October 11, 2018

Australian Power Boat Magazine Review: The Bottom Line

One of the bugbears of owning a power boat that’s always moored in the water is keeping the hull free of unwanted marine life.

Boats that are kept in dry storage on trailers aren’t completely protected from the hassles associated with moored craft either. Many owners of shiny fiberglass power boats will have painful memories of lying on their backs, barking their knuckles on trailer beams, trying to clean off barnacles that have been allowed to dry whilst the boat was towed home or left sitting on the trailer after an extended cruising holiday.

The kinds of marine life that are likely to take up residence on a gleaming hull that isn’t anti-fouled or a hull where the anti-foul is past its use-by-date are many and varied. 

In general there are three stages in the fouling process. The first stage occurs immediately when you launch the boat. An organic film begins to adhere to and build up on the hull. Within an hour, this film is quickly colonized by micro-organisms, including protozoa’s, bacteria, and single-celled algae. This microscopic community called the “primary” or “slime” film forms the base and food chain for the growth of other sea life. Its quick growth is the reason why boats should be cleaned off at every possible opportunity.

The second layer, the macro-fouling group, is the one most of us get upset about. It consists of shellfish, barnacles, sponges, seaweeds, sea squirts, and even corals. As well as looking terrible and robbing you of boat speed, the macro group will attract a third layer of creatures that feed on and hide amongst the masses. This includes small crabs, free-swimming worms, starfish and even fish. But if you have left it to this stage, even your partner is likely to complain.

The pattern of arrival and the rate of growth of the various types depend upon a number of variables. Tropical areas can expect “more and faster” effects than temperate zones. Thirty days is long enough for heavy fouling to occur. 

The species that generally dominate are the ones that get there first. Smooth surfaces are less likely to be fouled than rough ones. Pits, grooves, seams and projections are colonized first. Many species are able to send out chemical cues to their own species that cause more settling in the vicinity. Organic pollution can add to the slime layer as a food source, increasing growth rates dramatically. Currents moving past the boat continually bring the food to the growths.

Since fouling rates are exponential, it doesn’t pay to procrastinate on cleaning. A little more often easily beats a massive once-a-season effort. 

Even a relatively light wipe down to get rid of the slime film will retard fouling. All this means that it pays to store your boat out of the water as much as possible. But if your boat is in the water for extended periods, 
It pays to:
  • Keep the hull clean, polished or anti-fouled.
  • Wash the bottom down each time it is pulled out, and remove barnacles etc. before towing the boat home.
  • Give the hull a wipe over each time you have a swim during extended cruises.
  • Avoid anchoring in tidal flows or polluted water.

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