Bitz Scuba Diving Equipment Guide - Buoyancy Compensators

Introduction

Which Attachments?

Which Buoyancy Compensator?

Which Computer/ Dive Timer?

Which Compass?

Which Contents Gauge?

Which Dive Bag?

Which Fins?

Which Knife?

Which Mask?

Which Reel?

Which Regulator?

Which Snorkel?

Which Surface Marker Buoy?

Which Suit and Options?

Which Tanks? Overview

- Which Single Cylinders?

- Which Pony Cylinders?

- Which Twin Sets?

- Which Deco/ Stage Tank?

- Which Argon System?

Which Torch?

- Which Back-up Torch?

- Which Main Torch?

Which Watch?

Which Weight System?

Marking Template for EAN50

Marking Template for O2

Modifying AP Valve SMB's

Modifying Other Style SMB's

What Do I Need to Make My Own B'C'?

Introduction

Modified Valve Drill

Valve Drill

Modified S-Drill

S-Drill

Switching to Deco Bottle

Which Buoyancy Compensator?

There are two main options available - Stab Jackets (aka Stabiliser jackets or BCD's) and wings (which are also BCD's). Both do exactly the same job but have different features.

Stabiliser Jackets are typically of a sleeveless jacket style design with buoyant areas around the back, under the arms and over the shoulders. These are increasingly falling from fashion.

Wing Style Designs incorporate all the buoyancy around the back with some kind of harness to attach them to the diver (left).

There are any number of styles of buoyancy compensator with more features available than you can frequently shake a stick at. Many of the perceived benefits are illusory, of no practical use at best or at worst a liability. This section has tried to cover as many of these features as possible and consequently may appear long. It is rare that you find a buoyancy compensator which features none of these items.

Things to look for:

Will it provide enough lift? About 14kg is typically enough for a single cylinder diver.

Is it streamlined in the water?

Does it have an internal bladder, which is protected by an outer shell?

Does it have an over-pressure relief valve?

Is the internal bladder bigger than the external shell to prevent it over-expanding and bursting?

Can the bladder be easily inspected for punctures?

Is it a reliable and proven design?

Are the attachment points (D-Rings) in the right places? Can I move them about, as I need to, remove them or add to them?

Will the buoyancy aid fit your size and shape and be capable of being tailored to you even if you put on weight or go on a diet? Poorly fitting equipment which shifts when the diver moves causes discomfort, stress and can affect the divers breathing.

Does it incorporate a "hard" backplate to properly support the tank and fittings? "Soft" style supports generally move during use and are less efficient and secure.

Is it a modular design which will grow with your diving?

Does it have any impact on your upper torso dexterity, eg movement of arms, head etc?

Is the corrugated hose the right length? Too long a hose will get in the way and is difficult to streamline.

Will it provide too much lift? Do you really need a 100kg wing flapping around behind you, increasing the drag?

Will it restrict your breathing if fully inflated leading to carbon dioxide retention by the body and increased narcosis amongst other symptoms? This flaw in particular can be present in stabiliser jacket style designs.

You need to ask yourself if there are any superfluous/unnecessary features. This includes a range of things such as:

Pull dumps - "string and bobble" pull dumps are subject to getting tangled up and are an unnecessary complication. Pull dumps can jam open making the buoyancy compensator useless. Sometimes the pull dump is attached to the corrugated hose, frequently pulling it may strain the connections and cause it to break free, causing the buoyancy compensator to become useless.

Integrated weight systems - these clutter your upper torso as well as making the buoyancy aid unnecessarily heavy as a single item. They may also make the cylinder / BCD / harness so heavy that it will not float when taken off, this can get expensive if you need to remove it to get back into a small boat.

Pockets - These clutter the upper torso and it is almost impossible to access anything contained within them without assistance from your buddy. The best place for pockets is normally on your suit.

Double bladders (ie two BCD's in a single outer case)- the complications which arise can be self-defeating and can result in additional difficulties or tasking loading if a problem were to arise, eg if the spare inflator were to leak the diver may be unaware of the problem and try to correct it with the alternate inflator leading to an uncontrolled ascent. They are also larger than single bladder style wings, creating more drag

Power inflates - these are bad news if they stick open since you will find yourself hurtling towards the surface before you have a real chance to control it.

Bungies - These compress the buoyancy aid to correct the excessive bulk introduced by having too large a bladder in the first place. This can make it difficult to inflate manually if you have to; it creates additional drag due to turbulence over the uneven surfacecompared with simply using the right size of bladder or a "smooth" design and there is a greater risk of entanglement. It also suffers from problems of uneven inflation and off-balanced buoyancy due to potential excess compression on one side. Worst of all, if the buoyancy aid becomes punctured, it will deflate even if the hole is at the bottom whereas simple, non-bungied designs wouldn't.

