BCD Styles Explained
BCD Styles Explained
Hopefully when you learned to dive you got to use different types of BCD's, regulators, computers and fins.
Even if you didn't, you were told about the options, perhaps you even tried them on?
Well if you were just rushed through your course and weren't given that opportunity and have only used or know one type, how are you supposed to choose what's right for you when it comes to spending your hard earned money?
I have been lucky to use a wide range of BCD's in different styles and by the major manufacturers and know what I prefer to use, but here's a little information about what types of BCD's are out there.
We stock a variety of BCD styles and manufacturers in our store and use our favourite styles in our school's training fleet for this very reason.
What is a BCD used for?
The roles of the modern BCD is to attach one or more SCUBA cylinders to the diver and allow the diver to adjust buoyancy (neutral, positive & negative) easily throughout a dive by adding or removing air from a bladder of the BCD as desired.
A diver will want to be neutrally buoyancy throughout most of the dive, they will adjust the gas in the BCD's bladder as they change depths to achieve this. They will want to be positively buoyant with their head clear of the water when floating on the surface and slightly negatively buoyant for descending. The bladder must have enough lift (buoyancy) and dumps in the appropriate place to achieve this.
A brief history of the modern BCD
In 1957, the US Navy Experimental Diving Unit, (NEDU) began testing manual and automatic Buoyancy Compensators. These used separate gas cylinders from the divers breathing gas for inflation, but this was not like the comfortable devices we use today.
By 1968, Joe Schuch and Jack Schammel, US dive shop owners, had developed a more comfortable buoyancy compensator vest that featured a small buoyancy ring behind the diver's head and at midriff section with sufficient volume to lift the diver's head out of the water.
In 1969, the original Control Buoyancy Jacket or "CBJ" was manufactured by Waverly Air Products of Chemung, NY and sold in dive shops throughout the east coast of the United States.
By 1970, a push-button inflator using air from the diver's SCUBA tank augmented the manual inflation hose which is how we control our modern BCD’s.
Jacket style BCD's
In 1985, Seaquest, Inc (which is part of the Aqualung and Apeks family), introduced the ADV (Advanced Design Vest). It is the wrap around jacket style BCD that is still in use today by many manufacturers. It features an under-arm wrap, shoulder buckles and a cummerbund. The original jacket style BCD would be used in conjunction with a weight belt and may have pockets for accessories. Today we also have the option of an integrated weight system.
The humble Jacket design BCD is still very popular in many places today as it is cheap and is what many divers were trained in. For some divers, it is hard to move away from this style as it is all that they know.
Pockets are useful for stowing tools and spares such as; DSMB & Reel, Torch, Spare Mask, Wetnotes or a Seafood Measurer. But on a BCD that incorporates integrated weights and inflates around the torso, they tend to be too bulky and so pockets on thighs for accessories is a more streamlined option. This can be achieved by either wearing pocket shorts over the wetsuit or having pockets glued on. Most dry suits have thigh pockets.
- When inflated on the surface it is extremely stable and keeps the diver vertical with their head clear of the water without much effort.
- Easy to deflate as the air trapped in the chest area of the vest which have straps that press against it making it easier to deflate.
- They are bulkier and so create more drag in the water.
- If the diver is incorrectly weighted or the BCD is poorly fitted, if can alter a divers position and make them slightly vertical in the water with their feet and fins pointing down.
- More restrictive across the stomach and chest which some divers complain about the "squeeze".
By the early 2000’s weight integrated BCD’s with trim weight pockets were available to buy. This meant that the diver now had more control in the water by being able to adjust their trim position, allowing them to obtain a more horizontal streamline positon. It also made accidental weight loss a more controllable event. In the event of weight belt failure and loss, the diver has lost all of their additional weight and they would ascend rapidly to the surface. If a single weight pocket was to fail, they have lost only half of their weight. If they had some weight in a trim pocket and lost a weight pocket, then they have lost less than half of their weight, resulting in a more controllable situation.
