TUNED SPAR BUOY SYSTEM 



L. 0. Olson 



Ocean Physics Group 



Applied Physics Laboratory 



University of Washington 



ABSTRACT 



The Ocean Physics Group of the Applied Physics Laboratory, 

 University of Washington, has developed a portable, tuned spar- 

 buoy system as a stable support for oceanographic instrumentation 

 packages in the ocean. This system can be disassembled, shipped 

 on conventional transportation and reassembled on station. 

 Tuning is accomplished by a captured water mass that fixes the 

 natural period of oscillation many times longer than the expected 

 driving wave period. With the spar system free-floating on 

 station, the payload package can be checked or changed from a 

 ship easily. All the buoyancy elements of the system are compart- 

 mentalized; seal failure in any area will not cause loss of the 

 spar or equipment. Should the spar system sink or be towed under, 

 a pressure-releasable ballast will return the spar to the surface 

 for recovery. 



Operations in rough seas off the Washington coast on the USNS 

 CHARLES H. DAVIS have shown that this half-ton system is capable 

 of supporting self-contained packages to depths of several 

 thousand feet in the ocean while coupling less than 107o of the 

 vertical, surface-wave motion to the payload. 



INTRODUCTION 



A portable spar buoy system was developed by the Applied 

 Physics Laboratory, University of Washington during 1968 to serve 

 as a stable support for an array that records temperature 

 structure at various depths in the ocean. 



Originally, the temperature array was hung on a coaxial 

 cable from the fantail of the research ship. This scheme imposed 

 amplified ship motion on the temperature data and necessitated an 

 independent support platform that would isolate the array from 

 surface wave motion. An initial spar system constructed from 

 snap-together sections of foam-filled, plastic pipe was easy to 

 launch and helped reduce vertical motion, but proved too fragile. 

 Even in mild seas, ship maneuvering could not keep the data- 

 linking umbilical cord between the ship and the spar slack, and 

 eventually the spar was towed under the surface and collapsed. 



The objectives for the tuned spar system were: a) support a 



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