A moulded fin is produced with the help of sandwich technology and a female mould. This technique also brings about advantages and disadvantages.

The epoxy resin used should be of top quality; it should stand vibrations and sun heat; it should offer excellent adhesion to the enforcement fabrics and little shrinkage. Resins of minor quality do not stand the vibrations for a longer period of time, endurance is drastically reduced and therefore the fins can break easily.

Enforcement fabrics should also be of top quality. They should be able to stand permanent vibrations, they should have a low volumetric weight and high tensile strength for stiff composite constructions.

A sandwich construction is a structural panel consisting of two relatively thin, dense, high strength sheets of structural material with their faces bonded to and separated by a core. The structural material has to cope with the tensile and pressure forces. The core serves as a distance holder, maintains the fin profile and has to cope with the shearing forces.

The structural material can be unidirectional and/or multi-directional carbon inlays. The carbon fibres consist of microscopically thin and parallel single filaments. This parallel position makes it possible to meet all the lines of force in the laminate. In this way, the construction can be adapted to the stress which leads to less weight and higher durability. In addition the flexibility in terms of twist and flex can be controlled more precisely. For the construction of an extremely thin fin, high modular carbon can be used.

The core material has to be quite robust which is met by using epoxy resin.

The process of production starts with the construction of the female mould. The two symmetric halves can be made from enforced resin, aluminium or steel.

The inside of the female mould has to be covered with a release agent. Then the fibre inlays and the resin can be applied.

In the case of injection technique, the fibre inlays will be put into the mould, then the mould will be sealed. Resin will be pressed into the mould and air will be sucked out.

The other possibility is to laminate by hand. For the construction of the carbon laminate, the carbon inlays are put into the female mould in a defined angle. Then they are soaked with the resin-hardener mixture and de-aerated. All layers are laminated “wet-in-wet”. Record of the angle of the carbon inlays has to be kept for reproducibility.

The next step involves the hardening of the resin. Depending on the type of resin, it will be necessary to temper the resin at a higher temperature.

After demoulding, the fin has to be deburred, inserts will have to be built in and the surface will be finished.

A good moulded fin will have the desired profile plus the desired twist and flex. By using carbon inlays, the fin responsiveness will be high and the weight will be low. Its performance will be excellent; and as long as there is no damage it is extremely durable. All the desired parameters can be influenced by the producer so they can truly be custom made.

The only disadvantages are that the process of production is laborious as most of the work is performed by hand as well as the costs of the materials. The sailor will have to pay a higher price for a delicate high tech product.