MSc Individual Project

1. A free standing wing mast
for a recreational cat-boat
Dott. Ing. Floriano Bonfigli
in collaboration with
supervised by Dr. John M Hodgkinson

2. Outline of talk
Introduction – Sailing with composites at Imperial College…
•
What a free standing wing mast is – No more columns but wings!!!
•
Manufacturing method and raw materials – A “cheap” production
•
is possible!
The mast cross-section – An innovative airfoil …
•
The mast engineering – A quite fast and reliable optimization
•
process
Conclusions and further work – A prototype is needed!
•

3. Sailing with composites at Imperial
College…
• Designing with composite materials is not very
straightforward…
• Even at the highest level!

4. Sailing with composites at Imperial
College…
• A free standing wing mast for a recreational trailer cat-
boat
• A challenging real case study

5. What a free standing wing mast is
1. A simpler then safer structure
With a keel stepped mast, there
are just two very accessible
joints to check

6. What a free standing wing mast is
2. Much more room to enjoy on board!
Every naval architect should
look with favour upon free
standing masts.

7. What a free standing wing mast is
3. No more bulky columns but wings!!!
A wing mast which
cannot rotate is
basically useless.
The mainsail
efficiency may
increase up to
30%.

8. Manufacturing methods - raw materials
2 yacht projects
Most convenient process and
5 mast builders
were reviewed
Get the right
Pertinent raw materials resin!
Which fibre?
UD ply data
Mechanical properties are strongly
recommended
Structure modelling

9. A “cheap” production is possible
• The autoclave method is not the rule
Vacuum bagging
and heater blankets
were adopted for the 5
parts building the mast

10. A “cheap” production is possible
• Reduced
degradation
• It is twice
Low
from
as expensive
water ingress
temperature
-
+ as vinyl ester
curing and four times
• Increased as expensive
epoxy
resistance as polyester
to osmosis
Long term gain of
better durability,
therefore
better resale value
Higher value
for money

11. The mast cross-section
NACA section database
6-digit series
63-0xy
X-Foil
6x-020
65-020
…

12. The mast cross-section (II)
65-020
170
symmetrical Profili
airfoils
Eppler E838

13. The mast cross-section (III)
2. Fully aerodynamic mast,
with composite
1. Masts sharply cut
sail tracks
This solutions allows
to save some composite
Airflow
and to maintain its
aerodynamic efficiency

14. The mast engineering – starting point
Boundary
conditions
Wind force
Sail area
Mast geometry
Classical structural
analisys
Classical modelling
approach
Young’s
modulus
Density
Quasi- isotropic
laminate
Ply number
properties

15. The mast engineering – FEM analisys at
1. Method analysis
New mast-sail interaction model
2. Product analysis
Weight optimization

16. 1. Method Analysis
• Loads given through the track
• Sail acting like a membrane
Wind pressure concentrated in a node
located into the sail centre.
Node connected along the rear end of
the mast by a set of RBE3 elements.

17. 1. Method analysis (II)
Old
way
New
model

18. Graphs
Lateral deflections, load uniformly distributed
200
Displacement, mm
150
100
50
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500
Mast height, mm
Lateral deflections, new approach
100
Displacement, mm
80
60
40
20
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500
Mast height, mm

19. 2. Product analysis
Optimization process
• The model is firstly run.
• Secondly, it is characterized in terms of
weight, lateral deflections and failure index
map. SF>2
SF>2
• Then, the most critical areas are detected
and reasons for that stated.
• Final conclusions and next model to test
are proposed.
Lateral
displacements
A typical
failure index
map

20. 2. Product analysis (II)
Excel starting point, 16 UD quasi-isotropic lay-up
14 UD lay-up, less 0° plies 14 UD plies, less 90° plies
4 zone optimized lay-up
12 UD lay-up, less 0° plies
anti-symmetric lay-up version
woven fabric version

21. 2. Product analysis (III)

22. Conclusions and further work
• Design of a free standing wing mast for
a recreational boat
• Innovative solutions
– Aerodynamic cross-section
– Mast-sail interaction model
• Lighter products
• A prototype is needed…
– To validate the manufacturing process
– To validate the FEM model