This week we have been using the better weather to move forward the exterior winter tasks on our Sigma 38, Rho. Foremost amongst these has been the painting of the hull with anti-foul paint, designed to prevent/lessen the growth of weeds, barnacles, worms and other life on the hull, keel and rudder.
Even with the use of anti-foul there is a noticeable growth of slime and a beard of weed, which builds up once the boat has been placed in the water. On areas that are not covered in anti-foul, such as the propeller, there is often a healthy growth of worm casts.
There is no substitute for keeping up the sea mileage to reduce the growth – but practically we need to spend many weeks of the year at berth in muddy estuaries, such as our home in the River Hamble.
We have used many different brands of paint over the years – some seem to have almost encouraged the settling and growth.
The ethics of anti-foul are very direct:
- In essence any effective anti-foul is effective because it is toxic, thereby stopping the growth
of weed and crustacean. Traditionally the copper-bottomed warships of the Royal Navy were covered in sheets of Swansea copper. Copper is very toxic to plants and not good for animals. There is strong evidence that the Royal Navy ships could significantly out sail the French and Spanish because they have clean, low drag hulls and rudders
- Copper is no longer the chemical basis of anti-fouling. However anti-foul paints are self-polishing, so that over time the top surface is slowly eroded to expose weeds to a fresh chemical surface. Before big races or regattas we get divers to scrub the bottom to clean weed and expose fresh layers of anti-foul. It is not clear if the particles of paint that “self-polish” are part of the ocean’s micro-plastics problem
- We want a weed-free bottom to sail faster and more efficiently. But we gain this performance at the expense of shedding toxins into the environment
- We have considered dry-sailing (i.e. keeping Rho high and dry until she is needed for sailing), but we would still need to anti-foul for our summer races, cruising and longer courses.
The first step in anti-fouling is to remove the old paint. We always do this with wet sanding –to prevent dry dust being breathed in and being carried away by the air. Dedicated drains take the run-off water for recycling.
After stripping back we paint on 2-4 layers of new anti-foul, with the extra layers on the high wear areas of the hull, keel and rudder. Different layers are painted in alternate colours to ensure proper coverage. This year will be have a final layer of grey, on top of blue and black base layers.
We are trying sonic anti-foul devices, which are supposed to deter the settlement of weed with high frequency vibration, but we are yet to have the confidence to use these entirely instead of the anti-foul paint.