Design and manufacture of structure and hull for large AUV

Abstract: The main goal with the master thesis was to design and manufacture a frame and hull to a large AUV which KTH will use in research. The general aim for the Maribot LoLo (Long Endurance, Long Range AUV) is to act as an experimental platform and tool for a wide range of research activities, where all four capabilities within the SMaRC area (Autonomy, Perception, Endurance and Communication) can be tested, improved and demonstrated.The frame was designed and shall be built in aluminum profiles from Bosch Rexroth with custom made brackets, manufactured in a corrosion resistant steal. When the frame was designed, the associated load case and beam elementary case was implemented. No mechanical calculations have been executed since the frame is planned to be tested against the above mentioned load case.The hull was manufactured in glass fiber with a laminate built from 0/90 and ±45 fabrics. The laminates total weight per square meter was 4800 g/m2. The hull was manufactured by performing vacuum infusion onto a female-mould. The method used and the result is presented in appendix 1. The total cost for manufacturing the frame and hull was about 129 000 SEK, where the largest expenses were due to the manufacturing cost of the male-mould, and the labor cost when manufacturing the hull. Manufacturing a new glass fiber hull would in the future cost approximately 16 000 SEK, given it’s manufactured by students at KTH and in the same female-mould. Manufacturing the hull in carbon fiber would cost approximately 60 000 SEK.The future work required before the AUV is seaworthy are; assemble the frame, cut the hull to its correct dimensions, design and manufacture the attachment solutions between the hull and frame, and to test the frame against the applied loads. Future optimization work would be applying laminate theory and extract the mechanical properties of the hull. Combine the laminate properties with beam theory in order to estimate the deflection of the laminate when evacuating the water. Mechanical calculations on the frame could as well lead to optimizing the weight of the frame, where hopefully smaller dimensions on the profiles could be used.