(Ventilation Cont)

Benefits for FRP boats

The benefits to a Fiber Reinforced Plastic (FRP), or “fiberglass” boat are many. A good ventilation system will remove moisture from the interior, preventing mold and mildew from forming. A nice dry boat will also prevent the clammy feeling caused by damp clothing and bedding. The boat will smell better because bilge water will evaporate, and engine room smells will be removed. The box of snack crackers will remain fresher longer, and the canned goods in the galley won’t rust. There is less moisture-related damage to the electrical and plumbing systems, and the engine and mechanical systems will not be as likely to rust or corrode.

Condensation is a primary source of moisture inside an FRP boat. On my boat, there is a storage locker that is pretty well sealed from the rest of the boat. We keep our cold weather clothes in this locker so that they will be nice and dry when we need them on a cold and windy day. However, each time we needed to use these clothes, they were wet. I looked and looked for the leak that allowed water into the locker. After a couple of seasons of confusion, it finally dawned on me that the moisture in the locker was condensation. We installed a couple of small plastic soffit vents in the locker walls, and no more wet clothes.

Another issue that should be considered is that any fiberglass boat afflicted with gel coat blistering or osmotic moisture absorption will benefit. Fresh air moving through a boat will remove moisture from the inside. This is important. There are documented cases of boats that were not kept in the water, but water was left in the bilge, and the resulting high moisture vapor levels (humidity) inside the boat caused blisters to form on the hull. The hull laminate can actually dry from the inside, and conversely, hull moisture content can actually increase from the inside out.

Benefits for wood boats

We are often asked if coating only the outside of a wood boat with epoxy, effectively sealing it up, will cause the boat to rot from the inside out. My response to that question is always the same. If an uncoated wood boat is not well ventilated, it will rot from the inside out. As a matter of fact, most boats that rot do so from the inside out. There are a lot of wood boats in every major harbor, that you can smell as you walk by. These boats are not coated with epoxy on the outside, but they are definitely rotting from the inside out.

So the answer, in a literal sense is yes, an epoxy coated wood boat can rot from the inside. However, the epoxy-coated boat should have a much drier bilge, and therefore be easier to ventilate and keep dry on the inside. This dry, well ventilated boat will be lighter, stiffer, and will last much longer. The epoxy coating will certainly make the task of maintaining and ventilating the boat much easier. But an epoxy coated boat will not have a greater tendency to rot than an uncoated boat. The question of coating the wood boat hull with epoxy is more a question of how well you plan to ventilate it. If you do not intend to insure that the boat will be well ventilated, then do not glue planks together and coat the exterior. However, you can only improve the boat if you intend to keep it ventilated. There is nothing I like better than the smell of a well kept, well ventilated wood boat. But there is nothing I dislike more than the distinct smell of a rotting wood boat.

Storage covers

Storage covers should also have vents installed in them. Without proper ventilation, storage covers can do major damage to a boat. Many boats are uncovered in the spring to find mold and mildew growing inside. On a FRP boat, this is a big inconvenience. On a wood boat, this can be the beginning of the end. Once rot begins in a wood boat, it is very difficult to fix.

Nicro makes nice little clamshell vents that are designed to mount in either a winter storage cover or in a mooring cover. If the cover does not include vents, be sure to pull the cover out away from the hull so air can circulate around and under the cover.

One very important fact to remember is that a boat hull's purpose is to keep the water on the outside. Ventilating the boat will help keep the wet out and the dry in.

Photos and illustrations courtesy of Nicro Ventilation, A division of MARINCO-AFI. For information contact Nicro Customer Service, 2655 Napa Valley Corporate Drive, Napa, CA 94558, phone 707-226-96700.

Epoxyworks #13
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