TRIED & TESTED


Ultrasonic antifouling F


or the past seven months, my fiancée Kirsty and I have been testing the Ultra 10 unit from Ultrasonic Antifouling on


our Sadler 32, Pixie. Throughout the last sailing season the unit has been quietly chirping away, day and night, like a small bird trapped under the cockpit. It cycles through frequencies from 20kHz to 140kHz, avoiding 200kHz (used by echo sounders) and 50kHz (used by fishfinders). To be effective, it has to operate for at least 15 hours a day, or during daylight hours.


Bad vibes The theory behind ultrasonic


antifoul is that these frequencies resonate the single-cell life forms that settle on our hulls in their millions, in much the same way as a wet finger resonates the rim of a wineglass. Find the right frequency and the glass will resonate so much that it cracks; do the same


with the single-celled organisms and they will be destroyed. Destroy the source of food for barnacles, sea-squirts and other fouling nasties, and your hull is no longer a good place for them to set up home. The transducer needs a secure bond to the hull (see the May


Graham Snook reports on a seven-month test of a revolutionary


antifouling system that uses ultrasonic sound waves, rather than paint, to keep a yacht’s bottom clean


LEFT: Ultra 10 transducer and control unit. BELOW LEFT: We fitted the control unit under the chart table seat. BELOW: The transducer was epoxied to the hull


Power problems That’s the theory, but does


2010 issue), and once fitted, the tightness of the unit needs to be checked at least monthly. Anything securely attached to the hull should conduct the sound well, but most rudders and propeller shafts are acoustically isolated from the hull, so they may suffer more fouling.


LEFT: The prop and shaft were encrusted with barnacles in 2009, but this year there was hardly any fouling. BELOW: There was a lot less slime than usual on Pixie’s keel at the end of 2010


it work? Before you get your credit card out, consider the power consumption. Ultrasonic Antifouling offers units that run on AC (shore power), DC (the ship’s batteries) or both AC and DC. I chose the 12v DC version. When we are plugged into shore power, the battery charger powers the 12v system. All was going well until Pixie’s circuit breaker tripped when we weren’t on board. With no shore power and our wind generator switched off, the Ultrasonic Antifoul merrily ran the house batteries down to 26%. The manufacturer has now


rectified this problem, so the unit will switch off when the batteries reach 11.8v. From then on, we left the wind generator charging all the time. Having a constant battery drain is worrying for long-term cruising – the unit needs around 16A every 24 hours. Finding power is easy if you can plug in every few days to top up the batteries, but in the Scottish Highlands, with an alternator that wasn’t charging, the chirping was a nagging reminder that we were using up precious power. The circuit breaker tripped again, when we’d left Pixie for six weeks. Even with the Rutland 913 wind generator on, the batteries were down to 68%. (The Rutland needs at least 8 knots of wind to work effectively – see group test, October 2010 issue.)


Did it work? Pixie’s performance usually


declines gradually over the season as the hull fouls progressively, but I haven’t noticed any decline in boatspeed this year. Also, I no longer have to clear the log impeller if we haven’t left our berth for a few weeks. When I first saw Pixie’s hull rise out of the water at the end of the season, I was disappointed. I was expecting her bottom to look like the day she was launched, back in March, completely slime free


PHOTOS: GRAHAM SNOOK, LESTER MCCARTHY


Antifoul paint only


Antifoul paint + ultrasonic


Antifoul paint only


Antifoul paint + ultrasonic


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