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Experimental Strain Analysis of the Mastof a 420 Sailboat During Sailing
G. Pellicioli and N. Petrone
Dipartimento di Ingegneria Meccanica, Universita di Padova, Via Venezia, 1 35100 Padova, Italy
ABSTRACT: Aim of the work was the experimental strain analysis of a 420 sailboat mast during
sailing: this type of data is of great interest in the structural design of sailboat masts and hulls as well as
in the sail-making. The work involved the design, calibration and installation of strain gauge bridges at
seven sections of an instrumented mast and at the shrouds: this was followed by the collection of
strain data during simulated laboratory rigging tests and real sailing sessions with medium/strong
wind. Compression loads at the mast step were recorded with a customised load cell calibrated on a
force platform. On the basis of laboratory calibration constants, the strain measurements were
converted into structural loads and averaged over steady states during rigging and sailing either close
to the wind or beam reach: the longitudinal bending moment, the lateral bending moment and theaxial loads were analysed and plotted along the 6.20 m mast length. Highest values of lateral bending
(146 14.5 Nm) were recorded at the mast head, whereas longitudinal bending showed highest
values at the vang connection to the mast (229 29 Nm). Tension loads acting on the shrouds were
also measured with highest values of 2887 167 N. The knowledge of loads acting along the mast
will support the designers in improving the masts cross section profile, the material selection and the
validation of numerical structural analysis. Moreover, experimental data about the loads acting on the
standing rigging and on the mast-step during sailing will support the optimised design of the boat shell.
KEY WORDS: 420 sailboat, mast, sailing loads, shrouds, strain analysis
Introduction
Innovation in masts cross sections and appropriate
selection of materials oriented to the optimum
stiffness, strength and durability are possible only if
reliable data about the distribution of bending
moments acting along the mast during sailing are
available. In addition, the accurate knowledge of
loads acting on the standing rigging and on the
mast step supports a possible optimised design of
the boat shell. Furthermore, experimental data may
also be used to validate computational fluid
dynamics predictions of the sail behaviour and
numerical structural models of the redundant mast-
hull system [1]. Finally, from a sail designer point of
view, the knowledge of the masts deflection line in
the longitudinal and lateral planes is fundamental
for an efficient sail design: displacement measure-
ments are difficult to perform in a rough environ-
ment like a sail regatta, so an indirect structural
approach can be adopted to estimate the deflection
state of the mast.
Very few experimental data from real sailing ses-sions are available, or they are restricted to few
components and not to the whole mast-hull system:
in some cases, only laboratory tests under simplified
loading conditions were performed [1] and compared
with numerical structural simulations. Other
approaches to the problem such as numerical models
without experimental validations or scale models are
possibly characterised by high unreliability levels: at
present it is very difficult to predict numerically the
real load and displacement conditions during sailing
because of the complexity and variability of sea-
wind-sailboat dynamics.
Given these facts, the first objective of the work
was the development of an integrated system for
measuring the structural loads on the mast and the
standing rigging of a 420 dinghy. The main research
requirement was the minimum modification of the
real mast-hull system and the possibility of transfer-
ring the instrumented components and the adopted
methodology to other dinghies.
The second objective of the study was the measure
of bending moment diagrams in the longitudinal and
lateral planes corresponding to well defined states of
the rigging and to different point of sailing underknown wind and sea conditions.
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492482 doi: 10.1111/j.1475-1305.2009.00673.x
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Materials
The boat reference frame adopted is a system of three
orthogonal axes X, Y, Z. The origin of the coordinate
system is placed in correspondence of the centroid of
the masts cross section, at the mast step. Then, X
axis is oriented in the direction of the axis of sym-
metry of the section, that is the direction of thelongitudinal axis of the boat; Z axis develops in the
direction from the step to the head of the mast and Y
axis complete the triad (Figure 1).
The mast and the standing rigging measurement
systems were designed, calibrated and installed in
order to measure the dynamic structural loads during
sailing with minimum disturb effect: strain gauges
were directly applied to components such as the mast
and the shrouds, whereas a low profile two compo-
nent load cell was specifically designed to measure
the vertical and the longitudinal loads at the maststep, as described in what follows.
