| Antifoulings
There continues to be many changes
in the technology used to stop the growth of the
three main types of fouling (slime, weed and barnacles)
onto hulls and to prevent the damage caused by burrowing
organisms on immersed wooden structures. Small marine
organisms attach themselves to the surface and develop
into slime, crustacea and weed, all of which can
be extremely difficult to remove. The detrimental
effects of fouling on vessels are well documented.
Both the quantity and composition of the fouling
community varies widely from site to site and is
affected by temperature, salinity and water quality.
The different levels and types of fouling experienced
on vessels which are moored within, what would appear
to be, the same environment, can be quite dramatic,
as fouling conditions are affected by sunlight and
shade, the temperature and flow of the water, pollution
levels and freshwater inflows.
The right choice
Choosing the correct antifouling
is important. Factors such as vessel type, sailing
pattern & speed, geographic location and the
characteristics of the mooring should all be taken
into account. As well as environmental and legislative
issues where you sail.
Types of antifouling
Modern antifoulings tend to fall
into three different categories which are; Erodible
(sometimes called Self Polishing), Hard and Traditional/Soft.
Generally the raw materials used to make up antifoulings
in each of these categories is similar and it is
the proportions and quality of each raw material
that will determine the antifouling type.
Erodible
The most widely used antifoulings
at present are the erodible (self polishing) products.
By adjusting the nature of the resin systems used
it is possible to modify the characteristics and
the polishing rate of the antifouling. The resin
system is packed with active ingredients (added
to repel/discourage fouling growth), which once
immersed break down in a controlled manner, continually
exposing a fresh layer of biocide to the water.
In this way they provide consistently good performance
throughout the sailing season and reduce the unwanted
build up of spent antifouling on the hull. The new
generations of erodible antifoulings are faster
polishing than their predecessors, this gives you
the advantage of not having the build up of many
layers of old product and gives a more efficient
antifouling.
Traditional/soft
Traditional/soft antifoulings
are based on long established technology. Their
simple resin formulation means the active ingredients
are dispersed along with the binder, offering good
protection at an economical price. Traditional antifoulings
should not be sanded and should not be overcoating
with hard or erodible antifoulings, unless a sealer
coat is used, such as Underwater Primer. This type
of antifouling needs to be immersed shortly after
application - always check immersion times.
Hard
Hard antifoulings work
on a principle known as contact leaching. The resin
of a hard antifouling has a high proportion of insoluble
resin which does not allow it to erode. The resin
is packed with active ingredients so that each particle
is in direct contact with its neighbour and as each
particle is dissolved by the water the particle
immediately behind it is exposed.
Due to the hard nature of the antifouling it is
resistant to abrasion which makes it ideal for high
speed power boats, vessels which are mud berthed
and racing yachts where, if required, a smooth hull
can be achieved by burnishing the antifouling with
wet abrasive paper prior to the boat's launch.
Fouling grows faster in sunlight and is therefore
first seen on the waterline and the rudder. Dirt
and pollution in the water surface can close the
active material in the antifouling. It is therefore
recommended to apply extra layers of antifouling
on the rudder and the waterline to make these areas
resistant to frequent washing.
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