Clockwise from left: powerboat control systems already in development provided the original inspiration for the final semi automated TF35 arrangement; horn and pull rod arrangement; the main foil bulb configuration; calibrating the elevator flap angles. The horizontal foil is solid while the radiused vertical features shear webs. Both elements plug into a solid steel bulb
chainplate width as much as possible to allow the gennaker to be carried upwind in the very light. The mainsail is a deck- sweeper onto the central pod, with a ‘half- wishboom’ to maximise the mainsail span while allowing for a lower centre of effort.
forces lower, which was necessary to avoid the need for complex and expensive (and heavy) hydraulics. But all this adds complexity. Hinge/actua-
tor-horn/pull rod all needs to be integrated in the assembly. The flap hinge also demands that the foils need to be straight. The main foil has anhedral, so this flap is split in the middle which required a special solution for the actuator horn. The rudder elevator foil is straight, so the flap is continuous. The flap hinges are flexible composite
(not Sikaflex as is commonly used on Moths!). This maintains a smoother shape-transition in the hinge area. There is quite a bit of work involved in matching the actuator forces and rates of movement to the flap configuration moments and foil/flap section design.
Rig The rig under the lake rules is simply lim- ited by an air-draft (21m), and an overall boat length from the end of the bowsprit to the aftmost part of the boat (15m). Given the light airs on Lake Geneva, you need to pretty much go to the limit on both. The D35 had some rig issues early on in its development, so a relatively conservative approach was warranted for the new class. We settled on a fairly straightforward
single-diamond rotating mast. We wanted to keep the rig as simple as possible and also eliminated the runners – although this marginally restricts the hoist of the gen- naker. We felt, however, that the gains in simplicity and windage outweighed a slight compromise in sail area. As mentioned earlier, we reduced the
Boat-0 The first boat (Boat-0) was launched in August 2019 and was extensively trialled by all the teams on Lake Geneva. The purpose was to debug and shake down the boat, as well as give the teams an opportu- nity to get familiar with the intricacies of sailing a new and quite different platform. During this period there was also input from the sailing group prompting further development on sail-sheeting techniques and more detailed refinement of sail design. Load checks were performed and a routine NDT programme was established. The flight-control programme was pro-
gressed further but now with real-life data. The season came to an end on the lake quite quickly and we moved south to the Mar Menor in Spain to continue testing and sail training for the teams. This worked out very well, and was the ticket we needed to start the 2020 season with our new fleet at full speed… And then Covid happened. Nevertheless, by this point we had logged 72 good days of sail- ing on Boat-0 so in spite of a full year’s delay we have a reliable baseline to start racing on 30 April. Fingers crossed.
q SEAHORSE 55
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