There are many methods and different materials for building a boat these days. The four main materials most used for yacht construction are Wood, Steel, Aluminium and Fibre Reinforced Plastic (FRP). Glass Reinforced Plastic (GRP) is the well-known name for fibre glass boats. However, it is only one type of Fibre Reinforced Plastic (FRP) which is used these days. A lot of people have differing opinions of which is the best materials for yacht construction, and which is their favourite. There is no such thing as the perfect material, they all have good and bad points.
The beauty, warmth, and pure romance of wood as a boat building material is a virtue, compared with plastic or metal. Wood has good thermal and acoustic properties which other materials can’t match. With boats being mass produced these days, a wooden boat is as unique as her owner. Wooden boats are the best-known traditional way of building yachts. There are wooden yachts still afloat today which were built over one hundred years ago.
Most wooden boats built today are cold moulded using strips of wood and resin. Coating the wood in resin can reduce maintenance but will not eliminate all problems. Unfortunately, yachts were mostly made of wood, now they are mostly made of fibreglass. This has led to a shortage of skilled wooden boat builders. Ideally, wooden boats need to be built from hardwoods like teak or mahogany which is expensive. With forests shrinking, wood should be from a responsible source. Never from places where they destroy the forests. Responsible sources replant trees to make the supply of wood sustainable.
Steel is a material formed of Iron Ore and Carbon plus other elements. The elements used give the steel producers the mechanical and chemical properties they want to achieve. Steel has been used to build ships for over 200 years now. A yacht made from steel will be the heaviest out of all the materials. A steel hull can lose some plate thickness every year, so must be made thicker to allow for this.
Steel is very strong but being heavy it will have a high centre of gravity and not sail well. A superstructure made of Aluminium, Wood or FRP can help to lower the centre of gravity. Corrosion on steel can be a continuing problem and a maintenance headache. Some very good marine coatings are available on the market these days to help protect steel. However, if the yacht knocks or scrapes into something this can get damaged. Wood, Aluminium and FRP all burn, this makes steel the only fireproof material for yacht construction. It also has good green credentials as steel can be recycled.
Good strength to weight ratio, Aluminium is lighter than steel for the same strength. Aluminium is about half the weight for the same strength. A lightweight boat means a lower centre of gravity for better stability and sea worthiness. More speed for less power or sail area which means improved performance. Which is the main reason aluminium was used for racing yachts for many years.
Aluminium being a softer metal, it is easier to work into any shape required for a hull. Aluminium does not rust as the surface forms an oxide coating which protects it. It can suffer corrosion if dissimilar metals are in contact with it, or stray currents, but so can steel. It does not require added plate thickness to allow for corrosion. Aluminium is expensive but if you compare it with the weight of steel needed to build the same size yacht. With metal being bought in £’s per lb in weight, it will be nearly half the weight of the steel needed. Aluminium has good green credentials as a boat building material which can be recycled. Aluminium has a higher scrap value compared with Steel.
Fibre reinforced Plastic (FRP)
Fibre Reinforced Plastic (FRP). Glass Reinforced Plastic (GRP). Most people mistakenly call all fibreglass yachts GRP. However, some composite yachts are now built with other fibres like, Carbon Fibre and aramid fibres such as Kevlar® and Nomex®. Composite construction is basically a binder (usually resin) reinforced with a fibre material (like glass strands, carbon fibres, aramid fibres).
The three types of resin used is polyester, vinylester and epoxy. In the earlier days there were only Orthophthalic resins and they are still the cheapest. Isophthalic polyesters are more expensive but more water resistant. GRP boats moulded since about 1995 are now being moulded with the more moisture resistant Isophthalic resin. They are used for the gel coat and the outer layers of the hull, as water absorption into the hull, is the main cause of blistering.
E-glass is the cheapest fibreglass cloth commonly used. S-glass is the strongest cloth and has the best mechanical performance of the two. It has come from the aircraft industry and is expensive. There are various types of fibreglass mats and cloths used for boat construction. Ordinary mat (Chopped strand) is made up of random fibres held in place by a resin soluble binder. Woven Rovings is a bulky loose fabric and is used to build up bulk quickly and cheaply. Its interlaminar bond is weak so a good practice is to be inter-layered with chopped strand mat.
Fibreglass yacht hulls can be built with layers of fibreglass only. However, to achieve the strength and stiffness required, they must be made thick and then end up heavy. To keep the weight of a yacht hull down and achieve enough strength and stiffness. A lot of fibreglass yacht hulls are built with a material core. This can be end-grain balsa, foam or a honeycomb material. One method of infusing the fibre mat is hand lay-up. This is done by wetting the fibres by hand with a brush or roller.