Full details with prices and availability will be ready for the January club meeting on Wednesday January 4^th so make a note in your Diaries as we’ve already got some names with deposits down.

And Finally

Thank you very much to all the people who have supported the Dive Centre in 2005 and we know that most people in the club or just local to the dive centre are very loyal to us. We are fully aware that sometimes offers come along on either the internet or at the dive shows that seem to make the kit in the shop look more expensive, although on closer inspection this is not always the case.

In a year that has seen rents increase by 45% and sales drop by 12% nationwide every little helps. Add to this the fact that 5 Dive Centres have gone out of business in 2005 (2 in November) who all cited the main reason being a lack of loyalty from their own customers when the Dive Show rolls into town and internet stores selling cheap kit.

In the first instance this must be very tempting but keep in mind it’s the local Dive Centres that do training, trips, free advice and organize the clubs. It’s your call..

Merry Christmas and a very prosperous New Year 

FEATURE ARTICLES BY CLUB MEMBERS

From Rec to Tec. By Paul Hart

One of the most common questions I get asked by people new to diving, or those that know I dive but don’t dive themselves, is ‘how deep have you been ?'. My answer is generally the same – it doesn’t matter how deep you go, it’s how long you get to stay there that is important.

As we all know from our PADI training the maximum depth for Recreational Diving, even with deep diving experience is 40 metres, and you only get a few minutes there before you need to come up. Any idiot can make a 60 metre bounce dive on a single cylinder and, with a little luck, will probably get away with it if nothing goes wrong. However we regularly read and hear about people diving to much greater depths and staying much longer and still coming back to talk about it, so what gives - How do they do it ?  The answer is Technical Diving. This article hopes to explain a bit about the road to technical diving.

Technical Diving moves on from what we learned on our first few courses and extends our depth and time options. However it also requires very good dive skills, a commitment to training, more equipment, money and most importantly a change in attitude to dive planning. No longer can you just turn up jump in and do a dive. It requires the planning of every part of the dive, from depths and times to how much gas is required to complete the dive and still have reserves if your buddy needs them. Technical Diving means you will probably need  to perform one or more decompression stops before you reach the surface. These are not optional like a safety stop, and therefore going straight to the surface is not something you can do in the event of a problem. You must have a plan and enough gas to sort the problem out underwater. You notice I have said gas and not air, as for the most part air is only one possible option for what you will breathe during a Tec dive.

OK, so you want to get technical but you aren’t sure if your skills are up to it. What do you do ? OK hold it. If you need to ask this one then you probably aren’t ready yet. As I said before, your dive skills need to be top notch before you start. That’s not just buoyancy control but being able to think through a problem, sort it out underwater, and still be calm while you do it. You get this through practice and experience, that means diving and practicing your skills so you know you are confident in your own abilities.

Next is equipment. If you are going to stay longer or go deeper there is no doubt about it you are still going to need to breathe, this means more gas. For most this means twin 12 litre cylinders fitted to a wing instead of the normal BCD. They will be joined together by a manifold which can be isolated in the middle so you can shut down one reg or cylinder in the event of a problem. On each cylinder will be a separate first and second stage regulator so you have the option to breath gas from both cylinders through each reg or shut down either side and breath from the other. Additional cylinders – normally 7 litres to start with can be clipped under each arm to hold different gases to help speed up decompression. More about that later.

OK, you’ve got the skills, you’ve bought the new shiny kit, lets go....... wait, wait not yet. Now you need to learn some more – time for more training.

First comes Nitrox. This is a slight grey area as an entry level Nitrox course like the PADI Nitrox Speciality would teach you to use Nitrox for no decompression diving. Most dive computers can now be programmed to use Nitrox and, if you don’t go beyond the depth or time limits, you can use it just like air - you just get longer in the water. But lets assume we are talking about Nitrox as a technical gas.

