Mechanical Design and Fabrication of a Data Buoy

Abstract

A data buoy for measuring coastal wave-action has been designed and constructed. The buoy is essentially a 0.6 m diameter sphere that is made of fiber-glass with aluminum, steel and polymer parts. While the overall geometry of the buoy is superficially similar to that of existing commercial spherical buoys (e.g. Wave-Rider by Datawell), the present design is based on a simple robust structure and mass-market electronics. A significant dual-use feature of this design is that the structure is usable as a float in a wave-energy generation device. This is possible due to the essentially isolated central structure and an electronics enclosure that is sealed both from the external environment and from the bulk shell of the buoy. This also allows the electronics to be mounted in an easily- modified, rack configuration that can be removed from the buoy shell. In a wave-energy generation set-up the electronics rack would be removed and the central cylinder will become part of a linear-motion type generator, with at least +/- 25 cm of internal movement available to it that is waterproof (for near surface or shallow immersions). Alternatively, for large wave motions, the buoy can couple to an energy-generating device using flanges that mate with its bolt circle pattern. However, at the moment, the buoy enclosure is dedicated to wave-action measurement, i.e., a data buoy with an onboard inertial measurement unit (IMU) and a radio-link to send real-time data to a receiving unit that can be on a boat or at the seashore. Basic GPS data are also transmitted. This is of interest if the buoy is being deployed in a drifting (un-moored) mode. This paper will only discuss the mechanical design and fabrication of the structure.