As Gavan pointed out on TodayFM on Neil Delamare's Sunday Best show, he is quite exposed and the rules prohibit the use of sun shades. He is at the 17 degree line of latitude now, well below the tropic of Cancer. The constant rowing alone dehydrates him but doing so under intense sunlight takes away even more fluid. Combine this with having to rehydrate more than 80% of his food means he easily uses 5 litres of water a day. At this point in the crossing he will have used 25 of the very big bottles of water available in shops. He will need at least that much again. The rules also require him to carry 50L just for for emergency use and he must arrive with those drums still sealed to get a result. Obviously the boats are not big enough to carry that much volume and weight so all the crews rely on desalination units or watermakers for their drinking water.
Gavan has been lucky to be sponsored by Mactra Marine in the UK who lend a watermaker to one competitor every year. The smallest of these specialist units costs £5000 so this makes Mactra a very significant sponsor for Gavan.
The watermaker runs off the two 12volt car type batteries aboard Doireann. You read about Gavan’s concern for sunlight to charge these batteries and the main reasons are to make water and to steer the boat. The water works bysucking up water through a hole in the bottom of the boat and then pumps it across a rolled up sheet of membrane that has holes big enough to allow water through but small enough to catch salt. It take huge pressure to force the water across the membrane hence the large power consumption.
You will see a small plastic pipe at Gavan’s feet on his home page. This delivers the fresh drinking water to a 5L drum. You cannot see the tens times amount of water gushing over the side that is consumed to produce pure stuff. It takes about 45 minutes a day to make his water and he tends to do this around midday when the sun is at its strongest for maximum solar charging.
In the event that Gavan has a total power failure Mactra have provided a hand operated emergency pump that would allow the production of enough water to survive.
Ironically Gavan cannot simply drink the water from the watermaker. It is actually too good at removing salt and were he to drink it pure he would actually dilute his body’s own salts. So he adds salt tablets back into the water he drinks to make it isotonic. The pure water can be used to reconstitute his freeze dried food and of course he needs a bit to wash the salt from his solar panels and from his now, well publicised, nudie body.
Hats off to Mactra for their huge support.