1. What is it?
Areté is a 15 ft acrobatic sailing skiff. It was designed and built by
engineering students of University of Padua (Italy).
Why?
“1001VelaCUP" competition takes place in different parts of Italy
every year. Students challenge themselves in races and in setting
the crafts before and after each regatta.
Key aspects
• Lightness
• Stiffness
• Sail Efficiency
• Water Drag
FLAX BOAT
MADE FOR RACINGARETÉ
Hull & Deck Design:
The first phase of the design defines the shape and the water line. The
main aim is to reduce drag and increase speed. Width of the hull is a
compromise between drag reduction and roll stability. Other features
defines the speed at which the boat begins to plane.
The analysis of sandwich structure are carried using simplified theories
which provides thickness of skin and core. In a second phase the local
conditions effects were evaluated, such as: skin-core interface problem
or other materials insert. Finally the structure characteristics were
improved.
Materials
One of the most important rule of the race is to use of natural materials for the hull and appendices.
The excellent mechanical properties of flax fibres can compete more and more with other synthetic fibres in the
composite world. Flax fibres are green by nature. But as a 100% renewable raw material, these sustainable
fibres are also perfectly recyclable, biodegradable and compostable. Furthermore, they are at the same time
exceptionally strong yet very lightweight. Flax fibres are characterized by high rigidity and low density (1.4 p
(g/cm³)) compared to glass fibres (2.54 p (g/cm³)) and other composite fibres. Furthermore, their low abrasion is
another strength to consider. The best mechanical properties in composite materials are achieved by using full
uni-directional layers rather than by applying yarns, fabrics or flax rovings. The mechanical properties of the uni-
directional layers are high because of the absence of twist and shrinkage. A cross-ply laminate of four UD layers
of flax and a epoxy matrix offers elastic modulus of 19 GPa in a fibre volume fraction of 50%. In a composite,
this has a ultimate tensile strength of 165 MPa and a density of 1.05 g/cm³ (source University of Padua).
The sandwich structure, which was chosen for hull and appendices, is composed by:
• External skin: made of epoxy matrix reinforced with flax fibres by Procotex
• Core: balsa wood
• Adhesive: used to connect skin with core made of epoxy resin.
The composite sandwich structure has excellent strength, stiffness and lightness properties. In a sandwich
structure the external surfaces are those undergoing the highest stresses; moreover, the higher is the distance
between external surfaces and neutral plane, the stronger and the stiffer the structure is. The sandwich panel
with highly resistant and stiff skin was bonded to a light core as the solution to the problem.
Conclusions:
This poster describes the work and developments of Areté, a project aiming
at the construction of a racing skiff in natural composite material. The
project carried out by the Team Project R3 resulted in the creation of a high
performance boat. In the last regattas "1001VelaCup" Areté gained the
third place of the podium. Future developments are oriented to the
identification and use of organic resin and the optimization of the internal
structure of the craft. The ultimate goal of Team Project R3 will be to build a
race boat entirely composed of natural materials and 100% eco-friendly.
Hull & Deck Construction:
Infusion process is the most cost-effective system for boats prototyping.
A three steps method was used for the main hull and deck:
1) Esternal skin infusion via VARTM
2) Core vacuum bonding
3) Internal skin infusion via VARTM
This stepped method allows to reduce the core impregnation during
infusion and it also permits the construction of a lighter shell.
A wooden internal structure was fitted to distribute stresses caused by
concentrated loads. Such loads are: hydrodynamic from the centerboard
and rudder, aerodynamic from sails and inertials from crew and waves.
Appendices Design & Construction:
In sailing boats appendices are usually considered the centerboard and
the rudder: the former offsets the force produced by the wind on the sails
and the latter gives control to the boat.
Both appendices were designed with a maximum efficiency criterium. Like
airplane’s wings, the more slender they are and more efficient they would
be but, on the countrary, the less easy to handle they would be. The plan
of the surfaces has an ellipitcal shape. A five digit foil was chosen for
centerboard whereas a NACA 0012 was used for the rudder.
After the preliminary structural design, FEM analisys were performed to
verify the stresses. A distribuited load of 800N was applied on the surface;
the upper end was considered simply supported.
Flax reinforcements and balsa core were employed as well but the
construction is simpler than the one used for the hull; it was a single step
infusion process.
Contact us
www.projectr3.com
team.projectr3@gmail.com
Team Project R3 Padova (facebook)
Centerboard
trunk
Mast base
Frame
Inner
keel
Simply
support
Elliptical
uniform
load
Stress diagram adopting Tsai-Hill criterion
-50
0
50
100
150
200
-0.005 0 0.005 0.01 0.015 0.02 0.025
Stress[MPa]
Strain [mm/mm]
TENSILE TESTING [0°]4
EPOXY MATRIX REINFORCED WITH FLAX FIBER 180 gmq
00-01
00-02
00-03
-5
0
5
10
15
20
25
-0.001 0 0.001 0.002 0.003 0.004 0.005 0.006
Stress[MPa]
Strain [mm/mm]
TENSILE TESTING [90°]4
EPOXY MATRIX REINFORCED WITH FLAX FIBER 180 gmq
90-01
90-02
90-03
0
0.5
1
1.5
2
2.5
3
3.5
0 0.0002 0.0004 0.0006 0.0008 0.001
Stress[MPa]
Strain [mm/mm
TENSILE TESTING [90°]4
EPOXY MATRIX REINFORCED WITH FLAX FIBER 180 gmq
90-01
90-02
90-03
0
2
4
6
8
10
12
0 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006
Stress[MPa]
Strain [mm/mm]
TENSILE TESTING [0°]4
EPOXY MATRIX REINFORCED WITH FLAX FIBER 180 gmq
00-01
00-02
00-03
CFD analysis of ceneterboard and rudder
Ceneterboard infused halves
Ceneterboard moulds
1 2 3
FEM analysis of the hull + deck
Internal structure
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