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Comparative Performance Prediction of Historical Thames A Rater Class Designs

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Abstract and Figures

The Thames A-Rater fleet is a unique class both in appearance and in its combination of historic and modern technologies. With high aspect ratio, carbon fibre rigs fitted onto wooden hulls, many of which have survived two World Wars, the class is a demonstration of the evolution of sailing technology. In more recent decades, various attempts have been made to expand the class with new composite boats. However, due to the strict rules issued by the class association, new hulls must be exact replicas of existing A-Raters, with a 1.5 inch tolerance. Furthermore, as only one linesplan exists in the public domain, the expansion of the fleet is extremely limited. Consequently, in order to ensure the conservation of some of these historic designs, the lines of several vessels were taken off and used to create accurate linesplan and 3D models. The comparative performance of the various crafts was then assessed through a Velocity Prediction Programme, focused on the specific environmental conditions of the vessels' main operating area, eventually ascertaining the hull with the best racing potential by design.
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Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
COMPARATIVE PERFORMANCE PREDICTION OF HISTORICAL THAMES A RATER
CLASS DESIGNS
J E THOMAS and J-B R G SOUPPEZ, Solent University, UK.
SUMMARY
The Thames A-Rater fleet is a unique class both in appearance and in its combination of historic and modern technologies.
With high aspect ratio, carbon fibre rigs fitted onto wooden hulls, many of which have survived two World Wars, the class
is a demonstration of the evolution of sailing technology. In more recent decades, various attempts have been made to
expand the class with new composite boats. However, due to the strict rules issued by the class association, new hulls must
be exact replicas of existing A-Raters, with a 1.5 inch tolerance. Furthermore, as only one linesplan exists in the public
domain, the expansion of the fleet is extremely limited.
Consequently, in order to ensure the conservation of some of these historic designs, the lines of several vessels were taken
off and used to create accurate linesplan and 3D models. The comparative performance of the various crafts was then
assessed through a Velocity Prediction Programme, focused on the specific environmental conditions of the vessels’ main
operating area, eventually ascertaining the hull with the best racing potential by design.
1. INTRODUCTION
Advances in naval architecture theory and inherent
technology has allowed to take a closer and more refined
approach to the analysis of historical crafts. The intention
is not only to widen the knowledge of past designs, but
also to ensure their conservation. This particular paper
focuses on the British Thames A Rater class, with the
ambition to contribute to the conservation of these historic
designs, as well as identify the best performing one, to
further promote the revival and growth of the class.
Firstly, the history underpinning the Thames A Rater class
will be introduced, with a strong focus on the novelty and
innovations that this atypical racing class has provided for
over a century. Then, two methods of conservations will
be presented, namely modelling hulls from either original
linesplan, or by taking the lines off existing vessels. In
both cases, the final product is a table of offsets, allowing
for an accurate 3D model to be made. Finally, the
performance of the various hulls fitted with identical rig,
sails and appendages will be ascertained using a velocity
prediction programme (VPP), thus identifying the fastest
design.
2. HISTORICAL BACKGROUND
2.1 THAMES SAILING CLUB
Created in 1870, the Thames Sailing Club (TSC) is the
second oldest inland sailing club in Britain. The success
of the first years of racing quickly highlighted two major
issues: boats of highly diverse performance were
competing together and no racing rules were applied.
Despite those two constraints, the Thames Sailing Club
became so important that in 1887, Queen Victoria herself
awarded the Thames Champions Cup. This particular
event revealed the potential of inland sailing events, and
called for a prompt remedy to previously mentioned
issues. The following year saw the creation of the Sailing
Boat Association (SBA) that established racing rules, and
introduced a handicap system, based on the popular Dixon
Kemp’s rating formula, dating 1880 [1]:
𝑅𝑎𝑡𝑖𝑛𝑔 = 𝐿𝑤𝑙 × 𝑆𝐴
6000
Eq. 1
In which:
Lwl
Waterline length.
𝑓𝑡
SA
Sail area.
𝑓𝑡2
This gave birth to the term Rater’, defining yachts
designed under this particular rule; a One-Rater rating 1, a
Half-Rater rating 0.5, etc. Later, a class gathering boats
rating from 0.8 to 1 was created: the A Rater class.
