June 1, 2012

Sensors in the sails, mast and hull – racing the boat close to the wind and at the outer limits of endurance

A fiber optics-based measurement technique for yachting

As yacht racing surges forward to set ever new records, the builders of racing yachts are on the lookout for ever more new technologies. The holy grail of yacht racing is a yacht that can outstrip the wind while also resisting the harsh conditions prevalent on the high seas. Newly developed fiber optic sensors now enable safe sailing at the outer limits of the boat’s endurance. These sensors enable the yachting crew to measure in real-time the exact strength of the forces the sails, mast and hull have to contend while the boat is on the seas.

Harsh conditions on the open seas overstretch the materials of racing yachts

Today's generation of racing yachts are sports machines trimmed for ultra-high speeds. Yet the boats are often unable to withstand the fury of the high seas. In the fifth stretch of the Volvo Ocean Race held in spring this year, for instance, only one of six boats reached the finishing line undamaged.

Sensors identify the weak points

Fraunhofer HHI has developed a sensor system that identifies critical weak points and gives the yacht's crew timely warning when the stress limit has been reached which means, for instance, that micro cracks can be safely dealt with long before they turn into major breaks. This new system is based on fiber Bragg grating (FBG) sensors which are sensors inscribed in optical fiber. These sensors are integrated in a fiber optical cable which is attached to the sail or the hull or – in the latest development – to the mast itself. As the sail moves while the boat is in motion, it has an expanding or contracting effect on the fiber Bragg gratings thus causing the light transported in the fiber optical cables to strike different structures in the sensors. Depending on the degree of distortion, different lengths of light waves are reflected which the sensors then measure.

Crew members receive data on their smart phones

Specially developed software presents the data received in a graphic form on the onboard computer which sends it via WLAN to a smart phone or iPod. This information can then be used by an onboard trimmer to effect immediate and optimal adjustment of the yacht’s sails and rigging to the new conditions.

A world premier – sensors capture data in high-tech carbon masts

Fraunhofer HHI has recently applied such a sensor system for data capture from high-tech carbon masts. These sensors enable three dimensional imaging of the deformation to which the mast is subject with a degree of precision as high as one centimeter in a 25 meter long mast. Moreover, the sensors can also be calibrated to compute the strength of the forces to which the mast is exposed, which is not only vital for the proper trimming of the mast but also of tremendous importance for the design of the next generation of sailing masts. High-tech carbon masts are designed with numerical models which need to be fed with data about the strength of the forces occurring under different weather conditions. FBG sensor technology is the first technology to deliver such reliable experimental datasets for inspection and improvement of these models. The same goes for the hull of the yacht. In a project funded by the Federal Ministry of Economics and Technology (BMWi), these FBG sensors are now being used to optimize materials and develop the next generation of lighter and more robust hull materials.

The technology proves its worth in field trials

The fiber optic sensor system for racing yachts was developed by Fraunhofer HHI in conjunction with sailmaker Segelwerkstatt Stade and the sailcloth manufacturer Dimension Polyant. A number of yacht crews are now testing and refining the technology in field trials in Europe and the USA.