Instrumented mast
The mast used for this research project is produced by
Super Spars company (Fareham, New Hampshire,
England). It is made of aluminium alloy by extrusion,
cutting and welding. The surface is anodised to pre-
vent corrosion; linear density given by the con-
structor is 0.94 kg per meter of length. The mast is
6200 mm long, the main section measures 57.5
70.5 mm and it is uniform for about 4500 mm of the
total length, while the remaining part of the extru-
sion is tapered up to the top section that is 32.5
34.5 mm. In correspondence of the mast head and ofthe mast step there are two steel components that
respectively allow the movement of the mainsail
halyard and of running rigging.
After a preliminary study of the different possible
loading configurations and of the effects on the sys-
tem mast-hull generated by the combined action of
standing and running rigging, the seven measure-
ment sections were chosen as listed in Table 1 and
sketched in Figure 1.
Fundamental loads considered for the definition of
measuring systems were bending moments in thelateral (Mfx) and longitudinal planes (Mfy) together
with the axial load (N), as shown on Figures 2 and 3.
Against a structural analysis of the mast during the
navigation, the boat with sails hoisted was taken as
reference situation.
Wheatstone bridge circuits were used for the mea-
surement of resistance changes from strain gauges.
The types of connection used are: Quarter bridge,
Half bridge and Full bridge, depending on measured
loads [2]. The bending moment in the longitudinal
plane Mfy were measured at mast sections number 1,
2, 3, 4 and 5 (Figure 3) with four strain gauges at each
section connected with a Full Wheatstone bridge as
shown in Figure 4 (gauges from #1 to #4). Gauges
type HBM 0.6/120-LY43 were used having a 0.6 mm
measuring grid to match with the narrow available
planar surface (gauges #2 and #4) at the sides of the
mainsails head groove. The bending moment in
lateral plane Mfx was measured at sections 4 and 6
7
6
5
4
3
2
1
SR
MS
SL
Y
Z
X
Figure 1: Indication of measuring points along the mast andreference frame adopted on the sailboat
Table 1: List of measuring points, measured load components
and adopted names of measuring channels
Point Description
Measured
loads Measuring channels
7 Mast head Fz M7N
6 Above shrouds junction Mfx M6Mx
5 Under shrouds junction Fz, Mfx, Mfy M5My, M5eL, M5eR
4 Under cross-trees junction Mfx, Mfy M4My, M4Mx
3 Under the parrel Fz, Mfx, Mfy M3My, M3eL, M3eR
2 Mast hole Fz, Mfx, Mfy M2My, M2eL, M2eR
1 Above vangs connection
with the mast
Fz, Mfx, Mfy M1My, M1eL, M1eR
SR, SL Shrouds TL, TR S_SX, S_DX
MS Mast step Fz, Fx FX, FZ
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492doi: 10.1111/j.1475-1305.2009.00673.x 483
G. Pellicioli and N. Petrone : Experimental Analysis of a Sailing Mast
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(Figure 3) with two couples of strain gauges (#L and
#R) connected as Half bridge and placed exactly on
the cross section principal inertial axis (the neutral
axis of bending moment Mfy). At sections 1, 2, 3 and
5 both lateral bending moment and axial load were
measured, by means of lateral strain gauges #L and
#R in a three wires Quarter bridge configuration.
Assuming a linear elastic behaviour it was possible to
calculate lateral bending moment Mfx from the Left/
Right strain values difference and normal stress N
from the strain values average. Quarter bridges were
adopted to reduce the overall number of strain gau-
ges applied on the mast, and the three wire connec-
tion allowed for temperature compensation: for the
purpose of this work this approach was considered
effective for estimating the axial load trend across the
mast on the basis of the channels laboratory cali-
bration in bending and axial loads. On the other
hand, the axial load was measured with a Full
Wheatstone bridge at all sections where it was con-
sidered fundamental (at the mast head section 7 andat mast step).
To prevent damages or short circuit on the mea-
suring system, all strain gauges and their connectionswere insulated with silicone.
