A REPORT ON THE EFFECTIVENESS OF THE ULTRA ANTIFOULING SYSTEM

By Dr. Eshelby-Burnham on Crouch

The Ultrasonic acoustic antifouling system was installed in May 2008, about two weeks after the boat had been launched. The objective was to reduce the barnacle infestation of the propeller, which had been a particular problem.  The boat is moored in Burnham-on-Crouch Marina. The River Crouch is tidal and, by receiving run-off water from agricultural land, is very nutritious; it is an area notable for build-up of hull fouling, both vegetable and animal.

Installation of the system was straightforward and the transducer ring was mounted on the hull with GRP filler; it was necessary to abrade the mounting surface of the ring to achieve good adhesion to the filler.  As recommended, Glycerine was used to provide the acoustic coupling to the hull.  The transducer was positioned just below the pear shaped anode, Fig 1, which was the only internally accessible place with a reasonably flat surface.

The system was connected to the Marina mains power supply through a power meter thus enabling power consumption to be monitored. The system was run continuously when the boat was left on its mooring and over a number of periods, each of several days, the average consumption was found to be about one unit per five days.

Apart from the Ultra system, the boat was anti-fouled with International Cruising Uno before launch. However, the propeller was left untreated as attempts at anti-fouling have been ineffective in the past; this is most probably due to the antifouling paint being stripped off by the hydrodynamic pressures acting on the propeller blades when under power. At the end of the previous season the propeller was very heavily fouled with barnacles, which adhered to both forward and rearward faces of the propeller blades and covered most of the surface.  There was also considerable barnacle infestation of the rudder and other underwater metallic parts.

The boat was lifted out for the winter in late October 2008 after six months in the water. There were a few barnacles on the propeller, but far less than before, perhaps 95%less. Fig 2 shows the extent of the infestation after pressure washing the slime from the propeller; visual inspection before pressure washing did not show substantially more barnacles present. It is notable that there was no calcium concretion on the propeller blades and that after pressure washing the bronze surface was clean. In previous years a concretion, presumable the result of barnacle attachment, has covered the blade surfaces. This would appear to support the claim that the system discourages barnacles from attaching to the boat rather than killing them after attachment. Unfortunately, there is only one photographs of the propeller from previous years for comparison, fig 3, and as some painting of the rudder and metalwork has been carried out it was probably taken some time after lift-out. It can be seen that there was considerable barnacle infestation present when compared with Fig 2.

There were very few barnacles to be seen on other parts of the hull, although this may be due to the conventional anti-fouling paint used on all other underwater surfaces. A few were present at the base of the rudder, around the skeg at the rudder support and on the steel keel strip. Vegetable fouling was not prevented and the usual build-up of slime occurred.

In conclusion, it can be said that the Ultra system has considerably reduced the infestation of barnacles and that the performance of the boat did not deteriorate significantly during the season.  The system has proved to be effective in discouraging barnacles and other animal marine fouling.

Fig 1

Fig2

Fig 3