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How to sail faster, use less fuel, and
reduce boat maintenance
Growth on the bottom of a boat can reduce its efficiency by as much as
10%. Once fouling has established a hold on a boat hull it will rapidly
spread or "colonize" the surface. Prevention is therefore better than the
cure of having to remove the fouling by scraping.
Fouling can pose a safety risk. Heavy fouling growth reduces
responsiveness of the craft. The added weight of the fouling can make the
boat sit lower in the water than intended. This can have obvious
implications in heavy weather conditions.
Furthermore, fouling can damage the boat. Prolonged growth of certain
types of fouling can damage the substrate of the hull. For example, the
natural glues which organisms use to attach to the hull can damage wood
and fiberglass. Fouling can also clog water intakes and cause damage to
Fouling also causes 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 on plane. For racing boats, this can be the difference between
winning and losing a race.
The best preventive measure is to coat the hull with a specially
manufactured boat bottom paint designed to inhibit growth and barnacle
attachment, to provide a reduction in friction with the water, and to
protect the hull for a long time. The benefits of coating the bottom are
less fuel use, faster sailing or motoring, the ability to clean the hull
by pressure washing rather than scraping, and less long term maintenance
with better resale value.
Antifouling boat bottom coatings are not meant to be cosmetic or
decorative. The best boat bottom coatings incorporate the large
polytetrafluoroethylene (PTFE) molecule which produces a drag coefficient
smoother than ice. One implementation, fluorourethane was originated by
the U.S. Naval Research Laboratories (NRL) in the early 1970s. It was a
combination of a fluorocarbon (Teflon™) molecule with a urethane molecule.
The material was unique in that it provided a surface with approximately
the same coefficient of friction as the Teflon®, was hydrophobic, UV
resistant, and at the same time provided an abrasion resistance four times
that of Teflon. The fluorourethane was originally tested on several ship
hulls for the U.S. Navy. One boat tested was a harbor tugboat in
Chesapeake Bay. The coating lasted 11-1/2 years compared to a conventional
hull coating which lasted only 18-24 months. Of major interest was the
fact that no rust or corrosion occurred under the coating.
The best coatings also employ copper. Copper has been protecting boat
bottoms from growth since the 1700s when Britain's Fast Ships, like the
Cutty Sark, raced from the Orient to England with cargoes of fresh tea.
While tin and other biocides have been used on boat bottoms over the
years, the proven standard still relates to the level of copper used. Yet
copper is not the only determining factor of how well an antifouling paint
will perform. The resin-binder system, the material that holds the paint
together, is equally important. In addition to holding the paint together,
the resin-binder system determines how fast the copper and other biocides
are released. The resin-binder system should be carefully tailored for the
amount and type of copper used to obtain maximum efficiency. The amount of
copper affects the life of an antifouling coating but the sophistication
of the resin-binder system to hold and release copper is far more
important to the effectiveness of the antifouling effect. The best
antifouling boat coatings release biocide at a nearly constant rate
throughout their lives. If the resin-binder is correct, lesser amounts of
the highly efficient copper biocide are needed to deliver the best
Antifouling coatings will retain their antifouling properties as long as
the coating is on the hull. Sanding between coats will add to the
longevity of the bottom jobs. By sanding the bottom you can get more coats
to adhere and forestall the day when too many coats means that you must
remove all the antifouling coatings from the surface and start over. The
boat bottom should always be sanded before an additional coat even if it
has just been power washed.
For more information, contact Harvey Chichester at
or phone 612-226-5200 (24/7).