Design matters, but material also counts: when buying a boat, in addition to technical evaluations, one might also choose to favour a wooden hull, for example, over a metal or fibreglass one. Let’s look at the various types of wooden boats, with their construction techniques, and some of their most common problems.
Old Wooden Boat Construction
Once upon a time, when wood was the only material available for building boats, wooden hulls were built around a strong solid wood structure using the planking method.
At some point, we saw the invention of marine plywood, and this construction technique changed. Basically, sheets of plywood were created and then laid around frames according to a process called cold moulding.
Carvel Method
Some planking boats were built in ‘carvel’ mode, where each plank simply rested against the next. The wedge-shaped spaces between the planks were plugged or caulked with a fibrous rope called caulking cotton. This ‘caulking’ was wedged between the plank joints with a hammer and a caulking iron to form a watertight seal for a few days, until the water swelled the caulking enough to completely seal each joint. When the boat was first launched, a few drops of water would often enter for a few days, but slowly the plywood sealed all its small holes and began to provide a watertight seal.
Clinker
Other types of wooden boats were built according to the clinker principle, whereby each plank is laid so that it overlaps, rather than rests on, the adjacent lower plank. The ribs and frames used are as in a carvel boat, but the clinker planking is usually slightly thinner, so the hulls are somewhat lighter.
Wooden boats: choosing plywood
Another popular and relatively inexpensive method of timber construction is the use of a special type of plywood, Bruynzeel marine plywood.
There are various methods of constructing plywood hulls. Hard chine’ hulls have plywood panels attached to frames as flat sheets. This technique is also used for some metal hulls, as it avoids the complication of bending the material to fit the required curves.
Or, we have the cold moulding method, in which a flat sheet of plywood is simply bent over a series of frames and fixed. Being quite flexible, plywood adapts relatively easily to this method of construction and the wood eventually settles into the shape naturally, even if it does put more pressure on the fasteners at first.
We often hear of ‘diagonal planking’, where ⅔ layers of plywood are arranged diagonally on top of each other. This increases the strength of the wooden hull and covers internal seams.
The benefit of plywood
The main advantage of plywood is its strength in whatever direction the load is applied. Conversely, plywood is inherently weaker along its grain and needs strong frames to support it precisely at the grain. If bare plywood is then coated with epoxy resin, it behaves similarly to an all-glass hull and is almost as water-resistant.
Furthermore, plywood is easy for amateur boat builders to use and creates a very strong monocoque construction that does not rely too heavily on the internal structure for strength and overall integrity.
Problems with wooden hulls
If a plywood hull is damaged or punctured and repairs are not carried out immediately, the unsheathed wood will act like blotting paper and absorb water into its veneer structure, quickly softening the glue and causing the wood to rot.
Wooden hulls have character, and like all creatures with character, they conceal much beneath their appearance. For anyone who has to buy a boat, having someone with solid expertise in wooden boats at their side is crucial.
For while a poorly maintained, old or flawed wooden boat will be a real pain to maintain, a good wooden hull can be perfectly equivalent to a metal or fibreglass one in terms of performance and maintenance.
Nowadays, the few boats built entirely of wood are often coated with an epoxy coating to protect the wood from the effects of ultraviolet (UV) sunlight and to make it completely impermeable to water.
Unfortunately, the most vulnerable areas of a wooden hull are usually the ones that are hardest to reach, and require just as much maintenance as the more accessible areas.
The deck beams are an area commonly prone to rot, as are the joints where the coach roof is attached to the deck. In particular, pay attention to the vertical planking, where vulnerable ends may have a piece of trim that keeps water out of the wood grain. In fact, wherever there is an added trim piece, you are more likely to have problems with water ingress and/or rot.
In any case, for wooden hulls even more than for others, it is advisable to seek expert advice.
Do you need the help of a marine surveyor to buy a wooden boat?