The single worst problem with the overwhelming majority of todays boats is excess moisture trapped belowdecks. When a boat sits on a mooring, there is usually a big differential between the temperatures inside and outside. This is because boat decks can reach 120 degrees or more (darker colors can reach 170 degrees) on a sunny day, even if the air temperature is only 75 degrees. The hot deck heats the interior air, which, without ventilation, can reach high temperatures.
This in itself would not be a problem without a ready source of moisture, the worst being a wet bilge that can quickly create 100-percent humidity inside the boat. Air that is 100 degrees or hotter at 100-percent humidity can support 18 grains of moisture per cubic foot of air. In comparison, the 75-degree air outside a boat, at a normal 60-percent humidity would hold less than six grains of moisture.
Unless this large disparity is corrected with appropriate ventilation, dire consequences will result. Moisture vapor in combination with air is a potent gas that can permeate most materials, including fiberglass and wood, with surprising rapidity. The carnage resulting from this subtle and little understood enemy is huge. In fact, it may be the major contributor to the aging process of todays fleet.
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