Up until now you’ve been breathing air – 21% oxygen and 79 % nitrogen (more or less).  Nitrox uses the same gases but you get to choose different percentages, normally containing more oxygen. The most popular mixes are 32% and 36% oxygen sometimes call Enriched Air Nitrox or EAN 32 and EAN 36 although nowadays with modern gas blending systems almost any mix is easily achieved. Adding more oxygen means less nitrogen so less narcosis and longer dives than when using air at the same depth – sounds great but there is a catch. Oxygen is toxic and our bodies are designed to breathe 21% at ambient pressure. As we dive deeper the pressure of the gas we breathe goes up forcing more nitrogen and oxygen into our bodies. The nitrogen goes into our tissues and we deal with that by slow ascents and/or decompression stops, but we burn, or metabolise the oxygen. Feed your body too much oxygen and it will be unable to deal with it and bad things happen, normally convulsions or unconsciousness – both very bad underwater. So Nitrox is great for giving us longer times at shallower depths and can make shorter dives safer by reducing nitrogen build up. And, as long as we stay above the oxygen toxicity depths, it can be used just like air. For Technical Diving we use Nitrox to extend dive time at recreational depths and at higher oxygen percentages during decompression. Mixes of 50% or more are commonly used and sometimes 100% oxygen. This helps to flush the nitrogen out of out bodies faster and reduces decompression time. High oxygen percentages are only used at very shallow depths during decompression – 100% oxygen is toxic below 6 metres !

Right, now we can stay longer but we can’t go deeper because of oxygen toxicity if using Nitrox. OK, lets go back to air – air has less oxygen so we can go deeper but all that nitrogen means if we want longer dives  we’ll go into deco. We still have a depth limit even on air, that oxygen is still there and toxicity is still a problem, however the limit is now around the 55 – 65 metre mark depending on how hard you want to push the limits – and, for the reasons above, you do not want to push the oxygen limits. At these depths bottom time is a couple of minutes then you are into deco. Damn, all that nitrogen is going to take ages to get rid of and now we have to stop on the way up to let it come out slowly. But wait..... if we breathe Nitrox with a high oxygen percentage on our deco stops it will flush that nitrogen out quicker – if we breathe the maximum oxygen percentage we can, it will come out really fast compared to doing the deco stops on air. Welcome to Extended Range diving. This course teaches deep diving on air and how to use a different gas mix, up to 100% oxygen to reduce decompression times.

OK now we are cooking, deep diving here I come I hear you shout. Nope ‘fraid not, you forgot narcosis. All that nitrogen is going to cloud your brain the deeper you go, just like drinking alcohol your reactions and ability to think a problem through will slow down. In fact the tongue in cheek Martini’s law states that 30 metres has the potency of 1 Martini, for every 15 metres after this add another one. Everyone is different when it comes to narcosis and some are affected much more than others, but everyone is affected, that is a fact. Learning to recognise and deal with it can only be done by progressively building up your deep diving experience. Anyone who says they do not get affected by narcosis is just like the drunk who says he isn’t – the only one that can’t see he’s drunk is him.

So it seems we are stuck with shallower dives on Nitrox or deep dives on air and all that narcosis and deco. Not quite. Enter more training and the wonderful world of Trimix. What if we could take some of the oxygen out to let us go deep AND take some of the nitrogen out to reduce that narcosis. Sounds great but if we do that we need to add something. That something is helium, a very light gas that isn’t toxic at depth and has a very low narcotic effect compared to nitrogen. Now we can dive to very deep depths and still have a clear(ish) head, and if we get the oxygen levels correct in the mix, we have no problems with oxygen toxicity. So now you can get to see that wreck at 55 metres and remember what it actually looked like and spend a bit of time there before heading back to the surface. Only one last problem and nobody can fix this one – deco time. Helium doesn’t help, if anything it’s worse, so you are still going to spend time doing the deco stops - get used to some boredom and holding your bladder ! However, if you are interested in club trips like those to Scapa Flow which involve deeper diving the benefits of Nitrox and decompression diving will be obvious – you get to spend more time on the wrecks.

Copyright Harry Hayward (in Red Sea, Egypt)- Technical Diving Instructor

Oh and one last thing, money, yes all this is going to cost you. You'll need more kit and the cost of gases like trimix can be expensive. Some would say is it all worth it, and for many it’s not what they want from diving. However the next time you are diving a beautiful wreck in 40 metres and you run out of bottom time in about 9 minutes, give me a wave as you leave – I’ll see you back on the boat in about an hour. 

For those that want to stay a while longer or visit places beyond the reach of recreational diving, have a chat with the shop about Nitrox courses, the first step towards technical diving, or come and have a chat at the club meetings.

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