A comparison of the motions of trimarans, catamarans and monohulls

The seakeeping motions of catamarans and trimarans are computed using a time domain seakeeping method, which has been accurately validated across a range of Froude numbers from 0.2 to 0.8. Both vertical and horizontal accelerations are evaluated. No motion controls are fitted. It is found that the rolling of a trimaran increases as the buoyancy in the outboard hulls is reduced, and exceeds the rolling of an equivalent catamaran by a factor of two when 5% of the total displacement is in the outboard hulls. In head seas, the greater length of the trimaran reduces the maximum heave motions relative to wave height as a consequence of the reduced length-based Froude number.