DevonDiver
N/A
I started this a quick response, but it's a rainy day here in Manila... so it grew into an article... 
PART 1
Shopping for a scuba buoyancy control device (BCD) is like completing a jigsaw. There is a huge variety of products and options available for the diver to chose from. The diver needs certain functions, but may also want certain additional functionality. Manufacturers/retailers will always try and make divers want more functionality, because that is where profits are made.
Making the best purchase decision can be difficult if the diver is not sufficiently experienced to know what their needs are, or understand both the 'pros' and the 'cons' to the various designs, features and functions that they will be presented with.
BCD manufacturers complicate this further, by marketing their products in a way that confuses the diver about what their needs actually are. They often attempt to sell higher priced BCD options by adding superfluous functionality and complexity to their basic designs. The difference between a $200 BCD and a $600 BCD is often nothing more than the addition of numerous unnecessary gimmick features that the diver will never use. Quite often, those gimmick features can actually detract from the performance of the BCD, impacting on its inherent buoyancy/weight, streamlining and ease of operation. Also, the more components that a device has, the more chance that a component will fail. Thus, the more complex a BCD design is, the more likelihood exists that it will let you down at some point.
Be wary of scuba advertising that stresses how many features a BCD has. The quantity and complexity of features is quite often more of a drawback than a benefit. You'll certainly be paying for every one of those features... every inch of fabric, every strap, every buckle, every quick-release, every screw, every bolt, every strip of Velcro.....every stitch.
Learn to look critically at a BCD design so that you can decipher what design features/functions are there for your benefit as a diver.... and what features/functions are included so that the manufacturer can charge you a premium cost.
A sceptical and questioning mindset is needed to separate the wheat from the chaff, when it comes to BCD advertising!
When considering a purchase, you should always seek to make your own comparison and evaluation of the options. Be aware that many dive shops/schools will have financial incentives to sell you specific equipment. Where possible, compare as many models and brands as you can. Be prepared to shop around at different retailers, especially if one retailer doesn't stock from a range of different manufacturers.
Use the internet to aid your research. Be wary of non-consumer based reviews. Some diving magazines and online equipment review sites receive financial incentives from manufacturers for their reviews Consequently, what is often announced as an impartial review can be nothing more than a manufacturer sponsored advert! Again, remain sceptical. Online scuba community forums are a good place to seek opinions, reviews and advice. You can be more sure that the information here will be less influenced by financially induced bias; but remain aware that many experienced divers hold strong opinions about scuba equipment choices, and those opinions may not suit your individual requirements.
So, here's my step-by-step guide on how to critically consider a BCD for purchase. I've tried to make it as unbiased as possible, but please forgive me if my own preferences, likes and dislikes are evident in the advice given....
Core BCD Functions (what a diver needs):
1) Surface Floatation: The BCD should offer sufficient buoyancy to float you on the surface with all of your gear in place. The exact amount of buoyancy needed to do that is specific to the diver and the equipment they use. This can be calculated accurately (see here). Excess buoyancy beyond that requirement is absolutely superfluous and only likely to cause you problems.
2) Variable Buoyancy Underwater: The BCD should provide variable buoyancy underwater, based on greater/lesser water displacement through adding or removing air from the BCD bladder. A properly weighted diver does not require a large amount of buoyancy compensation. The main reason for adding air at depth is to compensate for the reduced buoyancy of exposure suits as you descend (water pressure compresses the suit material and reduces its buoyancy). Cold water divers, in thick neoprene, suffer that largest loss of buoyancy from exposure suit compression on descent. Warm water divers in thin wetsuits (or no wetsuits) require only a negligible amount of buoyancy compensation underwater. You should understand your variable buoyancy compensation requirements, when investigating BCD bladder capacity. This is essentially an understanding of how much buoyancy your exposure suit will lose at maximum recreational diving depths.
