After tow testing Sailrocket to measure the boat's hump drag, we settled on 16m² wing area as sufficient for lift-out and high speed. With the aerodynamic configuration fixed, we applied the same criteria of practicality and performance to the structural design.

A monocoque sandwich shell would have assured an excellent shape all over, but would be vulnerable and hard to repair when built down to the weight target of 45kg. It would also have needed large expensive moulds.

Recent experience with a rigid wing hang-glider project led us to favour a tubular carbon spar, lightweight foam sandwich ribs and Mylar film covering for the Sailrocket wing sail.

The spar provides a reliable and robust structural spine that can carry compact fittings for the mast foot, stays etc. The leading edge is a non-structural fairing that can be repaired more readily than a structural shell if it gets damaged. The whole wing was completely 3D modelled in CAD, allowing us to extract the profiles for the ribs and webs to be cut out of flat panels.

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