2.2 THAMES A RATER
Towards the end of the 19th century, the design of inland
racing yachts is generally defined as a ‘skimming dish’, a
philosophy that reached a plateau with the A Rater’s fleet
[2]. Out of the 13 original A Raters still racing today,
twelve were built between 1898 and 1911 and the last one
post WWI in 1922. The majority of the A Raters were
designed by Alfred Burgoine and Linton Hope, each
having a radically different approach to the rating rule that
only accounts for the waterline length and the sail area.
Burgoine’s yachts are characterized by a large sail area,
the counterpart being a shorter waterline length. While the
latter restricts the speed for a given Froude number, the
larger sail area will offer a more powerful boat that
therefore has to be made wider to increase form stability
and the ability to carry sail. On the other hand, Hope
favoured a longer waterline and narrower beam, and
consequently a smaller sail area as dictated by the rating
rule. The opposition of those two design philosophies is
illustrated in Table 1, comparing two original A Raters,
namely Ulva (1898) and Scamp (1902), respectively
designed by Burgoine and Hope.
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
Yacht
Lwl (m)
SA (m²)
Rating
Ulva
4.80
35.00
0.99
Scamp
5.15
33.00
1.00
Table 1: Burgoine and Hope designs comparison.
The radically opposed specifications led to distinctive
performances, with Hope’s yachts being better suited to
upwind sailing while Burgoine’s ones sailed faster
downwind.
2.3 CHEATING THE RULE
Looking at the various attempts to cheat the A Rater class
rules provides some insights into the critical design areas
to be improved; in this case the waterline length, the
stability and the mast weight.
Firstly, the work of William Froude published a few
decades before the A Raters [3, 4] identified the waterline
length as the main speed restricting factor, hence the
interest in a longer waterline length. For the typical
resistance hump occurring at a Froude number of 0.33,
Ulva would achieve 4.40 knots, while Scamp would reach
4.56 knots. As a result, some boats were fitted with rods
and wires at each end. By winding up the wires, the yacht
could artificially be sagged to offer a shorter waterline
length when measured. The wires would then be loosened
when racing, thus extending the actual waterline length.
Secondly, stability is a major factor for such a light
displacement craft carrying a large sail area. Some of the
main innovations with regard to stability have been
experimented on Vagabond, designed in 1907 by Hope.
The ancestor of the trapeze was named the ‘bell rope’: a
crew member, the ‘bell boy’, holding onto a rope attached
at the top of the mast could stand to windward, as depicted
in Figure 1, thus increasing the righting moment.
After the bell rope was made illegal, Vagabond was
fitted with sliding seats (see Figure 2), with the same effect
of increasing the righting moment, and the same fate of
being banned.
Finally, removable top masts were introduced to minimise
the heeling moment in high winds. While this practice was
prohibited, the masts would undergo several
improvements in the future.
2.4 EVOLUTION
While the hulls and appendages have been untouched
since the beginning of the 20th century, the rig and sails
have significantly evolved. Originally designed as a low
aspect ratio gaff rigs, the masts evolved from bamboo to
the current carbon fibre, via solid and hollow wooden and
aluminium spars. With the improving mast technology,
higher spans could be achieved, and the A Raters are now
famous for their impressive 43 feet (13.1m) tall rigs,
depicted in Figure 3.
One of the downsides of the early gaff rigs was the
eccentric location of the centre of effort of the sails
downwind, requiring tremendous efforts from the
helmsman to keep the boat on course in the narrow
waterways. Remains of this behaviour can be seen today
with some of the original tillers, clearly made for the
helmsman to hold onto it firmly, as shown in Figure 4.
Figure 1: The ‘bell boy’ and the ‘bell rope’ [2].
Figure 2: Sliding seats on Vagabond [2].
Figure 3: Rig in 1907 (left) [2] and 2014 (right) [5].
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
Along with the evolution of masts, cotton sails have been
replaced with more advanced materials. Those
innovations contributed to the success of the A Rater class,
and so did the Glass Reinforced Plastic (GRP) technology
that sparked a renewed interest in the class in the late
1970s.