(For a greater understanding of buoyancy and weighting; please see here: Buoyancy Masterclass)
3) Securing Cylinder/s to the Diver: The BCD must offer a secure and stable method of attaching scuba cylinder to the diver;
c) 'Jacket style' BCDs: These are BCDs in which the air bladder runs up that back and also surrounds the divers' torso. They are typically used in open-water classes, which makes them a familiar option for the novice diver. They adjust in fit as the air volume of the bladder is adjusted. When inflated, they are tight. When deflated, they are loose. As the diver varies their buoyancy during the course of a dive, they need to re-adjust the fit of the BCD using adjustments on the shoulder and waist straps. If they fail to tighten the straps when they empty the BCD to descend, the BCD will become too loose...and will roll and wallow around their torso. This causes them to feel less control during the dive. Also be aware that all of those adjustable straps will float around the diver once underwater. Many divers find an excess of long floating adjustment straps to be a considerable distraction and annoyance.
d) 'Rear-Inflate' BCDs: These are BCDs that have the air bladder behind the diver. Adjusting the buoyancy of the BCD does not interfere with the fit of the BCD to the diver. No adjustments to fit are required as the relative displacement of the BCD is varied. They typically have a similar design of adjustable harness to jacket BCDs, which brings some familiarity to divers who previously trained in a jacket BCD.
e) BP&W BCDs: Backplate and Wing (BP&W) BCDs are a sub-class of 'Rear Inflate' BCD, which have a modular construction. This modular function is based around a rugged backplate, to which attach cam-band/s, harness and the buoyancy bladder ('wing'). The diver can choose between different styles/materials of backplate, different cam-band options, different designs of harness and different designs and volumes of 'wing' bladder. A crotch-strap is typically seen as an essential add-on, as this ensures security and fit of the harness. The use of a plain webbing-style harness enables the user to add ancillary and storage options as they desire, including pockets, knife sheaths etc. Divers can purchase typical 'adjustable' harnesses, or they can opt for a 'single-piece' webbing harness which is initially trimmed to fit them perfectly and requires no further adjustment before, during or after diving.
These BCDs are very popular with divers who seek a 'minimalist' (less is more) approach to their configuration, as they can pick and choose exactly which features they wish to include. The use of metal (steel or aluminium) backplates reduces the need to carry weights on a weight-belt and helps encourage instinctive horizontal trim by spreading weight across the length of the divers' torso. BP&W also tend to be more streamlined and less bulky - offering considerable advantages in reducing exertion underwater and when operating in confined spaces (wrecks/caves). The drawback to the modular design, is that the diver must pay more attention to the initial set-up and fitting of the configuration. As such, they are less convenient when first purchased/used.
4) BCD Bladder Inflation: The BCD utilises a Low-Pressure Inflator (LPI) to add air to the BCD. This is typically on the end of a corrugated hose attached to the left shoulder of the BCD, although some BCDs use more complicated methods with 'remote' inflators incorporated into the body of the BCD (these are often more failure prone and less intuitive to control). LPIs can vary in performance; offering different speeds of inflation (i.e. high 'power' inflators). Whilst a quicker, more 'powerful', inflator may seem attractive (and is often marketed by BCD manufacturers as such...), it is worth bearing in mind that most novice-intermediate divers find that precise inflator control is a difficult skill to master. In many cases, a slower, less 'powerful' inflator is preferable as it offers more fine control when adding air to the BCD. There are few occasions where a 'high power' inflator offers any tangible benefits to the recreational scuba diver. The length of the corrugated hose should also be considered, as some divers find the standard length hose is too long and, consequently, always dangles below them. Some BCDs offer shorter length corrugated hoses.
5) BCD Bladder Deflation: The BCD must have methods to vent air from the bladder. Firstly, the LPI module will normally have a dump button for releasing air. In order for this to be use, the LPI corrugated hose must be raised above the level of the BCD bladder...typically with the diver in a vertical orientation in the water. Check that the BCD design does not limit your ability to raise the LPI hose to access this feature. Secondly, the BCD will have one, or more, dump-valves that offer alternative methods of deflation. The location of these is important for dumping air if the diver is not in a vertical orientation. As a minimum, the BCD should have a dump valve at the lower/bottom area of the BCD for deflation when in a horizontal or head-down orientation. Dump-valves also allow a more rapid deflation, should circumstances require it (i.e. uncontrolled ascent). The effectiveness of any venting method is also determined by the ability/design of the bladder to permit air to migrate around it. Overly complicated designs, particularly some jacket BCD types, may not permit easy air migration inside the BCD.
PART 1
Shopping for a scuba buoyancy control device (BCD) is like completing a jigsaw. There is a huge variety of products and options available for the diver to chose from. The diver needs certain functions, but may also want certain additional functionality. Manufacturers/retailers will always try and make divers want more functionality, because that is where profits are made.
