Images © Van Oossanen & Associates b.v.

Late in 2001 we received a commission to design a series of 50 ft high-speed motor yachts with an advanced hull form for optimum performance at high speed. Resistance, propulsion, seakeeping and manoeuvring model tests were carried out in June through to October of 2002. Three different models were tested to ascertain the best possible hull form, particularly with respect to the shape of the propeller tunnels in the hull.

The hull form has been designed to maintain a cruising speed of 22 knots in waves and a top speed in excess of 30 knots. We have developed a light GRP sandwich construction meeting the harsh requirements set by Lloyds Register. The vessels were built using a vacuum-infusion technique. Details of this design were released at the 2003 Dusseldorf boat show.

Trials were carried out with the first Guardian 50 late in November 2004. Allthough the weight of the first vessel was greater than the prescribed weight, due to the use of non-prescribed materials, the power-speed performance of the yacht and the noise and vibration properties were found to be good, thereby validating the performance that was determined from model tests and extensive calculations. Measures are being taken to improve this even more for the next vessel to be built. We have received an order from Blue Print Marine to study changes to the design in certain areas for this purpose. The first Guardian 50 was presented to the public at the 2005 Dusseldorf Boat Show.

The Guardian 50 has been designed for efficient building, through use of:

• Flexible top hat stiffener formers
• Minimizing the number of parts and different materials
• A complete 3D model to test-fit all parts of construction and systems.

For the Guardian 50, Van Oossanen & Associates have carried out the following work:

• Hull design and general arrangement drawings
• Weight and stability calculations
• Resistance and propulsion calculations
• Model testing
• 3D Modelling, design and engineering of the GRP construction of hull and superstructure
• All work for Classification Plan Approval
• Conducting of trials
• Working drawings

For more information see also www.oossanen.nl/vpp/