Design of a 40ft charter catamaran "the Freerider" with special reference to a novel stepped hull.

This project is based on an existing demand coming from the holidays centre for a day charter to one week trip boat. That imposes many requirements for the boat to be accessible, comfortable and safe. To meet the requests, a catamaran of 40ft is designed with a novel stepped hull. The objective of this project is to establish the preliminary design on the first part and then use it a base for more studies on different elements. Once the preliminary design is achieved, the first research established is on the behaviour of the steps in waves via the towing tank and the wave maker. The measurements obtained are tricky to interpret and others tools are used to help on the conclusion. Finally, the measurements obtained are not reliable and cannot be used further. Nevertheless, the video taken onboard helps to improve the shape of the steps to reduce the drag. Then for the mast, a complete study is achieved on the rig forces. As the tension on the diamonds cannot be calculated statically, a Finite Element Analysis is carried out to determine the applied tension on each wire and then select the correct diameter. For credible results, the analysis is established step by step which validates the computer model with reality. Via the tank testing, different daggerboards can be tested and compared. The efficiency of an end plate can then be analysed and compared to a conventional one. The results show that the end plate diminishes the yaw angle but generates a bit more drag. For a practical reason, the end plate is kept for the design. Finally, a FEA study is achieved on the crossbeam structure including the rig effect. The simple computer model without the mast is first verified comparing the hand calculations with the results obtained. The final scantling is quite simple and need a complete investigation on the best profile with the best material to obtain the best compromise