Mfx
6
5
4
3
Z
Y
2
1
Figure 2: Sketch of the lateral bending moments Mfx at thecorresponding measuring sections
Mfy
5
4
3
2
1
Z
X
Figure 3: Sketch of the longitudinal bending moments Mfy at
the corresponding measuring sections
3
L RCentroid
24
Y
X
1
Figure 4: Main cross section of the mast with indication of the
strain gauges positions
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492484 doi: 10.1111/j.1475-1305.2009.00673.x
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Shrouds and mast step
Shrouds tension was measured with four strain gaugesconnected as Full bridge, installed directly applied
in correspondence of the chain-plates as shown in
Figure 5 and calibrated on a servohydraulic test
machine in tension. This ensured the possibility of
measuring loads without changing some important
parameters such as the length and stiffness of the
shroud, by preserving the possibility of fine tuning
given by different pin positions at the chain-plate.
For the measurement of loads at the mast step, a two
component load cell (Figure 6) was specifically de-
signed and calibrated. It consists in a stainless steel
block that was CNC machined in order to match
upwards with the mast step stud and downwards with
the standard connection rail fixed to the sailboat hull.
Themast step stud was hosted in the elongated hole of
anupperplateconnectedtothelowerplatebymeansof
two horizontal lamina (measuring the vertical load Fz)
andtwoverticallamina(measuringthehorizontalload
Fx). On each pair of laminas, four strain gauges con-
nectedasFullbridgeswereproperlyplacedtoobtainthe
two decoupled FX, FZ force channels [3]: strain gauges
measuringdeformation zduetoFZforcewereplacedat
the most external part of the upper and lower faces of
the horizontal laminas and strain gauges measuring zduetoFXforcewereplacedatthelowerpartoftheinner
and outer faces of the vertical laminas (Figure 7).
Data acquisition systems
A Somat 2300 CC data acquisition system was used
for data collection both during laboratory and sailing
tests: the system can record 16 strain channels and 16
Figure 5: Instrumented chain-plate at the left shroud
Figure 6: Top-side view of the instrumented load cell at the
mast step
Fz
Fx
x
MN
MX
XZ
Z
e1 = ez
e2 = ez
e3 = ez
e4 = ez
e7 = eze6 = eze5 = eze8 = ez
Figure 7: Placement of sensing strain gauges for FZ and FX Full bridges on the mast step load cell
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492doi: 10.1111/j.1475-1305.2009.00673.x 485
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analog channels. Sampling rate of 40 Hz and 500 Hz
per channel were used respectively during laboratory
and sailing tests.
An inertial platform MTi Xsens (miniature Attitude
and Heading Reference System AHRS) was applied at
the mast hole for measuring the boat orientation
during sailing, synchronously connected to the Somat
2300 system: the boat roll, pitch andyaw anglesduringsailing were therefore available and allowed to recog-
nise the different point of sailing during a sailing
session. The sailing test was entirely filmed also via
commercial video camera from a motorboat.
Methods
Calibration tests
All measuring systems were calibrated in the labora-
tory. Strain gauge bridges installed on the mast were
calibrated with several static tests after applying canti-lever loads in the two bending planes at each sections.
Bythismethod,calibrationconstantsexpressedinNm/
mV/V were obtained at each mast section. These values
were used during data analysis to estimate bending
moments Mfx, Mfy and axial load N from the bridge
voltage output during the measurement tests [3].
The two chain-plates mounted on the shrouds were
calibrated on a servohydraulic machine at each po-
sition of the pin in the plate.
The mast step load cell was calibrated on a labora-
tory rig reproducing the bottom rail on a BERTECforceplatform fixed to the ground and the mast step stud for
load application with servohydraulic cylinders.
Full scale laboratory tests
In order to assess the complete system reliability
before putting to sea for the sailing tests, a restraint
system similar for dimensions and disposition to the
mast hole and the shrouds connections existing on
the 420 was accurately reproduced on a laboratory
bench. During the laboratory tests a BERTEC dyna-
mometric platform was used to measure forces Fx and
Fz acting at mast step and validate measurement
coming from the mast step load cell.
The laboratory tests aimed to reproduce the normal
procedure of boat manning and to evaluate the pureeffect of a man hanging on the trapeze. In particular,
several states were recorded in sequence correspond-
ing to typical rigging and manning states:
state A: jib joisted from resting state;
state B: from state A, applying loads at the
mainsail halyard;
state C: from state A, man of 75 kg at the right
trapeze;
state D: from state A, man of 75 kg at the left
trapeze.
