Simultaneous multi-point measurement of yacht freeboards by means of a wireless sensor network

The freeboard height (i.e. the distance between the upper deck of a boat and the water line) is a very important parameter for boat builders: it gives information about the boat displacement extracting the hull immersion from its construction planes. Freeboard measurements should be taken in different points of the deck, so that information about the boat trim is also extracted. Unfortunately, no electronic system to perform simultaneous multi-point freeboard measurements exists nowadays. This paper describes a wireless (Bluetooth) sensor network nowadays, consisting of three magnetostrictive level sensors, an inclinometer and a central unit, that automatically performs the freeboard measurements in three different points of a yacht. The level sensors have been customized with a battery power supply and a Bluetooth connection, so that they operate as slaves of a wireless sensor network, managed by the central unit. Besides the automation and simultaneity of the readings and the user-friendliness, the instrument stands for its accuracy (estimated around 1 mm) with respect to traditional manual readings. The experimental results show the functionality of the system and its potentiality in the yacht characterization.