Making the best purchase decision can be difficult if the diver is not sufficiently experienced to know what their needs are, or understand both the 'pros' and the 'cons' to the various designs, features and functions that they will be presented with.
BCD manufacturers complicate this further, by marketing their products in a way that confuses the diver about what their needs actually are. They often attempt to sell higher priced BCD options by adding superfluous functionality and complexity to their basic designs. The difference between a $200 BCD and a $600 BCD is often nothing more than the addition of numerous unnecessary gimmick features that the diver will never use. Quite often, those gimmick features can actually detract from the performance of the BCD, impacting on its inherent buoyancy/weight, streamlining and ease of operation. Also, the more components that a device has, the more chance that a component will fail. Thus, the more complex a BCD design is, the more likelihood exists that it will let you down at some point.
Be wary of scuba advertising that stresses how many features a BCD has. The quantity and complexity of features is quite often more of a drawback than a benefit. You'll certainly be paying for every one of those features... every inch of fabric, every strap, every buckle, every quick-release, every screw, every bolt, every strip of Velcro.....every stitch.
Learn to look critically at a BCD design so that you can decipher what design features/functions are there for your benefit as a diver.... and what features/functions are included so that the manufacturer can charge you a premium cost.
A sceptical and questioning mindset is needed to separate the wheat from the chaff, when it comes to BCD advertising!
When considering a purchase, you should always seek to make your own comparison and evaluation of the options. Be aware that many dive shops/schools will have financial incentives to sell you specific equipment. Where possible, compare as many models and brands as you can. Be prepared to shop around at different retailers, especially if one retailer doesn't stock from a range of different manufacturers.
Use the internet to aid your research. Be wary of non-consumer based reviews. Some diving magazines and online equipment review sites receive financial incentives from manufacturers for their reviews Consequently, what is often announced as an impartial review can be nothing more than a manufacturer sponsored advert! Again, remain sceptical. Online scuba community forums are a good place to seek opinions, reviews and advice. You can be more sure that the information here will be less influenced by financially induced bias; but remain aware that many experienced divers hold strong opinions about scuba equipment choices, and those opinions may not suit your individual requirements.
So, here's my step-by-step guide on how to critically consider a BCD for purchase. I've tried to make it as unbiased as possible, but please forgive me if my own preferences, likes and dislikes are evident in the advice given....
Core BCD Functions (what a diver needs):
1) Surface Floatation: The BCD should offer sufficient buoyancy to float you on the surface with all of your gear in place. The exact amount of buoyancy needed to do that is specific to the diver and the equipment they use. This can be calculated accurately (see here). Excess buoyancy beyond that requirement is absolutely superfluous and only likely to cause you problems.
2) Variable Buoyancy Underwater: The BCD should provide variable buoyancy underwater, based on greater/lesser water displacement through adding or removing air from the BCD bladder. A properly weighted diver does not require a large amount of buoyancy compensation. The main reason for adding air at depth is to compensate for the reduced buoyancy of exposure suits as you descend (water pressure compresses the suit material and reduces its buoyancy). Cold water divers, in thick neoprene, suffer that largest loss of buoyancy from exposure suit compression on descent. Warm water divers in thin wetsuits (or no wetsuits) require only a negligible amount of buoyancy compensation underwater. You should understand your variable buoyancy compensation requirements, when investigating BCD bladder capacity. This is essentially an understanding of how much buoyancy your exposure suit will lose at maximum recreational diving depths.
(For a greater understanding of buoyancy and weighting; please see here: Buoyancy Masterclass)
3) Securing Cylinder/s to the Diver: The BCD must offer a secure and stable method of attaching scuba cylinder to the diver;
a) Secure Cylinder Attachment: The cylinder should not slip or move within the attachment. BCDs have cam-bands to secure cylinders. Cylinders 'dropping' from cam-bands can happen. A BCD with 2 cam-bands offers more secure cylinder attachment. Cam-bands vary in quality of construction. Investigate those factors.
