Hovercraft Skirt Design and Manufacture

Skirts are the inflated structure which extend around and beneath a hovercraft that allow the craft to operate in rough seas and over uneven ground. The early skirts were designed on the basis of model testing and practical experience, but as the size of craft increased and improved performance was required it became evident that a more sophisticated approach was needed. This was carried out by developing computer programs to design the sectional shapes, investigate the quasi-static behaviour and derive the flat pat tern shapes from which the skirt is made. The responsive skirts fitted to large cross-Channel hovercraft, the Super 4, and the latest coastal craft, the AP 1-88/100 were developed using these techniques. Investigations into the cutting of sheets of non-metallic materials by a high-pressure water jet showed that this was ideal for the nylon woven fabric coated with either natural rubber or neoprene from which skirts are made. A cutting table with a NC tape-fed controller has been developed with a jet of 0.15 mm (0.006 in) diameter operating at 379 MPa (55000 lbf/in 2 ). All the processes of producing a skirt, design, detailing with CADAM, part programming and cutting out are now integrated via computer links giving significant savings of time and costs.