Noise Measurements and Mitigation for a Foil Assisted Catamaran

Abstract

Noise control recommendations and mitigation approaches for a foil-assisted catamaran become very sensitive when it comes to weight tradeoff. While weight control on a fast marine craft is critical, it reaches the uppermost limit when it comes to a foil-assisted catamaran. A foil-assisted catamaran is very sensitive to weight growth as well as the Longitudinal Center of Gravity (LCG) of the vessel in terms of reaching foil-assisted planing speeds. An increase in weight leads to a slow pre-planing speed which does not generate sufficient foil lift to transition the vessel into full planing speed. Whereas incorrect LCG of the vessel leads to wrong foil attack angle and thus leading to insufficient foil lift. This paper covers design philosophy, risk management, onboard measurements, weight management, mitigation approaches, and recommendations associated with the design of a 61 ft foil-assisted catamaran designed to reach 38+ knots and meet specific noise criteria limits at the maximum cruising speed as well as other operational conditions. An initial solution was applied, and the noise reduced at intermediate design speeds, however, at design cruising speeds the noise levels still exceeded the limits. Further computational analyses and mitigation methods such as insulation, mass-loaded vinyl, joiner barriers, viscoelastic coatings, trim adjustment, and floating floors were implemented on a trial-and-error basis to minimize the overall weight added to the vessel while achieving vessel design speed.