In this blog we examine the buoyancy compensator (BC)/jacket options for backmount single cylinder decompression diving. Your equipment choices for the SSI Decompression Diving program will have a significant impact on your performance level and comfort during and after your training. It will also help you manage the challenges of decompression diving. You can complete the SSI Decompression Diving program in the same recreational Total Diving System you use for other recreational training programs with a few additions. There are many different buoyancy compensator configurations that are perfectly acceptable for decompression diving. Ultimately, it is your responsibility to understand the design and service limitations of the equipment you use, and to verify that it is suitable for the type of diving you want to accomplish.
There are two types of backmount BCs that can be used for single-cylinder decompression dives, the traditional jacket-style BC or a backplate and wing BC. Either configuration is appropriate, but each design has certain benefits and disadvantages.
The jacket-style design is the most widely used type of buoyancy compensator used by recreational, no-decompression divers. Almost every major equipment manufacturer has multiple models of jacket-style BCs in all shapes and sizes. Some designs are gender-specific for an improved fit, and some offer customizable configurations for alternate air sources, inflation options, weight configurations, accessory attachment options, and more.
Some jacket-style BCs have an internal air bladder that partially wraps around the diver’s body, creating a more comfortable upright position at the surface. The convenience and ease of use makes jacket-style BCs one of the more popular options for rental fleets and entry-level divers.
The wraparound design of the jacket-style means that the air migrates around the diver’s torso to fill the various regions of the bladder. This can create pockets of trapped air during depth changes, limiting the diver’s horizontal body position—their trim—or making it harder to add or remove air during ascents and descents. Even when neutrally buoyant, a diver wearing a jacket-style BC may be slightly out of trim, causing their legs to drop a bit and increasing their workload as they move through the water. This can be especially challenging when using a stage cylinder during decompression dives. The D-rings on a jacket-style buoyancy compensator may not be ideally oriented for attaching a stage cylinder. They may also be smaller than recommended, or they may be positioned over a storage or weight pocket, which can create problems during the dive.
The backplate and wing configuration was the buoyancy compensator of choice for technical divers but has become more popular with recreational divers as materials and configuration options improve. The basic configuration philosophy is very simple; the diver wears a harness made from a single piece of webbing that is woven through a metal—either aluminum or steel—backplate. A wing with an internal air bladder is mounted on the backplate so it sits between the diver and their cylinder.
Decompression divers typically use a backplate and wing because they can be customized to meet the diver’s specific needs. Other divers appreciate the simplicity of the configuration, or the benefits of a backmounted air bladder, which makes it easier to achieve a horizontal trim position while submerged. The smaller front profile also allows for a greater range of motion and less interference. The harness can often be adjusted to fit another diver through a series of simple adjustments, eliminating the need to know the diver’s size requirements. The wing can also be easily swapped for a wing with a greater lift capacity, allowing the diver to use one backplate for multiple cylinder or equipment configurations. The hip D-ring on the harness is often larger than the one on a jacket-style BC, making it easier to attach a stage cylinder. The backplate can be exchanged for a heavier or lighter one, or quick-release weight pockets can be added or removed to change the amount of weight carried during the dive.
Despite its popularity, the backplate and wing configuration has a few limitations. Since the harness is typically formed from a single piece of webbing, it can be less comfortable than the traditional jacket-style BC, especially if the diver carries a lot of weight. Some harnesses also lack a quick-release feature, which makes removal more difficult in an emergency. The backmounted wing improves horizontal trim underwater, but the air bladder has a tendency to push the diver’s head forward on the surface. This can be uncomfortable for inexperienced divers, especially if surface conditions are less than ideal. This obstacle is overcome by practicing with the wing on the surface until the diver is used to its characteristics.
Soon the SSI Decompression Diving course will be launched. In the meantime...do you want to learn more about diving equipment? Complete the SSI Equipment Technique course and find out everything you need to know about use, care and maintenance of diving equipment.