The different states were maintained for at least 10 s
in order to stabilise and clearly distinguish the load-
ing configurations: each state was also repeated at
least three times to allow for estimating correspond-
ing average values.
Sailing tests
Navigation tests were performed in the Adriatic
sea with medium/strong wind conditions (about
68 m s)1), under expert coaching. The acquisition
system was positioned with its battery close to the
mast step into a protective case: the additional mass
of the data acquisition system with cables and battery
was around 10 kg.
Before putting out to sea, an important measure-
ment of the rigging state was made. This state was
named A being equivalent of state A simulated dur-
ing the laboratory tests (jib hoisted).
M N O P Q R
1908.55Time (s)0
Figure 8: Schematic overview of a navigation test lasted about 30 min. The red plot is a qualitative representation of yaw signalcoming from the inertial platform
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492486 doi: 10.1111/j.1475-1305.2009.00673.x
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Several training and regatta operations (Figure 8)
were made with two expert sailors of total mass
135 kg. During this test the sailboat:
sailed close to the wind on starboard tack (M and
O) and on port tack (N and P) with bowman
(80 kg) at the trapeze;
sailed beam reach with the spinnaker on porttack (Q) and on starboard tack (R);
made several tacking and jibing between differ-
ent point of sailing.
Data analysis
Data collected from the strain signals were subse-
quently analysed introducing the static calibration
constants: bending moments Mfx, Mfy and axial load
N were calculated by direct linear transformation and
plotted on diagrams having the vertical axis coinci-dent with the Z coordinate along the mast and the
horizontal axis corresponding to the bending
moments under evaluation. It is worth noting that
the Mfx bending moment diagram will be plotted on
the side of fibres in tension, that means looking
at the sailboat mast from bow to aft (in the negative
X axis direction): likewise, the Mfy bending moment
diagrams will lay on the side of fibres in tension as if
looking at the boat from right to left (in the positive
Y axis direction).
Results
One of the major objectives of the work was to obtain
the bending moment diagrams in the longitudinal
and lateral planes corresponding to fundamental
states from the rigging action and the sailing events:
the results will then be presented in terms of plots
obtained from laboratory and sailing tests, high-
lighting noticeable differences to be further
addressed in the discussion.
Laboratory tests
A bent state of the mast in the lateral plane resulted
evident during state A (Figure 9), despite the maxi-
mum care in the rigging setup. In the further states
analysis, the subsequent additional bending
moments due to the man on a trapeze were referred
6
5
4
3
Z-coordinate(m)
2
1
06000 4000 2000 2000 4000
Axial load (C)
Axial load (A)
60000(N)
Figure 9: Results of laboratory tests. Values of the structural
bending moments along the mast axis in different states
170
240
130
130
180
120
180
3200 State M State N 426Time (s)
260M2Mx
(Nm)
M3Mx
(Nm)
M4Mx
(Nm)
M5Mx
(Nm)
M6Mx(Nm)
220
Figure 10: Results of laboratory tests. Diagram of lateral bending moments with man on the right (C) or left (D) trapeze
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492doi: 10.1111/j.1475-1305.2009.00673.x 487
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to the state A bending diagram as a baseline. These
additional bending moments were named Mfx* and
showed a high degree of symmetry as expected
(Figure 10).
Highest peak values of bending moments Mfy onthe longitudinal plane were recorded in correspon-
dence of section 4 (Figure 9): the shift from state (A)
to the other two states of man on the right (C) and on
the left trapeze (D) causes small changes. On the
other plane, the effect of the trapeze on the lateral
bending moment Mfx* is much more evident
(Figure 10).
The differences between the longitudinal and
lateral bending moments are appreciable both in
terms of absolute values of peaks of bending
moments (Mfy peaks are more than twice higher than
Mfx peaks) and of location of peaks: section 4
experiences maximum longitudinal bending, section
2 experiences maximum lateral bending.