A jacket style jacket with weight integrated pocket is slightly troublesome when putting weights in with the BCD inflated as the air bladder reduces the space the weights want to slide into.
Due to natural competition between manufacturers, different mechanisms have been developed for securing and removing weight pockets. Some are far superior than others, some “almost eject on their own” and some are very complicated to install. Choose a style that suits you, it should be relatively easy to slide the pocket in and you should be able to visually and/or audibly confirm the pocket is secured.
- Easy to install
- Easy to deploy
- Great weight distribution
- Reduces the chances of losing all weight resulting in an uncontrolled ascent
- More comfortable
- Some manufacturers have difficult locking mechanisms on the integrated weight pocket meaning some are hard to load or they come out too easily.
- Higher price point
Trim weights are weight pockets that are positioned on the BCD that allow the diver to adjust their dive trim position by moving some weight to a higher position. Be aware that some manufacturers use the term trim pocket, but their trim pockets are positioned in line with integrated weights so will not affect your trim position. Separate trim weights can also be attached to cylinder bands.
Rear inflation BCD's. Simon's No 2 choice
With the development of the recreational jacket BCD and the back plate and harness in the technical diver community, the different technologies were fused and so was born the rear inflation BCD. These BCD's feature; rear inflating bladder, weight integration and D rings (Non-adjustable).
With rear inflation there is no cumbersome bulk around you and so weights are easier to put in and you feel more comfortable. The rear inflation helps you gain greater stability in the water. On the surface, you just have to lay back and relax. To start with you may feel the forward force of the bladder, but this is quickly overcome.
Many non-harness rear inflation BCD’s have a wing lift capacity far greater than required and incorporate bungies to help the air escape the BCD and not get trapped when the diver is deflating the BCD.
Even with so much lift, they are still not designed to carry more than a single cylinder, with the exception of a cylinder slung from the D rings.
This has revolutionised the way we have dived for the past 15 years, but amazingly there are still thousands of divers that do not know about this style of BCD.
- With the inflation behind you, you feel freer and less constrictive.
- Better and easier trim position in the water.
- Less bulk around your body.
Cons - Non in our eyes
- On the surface they push you forward slightly, not a strong force. Just lean back into it and you will float comfortably.
- If you are over-weighted then the excess air you add to the BCD to compensate for your buoyancy will "taco" around the tank and so this air can be slightly difficult to migrate to the dumps without moving your body to aid it when you want to release it. Do not dive over-weighted and this should not be a problem unless the bladder is too large.
Scubapro Knighthawk was voted 2019 best back inflated BCD by "Scuba around the world".
Mares Bolts SLS was voted 2017 Best Buy Rear Inflated BCD by Scubalab
This style of BCD has continued to develop into a variety of great recreational BCD's that are now modular; like Scubapro’s impressive Hydros Pro and into Hybrid styles like the Mares PURE.
The Hydros Pro is made from materials that do not absorb water and so are quick to dry and are chlorine and UV resistant. Great for any diver, but especially someone who spends a lot of time in pools or in a sunny environment. It doesn’t absorb water and so is both quick drying and requires slightly less lead than other BCD’s, but it also packs down well for travel.
Scubapro Hydros Pro Winner of the Red Dot Design Awards
A combination of the jacket style and rear inflation. It inflates 3/4 of the back and 1/4 of the front, which contributes to both better buoyancy control than a jacket and great comfort. The diver can easily maintain horizontal and vertical positions. Is this just a style that is on the market because the manufacturers are unable to think of anything really new?
It's an option for divers who are transitioning from a jacket style to a rear inflation, but are worried about staying vertical on the surface.
Mares Hybrid PURE was voted 2019 best Hybrid BCD by "Scuba around the world".
