Fagerdala Hull System
- a truly revolutionary hull concept

• Increased shell-plate stiffness
The closed-cell foam sandwich increases the ability of a 4 mm aluminium plate to withstand local lateral forces by a factor of 65, and a 5-mm steel plate by a factor of 13. Frame distance can therefore be increased and shell-plating thickness decreased according to class requirements instead of buckling requirements. This ensures major weight and cost savings, see test section.

• Facilitates metal work and design features
There is no need for complex and costly metal work on the hull or superstructure since the foam is easily shaped. If a client wants to make any changes, even at a late stage of construction, this can easily be done by adding to or reducing the foam layer. Unlike traditional filler, foam thickness does not impair its strength.

• Optimised thermal insulation
The entire metal plating is covered by closed-cell foam, creating a completely homogenous insulation layer, with no air movements in the material. Just 25 mm of foam is equivalent to at least 50 mm of mineral wool. In practice, thanks to the elimination of cold bridges, convection and condensation, the mineral wool thickness comparison should be even greater.
   With the Fagerdala Hull System the shell plating will be only marginally affected by exterior heat or cold. For instance, the heat of a dark hull exposed to the sun will not affect the metal plating at all. (A dark hull with fairing can reach as high as 80°C, causing expansion and buckling of the metal plating). The insulation properties of the Fagerdala Hull System therefore substantially reduce the need for air conditioning capacity. Internal insulation by mineral wool of the hull, deck, and superstructure, is only needed around the engine room as fire protection.

• No condensation
Applying the insulation on the outside of the shell eliminates condensation on the inside since the shell temperature is always above the dew point. At 70% humidity and 20°C inside temperature, the dew point is 14°C. If the outside temperature is +4°C, the shell temperature is 17°C. If the outside temperature drops to -10°C, the shell temperature drops to 16°C, which is still within the limits. Eliminating the humidity normally occurring in the mineral wool also means elimination of mould and odours. The moisture problems associated with double-bottom fuel tanks when partly filled become a thing of the past.

• Hull resonance deadening
The visco-elastic glue applied to the shell plating greatly reduces tiresome resonance in the structure. The loss factor, compared to a traditional construction, is improved by 20% (logarithmic scale) between 250-2500 Hz. Heavy sound insulation and interior stiffening plates are no longer needed. Test data available on request.

• Reduced risk of galvanic corrosion
Since the hull is covered by closed-cell foam, galvanic corrosion caused by electrical current is easy to control. All small fittings are attached in the foam layer, not in the structure. This eliminates contact between different metals.

• Greater crash protection
The foam offers increased protection from shock and damage as its energy absorbing qualities help distribute impact over a greater area. If, however, an impact causes damage in the foam layer, this does not require urgent repair thanks to the closed-cell structure that prevents moisture from spreading to the surrounding area. This means that the vessel may continue cruising until a suitable time can be found for repair works.

The Fagerdala Hull System brouchure »
- a proven concept for ship building and renovation

GL, Germanischer Lloyd, has issued a Type approval for Fagerdala Marine System AB of: Visco-elastic bonding of fibre reinforced sandwich on metal structures. See GL approval (PDF) »

Hull System
information video »