The first Hybrid Wing prototype was fitted to Randy Smyth’s Everglades special Sizzor trimaran (left) – Smyth used the rig to win the 2014 edition of the 300-mile Everglades Challenge and set a new course record. An interim step-up trial rig was decided upon as the safer option before going ahead with the full-size rig for the Eagle 53, Hall Spars building this spar (right) for the ProSail 40 Caliente
in St John, USVI after her launch in Decem- ber 2018. The work-up has been meticu- lous. This first phase of Eagle testing has the Hybrid Wing sailplan combined with a C- foil and winglet-rudder package. Phase two will be with the T-foils installed, plus differ- ential elevators, all managed electronically. Finally, how does the Eagle 53 perform?
As with Caliente, hull flying has been smooth and controlled. At 14kt the C-foils provide initial skimming-lift which pro- gressively reduces hull immersion with speed. Short-term bursts of full flight have been achieved at speeds in the low 20s. Plus we have been hitting upwind speeds of 16kt with ease and the mid-20s when reaching. During my short time sailing in February we sailed with only the mainsail, Hybrid Wing and jib. Next we will test the Hybrid Wing with the screacher to open the door for VMG performance downwind. Thanks to the electric winches, a central
control station, the self-tacking jib, the furling screacher and boomless self-tack- ing mainsail (with those low clew loads) and the 360° feathering Hybrid Wing, Eagle can be sailed efficiently with only the owner Mr Sussman onboard, plus Tommy and his first mate Amber. So the design requirement of the Eagle being able to be sailed without a boatload of professional sailors has been met. I personally look forward to continued
sailing adventures on the Eagle while push- ing the envelope of performance, ease of handling and electronically controlled foil- ing. I have particular admiration for the build team that Tommy assembled at Fast Forward Composites to make Paul
44 SEAHORSE
Bieker’s design vision become reality. The Eagle story has only just begun.
STANDING IT UP – Steven Robert, ST2 Design We became involved in this project thanks to Paul Bieker, after having worked together on a number of America’s Cup campaigns and other projects. The design team assembled was made of familiar faces, and discussions were immediately fruitful. We were talking the same language, from designer to structural engineer to builders. The Hybrid Wing structural design group consisted of myself and Xavier Douin. The challenge proposed by Tommy and
the team at Fast Forward Composites was a refreshing concept, but at the same time it uses designs and techniques that have been developed and proven over the last few America’s Cup cycles. The Hybrid Wing is similar to the wings
that were stepped on the multihulls for the AC33/34/35, in a sense that we have a main front element carrying most of the load. This element is like a long chord mast and has several familiar features: to facilitate transport the wing is split into two parts, the design of the splice tailored to maintain the desired aero shape while keeping the weight in control. The aft part of the Hybrid Wing is made of frames and covered with film in the normal way. The structural part of the Hybrid Wing
is a D-section, built with two sides and the lateral shear web. The design brief was to have a reliable
and robust rig, so some of the features have been adapted to be less fragile than
for a pure inshore racing spar. For exam- ple, the ribs that define the wing shape are made of single skin top-hat sections rather than honeycomb cored flat stock. The design process of these parts involved a collaborative discussion to achieve robust parts that could be efficiently built. The distinctive characteristic of the
Hybrid Wing is its ability to feather in the wind and rotate freely 360° when at the dock. The preliminary small-scale hybrid wings proved to be a valuable foundation for our work; however, the scaling is always a challenge and some further detailing and refinements were developed. The planform shape of the wing was
drawn by the design team to reach the maximum performance while achieving the free-rotation feature. Thus the chord of the wing at the top is a compromise between aerodynamic efficiency and the transfer of the load from the rigging. The two shrouds and the forestay are attached on a three- legged crane that we called the ‘top hat’. To keep the wing rotating freely the
chainplates on the top hat have to be offset from the rotation axis and this offset cor- responds to the half chord of the wing at the top. This induces cantilevered loads which need to be transferred to the Hybrid Wing through the top hat, on which all legs are bending members. On the wing itself the load is transferred to the spar through a set of bearings and a composite structure that we called the ‘backpack’. This struc- ture sits in the middle of the chord at the top of the wing, while the structural spar is the front part of the section. The Hybrid Wing is secured at only two
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