2.5 MODERN DAYS
The A Rater class is one of the rare racing classes that
survived after World War II, but with the last wooden A
Rater dating from 1922, the number of boats was
becoming smaller and smaller over time. In 1978, a female
mould tool of Ulva was made, and new GRP hulls were
built, thus ensuring the future of the class. Around this
time a change in rules also took palce: no new design
would be allowed, and any new A Rater would have to be
an exact replica of an original one; as stated by the Thames
A Rater class rule [7] and further discussed in Section 3.1.
In addition, to stop the arms race resulting from the new
composite manufacturing, a minimum class weight was
imposed.
The early 2010s saw the appearance of the first full carbon
boats, fitted with a new deck inspired from the 5o5 class,
and thus moving away from the traditional designs; the
latest A Rater to have been built is pictured in Figure 5.
2.6 DEVELOPMENT AND GROWTH
The current challenge is to provide a new opportunity for
the Thames A Rater class to grow and develop its racing
fleet. In order to support this ambition, a number of
linesplan for existing vessels will be gathered, and
converted into 3D models. This will either be based on
existing linesplan, as detailed in Section 3, or by taking the
lines off existing vessels, as presented in Section 4. From
the database of designs, the most efficient hull leading to
the fastest boat of the water will be identified. This will
then be adopted as the base hull for the next generation of
Thames A Raters.
3. LINESPLANS CONSERVATION
3.1 ORIGINAL LINESPLAN LOFTING
The Thames A Rater class rules [7] specifies the
requirements for a craft to meet the one design rule. This
ranges from a minimum lightship weight of 750 lbs
(340kg), to a maximum mast height from the sheerline of
43ft, and a sail area of 350 ft2 (32.51m2). But the primary
design constraint is given by rule D2 [7]:
“D2 New Yachts
A new hull will only be considered to be an A class rater
hull if it is an exact replica of an existing Rater as defined
above, taken from either an existing hull, or original lines,
subject in both cases to a tolerance of one and one half
inches.”
While some linesplans are still in existence, owners are
very protective of those. The linesplan of an original
Thames A Rater therefore has to be found in the public
domain in order to provide the basis of the new yacht. The
only publicly available linesplan is featured in the 11th
edition of Dixon’s Kemp manual of yacht and boat sailing
[8], reviewed by Linton Hope, who added the linesplan of
the Thames A Rater Scamp.
3.2 TAKING THE LINES
Designed in 1902, Scamp has always been a successful
boat and, being one of the original Thames A Rater, it
qualifies as an exact replica of an existing A Rater and will
therefore be adopted as the basis hull of the new design.
When dealing with one of the last drawings of an historic
craft, the priority is to ensure the integrity of the document
and avoid any form of damage to it. With this is mind, the
state-of-the-art facilities available at the British Library
have been utilised to obtain a digital copy of the linesplan,
as shown in Figure 6.
Figure 4: The bracing tiller of Ulva [6].
Figure 5: The latest A Rater built [5].
Figure 6: Original linesplan of Scamp (1902) [8].
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
Unfortunately, the drawing was slightly distorted due to
the folds and the deformation due to aging. While it
constitutes a good graphical representation, it does not
allow for an accurate enough modelling of the boat.
As a result, the lines were manually taken off by physical
measurements of all the offsets to the closest 1/64th of an
inch (accuracy of ± 1/128th of an inch). The lines were
taken solely from the body plan. Indeed, since the body
plan was drawn over a small area, it had been less affected
by distortion and aging or folds compared to the half-
breadth and profile view extending the full length of the
plan.
3.3 2D DRAWING
The table of offsets realised was then scaled up to full size,
converted from imperial to metric, and numerically lofted
using computer aided design (CAD). This process enabled
the redrawing of the 2D linesplan, ensuring an exact
replica is achieved, as shown in Figure 7.
Note that this linesplan is an exact replica of the original
one, reproducing every detail, even where discrepancies
have been noticed, as it is the case with the centreboard.
3.4 3D MODELLING
Scamp was then modelled in 3 dimensions, in a process
very similar to the one of traditional boatbuilding. First,
the stations are positioned along the length of the craft; a
surface is then lofted along those stations with a specified
accuracy of 0.01 mm. The process can be observed in
Figure 8.
The hull surface then allows to ascertain the hydrostatics,
compared to the expected values derived from the
linesplan, in order to ensure the accuracy of the modeeling
process, and thus compliance with the strict tolerance of
the class rule.
