The Hull-to-Deck Joint

Have you ever seen, or been in a boat where the interior was full of mildew, the cabinets and storage areas have rust stains, or the rails were dented with screws missing or protruding? Maybe there’s puddles of water, water stains and mildew in cabins and perhaps the hull is “decorated” with protruding screws and water stains. If you have, then what you probably saw was the effects of a leaking hull-to-deck joint.

Unfortunately, a lot of boat builders, and owners, don’t really give much attention on how the deck is attached to the hull. That’s because creating a deck joint that is both strong and water tight is a time-consuming operation, and the results may not immediately recognizable.

In fact a many boats, large and small, power and sail, will have inferior deck joints, due to the fact that the effects of a weak joint doesn’t show up until the boat is been used for a long time, probably years after its “maiden voyage”.

Here’s why. Most decks are simply attached by screws. The deck essentially fits over the hull much like a shoe box lid and then an application of some caulking in the gaps and driving screws through the two parts, as shown below:

You can imagine what would happen if you drilled a hole in a plate glass window and ran a screw into it. Plastic and glass fibers are not much better in supporting screws subjected to impacts and heavy loads, as a deck joint will certainly be. Eventually, the screws will work out and the boat starts leaking, and those telltale signs appear.

While you’re checking those joints, check the rest of your boat’s condition as well. Investing in high quality canvas coverings from CMC Canvas LLC will protect and everything on and in it as well.