- Indecision - Just go for a full Rear inflation
Backplate and Wing - Simon's No1 choice
The backplate and wing is a modular system, in that it consists of separable components. The core components of this system are a harness, backplate and a wing bladder. This means that you have more choices and that in the event that you damage your BCD, repairs or replacements don’t mean a whole new BCD.
DiveRite marketed the first commercially manufactured backplates in 1984, and a wing for diving twin cylinders in 1985.
A harness, which attaches the system to the diver, and may support other accessories via adjustable D rings. A purists thought of a harness may be a single continuous weaved webbing that is sized up by the diver before fitting the wing.
The backplate, usually made from metal (either Stainless Steel approx 2.7kg to 4.5kg or Aluminium 0.9kg ), is held against the diver’s back by the harness. Attached to the harness are the diver’s primary cylinder/s. Hardened plastic and carbon fibre plates are on the market, but offer no weight.
With a weighted backplate, the diver can distribute some of their required weight across their back helping them achieve greater buoyancy control. Dump-able weight pockets can be attached if not provided.
Softpacks are also available on the market. These allow divers the benefits of a wing, but with the comfort of a soft backplate. The diver may require larger weight pockets as there is no weight in this system.
An inflatable buoyancy bladder known as a wing, is placed between the backplate and the cylinder(s), used for adjusting the buoyancy of the diver when in the water. There are various sized and shaped wings on the market to suit various factors. They are accessed via a zip on the outside of the protective cover, so can be repaired or replaced if required.
Hybrid harness, rear inflation with soft backplate wing.
For divers who have dived a jacket style BCD, but have been exposed to the backplate and wing, the design may seem too alien with the bare webbing harnesses without padding, quick release clips and velcro cumberbands. So the best of both worlds were brought together in BCD's like the OMS IQ Lite.
Doughnut versus Horse shoe Bladders.
It’s all about gas migration in the wing. As long as you are not over-weight, the wing should not “taco” too much around the cylinder during the dive, unless it is too large. With a horse shoe wing, gas can get trapped at the ends and so either you need to migrate the gas or have a wing with multiple dumps.
This is also true with doughut wings, just remember that you may need to help any gas move from the right to the left where the dumps are by rolling your body slightly.
Bungee versus non bungee
Bungee around the bladder is designed to reduce the size of the wing when not inflated fully to aid streamlining, it also helps preventing air being trapped in the wing. The downside is that if the wing gets damaged and a hole is made in the bladder, the bungee will squeeze the air required for buoyancy out. This would be very problematic for a diver.
When diving in cooler waters like New Zealand, we often use drysuits, especially when twin tank and rebreather diving and so the drysuit is a second buoyancy device. What about when we are diving in the tropics? The options really are using a wing that has a redundancy bladder, a second bladder or by adding a second wing to your harness. The only wings I have found with redundancy bladders are horse shoe shaped. Using either system, it is best not to have both bladders attached to a LPI during the dive in case both are mistakenly inflated.
Perhaps the newest kid on the block.
It consists of using a special harness style BCD, where the tanks, usually two tanks are mounted not on the divers back, but under the shoulders and along the torso and hips. This creates a greatly streamlined diver. The bladder is across the divers back. The inflator sits across the divers chest and a lower dump is in the centre at the base of the bladder. Trim weights are positioned along the divers spinal region.
It was originally introduced by cave divers who wanted to get through very small spaces where back mounted tanks would not fit.
The BCD’s are specific to this role and so will not suit back mounted divers. The BCD that is very popular amongst the Sidemount population, especially those that carry additional stage bottles is the XDeep 2.0 Stealth.
Drycave explorers who have to pass through sumps usually incorporate sidemount, but their harnesses also incorporate their abseiling harness. Golem Gears Armadillo Exploration Harness A2 can also be attached to a climbing harness to create a more streamlined rappelling/climbing system.
Multi Purporse BCD's
BCD's that can dive back mount and side mount, single tank and twin tank convertible are out there. But any piece of equipment that can function in multiple roles are generally ok in each role, but never fantastic at any one.