Why do wooden boats sink?

Answer 1

boats need buoyancy to float, any boat is heavier than the buoyancy of its materials can support that is why a boat has the familiar hull shape. Water is displaced by the v shape of the hull, the width and depth of the hull is determined by the weight of the boat and its cargo. An air filled cavity is formed below the water level that is equal to or more than the amount of air space ( water displaced ) to support the boats weight in the water. If you have ever noticed the more weight you put in a boat the lower it gets in the water or the less buoyancy it has. Once this cavity is breached either by a hole in the side or water spilling over the side and filling up the hull it adds weight to the boat and lessens its buoyancy until the vessels weight overcomes the hulls ability to hold it above water and it sinks. You can test this by floating a board on water, it sits pretty much on top of the water proving that a piece of wood has enough buoyancy to stay afloat. Add another piece of wood on top and the combined weight of the two makes the first piece sink below the water line of the second piece. Some types of wood have more air trapped inside and therefore have more buoyancy but never really enough to support the weight of multiple pieces. In every instance an air cavity must be formed to increase the buoyancy of the material to compensate for its weight. A solid wooden boat will not sink. Well not at first. If the boat is truly made of nothing more than wood, it will float even if completely full of water. This is due to the cells of the wood still has trapped air in the cells of the wood. Over time the water will saturate this area and it will then sink. This is called being water logged. The reason modern wooden ships sank was because they carried ballast stones and cargo that weighed it down. Older wooden ships had bronze cannons, metal buckling and lead ammunition that addded to the negative bouyancy of the wood (usually English oak) and it would sink like a stone. One of the exceptions to the rule is cypress. It is so dense, it will not float.