Plastic quick releases - these are subject to breaking at the most inopportune moments in what may be a potentially dangerous situation.

Chest straps can put additional pressure on the diaphragm, increasing stress and discomfort and can again lead to carbon dioxide retention; increased narcosis etc

Integrated alternate air supplies - this includes the "Autoair" and "Air II". These are supposed to eliminate the need for a separate octopus, but generally are of poorer performance and are subject to greater wear, tear and failure than a normal regulator, since it is not as easy to properly protect them.

Mini/emergency cylinders - these are illegal in some countries, and for good reason. The mini cylinder is supposed to be used in an emergency either to inflate your jacket or to provide you with a couple of extra breaths. In practice, it should not be needed for emergency inflation because you would simply jettison your weight belt. The volume of air contained is also completely inadequate for an emergency air supply and the task loading required to competently use one in an emergency is too great. Mini cylinders have been known to be accidentally operated by being knocked and sending the diver rocketing to the surface.

ABS and/or Plastic Backplates - whilst lighter weight, these can flex and break and should be avoided.

D-Rings fitted to the side of the bladder in wing style designs. These are at best difficult to reach and worse if anything is carried here it will distort the shape of the wing, increasing drag. They offer nothing to the diver and are just another potential snag point to get caught or entangled.

Reverse Bent Backplates - These include the Custom Divers Backplate and Portland Oceaneering Mk 2 Design. The Backplate is bent inwards towards your back to take a single cylinder. These have proved to be uncomfortable and are particularly unsuitable for diving with twin tanks. A single tank adaptor is more than suitable for use with a standard shaped backplate.

The essential message here is to keep it simple.

The following site has a series of pages explaining how you service a "typical" inflator. This may be of use but try this at your own risk, you should be qualified before trying this! See:

http://www.amer-sea.com/serviceGuides/BCD%20service%20manual%20DRAFT.pdf

There is also a section on replacing the string on the over pressure relief valve below:

http://dir-diver.com/en/equipment/dumpvalve_mod.html

Recommendations

Unfortunately asking this list of questions will probably lead you to one answer - the solution isn't in your local dive shop, unless you are very lucky!

This may only leave you with two possibilities:

To go to one of the few specialist Halcyon/Extreme Exposure retailers like "Underwater Explorers" and buy a ready made backplate/harness and wing like the one above, whether by mail order or in person. This can be easily used with single cylinders and twin sets. (Links on fitting such systems are shown in "What Do I Need to Make My Own Buoyancy Compensator")
To buy the parts separately and make your own backplate/harness to which a wing can be attached. This should save you about £120 compared to buying the nearest equivalent backplate/harness straight off your local dive shop shelf. The pieces you would need are in "What Do I Need to Make My Own Buoyancy Compensator"together with a link to a site with directions.

If you should however decide to buy an alternate design, whether, a stab jacket or a wing, then it is worth seriously considering buying either second-hand or one of the cheaper more functional (simpler) designs. If you should then subsequently wish to upgrade, it won't break your heart. Second-hand buoyancy compensators can be easily leak tested by inflating them and waiting to see if they deflate; the valves can also normally be serviced quite cheaply as well. There are lots of second-hand stab jackets available at the moment, as divers upgrade to wings - which partly goes to show that they are the better option.

Return to

Home Page

Key:

Good/Essential Features.

Mixed Good/Bad features depending on the circumstances.

Bad Features.

Points requiring your consideration depending on your personal circumstances.

Warnings - Points to be very careful of.

Bitz Health Warning. This feature may seriously damage your health.

Tips, Ideas and general information for your attention.

General bullets.

Hit Counter Complements of http://www.digits.com.

Diving can be a hazardous sport and the information contained within this site is not intended to replace formal training.
Furthermore no responsibility will be accepted for any accidents, injuries or financial disadvantage, howsoever caused.