Shrouds tension loads recorded in state A were
1674 N at the right and 1190 N at the left side,
confirming an asymmetric mast rigging state. The
axial load curve along the mast axis had a maxi-
mum values between the shrouds connection and
the mast hole and showed the comparison of
additional loads due to the man on the trapeze
(Figure 11). In this last condition, the maximum
values of forces at the mast step, Fz =)
5090 N andFx = 370 N, were recorded.
Sailing tests
After sailing tests, strain data were again convertedby means of the calibration constants into bending
moments Mfx, Mfy and axial load N and studied in
the time domain. Due to the maximum available
number of 16 channels, the two quarter bridge
channels named M1eL and M1eR were not recorded
so that the lateral bending moment Mfx and the
axial load N at section 1 were only linearly esti-
mated from the values of the adjacent sections.
Moreover, some data at section 3 of moment Mfywere showing unrealistic patterns: the correspond-
ing values were linearly interpolated from the
adjacent sections 2 and 4.
The strain signal showed consistently a stable
mean value for each sailing state with a variable
superimposed oscillating signal due to the sea waves
and the wind gusts (Figure 12).
Considering the aim of the study, oriented to an
evaluation of steady state loading conditions, the
measured data were averaged over all the time
interval corresponding to a certain state: the mean
values of bending moments along the mast are
collected in Tables 2 and 3 with the corresponding
standard deviations. The bending moment curves ofmean values are presented in Figures 13 to 16.
6
5
4
3
Z-coordinate(m)
2
1
0250 150200 50100 15010050 200
Mx (A)
My (C)
My (A)
My (D)
2500(Nm)
Figure 11: Results of laboratory tests. Diagram of axial load
6
5
4
3
Z-coordinate(m)
2
1
0250 150200 50100 15010050 200
Mfx* (C)
Mfx* (D)
2500(Nm)
Figure 12: Example plots of the time series of five channels
from the strain measurements, showing the transition between
state M and N due to a tacking manoeuvre
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The first significant result from sailing test was the
correspondence of state A (Figure 13) with state A of
laboratory test (Figure 9), mainly in terms of Mfy: also
the Mfx curve from sailing tests is very similar to the
Mfx curve in the laboratory tests but much more
closer to the vertical axis in the case of sailing tests.
This was interpreted as due to a much more realistic
rigging state than in the laboratory simulation, to-
gether with a more accurate setup procedure followed
in the sailing session under the supervision of an
expert coach.
During sailing, the six significant sailing states
from letter M to letter R (Figure 8) were analysed, but
for the present discussion structural loads of only
three significant sailing states M, N, Q have beenplotted (Figures 14, 15 and 16).
The second evident result is the high negative peak
values of Mfy at sections 1 and 2 in state M (Fig-
ure 14), that is very different from Mfy in state A and
A (Figures 9 and 13): this is correlated with the ten-
sioning of the vang, acting between the boom and
the mast, that was not present neither in the labo-
ratory tests nor in the state A. The particular vang
configuration showed an unexpected major influence
on the mast stress condition, that should be consid-
ered both in the planning stage of an experimental
measurement and in the mast design.
A third evident difference between laboratory
(Figure 10) and sailing tests (Figures 1415) can be
observed in the Mfx diagrams with a man on the
trapeze: during sailing tests the effect of thewind clearly modifies moment diagrams: this is
Table 2: Lateral bending moments during sailing
Mfx (Nm)
Close to the wind Beam reach with spinnaker
On starboard tack (M)
(Wind angle = )35)
(Dt = 178 s)
On port tack (N)
(Wind angle = +35)
(Dt = 248 s)
On port tack (Q)
(Wind angle = +130)
(Dt = 447 s)
On starboard tack (R)
(Wind an-
gle = )140)
(Dt = 334 s)
Section Mean SD Mean SD Mean SD Mean SD
Mfx_7* 0.0 n.d. 0.0 n.d. 0.0 n.d. 0.0 n.d.
Mfx_6 )131.0 10.8 145.9 14.5 124.7 22.6 )97.7 17.8
Mfx_5 76.2 9.1 )97.1 12.0 )102.1 20.0 64.2 15.4
Mfx_4 23.8 17.5 )54.6 16.0 38.0 22.0 )3.9 19.3
Mfx_3 103.8 13.5 )41.0 16.7 15.7 23.6 99.6 20.4
Mfx_2 )5.0 29.5 13.1 29.4 124.4 37.6 )56.5 36.1
Mfx_1* )2.4 n.d. 6.4 n.d. 60.9 n.d. )27.6 n.d.
