Word on a wing
I am thinking of changing from a standard BC system to a wing. Which ones are best?
The prime feature to look for when shopping around for a wing is the bag volume you need to support your equipment configuration. For example, a single 10 litre cylinder will not require the same lift as twin 15 litres.
Look at the inflate and deflate systems offered by the wing. Does it have a dump valve at top and bottom so that you can use it in the vertical and horizontal positions? I use my drysuit for buoyancy and the wing provides redundancy, so I require only one inner bladder, but some come with twin bladders for wetsuit divers.
I prefer the wing to have rubber bungees around it, as these keep it stowed away neatly when not inflated, and reduce drag while swimming under water. It's also important to ensure that the material is robust enough to stand up to rough treatment in and out of the water.
The whole point of using a wing system is to keep the diver's chest area free of clutter, so I would avoid systems that add extra clutter - those with pouches, for example.
Where to put my hose
I have bought a 2m hose but I'm not sure how to stow it to make it easy to use and neat with my configuration.
There are two main ways of stowing loose hoses.
One is the "Hogarthian" system, where the hose goes under the arm and around the neck. This works well, even if you need to pass it to a buddy quickly - just dip your head.
I don't use the method, because my second regulator is stowed around my neck on a bungee necklace system and the long hose would sit over it, making access difficult. Instead I use rubber bungees on my right-hand cylinder and stow the long hose neatly up and down the cylinder. Access is very simple and quick.
I have been increasing my dive durations, which has led to the inevitable: I'm in dire need of going to the toilet by the end of the dive. Any suggestions?
This has always been a problem for technical divers, and I assume you are referring to urination, although you would not be the first diver to have an accident in a suit. However the drysuit diver needs an answer. I use large nappies. These are available from most chemists, though it is a little embarrassing asking for them, as the assistant will assume you have an incontinence problem!
The other option is the condom catheter (yes, they make female ones as well) attached to an overboard dump system on your drysuit. Both systems take some practice, and I have found that slow urination works best. If you're using the condom system, don't invert, as it gets messy! Good luck.
To manifold or not
I've started to carry out deeper dives and feel I need a twinset for the extra gas. Should these cylinders be independent or manifolded?
There are pros and cons for both systems. Independent cylinders give you a superb redundancy system, the downside being that you need to switch regulators throughout the dive to ensure that you are breathing each cylinder down equally. If you breathe one down to nothing and then have a problem with the second, you have no redundant gas.
With the manifolded system you can use the same regulator throughout the dive. However, if you have a gas-loss problem, for whatever reason, you need to be able to shut down the side with the problem, as you will be losing gas from both cylinders.
This shutdown can be done in a number of ways: I favour an isolator valve and an extended remote, which makes shutdown easy and quick, but it does require practice.
With either system, it is critical that the diver is always aware of which regulator comes from which cylinder.
Clear your head
After some dives, especially those on which I have been working quite hard,I surface with a severe headache. What is causing this?
This sounds like a Medical Q & A question, but in technical diving training I spend a lot of time teaching the correct breathing method to ensure that we flush out carbon dioxide. This is the waste matter produced by our bodies during metabolism, and what you have described are textbook symptoms of CO2 toxicity.
Early symptoms include an increased breathing rate and, in the worst scenario, blacking-out under water could occur, with the attendant risk of regulator loss and drowning.
Practise some breathing exercises next time you're in the pool. Inhale by slowly sucking the gas through the regulator for a count of about five seconds and exhale slowly for seven seconds, which ensures that you really flush out the CO2.
Ensure that your regulator is work-ing well, is easy to breathe from and regularly serviced. Never skip-breathe - taking a breath and holding it for a while before exhaling - because this builds up CO2. And don't wear diving suits or equipment that restrict your breathing.
CO2 toxicity is a killer. It also increases your risk of decompression sickness and oxygen poisoning, so do everything to avoid it.
Face the facts
I have seen full-face masks advertised - what are the benefits of this equipment?
A full-face mask (FFM) offers a number of advantages and, like everything, some disadvantages too. It is the perfect tool when diving in very cold or polluted water, as the face is completely enclosed. It also allows you to use underwater communication systems to talk to another diver or the surface party.
Also, if for any reason a diver became unconscious under water, he or she would still have a gas source, in contrast with the standard demand valve, which would fall from the diver's mouth.
Using an FFM ensures natural breathing from mouth and nose, which decreases the effort needed. However, this also increases a diver's consumption rate.
The FFM is secured to the face with a head harness, or spider, which ensures a secure fit and prevents jaw ache.
Some masks have been used for diver training and some disabled divers might find this equipment beneficial.
On the downside is the obvious problem of air-sharing in an emergency. All FFM divers are advised to dive with a spare half-mask and an alternative air source with a standard dv, so that in an emergency they or their buddy could use the back-up equipment.
Technical divers use various gases throughout a dive, and if you want to do this with an FFM you need a gas-switching block. The diver uses this device to plug in the gas required at that point of the dive, but must of course be certain of knowing which hose is for which gas. Most importantly the FFM, being so different from the standard dv and half-mask, requires practice.