The research aimed to develop air-inflated equipment for lift components of catamarans during the construction process. The main structural parts of a newly developed catamaran are two hulls and three closed boxes. The three boxes connect the hulls and hold the deck. Different construction procedures were analysed to connect the main structural parts. One possibility is to float the hulls and the three boxes one-by-one on the water, lift the boxes to the required position with inflated pillows and connect the parts. Air-inflated pillows were analysed with the help of the Dynamic Relaxation Method (DRM). DRM is a well-known step-by-step numerical method which is often used for the analysis of different tensile membrane structures. The deformed shape of the floating pillows (Fig.1), the membrane stresses in warp and fill directions in the membrane material, and the lifting forces were calculated for pillows with different geometry, different internal pressure values and different lift heights. A real-size mock-up was constructed to validate the numerical results. The material of the pillows is conventional PVC-coated polyester textile.