Mfx_0* 0.0 n.d. 0.0 n.d. 0.0 n.d. 0.0 n.d.
*Theoretically assumed values; Standard Deviations are not defined (n.d.).
Table 3: Longitudinal bending moments during sailing
Mfy (Nm)
Close to the wind Beam reach with spinnaker
On starboard tack (M)
(Wind angle = )35)
(Dt = 178 s)
On port tack (N)
(Wind angle = +35)
(Dt = 248 s)
On port tack (Q)
(Wind an-
gle = +130)
(Dt = 447 s)
On starboard tack (R)
(Wind angle = )140)
(Dt = 334 s)
Section Mean SD Mean SD Mean SD Mean SD
Mfy_7* 0.0 n.d. 0.0 n.d. 0.0 n.d. 0.0 n.d.
Mfy_6* 61.4 n.d. 64.3 n.d. 4.0 n.d. 14.7 n.d.
Mfy_5 71.9 14.2 75.3 10.5 4.7 10.9 17.2 11.0Mfy_4 205.2 20.1 214.9 16.7 204.8 21.3 204.8 23.2
Mfy_3* )102.6 n.d. )102.8 n.d. 2.6 n.d. )45.2 n.d.
Mfy_2 )225.0 19.0 )229.3 29.0 )77.8 32.3 )144.7 35.8
Mfy_1 )224.2 27.1 )228.1 10.5 )94.0 20.6 )127.7 22.9
Mfy_0* 0.0 n.d. 0.0 n.d. 0.0 n.d. 0.0 n.d.
*Theoretically assumed values; Standard Deviations are not defined (n.d.).
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492doi: 10.1111/j.1475-1305.2009.00673.x 489
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particularly evident at the mast head where the lat-
eral bending is due only to the wind pressure on themainsail.
Finally, when the point of sailing changes from M
(Figure 14) to N (Figure 15), the angle between thewind and the boat changes almost symmetrically and
6
5
4
3
Z-coordinate(m)
2
1
0250 150200 50100 15010050 200
My (A)
Mx (A)
2500(Nm)
Figure 13: Results of sailing tests. Diagram of lateral and lon-
gitudinal bending moments after hoisting the jib
6
5
4
3
Z-coordinate(m)
2
1
0250 150200 50100 15010050 200
Mx (M)
My (M)
2500(Nm)
Figure 14: Results of sailing tests. Diagram of lateral and lon-
gitudinal bending moments sailing close to the wind on star-
board tack (state M)
6
5
4
3
Z-coordinate(m)
2
1
0250 150200 50100 15010050 200
Mx (N)
My (N)
2500(Nm)
Figure 15: Results of sailing tests. Diagram of lateral and lon-
gitudinal bending moments sailing close to the wind on port
tack (state N)
6
5
4
3
Z-coordinate(m)
2
1
0250 150200 50100 15010050 200
Mx (Q)
My (Q)
2500(Nm)
Figure 16: Results of sailing tests. Diagram of lateral and lon-
gitudinal bending moments sailing beam reach on port tack
(state Q)
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the two diagrams of Mfx show almost symmetric
changes in the curves, as expected. Major differences
are evident when state Q (Figure 16) is compared
with state N: in this case, state Q corresponds to the
hoisting of the spinnaker and the surging of the vang
that justify the great changes in the longitudinalbending moment diagrams both at the mast head
and at the mast step. On the other plane, the lateral
bending moment Mfx shows changes due to the effect
of the different mainsail orientation and the spin-
naker boom connected to the mast.
The values of shroud loads in the different points
of sailing (Figure 17) are justified by the upwind or
downwind position of each shroud during starboard
(M, O, R) and port tack (N, P, Q): sailing beam reach
gives highest tension values as expected due to the aft
wind sailing and the presence of the spinnaker.
Discussion
The rationale of the work was the development of an
experimental method to measure the bending and
axial loads acting on the mast and shrouds of a sail-
boat during sailing: this would allows the collection
of significant structural load data, useful for an opti-
mised design of innovative masts and hulls.
