A summary description and evaluation of the products in the four groups:

Less environmentally harmful and biocide-free paints

It is estimated that a sufficiently efficient biocide-free alternatives for use on most of the Danish pleasure boats, meaning slow boats as sailing and motor boats have not been developed.

The biocide-free paints found on the market are in general very sensitive to the sailing activity. The anti-fouling effect is therefore very much dependent on how much and how fast the boat sails

On boats that do not sail very often, considerably more fouling was observed compared to the boats that sail very often.

Contrary to the biocide-containing paints, the biocide-free paints often result in speed reduction and impair the steerability of the boat. The sailing properties, speed and manoeuvrability of a sailing boat are reduced with these paints and must be described as unsatisfactory. Therefore, frequent cleaning on shore is required if these paints are used.

Some of the biocide-free products will, however, probably result in a reasonable antifouling effect on fast motor boats (over 15 knots) that sail frequently, as the fouling can be "sailed off" during navigation.

Of the biocide-containing paints, two of the copper based paints (Mille Ocean Test and Mille Solo Test) are good potentials for less environmentally harmful bottom paints that offer reasonable protection against fouling. It is true that more fouling is found on these paints compared to traditional bottom paints. But on the basis of a number of test, they are assessed to be acceptable for the majority of Danish pleasure boats, namely slow boats such as sailing and motor boats (Mille Ocean Test) and wooden motor boats and cutters (Mille Solo Test). These paints are formulated in low polishing versions (Hard Racing Test) designed for high-speed boats. Documentation for the effect of Hard Racing Test is very scarce.

The antifouling properties of the paints are, however, considered to be at the absolutely lowest limit. The copper release for the first 42 days is reduced by 50% compared to traditional bottom paints. It is an environmental advantage, as the bloom of algae takes place exactly when the boats are set afloat.

The paint SSC-44 (copper-free), is also assessed to be acceptable for the majority of Danish pleasure boat enthusiasts. It is, however, uncertain whether (due to the content of the biocide chlorothalonil) the product may be described as "less environmentally harmful".

Less environmentally harmful bottom paints

In general, all these bottom paints are assessed to cause more fouling than the above-mentioned paints (Mille Ocean Test, Mille Solo Test, Hard Racing Test and SSC-44).

The bottom coating will therefore primarily be suitable for high-speed motor boats and extensive sailing activity, as a certain amount of sailing will be necessary– especially with the biocide-free coatings – to keep the bottom free of fouling. Even at high sailing activity, supplementary washing will be required on certain coatings to maintain acceptable sailing properties.

It is probably only the epoxy-based copper paints that can be used on sailing boats, but as a high sailing activity is required in order to keep the bottom fouling-free, the copper coatings are probably not efficient enough for the typical sailing boat with a low or medium sailing activity. (It should be noted, however, that it has not been possible to procure much documentation for the effect of epoxy-based copper coatings in connection with this project).

Moreover,, the silicone coatings Seajet Speed and Veridian are assessed to be usable for extreme racing yachts that are taken ashore frequently and washed free of fouling.

In the light of these facts, the conclusion is that no sufficiently efficient biocide-free bottom coatings have been developed yet, that are usable for the majority of the Danish pleasure boats (slow sailing and motor boats), but that some of these coatings are suitable for high-speed motor boats and boats that are used very often.

Underwater washers

During the course of the project, four underwater washers were identified on the market, of which one (Rule) has, however, gone bankrupt.

Experience with testing the washers in salt water is scarce. Marina-Tec has so far only been tested in fresh water and Boat Scrubber is according to available information only used for cleaning of boats that have been treated with biocide-bearing bottom paint.

Only the Stark washer has been tested in salt water on the west coast of Sweden. Svenska Båtunionen (SBU) and Sjöfartsverket do not see the Stark washer as an alternative to the biocide-containing bottom paints in salt water. The washer is not efficient enough to cope with the heavy fouling – especially acorn barnacles – that is found in seawater.

On the other hand, the washer could be an alternative for certain types of boats in fresh water and brackish water where the fouling primarily consists of slime and a modest growth of algae

SBU finds it, however, much more efficient to take the boats ashore and wash the fouling off with a high-pressure cleaner.

A general advantage of the washer is that the fouling washed off is biocide-free, if the boats are treated with biocide-free bottom paint. The fouling washed off must be expected to be brought ashore for destruction to avoid decomposing and the risk of sea upheaval in the harbour.

How to handle the washed off organic fouling must therefore be clarified.

A disadvantage is that the washers are very bulky and take up space that corresponds to min. 5 berths. The location of washers will cause problems in most Danish ports. Especially the draught will be a problem many places.

Wear and tear of the boats due to the repeated mechanical washing process has not been evaluated but might be a problem, especially if the fouling on the bottom is hard, as is the experience in Sweden. Further, the Boat Scrubber is said to scratch the bottom of the boat if it is fouled with acorn barnacles.

Finally, the question about logistics is an essential problem. The Swedish Sjöfartsverket assess that boats in salt water must be washed once a week. In larger ports with for example 800 boats, 8 washers are needed, if they run 8 hours daily, 5 days a week.

A Stark washer is the cheapest solution. The price is about 350,000 SEK. In this example, it will probably be necessary to employ staff to carry out the many washings to avoid bottlenecks, and that will increase the washing price considerably.

Therefore, the conclusion is that presently the use of washers in Denmark is not a suitable solution

Other methods

The algae cloth is a, antifouling alternative that consists of a tarpaulin cloth fitted tightly around the underwater hull of the boat. The tarpaulin cloth prevents fouling from attachingto the bottom of the boat. 50 acorn barnacles were, however, observed on a test boat, and that is not acceptable for racing yachts and pleasure boats, as the sailing properties thereby are reduced. The tarpaulin cloth fouls on the outside (28 kg in a season), and widespread use of the cloth concept will require facilities for collection and removal of the large amounts of fouling.

The boat lifters either work by means of pontoons that are filled or emptied of water (Eurolifts) or by means of a lifting system that is mounted on a number of piles (Golden Boat Lift and Magnum Boat Lift).

A problem with the algae cloth and the boat lifters is that the boats are unprotected when the cloth/lifter is left. For that reason they are primarily usable for boats that are not used for longer voyages – contrary to most pleasure boats, which sail out during weekends and vacations

Both types of alternatives are individual solutions that only suit one particular type and size of boat. For that reason, the berth will not be suitable as a guest place when the permanent boats are voyaging. Widespread use of algae cloths/boat lifters in Danish ports with many visiting boats is not a possible solution.

Boat lifters will over a period of 15 years be about eight times as expensive as traditional bottom paints, whereas in terms of economy they are at the same level as the bottom paints.

Mechanical cleaning ashore was tested in 1998, treating 29 boats with biocide-free bottom paint. The method is not possible for yachtsmen and ports and extremely expensive, if used on a larger scale.

Future alternatives

Today, a number of biocide-free and less environmentally harmful bottom paints/treatments are being developed. The paints in question are a hard smooth coating, a silicone coating and an enzyme-based paint. The products will all be tested during the coming seasons, to evaluate their antifouling effect. Especially the enzyme- based paint is interesting and innovative, as the enzymes prevent acorn barnacle larvae from attaching to the bottom of the boat, without killing them.

The same effect has been observed recently in a substance called Katemin. A couple of years will go by before the substance will be used in bottom paint, as Katemin must be combined with other substances that are active towards other fouling types.

Finally, a Danish washer is being developed. The washer is at the prototype stage at the moment, and it is not known when it will be ready

To sum up, some years will pass before we can say anything about the coming alternatives’ effect as antifouling agents on pleasure boats.

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