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Surfaces that receive indirect UV exposure, such as those below decks, will last much longer without a protective coating than directly exposed surfaces. While a clear coating has an inherently shorter life span than a paint finish, there is a tradition among wooden boat owners of using clear coatings to preserve and enhance the natural beauty of wood. For many, the major attraction of wooden boats is the beauty of wood itself and they are willing to invest a lot of time and money to achieve near perfection in their wood finishes. Unfortunately, these beautiful finishes distributors of bear board plastic lumberseldom last forever because of exposure to the sun. The boats must ultimately be stripped down and redone, usually at great expense. Because of this, owners want the finish to have the longest possible life span. The first phase of finish breakdown is loss of gloss, so surface gloss retention is essential for coating longevity.
Clear coating breakdown by sunlight has two root causes. The first is the gradual breakdown of the coating material. The second is the slight chemical and physical change which takes place within the surface wood cells affected by the sunlight through the clear coating. It is thought that this change in the wood cells contributes to the coating failure by promoting a physical separation of an already weakened coating from the ultraviolet-altered wood surface. We are often asked how long a coating will last over a wooden surface. The answer is not simple because the life span of any coating depends on many factors. We consider the following to be the most important: 1. The number of hours of exposure to sunlight in a given climate. Cloudy climates are less hostile than sunny climates. A southern Florida location is far worse than one in Maine because on average the solar radiation in Florida is less filtered by the atmosphere. aluminum fencing panels ukProtecting and Maintaining Wooden Boats 48 7 2. The angle of the exposed surface to the sunlight. For example, a deck will receive much more direct radiation at high noon, when the sun's destructive UV rays are most damaging, than would cabin sides.
3. Highly glossy surfaces are more reflective of UV rays (and thus less vulnerable) than are dull surfaces, no matter what the color. 4. Lighter colored woods are more reflective than darker colored woods, just as lighter colored paints are far more reflective than are darker colors (Figure 7-1). 5. Thicker clear coatings last longer and offer more protection than thinner coatings. 6. Varnishes with large amounts of UV inhibitors last much longer than varnishes without this additive. Modern two-part polyurethane varnishes last longer than the more traditional phenolic varnishes. attractive composite products suppliers7. A high-strength epoxy resin undercoating, such as WEST SYSTEM 105/207 mixture, when used as a saturation coat under a varnish, provides a greater life span than the use of varnish alone.
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