A spar buoy design for oceanographic data telemetry

Abstract

The design of a spar buoy, employed as one component of a current monitoring system deployed during 1980 in Davis Strait, and some of its response characteristics to ocean waves are presented. The buoy was 36.5 ft (11.13 m) in length with upper and lower masts 0.5ft (15.2 cm) in diameter and buoyancy hulls, centrally located, 2 ft (61.0 cm) in diameter. Power for the system was supplied from lead‐acid batteries in a ballast tank on the lower end. Telemetry electronics were located in a 1‐ft (30.5‐cm) diameter case on the upper end, below the antenna. The buoy weighed about 1,635 lb (746kg) and could be man‐handled at sea with relatively light lifting equipment. It had a damped period of 16s and a significant heave response of about 62% of the significant wave height of the forcing spectrum. Scale model tests indicated that the buoy would be operational in heavy sea swell up to about 20ft in height with pitching angles of less than 10° off vertical. Observations at sea have shown that the buoy followed swell waves better than the 62% heave response figure would imply and had negligible pitching motions except during severe storms. The design was judged to be successful in providing a stable base for VHF transmission and is recommended for use in other applications.