For those that are new to the sport after your basic kit you will need some form of Buoyancy Compensator, a regulator set and a cylinder. The good news is that the club has all of these for you to use!
- Firstly you need to get a BC that is the correct size for you, If you look on the inside you will see a letter – S, M or L, small, medium and large respectively. With the correct BC you now need a cylinder to attach to the BC.
- There are cam bands on the back of the BC that you drop the cylinder through, don’t take apart the buckle to put it on as it is far easier if you don’t have to re-thread this. Point the cylinder valvle towards the front of the BC and tighten up the cam bands. If you pick up the BC and give it a shake you can check if the cyclinder is tight (it shouldn’t move).
- Now you need a regulator set. Remove the dust cap and tighten the clamp onto the cyclinder valve, making sure that the regulators run over the right shoulder of the BC. Connect the BC feed into the direct feed and secure the hose into its retainer.
Your gear is now good to go, once you have done a self check of it.
The self check: hold the pressure gauge agaisnt the cylinder and turn the cylinder on. If everything is correct you won’t hear any hissing and you can check all of the gear. Check the cylinder is full, breathe off both regulators checking that the pressure gauge doesn’t flicker, the regs work and the air tastes fine. Inflate the BC to check that it holds air and it can dump the air again.
Assuming everthing is ok switch the air off and carry it into the pool if it’s a training night, or if you are going diving dissasemble the gear, pack it into cars and go diving
There are 3 types of Buoyancy Compensators available to the Scuba Diver. The old style ABLJ, the common STAB and the less common wing. They all do the same job which is to allow the diver to obtain neutral buoyancy whilst diving and provide positive buoyancy whilst on the surface.
The Club has a number of STABs, which are there for everyone to use, and a number of people in the club dive with wings.
The club has several STABs that we use for pool training and diving in sea. They are designed to be worn like a waistcoat and as a result are quite comfotable. On the back they have bands that are designed to strap a cyclinder to. On the front/sides there are pockets for stowing gear such as DSMBs or if you prefer you can clip gear onto the D-rings.
The corrugated hose is called the direct feed and is designed to allow the diver to be able to add and release air from the STAB to achieve neutral buoyancy. When setting your kit up you need to connect a low pressure hose from your reg set into this to allow air from your cyclinder to be added to the STAB.
This is the older style of BC and is no longer used by the club. They have a different nipple to the STAB’s and in the event of your buddy running out of air you can breathe off the direct feed so you don’t require an octopus on your reg set.
A number of club members own a type of BCD called a wing. They are very similar to a STAB execept that the bladder (the part that fills with air) is located on the back rather than the back and sides. Wings don’t have pockets.
- First Stage – Takes the cylinder pressure down to the interstage pressure which can be handled by the second stage
- Second Stage (Regulator) – Makes the air breathable at ambient pressure
- Octopus – Spare regulator on a longer hose for you or your buddy
- Pressure Gauge – Shows cylinder pressure in bar and all club regs must have a depth gauge.
- Drysuit Feed – All club ones must be old style posidon feeds which also fit the club ABLJs
- STAB Feed – These are AP Valves buddy feeds. They might fit other non-buddy equipment but should not be used on anything but club STABS.
The club currently uses steel cylinders for our diving. Most of these are 10 litre cylinders, but we do have some 12 litre cylinders that are kept O2 cleaned for use with nitrox. Note that there are certain cosmetic and technical differences between steel and aluminium cylinders.
Steel cylinders have a noticable neck and looking past the bottle-boot, a curved base. Steel cylinders weigh less then aluminiums of the same volume above water, and more below.
Aluminium cylinders have no neck and always have a flat base. You will require approx 4 pounds (2kg) more weight with an aluminium tank than when diving with a single 10 litre steel cylinder. Towards the end of a dive aluminium cylinders become more buoyant.
Note about relative buoyancy
As you may well remember from the joyous training lectures, Archimedes principal finds the weight of something in water is the difference between the weight of displaced water and the weight of the item above water. Large items displace more water so have a greater upthrust.
Aluminium (ally) cylinders require more material to make them strong enough so a 10 litre ally cylinder will be larger then a 10 litre steel. It will therefore have a greater upthrust. A good quality steel cylinder will also weigh less above water but being smaller makes it slightly heavier under water.
The slightly less obvious bit – A 10 litre cylinder holds around 2kg of air, both Ally and Steel cylinders will be this much lighter at the end of a dive but the Ally will feel much more boyant in the water because the difference in weight loss relative to its in-water weight is greater then the difference with steel.