What’s best for a cruiser’s bottom?
QI recently purchased my first GRP cruiser for the canal system. Do you think it is absolutely necessary to use anti-fouling on freshwater and if so, how often should this be done?
ATLANTA24, via the CB website
ATONY REPLIES... It is not absolutely necessary, and if you do use it how often it needs re-applying depends upon the type. Environmental legislation has resulted in some types of anti-fouling being withdrawn. Those that were best for slow speed freshwater boats had a high level of poisons in them, so the paint film killed anything trying to stick to it. Some are designed to shed their surface at speed so would probably not work at canal speeds, while others contain copper. Each type will have a different ‘life’. If you take the boat home rather than keep it afloat, a quick scrub down each time you pull it out will be effective.
It’s advisable to take GRP boats out of the water every two or three years to check for underwater hull damage and also to check the rudder, prop, shaft and bearing; I suspect many inland GRP boaters simply scrub the hull at that time, much as the steel boaters do. At canal speeds, any fouling is unlikely to make a significant difference to speed/ fuel consumption.
One other point; many GRP boats run with aluminium outdrives or outboard motors, and if you apply copper-type anti-fouling to them, the case may corrode into holes in just one season due to galvanic corrosion.