There are three basic types of bottom fouling, each of which has its own characteristics:
Weed comes in a variety of forms. Static objects will attract common seaweed, many forms of which will simply fall off when a boat hull begins to travel through the water. However, some weeds such as Brown Weed, are more resilient and can withstand quite high speeds through the water.
Why does fouling vary so much between areas? Different water qualities and temperatures produce different types and breeds of fouling. The differences can be quite dramatic, even in one region. This is due to outfalls, pollution, inflows from rivers and streams, the flow speed of the water, and even shading from cliffs, trees, and buildings that reduce sunlight. Once fouling has established a hold on a boat’s hull, it will rapidly spread or colonize the surface. Prevention is therefore a better approach than seeking some other cure or attempting to remove the fouling by periodic cleaning and scraping.
There are a number of key reasons to keep your hull free from these sources of fouling. Safety is the principal reason. Heavy fouling growth reduces the responsiveness of sailboats and powerboats as well. In extreme cases, the extra weight of the fouling can make the boat sit lower in the water than intended. This can have obvious implications in heavy-weather conditions.
Speed and efficiency also figure into the reasons why you’d want your hull to remain free of fouling because extraneous growth or materials on the hull cause drag. As drag is increased, fuel consumption increases and speed is reduced even to the point where a planing hull may not be able to get up on plane. For racing sailboats, this can be the difference between winning and losing, and for offshore and coastal cruisers, it can mean that a voyage takes longer than planned, which in itself has any number of consequences.
Recreational and commercial craft have been battling the fouling issue for centuries, and some progressive resolutions have begun to appear (see sidebar).
Keeping it Clean
Because the additives in bottom paint that deter marine growth also have been found to cause major damage to marine habitat, the evironmentally concerned boat owner should consider all the options. Here are a few alternative approaches to antifouling. Lack of experience with each makes difficult for us to offer recommendations, but they’re worth investigating on your own: Sounding Off The manufacturers of a number of different devices tout success with sonic antifouling. One that goes by the name Barnaclean features small electronic nodes installed inside the hull that create a low-frequency "shield" to keep the hull free of growth. The system reportedly uses a miniscule amount of current.
Smooth Skins Synthetic coatings designed to repel growth, such as Marine Skin, boast no cacinogens, nor copper or tin. Some, like Seal Coat are silicone based and use a series of electrostatically charged microfibers to repel growth. Others like Wearlon boast self cleaning properties if your boat travels as sufficient speeds.
The Bottom Paint Blues by Don Casey
Combatting Bottom Growth by Mark Matthews
Spring Hull Cleaning by Tom WoodSailNet Store Section: Cleaners, Polishes, and Coatings