Fagerdala Hull System
- a truly revolutionary hull concept

Tests performed by independent institutes
and laboratories

Adhesion to a metal surface
Tests conducted by the Dept. of Aeronautical Structures and Materials, at the Royal Institute of Technology, Stockholm, Sweden. Additional tension tests conducted by the DIAB laboratory in Sweden.
These tests were conducted to determine the best method for preparing the metal surface prior to applying the glue as well as determining the critical point at which oxidation of alloy steel hinders adhesion.

Result: Sandblasting is insignificantly more efficient than sanding with a 40-grade paper. Sanding is therefore recommended for environmental reasons.
No significant adhesion problems appear to arise from alloy oxidation within five days. As a precaution, however, the alloy surface should not remain exposed for more than 24 hours.

Physical properties analysis
Tests conducted by Professor K-A Olsson at the Royal Institute of Technology, Stockholm, Sweden.
These tests were conducted to find out if any weak links exist in the system and if so, in what part of the sandwich. They were also designed to measure the gain in strength compared to a traditional metal structure.

Result #1: Temperature of 65°C on both the metal and laminated surface. Panel height of 500 mm subjected to a vertical pressure of five tonnes. No delamination found. The test confirms that even high temperatures do not have a negative effect on strength.

Result #2: Stiffness. 25-mm closed-cell foam on 5-mm steel and 4-mm alloy. The global stiffness did not increase dramatically (3% for steel and 10% for alloy). For local stiffness the following remarkable results were recorded: Subjected to lateral forces (buckling), the stiffness of aluminium was improved by a factor of 65 and of steel by a factor of 13. This demonstrates that thinner metal plating may be used and frame/stringer distance increased while retaining or improving buckling resistance.

Thermal properties analysis
Analysis conducted by Carrier AC Sweden.
The analyses were designed to demonstrate the thermal benefits. Calculations are based on 4-mm alloy covered with 25-mm closed-cell foam at a density of 75 kg/m3 and 3 mm laminate. Total surface: 300 m2. Total wet surface: 100 m2. Ambient temp: -10° to +40°C. Inside temp: +20°C.

Result: The insulating effect is dramatically improved compared to a traditionally insulated metal hull. This is because the completely covered hull eliminates cold bridges.
The great advantage is that the metal structure, even under extreme conditions, will have a temperature above the dew point, eliminating all condensation problems, even below the waterline. Another great benefit in the case of yachts is that the temperature of the metal will never differ more than 4°C from the inside temperature. With a traditional faired dark hull, the temperature of the metal can rise to 80°C, resulting in plate-expansion and visual unevenness.

Acoustic properties
Tests conducted by Prof. A.C. Nilsson at the Dept. of Technical Acoustics at the Royal Institute of Technology, Stockholm Sweden.
The analyses were designed to determine the effectiveness of the visco-elastic glue in combination with the closed-cell foam. Tests were conducted full scale, with the aid of an accelerometer placed 0.5 metres above the waterline between two frames. The results were recorded and analysed in the laboratory.

Result: Compared to a traditional metal hull, the loss factor in the range 250-2500 Hz was 20 %. Note that sound is measured on a logarithmic scale.