Abstract: For different position of side hulls of pentamaran, the influence of side hulls layout on longitudinal motion was studied. Rankine panel method was used to calculate the motion response RAO of pentamaran with 12 side hulls layout schemes in regular wave and the effect of side hulls layout relative to main hull on motion was analyzed according to the results. Considering the nonlinear factor, the motion history of pentamaran in irregular wave was calculated and the statistic significant values of heave and pitch motion were compared. The influence of side hulls layout of pentamaran on longitudinal motion is closely related to sailing speed. Sailing at lower speed, the heave motion of pentamaran could decrease when the back side hulls lying near midship and converse trend appears at high speed. Reducing the height and lying near bow of front side hulls could help improve the heave and pitch motion of pentamaran.

Key words: pentamaran, side hulls layout, longitudinal motion, nonlinear