A first limitation of the present work can be found in
the maximum number of 16 synchronous strainchannels recorded during the tests; another limitation
is that reported results refer to a single sailing session,
with specific crew, wind and sea conditions. Further
activities such as the adoption of improved hardware
and the planning of additional sailing sessions will
help in overcoming the mentioned limitations.
Full scale laboratory tests were useful to analyse the
structural behaviour of the mast under simulated
realistic rigging conditions; further, these tests were
necessary to make the calibration procedures and to
check the measuring systems reliability. Results of
laboratory tests were important for a comparison
with corresponding data from sailing tests in order to
evaluate the effects of a correct simulated rigging
setup and the variation of the bending moment
diagrams due to the wind effect.
In sailing tests, the adopted approach to measure
the loading conditions on the mast was suitable to
give sufficiently reliable data that were not available
before to our knowledge for this class of sailboats.The bending moment diagrams in the longitudinal
plane (My) and the lateral plane (Mx) corresponding
to average values of steady states can be considered as
the main outcome of the work, both in terms of
average values and of data variability.
Several engineering analysis can be addressed and
carried out on the basis of the collected data, such as
(i) the estimation of the mast deflection line from the
combination of mast stiffness and bending diagrams,
(ii) the evaluation of mast safety factors with respect
to peak values in the two planes, (iii) the evaluationof mast axial behaviour and eulerian critical safety
factors, (iv) the analysis and redesign of the overall
hull structure, using the experimental data as load
conditions at the mast step and standing rigging
connections of a numerical model and (v) the local
hull strength verification at the shrouds fixation
points and at the mast step.
Conclusions
An instrumented mast developed for both laboratory
and sailing tests was used in combination with strain
gauged standing rigging components at the shrouds
and the mast step. After a first session of laboratory
tests when rigging loads were measured, strain data
were collected at seven mast sections during real
sailing with medium/strong wind in different point
of sailing.
The data were analysed to obtain the bending
moments along the mast in the lateral and longitu-
dinal planes as average values over steady states of
sailing either close to the wind or beam reach: lon-gitudinal and lateral bending moments were plotted
along the mast length. Highest values of lateral
bending (146 14.5 Nm) were recorded at the mast
head, whereas longitudinal bending showed highest
values at the vang connection to the mast
(229 29 Nm). Shrouds highest tension value of
2887 167 N was recorded during beam reach sail-
ing with spinnaker.
The collected data shall allow the sailboat designers
to improve the masts cross section profile and its
material selection or to perform the validation of
numerical models. Moreover, the accurate knowledge
3500
3000
2500
1500
500
0M N O P
Right shroud
2439
18432010
22752356
1924
2212
1998
2372
2746
2887
2230
Left shroud
Point of sailing
Shroudtension(N)
Q R
2000
1000
Figure 17: Results of sailing tests. Variation of the shroud
loads during sailing
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492doi: 10.1111/j.1475-1305.2009.00673.x 491
G. Pellicioli and N. Petrone : Experimental Analysis of a Sailing Mast
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8/7/2019 Carichi su albero
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of loads actingon thestanding rigging andon the mast
step will support an optimised design of theboat shell.
ACKNOWLEDGEMENTS
Compagnia della Vela Yacht Club (Venice, Italy); Super
Spars (Fareham, New Hampshire, England); Dr. Renato
Pellicioli.
REFERENCES
1. Bottacin, G., Meneghetti, G., Quaresimin, M. and Zordan,
A. (2004) Analysis and testing of a new composite sailing mast.
By Sea, Milano.
2. Dalley, J. W., Riley, W. F. and Meconnel, K. G. (1999)
Instrumentation for Engineering Measurement. John Wiley & S,
Hoboken.
3. Pellicioli, G. and Petrone, N. (2008) Acquisition of struc-
tural loads acting on the mast of a 420 during sailing. Pro-
ceedings of 7th International Conference on the Engineering of
Sport, Biarritz, 26 June 2008, Vol. 2, 499508, Springer.
ISBN 978-2-287-09412-5.
2010 Blackwell Publishing Ltd j Strain (2010) 46, 482492492 doi: 10.1111/j.1475-1305.2009.00673.x
Experimental Analysis of a Sailing Mast : G. Pellicioli and N. Petrone