Centrebow design for wave-piercing catamarans

Wave-piercing catamarans are used extensively for both defence and commercial sea transportation. Advantages such as large deck area, stability and high speed make these catamarans suitable for transporting roll-on roll-off cargo and passengers. However, issues such as the impact of the bow into the water when operating in large waves, better known as wetdeck slamming, can affect their mission capability and can cause structural damage. Different strategies are used by the designers to reduce wetdeck slamming in catamarans. Wave-piercing catamarans often have a centrebow that provides reserve buoyancy under the wetdeck in the bow to reduce heave and pitch motions and avoid deck diving in following seas. Designing an efficient centrebow is crucial for these vessels to reduce motions and minimise structural loads. To evaluate the effect of various hull forms on motions and slamming loads, a hydroelastic segmented model was designed and constructed. This segmented model is a scaled model of a 112m INCAT wave-piercing catamaran and has two transverse cuts and a separate centrebow. The centrebow segment was equipped with two six degree of freedom force/torque sensors to allow for slam loads to be measured. Three centrebow volumes (lengths) were designed and tested in head seas in the AMC towing tank in regular waves. The results show a significant variation in slam loads when comparing the three centrebow lengths, with the highest loads found on the longest centrebow, caused by larger water volume constrained between the centrebow and demihulls. Results also showed that the longer centrebows have higher pitch motions in slamming conditions.