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have utilized aerospace technology in composite
elements manufacturing.
The simulator model implements a normal
daggerboard and - in order to give the sideforce
necessary to balance the heeling force - a NACA
0012 shape foil was added at its tip allowing the
boat lift. All the characteristics of this shape were
found on the literature and 3-D effects were added
later (Abbott I.H., von Doenhoff A.E., 1959.). As a
result the two parts of the daggerboard are
considered separately and all the parameters vary
independently from each other .
The other innovation of the 34°th America’s Cup
was the wing sail. It was showed to the big public
during the America’s Cup of 2010, when the Alinghi
catamaran lost the Cup versus the big trimaran of
Oracle which had a huge wing. The AC45 is
characterized by a symmetric wing sail formed by a
main wing rotating about the mast and three rear
flaps distributed spanwise rotating at 90% of the
chord of the forward wing. Due to the symmetry and
the possibility to rotate the four parts, the wing is
able to produce lift in both port and starboard tack.
The structure of the wing is made of a carbon fibre
frame covered with a light soft membrane. The
crew is able to change during the race the sheeting
angle of the main wing, the camber of the whole
wing and the twist of the flaps. The advantage of
the wing respect to a classic soft sail is the
possibility to produce a larger lift due to a absence
of turbulence behind the must yielding a more
uniform and continuous pressure on the sail surface
(Haack N., 2010/11.). Another important feature is
the possibility to have high lift even with low
apparent wind angle . That is very important on high
speed catamaran. In fact, they can reach speed two
times larger than true wind velocity
3.2 Equations
In order to have the possibility to insert the foils and
make the AC45 able to fly, the equations of pitch
and heave were added to the model:
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Where "z" reperesants the vertical lift, ω the pitch
rotation and the subscripts "H", "Wi", "A", "HS",
"WS", refer, respectively, to hull, windage,
appendages, headsail and wing sail.
The equations contain all the forces in the
vertical direction and the moments around the pitch
axis acting on the boat. The model has the
possibility to change the setting of the boat taking
into account the actions of the crew trimming, the
position of the headsail, wing and rudder or
modifying the twist of the wing or the flatting of the
headsail. Also the daggerboards position can be
modified as they assume a basic role on the ability
of the crew to complete the manoeuvres. The
America’s Cup showed the importance of fast
sailing with the hull lifted from the sea in order to
maintain constant high speed. The simulator allows
the crew to test all this manoeuvres in an immersive
environment, finding the best solution and acquiring
the skills to beat the other team.
The possibility to jibe without touching the water
was already known. The new challenge is now to
complete also the tack without wetting the hulls. The
team that will obtain this result will probably win the
Cup. The simulator can offer an interesting tool to
improve the catamaran features and the crew skills
(Masuyama Y., Fukasawa, T, 2011).
With the foil the problem of the pitch pole is
damped but still central on the catamarans. When the
boat bears away, the bow is pushed into the water
and the ability of the crew to set off, first all the sails
and then the headsail, is of fundamental importance.
The helmsman as well has to move smoothly the
rudder not to throw out of the boats the crew
members as happened to Dean Barker in the final
race of the Louis Vuitton Cup versus Luna Rossa.
3.3 Forces on the Model
In the sailing boats, there are different forces, which
are due both to aerodynamics and hydrodynamics
components that make the model complex (Keuning
J.A., Sonnenberg U.B, 1998). These two fluids are
very well know and there are many references in
literature; however, the interaction between them
make all the problem more complex and needs to be
simplified. Moreover, the model has to change
depending on the position of the boat. In fact, if the
boat is floating, the hull has a large resistance force
arising from the friction resistance, wave resistance,
induced resistance and heeling resistance. These
components can be evaluated with classical
formulae as presented on the ORC VPP
Documentation (ORC VPP 2012). The innovation of
the new catamarans is the lift forces of the foils.
These are found using the lift coefficients and the
wetted area of the foils.
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AnImprovedSimulatorofAC45FoilingCatamaransforCrewTraining
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