b) BCD Attachment to the Diver: The BCD is worn by the diver. At a minimum, this includes shoulder straps and a waist band. Crotch straps are included with some BCDs to enable further security and fit adjustment. The straps and harness may have adjustable buckles to enable a varied fit. There may also be quick-release buckles for convenient removal and to aid rescues. Wide velcro waist-bands are often included to compensate for a less precise fit, especially with 'jacket-style' BCDs (see below).c) 'Jacket style' BCDs: These are BCDs in which the air bladder runs up that back and also surrounds the divers' torso. They are typically used in open-water classes, which makes them a familiar option for the novice diver. They adjust in fit as the air volume of the bladder is adjusted. When inflated, they are tight. When deflated, they are loose. As the diver varies their buoyancy during the course of a dive, they need to re-adjust the fit of the BCD using adjustments on the shoulder and waist straps. If they fail to tighten the straps when they empty the BCD to descend, the BCD will become too loose...and will roll and wallow around their torso. This causes them to feel less control during the dive. Also be aware that all of those adjustable straps will float around the diver once underwater. Many divers find an excess of long floating adjustment straps to be a considerable distraction and annoyance.
d) 'Rear-Inflate' BCDs: These are BCDs that have the air bladder behind the diver. Adjusting the buoyancy of the BCD does not interfere with the fit of the BCD to the diver. No adjustments to fit are required as the relative displacement of the BCD is varied. They typically have a similar design of adjustable harness to jacket BCDs, which brings some familiarity to divers who previously trained in a jacket BCD.
e) BP&W BCDs: Backplate and Wing (BP&W) BCDs are a sub-class of 'Rear Inflate' BCD, which have a modular construction. This modular function is based around a rugged backplate, to which attach cam-band/s, harness and the buoyancy bladder ('wing'). The diver can choose between different styles/materials of backplate, different cam-band options, different designs of harness and different designs and volumes of 'wing' bladder. A crotch-strap is typically seen as an essential add-on, as this ensures security and fit of the harness. The use of a plain webbing-style harness enables the user to add ancillary and storage options as they desire, including pockets, knife sheaths etc. Divers can purchase typical 'adjustable' harnesses, or they can opt for a 'single-piece' webbing harness which is initially trimmed to fit them perfectly and requires no further adjustment before, during or after diving.
These BCDs are very popular with divers who seek a 'minimalist' (less is more) approach to their configuration, as they can pick and choose exactly which features they wish to include. The use of metal (steel or aluminium) backplates reduces the need to carry weights on a weight-belt and helps encourage instinctive horizontal trim by spreading weight across the length of the divers' torso. BP&W also tend to be more streamlined and less bulky - offering considerable advantages in reducing exertion underwater and when operating in confined spaces (wrecks/caves). The drawback to the modular design, is that the diver must pay more attention to the initial set-up and fitting of the configuration. As such, they are less convenient when first purchased/used.
4) BCD Bladder Inflation: The BCD utilises a Low-Pressure Inflator (LPI) to add air to the BCD. This is typically on the end of a corrugated hose attached to the left shoulder of the BCD, although some BCDs use more complicated methods with 'remote' inflators incorporated into the body of the BCD (these are often more failure prone and less intuitive to control). LPIs can vary in performance; offering different speeds of inflation (i.e. high 'power' inflators). Whilst a quicker, more 'powerful', inflator may seem attractive (and is often marketed by BCD manufacturers as such...), it is worth bearing in mind that most novice-intermediate divers find that precise inflator control is a difficult skill to master. In many cases, a slower, less 'powerful' inflator is preferable as it offers more fine control when adding air to the BCD. There are few occasions where a 'high power' inflator offers any tangible benefits to the recreational scuba diver. The length of the corrugated hose should also be considered, as some divers find the standard length hose is too long and, consequently, always dangles below them. Some BCDs offer shorter length corrugated hoses.
5) BCD Bladder Deflation: The BCD must have methods to vent air from the bladder. Firstly, the LPI module will normally have a dump button for releasing air. In order for this to be use, the LPI corrugated hose must be raised above the level of the BCD bladder...typically with the diver in a vertical orientation in the water. Check that the BCD design does not limit your ability to raise the LPI hose to access this feature. Secondly, the BCD will have one, or more, dump-valves that offer alternative methods of deflation. The location of these is important for dumping air if the diver is not in a vertical orientation. As a minimum, the BCD should have a dump valve at the lower/bottom area of the BCD for deflation when in a horizontal or head-down orientation. Dump-valves also allow a more rapid deflation, should circumstances require it (i.e. uncontrolled ascent). The effectiveness of any venting method is also determined by the ability/design of the bladder to permit air to migrate around it. Overly complicated designs, particularly some jacket BCD types, may not permit easy air migration inside the BCD.
