Composite materials in the superyacht industry
Written by Sarah Rowland.
Most of the hulls built in the marine industry today are created, in some part or form, with the use of marine ‘composites’; a combination of materials in which each part keeps some of its original traits. Read more about composite materials, here.
Glass fibre in its early form was originally discovered as a composite in the 1930s when researchers at Owens, Illinois Glass tried to spin glass into fibres to replace mineral wool for insulation and filters. Almost accidentally, they revolutionised boat building, and now, more than 90% of all boats are built from composites that started with their invention of fibreglass.
This glass fibre is remarkably similar to today’s silica-based fibreglass, which is strong and resistant to scratching and contamination by chemicals. These flexible fibres are remarkably easy to work with.
E-glass or S-Glass
Silica-based fibreglass comes in two forms; E-glass or S-glass.
E-glass is the workhorse of the contemporary boat building against which all others are measured. It delivers reasonable strength at a relatively low cost. S-glass is however, stronger, lighter and scratches less, but costs three to four times more than E-glass.
Arriving on the boat building scene in the last 30 years, aramid (along with carbon fibre) has changed the way in which boats and luxury superyachts are built. Aramid stands for ‘aromatic polyamide’.
Kevlar, Technora, Twaron, Heracon
Kevlar is the best-known aramid material. It is the trademarked fibre that DuPont (the company that created polyester resin in the 1940s) originally developed for tyres. Technora, Twaron and Heracon are other branded aramids.
Aramids offer twice the tensile strength of E-glass. It is lightweight, weave-able, resistant to puncture, impact and fatigue. However, they do absorb water and don’t withstand compression as well as glass fibres. This is why they are commonly used with other fibres.
As the most expensive of reinforcing fibres, carbon fibre is lightweight and stiff – roughly six times stiffer than E-glass. It therefore doesn’t corrode like aluminium or stainless steel, making it perfect for mast or rudderstock components, or entire boats.
Carbon fibre is however tricky to work with. It needs to be engineered carefully to account for its lack of stretch, providing little warning before it fails suddenly and catastrophically.
Why use carbon fibre?
According to Luke Hendy from Branagh Marine Composites, superyacht owners and project managers are increasingly requesting carbon fibre as the material of choice for a range of cosmetic and structural yacht equipment.
The unique qualities of carbon fibre include:
- Thermal stability
- Improved moisture stability
- Low weight and low mass
Carbonfibre is 70% lighter than steel, 40% lighter than aluminium and 35% lighter than magnesium alloy. It has excellent strength-to-weight ratio and optimal energy absorption properties for safety solutions and design flexibility.
In addition, carbonfibre yacht equipment has a unique aesthetic quality, which showcases the ultimate in high-end technology.
Core foam ‘sandwiching’
As a way to reduce cost and added weight in boat building, composite designers determined early on that ‘sandwiching’ a low-density, lightweight core material, such as foam, honeycomb or balsa wood, between thin face sheets of composite can dramatically increase a laminate’s thickness and stiffness, while requiring a lesser supporting structure.
This core composite service is a great way to distribute loads and stresses on the structure of a superyacht or vessel, preventing wrinkling and buckling during impact or stresses.
Open-moulding versus closed moulding composite technique
Luke Hendy from Branagh Marine Composites explained some of the jargon around composite services, and commented on the different types of core moulding techniques used in the industry.
He said, “There is a slow transition from open moulding techniques, such as hand lay-up and spray-up, which utilise more manual labour and consume more time, to a slew of closed moulding techniques such as resin transfer moulding (RTM), vacuum assisted RTM (VARTM), RTM Light, vacuum resin infusion moulding (VRIM), vacuum infusion processing (VIP), closed cavity bag moulding (CCBM) and the Seeman composites resin infusion moulding process (SCRIMP).
“These closed moulding processes offer more flexibility in terms of part size, complexity and faster production rates, (due to automation and less manual labour) resulting in a higher quality part and minimal void content.”