wings I increased the vertical height of the wings relative to the hull to increase the righting moment of the boat when heeled. In my mind the satisfying ‘S’ curve of the wing struts when viewed from in front should be better aerodynamically than straight wing beams. iXent spent a lot of time running computer laminate optimisa- tions for the slender tapered wing struts to maximise their strength to weight ratio.
Foils Designing and building foils are one of the biggest challenges of producing a Moth. I have had plenty of experience trying hinge and actuation details that do not translate well to the scale of these foils and hence I approach Moth foil design with a bit of trepidation – especially the main foils. In many ways Moth foils are like watch
making – if the watch needs to be able to be repeatedly thrown in the water and abused. Designing a successful Moth foil requires very good CAD lofting and
52 SEAHORSE
extreme attention to detail in construction. Luckily, we had Riley Dean to create the detailed models for the foil parts (as well as the hull and wing structures). The first thing we attacked in the Moth
foil project was minimising the size of the lower struts (aka daggerboard and centre- board) while trying not to lose strength. We did this by designing printed titanium
transition pieces to transmit the load from the foil struts into the foil sockets. Metal is always better than composites in zones where the load paths are complex – the connection between foil struts and wings is a classic example of that. Using titanium in the lower struts allowed us to make the lower ends of the struts significantly smaller and thinner than any of the other Moth struts that I am familiar with. The next thing we did is to design new
struts that are around 175mm longer than typical Moth struts. The idea behind this is to increase the righting moment of the boat when heeled. I believe it is this extra
righting moment and the improved aero- dynamics of the Bieker Moth that make it especially strong in 11kt TWS and up; however, I have realised that the extra wetted surface of these longer struts is espe- cially costly when taking off in light air. With that in mind we have also developed a set of conventional-length minimum wetted surface struts especially suited to sailing in light air (MV-V3 and RV-V3). I begged Scott to let us sidestep design-
ing and building the main foil by using main foils from one of the other foil suppliers. Scott insisted that we produce a complete foil set for the new boat. True to past experience, I managed to overthink the foil-building process such that it was pretty much impossible to execute prop- erly, despite Riley and James Gell’s best efforts. Struggles with the main foil plagued our first year on the water but our results improved when we started using Swift main foils from Damic Design. In the meantime, Scott refused to give
ANGELA TRAWOEGER
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