gas distribution
• Exposure protection
• Or some combination of these

I’ve had three wing failures during my diving experiences, including one approximately 3,000 feet inside a cave. That experience changed the way I look at redundancy and buoyancy.

A wing should be something you use to manage buoyancy, not something you depend on to correct a poorly balanced configuration. If your horizontal position disappears when your wing does, it was never really trim. It was compensation.

Consider the Worst Reasonable Configuration

When selecting wing lift, don’t size the wing only for the easiest version of your diving. Think about the heaviest reasonable configuration you will actually use.

For example, if your normal cave dives involve two primary cylinders and no stages, but you occasionally carry several additional cylinders, your wing needs to accommodate the latter configuration if you intend to use the same wing.

Likewise, if you normally dive aluminum cylinders but occasionally switch to large steel cylinders, consider how that changes your buoyancy requirements.

The important word is reasonable. You don’t necessarily need to size your wing for every possible piece of equipment you could theoretically attach to yourself. Size it for the configurations you actually dive.

Better yet, have a wing for each configuration that you dive the most often. I have three wings and harnesses that I use depending on the dives I do. One is for diving with heavy steel cylinders in Florida. One is for diving with aluminum cylinders in Cozumel. The third is for monkey diving with a single cylinder during recreational open water dives.

Stages Can Change Your Requirements

Stages deserve special attention because their buoyancy changes as they are consumed. An aluminum stage may begin a dive relatively negative but become significantly more positive as gas is consumed. A steel stage behaves differently.

If you’re carrying multiple stages, the buoyancy characteristics of the entire configuration need to be considered rather than simply adding the nominal lift requirement of each cylinder. And because stages are often staged and retrieved during cave dives, the configuration can change repeatedly. This is another reason why simply asking, “How many pounds/kilograms of lift do I need for two tanks?” isn’t enough.

The better question is:

What is the most negative configuration I will realistically have during this dive, and how much reserve lift do I want beyond that?

Don’t Confuse Wing Capacity With How Much Gas You Should Put in It

A 40 pound/18 kilogram wing doesn’t mean you should routinely carry 40 pounds/18 kilograms of lift. Wing capacity is available when you need it. You may only need a fraction of that capacity during normal diving.

The objective is to have enough capacity available without routinely inflating the wing to the point that it becomes part of your trim strategy. A properly balanced diver should be able to maintain position without relying on a large volume of gas in the wing. That is particularly important in sidemount because cylinder position and body position are closely connected.

How Much Reserve Lift Is Enough?

There isn’t one universal reserve number that applies to every sidemount diver.

Your reserve should reflect:

1. Your actual negative buoyancy
2. The equipment you carry
3. Your exposure protection
4. Your cylinder configuration
5. The maximum number of stages you normally carry
6. Your gas strategy
7. The type of diving you do
8. The environmental conditions

The important point is that you should have meaningful reserve capacity. You don’t want your normal configuration to require nearly all of the wing’s available lift. At the same time, there is little value in carrying an enormous wing simply because it gives you a large number on the specification sheet.

Test Your Configuration in the Water

Ultimately, calculations and specifications only get you part of the way. The final test is in the water.

Evaluate your complete configuration rather than testing the wing with an empty harness and a pair of cylinders. Look at the beginning and end of the dive.

Pay attention to:

• Surface buoyancy
• Neutral buoyancy at depth
• Trim with the wing minimally inflated
• Cylinder position
• Stability
• How much gas is required in the wing
• How the configuration changes as gas is consumed
• What happens when stages are added or removed
• Whether the wing interferes with your cylinders or equipment

The configuration should remain predictable throughout the dive. That’s much more important than whether the wing has the largest lift rating available.

What About Redundancy?

Wing redundancy is a separate consideration from wing size. If you’re diving a configuration where buoyancy failure is a serious concern, you need to think about how you will manage a failure.

That might involve:

• A redundant buoyancy system
• A drysuit
• Independent buoyancy devices
• Appropriate weighting
• A configuration that can remain manageable following a wing failure

But redundancy does not mean simply buying a larger wing. A larger single wing doesn’t make a system redundant. The question is what happens when your primary buoyancy system is no longer available.

This is one of those areas where equipment selection needs to be considered as part of the entire diving system rather than as an individual component.

A Practical Way to Choose Wing Size

Rather than starting with a wing size and trying to make your configuration fit it, work in the opposite direction.

Step 1: Establish your normal configuration

List the cylinders, exposure protection, ballast, harness, regulators, lights, and other equipment you actually use.

Step 2: Determine your most negative reasonable configuration

Consider the beginning of the dive, the end of the dive, and any point where you are carrying the greatest combination of negative equipment.

Step 3: Consider cylinder buoyancy changes

Look at how your primary cylinders and stages change as gas is consumed.

Step 4: Account for exposure protection

Include the buoyancy characteristics of your wetsuit or drysuit and undergarments.

Step 5: Choose adequate lift with reserve

Select a wing that comfortably handles your configuration without operating near its maximum capacity.

Step 6: Evaluate the physical shape

Make sure the wing works with your cylinder position and doesn’t create unnecessary bulk or drag.

Step 7: Test the complete system

Dive it.

Then dive it again as the cylinders become lighter and your configuration changes.

A Practical Way to Choose Wing Size

This is one of those sidemount questions where a single answer is attractive but misleading. A 20 pound/9 kilogram wing isn’t automatically better than a 30 pound/13.6 kilogram wing. A 30 pound/13.6 kilogram wing isn’t automatically better than a 40 pound/18 kilogram wing. The correct size depends on the system you’re building.

A recreational diver carrying two aluminum cylinders may have very different requirements from a cave diver carrying large steel primary cylinders and multiple stages. Even two cave divers with apparently similar equipment may have different requirements because of differences in exposure protection, ballast, cylinder choice, and configuration.

The goal is not to find the biggest wing you can buy. It’s to find the wing that provides adequate lift, useful reserve, and appropriate physical dimensions for the diving you actually do.

Final Thoughts

Wing size is another example of why sidemount equipment should be treated as a system. It’s easy to look at a specification sheet and decide that more lift must be better. It isn’t that simple.

Your cylinders, weighting, exposure protection, harness, stages, and diving environment all influence how much lift you actually need. And once you have enough lift, adding substantially more doesn’t automatically make the configuration safer or better.

For cave diving, I would rather have a properly balanced configuration with an appropriately sized wing than a poorly balanced configuration hidden behind a large amount of lift.

Choose your wing based on the configuration, not the other way around.

The right wing is the one that gives you enough buoyancy when you need it, enough reserve to handle the unexpected, and a profile that doesn’t interfere with everything else you’re trying to accomplish underwater.

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Related Articles

• The Anatomy of a Sidemount Configuration
• Steel vs Aluminum Cylinders in Sidemount
• How to Set Up a Sidemount Harness
• Why You Can’t Stay Horizontal in Sidemount (And How to Fix It)
• The Problem Isn’t Always Your Trim. It May Be Your Weighting