The Horn Mountain Production Spar was installed in 5,400 feet of water in June 2002. This was the deepest floating production unit at that time. A comprehensive instrumentation program was initiated to measure spar and riser responses (Edwards et al, DOT 2003). The present paper discusses the results of these measurements and comparison with analytical predictions of spar behavior during two selected events, hurricane Isidore in September 2002 and a summer storm in August 2003. Particular attention has been placed on the slowly varying surge and pitch motions and the importance of coupling with risers and mooring on hull motions. Our conclusion is that uncoupled analytical models for spar behavior predict accurately the wave frequency responses, however riser coupling has an influence on the slowly varying responses. This conclusion is consistent with earlier measurements of classic spar behavior (Gupta et al, OTC 2000, Prislin et al, OTC 1999).
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