		Will it provide enough lift? About 14kg is typically enough for a single cylinder diver.
		Is it streamlined in the water?
		Does it have an internal bladder, which is protected by an outer shell?
		Does it have an over-pressure relief valve?
		Is the internal bladder bigger than the external shell to prevent it over-expanding and bursting?
		Can the bladder be easily inspected for punctures?
		Is it a reliable and proven design?
		Are the attachment points (D-Rings) in the right places? Can I move them about, as I need to, remove them or add to them?
		Will the buoyancy aid fit your size and shape and be capable of being tailored to you even if you put on weight or go on a diet? Poorly fitting equipment which shifts when the diver moves causes discomfort, stress and can affect the divers breathing.
		Does it incorporate a "hard" backplate to properly support the tank and fittings? "Soft" style supports generally move during use and are less efficient and secure.
		Is it a modular design which will grow with your diving?
		Does it have any impact on your upper torso dexterity, eg movement of arms, head etc?
		Is the corrugated hose the right length? Too long a hose will get in the way and is difficult to streamline.
		Will it provide too much lift? Do you really need a 100kg wing flapping around behind you, increasing the drag?
		Will it restrict your breathing if fully inflated leading to carbon dioxide retention by the body and increased narcosis amongst other symptoms? This flaw in particular can be present in stabiliser jacket style designs.
		You need to ask yourself if there are any superfluous/unnecessary features. This includes a range of things such as:
		Pull dumps - "string and bobble" pull dumps are subject to getting tangled up and are an unnecessary complication. Pull dumps can jam open making the buoyancy compensator useless. Sometimes the pull dump is attached to the corrugated hose, frequently pulling it may strain the connections and cause it to break free, causing the buoyancy compensator to become useless.
		Integrated weight systems - these clutter your upper torso as well as making the buoyancy aid unnecessarily heavy as a single item. They may also make the cylinder / BCD / harness so heavy that it will not float when taken off, this can get expensive if you need to remove it to get back into a small boat.
		Pockets - These clutter the upper torso and it is almost impossible to access anything contained within them without assistance from your buddy. The best place for pockets is normally on your suit.
		Double bladders (ie two BCD's in a single outer case)- the complications which arise can be self-defeating and can result in additional difficulties or tasking loading if a problem were to arise, eg if the spare inflator were to leak the diver may be unaware of the problem and try to correct it with the alternate inflator leading to an uncontrolled ascent. They are also larger than single bladder style wings, creating more drag
		Power inflates - these are bad news if they stick open since you will find yourself hurtling towards the surface before you have a real chance to control it.
		Bungies - These compress the buoyancy aid to correct the excessive bulk introduced by having too large a bladder in the first place. This can make it difficult to inflate manually if you have to; it creates additional drag due to turbulence over the uneven surfacecompared with simply using the right size of bladder or a "smooth" design and there is a greater risk of entanglement. It also suffers from problems of uneven inflation and off-balanced buoyancy due to potential excess compression on one side. Worst of all, if the buoyancy aid becomes punctured, it will deflate even if the hole is at the bottom whereas simple, non-bungied designs wouldn't.
		Plastic quick releases - these are subject to breaking at the most inopportune moments in what may be a potentially dangerous situation.
		Chest straps can put additional pressure on the diaphragm, increasing stress and discomfort and can again lead to carbon dioxide retention; increased narcosis etc
		Integrated alternate air supplies - this includes the "Autoair" and "Air II". These are supposed to eliminate the need for a separate octopus, but generally are of poorer performance and are subject to greater wear, tear and failure than a normal regulator, since it is not as easy to properly protect them.
		Mini/emergency cylinders - these are illegal in some countries, and for good reason. The mini cylinder is supposed to be used in an emergency either to inflate your jacket or to provide you with a couple of extra breaths. In practice, it should not be needed for emergency inflation because you would simply jettison your weight belt. The volume of air contained is also completely inadequate for an emergency air supply and the task loading required to competently use one in an emergency is too great. Mini cylinders have been known to be accidentally operated by being knocked and sending the diver rocketing to the surface.
		ABS and/or Plastic Backplates - whilst lighter weight, these can flex and break and should be avoided.
		D-Rings fitted to the side of the bladder in wing style designs. These are at best difficult to reach and worse if anything is carried here it will distort the shape of the wing, increasing drag. They offer nothing to the diver and are just another potential snag point to get caught or entangled.
		Reverse Bent Backplates - These include the Custom Divers Backplate and Portland Oceaneering Mk 2 Design. The Backplate is bent inwards towards your back to take a single cylinder. These have proved to be uncomfortable and are particularly unsuitable for diving with twin tanks. A single tank adaptor is more than suitable for use with a standard shaped backplate.

Key:
	Good/Essential Features.
	Mixed Good/Bad features depending on the circumstances.
	Bad Features.
	Points requiring your consideration depending on your personal circumstances.
	Warnings - Points to be very careful of.
	Bitz Health Warning. This feature may seriously damage your health.
	Tips, Ideas and general information for your attention.
	General bullets.
	Hit Counter Complements of http://www.digits.com.

Diving can be a hazardous sport and the information contained within this site is not intended to replace formal training. Furthermore no responsibility will be accepted for any accidents, injuries or financial disadvantage, howsoever caused.