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 other options right?
Well if you weren't given that opertunity and have only used or know of one type, how are you suppposed to choose what's right for you?
I know what I prefer to use, but here's a little information about what types of BCD's are out there. Pop into the store if you want to know more. We have a few different types in our fleet for this very reason.
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) throughout a dive by adding or removing air from a bladder within the BCD as required.
A diver will want to be neutrally buoyancy throughout most of the dive, they will have to adjust the gas in the bladder as they change depths to achieve this. They will also want to be positively buoyant with their head clear of the water when floating on the surface and slightly negative buoyancy for descending. The bladder must have enough lift (buoyancy) to achieve this.
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.
In 1985, Seaquest, Inc (which is part of the Aqualung 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 there is the option of intergrated weight system.
The humble Jacket design BCD is still very popular in many places today, as it is cheap and it is what many divers were trained in. For some divers, it is hard to move away from this style as it is what they are used to.
Pockets are useful for stowing tools and spares such as; DSMB & Reel, Torch, Spare Mask, Wetnotes or a Seafood Measurer. But on a BCD where it inflates and weights need to go, they tend to be too bulky and so pockets on thighs for accessories is a more streamlined option.
By the early 2000’s weight intergrated BCD’s with trim weight pockets were available to buy. This meant that the diver now had more control in the water due to 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. 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 that half of their weight.
An ADV with weight intergrated 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”. Choose one that you can visually and audibly confirm have secured.
With the development of the back plate and harness, the different technologies have been fused. And so was born the rear inflation, weight integrated BCD with D rings (Non adjustable) and it has continued to develop into great recreational BCD’s that are now modular; like Scubapro’s impressive Hydros Pro. The Hydros Pro is made from materials that are chlorine and UV resistant, great for any diver, 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.
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.
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 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. Other options use webbing with quick release mechanisms more familiar to recreational BCD users.
The backplate, usually made from metal (either Stainless Steel approx 2.7kg 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. Harded 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.
Softpacks are also avaible 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.
It’s all about gas migration in the wing. As long as you are not overweighted, 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 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 drysuits, especially when twin tank diving and so the drysuit is a second buoyancy device. What about when we are diving twins in the tropics? The options really are using a wing that has a redundacy bladder, a second bladder or by adding 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 new kid on the block.
It consists of using a special harness style BCD, where the tanks usually twin 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 divers also incorporate sidemount, but their harnesses also incorporate their abseiling. Golem Gears Armadillo Exploration Harness A2 can also be attached to a climbing harness to create a more streamlined rappelling/climbing system.