Well, I started writing this article in May, and couldn’t believe it was mid way through the year then. I’m not sure where the time has gone since. I had only done 47 dives by then, so the year got off to a slow start. Most of those were teaching dives in Chepstow, I’ve not really done much this year for pleasure. Withdrawal symptoms are setting in.

So, what’s been going on this year? I was talking to Bob recently about dives and worked out that there have been opportunities to dive every month this year so far, and that many dives have taken place. That said, I’ve only received logs from one diver :P

There have been a good few trips, starting with a weekend diving from Skin Deeper in Weymouth in March. It was still a bit chilly, but it was a good set of first sea dives for some of the newer divers. 

Since then, we’ve had trips to Newquay, Eastbourne, Bracklesham, Swanage, and will hopefully have been to Lyme Bay by the time you read this. Of course, there have been the inland training sites of Chepstow, Buckland Lake, Stoney Cove, Vobster Quay and Wraysbury too.

For any dive, we normally have an idea of what the depth will be and how long we want to be in. The important thing here is to know the depth. Once we know what the depth is, we can decide how long we want to dive for. After that we can decide whether we have enough gas to do that dive, if we don’t we have to cut the dive duration back and re-plan.

So, once we have decided how deep we are going, and how long we want to stay we need to work out whether any decompression obligation will be incurred? This can be done via the BSAC 88 tables or by computer software. Some dive computers also have the ability to plan, however it can be tricky to do that on a small dive computer screen.

The goal here is to be confident that we are carrying enough gas to complete the dive with adequate reserve. The BSAC recommend using the rule of thirds. This means using one third of the gas to the halfway point, one third of the gas to get back from there to the surface out, and to surface with one third remaining. In order to be able to work out the gas effectively we need to know our surface consumption rate. This can be discovered by a number of means, the easiest of which is to sit on the surface breathing from a regulator and measure how long it takes to breathe a fixed amount in bar.

As long as we know the size of the cylinder we are breathing from we can then work out how many litres per minute of gas we breathe in every minute.

For example, let’s say we used 15 bar from a 12 litre cylinder in 10 minutes. We would know that we have used 180 litres of gas by multiplying the number of bar we used by the size of the cylinder. In this instance 15 x 12 = 180. If we divide this by the number of minutes we were breathing we discover that we are using 18 litres per minute.

It’s important to note that if we were sitting doing nothing while we were measuring how much gas we used, we would only discover how much we use at rest, so it is probably worth walking about gently while measuring.

Alternatively, measuring how much is used over a period of time while finning around a platform at an inland dive site would give a better result as it’s more realistic situation.

Once we know how much we breathe, what depth we are going to and how long we are planning to stay (including decompression stops), we can work out how much gas we need. Of course, we should include travel gas too as we need to breathe whilst moving between stops.

I’m happy to go over this if required. It’s part of the information that should be submitted prior to every dive in order to comply with the terms and conditions of the insurance.

So, it all got started with a warm up weekend in Weymouth. This was pretty much limited to Portland harbour due to weather, but was a good opportunity for early season shakedown. Lisa has another booked in February 2012, although I have a feeling it’s full now. Then we had Newquay over Easter, which was good fun and we were lucky with the weather. We dived in 30m of water or thereabouts which is quite unusual for Newquay. Fortunately for us, the skipper has ben given some new marks recently, so we got to dive some lovely wrecks in fairly shallow water. The viz was very reasonable too.

Speaking of viz, it was great on the Oceana on the dive from Eastbourne. Unfortunately the second day was blown out due to weather however the first day was excellent. I haven’t dived from Eastbourne for a while, so it was a welcome reminder of how good it can be. Dave and Sylvia who operate the boat are always good entertainment too. Since they are both qualified yachtmasters, one or other usually tries to get a dive in, and in this case it was Sylvia.

Swanage is always good, and we got to try out the new addition to the Swanage Diver fleet, Spike, as can be seen here 

This pic was taken just as the sun was coming up….

Pictures of Spike’s construction can be seen on the website here:- http://www.swanagediver.co.uk/default.aspx?p=newboat

It’s possibly a little bigger than Skin Deeper, and is very comfortable. There’ll be some dives booked next year on Spike I think.

Speaking of dives for next year, I am about to commence booking next year’s dives. Some of them are already on the calendar as you will have seen (it’s on the club website – http://www.batsac.org/DiveCalendar) and I’m about to add to it and also put some training dives on the training calendar. They’ll be on a first come first served basis.

I think I may also have procured a pool to use for training over the winter too. I bumped into a chap from Guildford SAC, and was discussing the lack of a pool. I’m going to meet the GSAC committee when I get back from Malta to discuss the detail, so fingers crossed!!

Speaking of Malta, I hope to have a longer article about the deep wrecks of Malta for the next issue of the newsletter. Lisa and I are looking forward to diving HMS Southwold – a Hunter class destroyer which lies in 70m, HMS Stubborn – a submarine in 56m, Le Polynesian – the 153m long 6650 ton troop ship torpedoed in 70m, Schnellboat S31 in 70m. If I’m lucky I might get the opportunity to dive HMS Russell – a pre Dreadnought, Duncan class battleship in 115m, or we may find HMS Olympus, an Odin class submarine known to be lost around Malta but still not located. I have to say, I am looking forward to a break, although have a lot of work to get done before we go on Sunday!!

See you all at the AGM if not before.

Jason