Blistering
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Fiberglass boats develop a condition known as blistering, generally below the water line. There are varying opinions on the precise causes of the condition, and some sensitivity among boat manufacturers about this issue. The appropriate method of repair is also somewhat controversial. Over the years this issue have seen the inside of many courtrooms.
There is little dispute that the condition is caused by the interaction of the components of a fiberglass hull and water. Some people believe that the condition is more prevalent in salt water and others believe that fresh water is more reactive. Fiberglass is not a 100% waterproof surface; over time water is absorbed into the resin either from the inside or the outside. Ironically efforts to seal the outside of the boat trap water which is absorbed from the inside. Many manufacturers do little to waterproof the boats from the inside, and ineveitably some water will collect in the bilge and other areas of a boat.
A common cause of blisters is a reaction between the water and the chemicals in the resin, which forms another fluid compound that collects between the fiberglass and the gelcoat which is the smooth surface over the fiberglass. Sometimes amateur repairs will cause more serious problems down the road, as negative synergistic reactions occur between the chemicals in the original glass-work and the compounds used for the repair.
A preventative measure is bottom-paint which is water proof, and protects the gelcoat. Bottom paint is expected to wear off with time and is periodically replaced every two to four years. Minimizing the water in the interior of the boat is also a good practice.
