November 2015 – What no bubbles?

Report by Paul Clunas who got all excited over his first try dive using a rebreather!!

First Rebreather Dive – Sunday 22nd November 2015

We have all observed these divers with what looks a vacuum cleaner strapped to their back and my curiosity as to the attraction of these ‘Dysonesque’ contraptions got the better of me last week-end, Vobster quay were offering a try dive on their Sentinel rebreather and I jumped at the chance.

The guys at Vobster (VMS) bought the right to make the recreational version of the Sentinel and have been refining the technology with a great deal of attention to detail and thought on safety, design and high quality components (the mushroom valves in the mouthpiece are also used on the Eurofighter!)

The result is the Sentinel Redhead which is an awesome piece of kit!

What appeals to me about the Sentinel is the fact that is not customizable, and requires the minimum of intervention, it’s like a car with all the necessary added extras and that’s the way the manufacturers like it as it is 95% user interference/error that kills rebreather divers (and rebreather divers partners when they find out how much they really costs!)

After the customary bacon butty and tea we had a briefing on the fundamentals of a rebreather and how the Sentinel has been engineered to deal with them. Then it was down to the water’s edge for a one to one briefing with my instructor, Martin Robson, who is acclaimed as one of the leading tec, rebreather and cave diving instructor trainers in the world and a brand ambassador for VMS.

The main issue with rebreathers is buoyancy control, with open circuit if you inhale (more gas) you rise and exhale (less gas) you drop whereas with a closed circuit the amount of gas in the loop remains constant, if for instance you clear your mask thereby taking gas out of the loop, the system knows and will add more gas in via the automatic diluent valve (ADV)!

What immediately strikes you on entering the water is the gas you are breathing is moist and warm; there is no breathing resistance and its quiet! It takes a little while to sort out buoyancy and get used to the breathing, it really does mean you have to learn to dive again. Before heading off basic drills had to be carried out such as using the bailout valve (BOV) and bailing out completely onto open circuit (11 litre ali’s)

After 40 minutes in water (surface 12 degrees/ depth 8 degrees) returned to surface and noted how warm I was, this coupled with the ideal PPO2 at all times, moist air (note open circuit air actually takes moisture out of your body leading to dehydration) I can really understand why these units take away many of the predisposing factors to DCI away as well as the depth and time advantage.

Would I buy one? The Redhead currently sells for £7,950 and service costs every two years/200 hours are £325, it’s like buying small car! Will Santa be able to get one in my stocking? Watch this space!

If you share my curiosity I would whole heartedly recommend a try dive – at £60 (including the usual entry fee) I feel it is excellent value and a great experience.

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