3.5 HYDROSTATICS
The hydrostatics of the 3D model have been compared to
those determined from the replica of the 2D linesplan
using Simpson’s rule. The results in Table 2 reveal a very
accurate modelling, with an average 0.46% difference,
well within the uncertainty inherent to each method.
Parameter
Linesplan
3D
Model
Diff.
Diff. (%)
LOA (m)
8.28
8.28
0.000
0.00%
Lwl (m)
5.15
5.17
0.019
0.37%
BOA (m)
1.90
1.90
0.000
0.00%
Bwl (m)
1.66
1.64
-0.020
-1.20%
Tc (m)
0.16
0.16
-0.002
-1.25%
Disp. (m3)
0.548
0.545
-0.003
0.00%
LCB (m)
2.84
2.80
-0.043
-1.53%
LCF (m)
2.81
2.78
-0.033
-1.16%
Cb
0.40
0.40
-0.003
-0.71%
Cp
0.59
0.59
-0.006
-1.04%
Table 2: Hydrostatics comparison.
An exact replica of Scamp has therefore been achieved,
thus complying with the class rule.
4. HULL MODELLING
4.1 HULL MEASUREMENTS
To satisfy the primary ambition of this project, namely to
preserve the Thames A Rater designs, a method for
producing a table of offsets from hand measurements was
applied.
A right-angled triangle jig was designed and built from
metal and wood with horizontal shelves at 50mm vertical
intervals, as shown in Figure 9.
Measurements were made to a high degree of accuracy,
ensuring it was perfectly level and square. The hull was
first measured for its overall length, breadth and depth.
The length of the vessel was then separated into 10 equally
spaced stations and the jig was lined up at right angles to
the centreline of the vessel at each station. The height of
the jig was adjusted so that the top shelf lined up with the
sheer line, the jig was levelled and the distance from the
Figure 7: Replica of the Scamp linesplan [9].
Figure 8: 3D modelling of Scamp.
Figure 9: Rig used to take offsets from hull
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
centreline to a known point on the jig was measured and
recorded. The distance from the known point to the sheer
line was then recorded with a meter rule to an accuracy of
±0.5mm. This procedure was then repeated on all the
shelves down from the sheer line and finally the canoe
body depth at the station was measured. The procedure
was performed for all the stations down the length of the
boat. The same method was also used to measure some of
the aesthetic features of the hull such as the reverse raked
transom and the bow curvature. Ultimately, a detailed
table of offsets was produced, as illustrated for the boat
Spindrift in Table 3.
Table 3: Example of table of offsets for Thames A Rater
4.2 POINT CLOUD MEDELLING
The table of offsets collected from the hull measurements
was formatted and imported into a hull modelling
software. The station spacing, and vessel base line was
defined. The result is a point cloud for the half-hull of the
vessel, depicted in Figure 10.
4.3 GENERATING SURFACE
An editable surface was then generated, with a web of
control points related to the markers, aiming for close
proximity. Using handmade adjustments of control points,
the surface was then minorly altered to bring it as close to
the markers as possible and increase the degree of
accuracy of the model to well within the required 1.5 inch
required by the class rule. The final faired 3D model for
Spindrift can be seen in Figure 11. The same process was
repeated for Dainty Too. The resulting linesplans for
Scamp introduced in Section 3 and those of Spindrift and
Dainty Too can be found in the Appendices.
5. VELOCITY PREDICTION PROGRAM
5.1 TECHNICAL BACKGROUND
At a design stage, the performance of sailing yachts can be
assessed by way of a velocity prediction programme. In
this particular instance, a three degrees of freedom VPP
was conducted, achieving equilibrium for the surge, sway
and roll.
The hydrodynamic resistance model was based on the
Delft Systematic Yacht Hull Series (DSYHS) [10], with
all the Rater hulls fitting within the series. The
aerodynamic model, based on Hazen coefficients [11],
allowed to quantify the sail forces, and in turn the drive
force, sail side force, and heeling moment. The boat speed,
leeway angle and heel angle required for equilibrium can
then be ascertained, thus providing the theoretical
optimum boat speed for each vessel at given points of sails
in given wind conditions.
To ensure that the ideal hull design, from a performance
perspective, is identified, only the hulls were varied for the
comparative performance assessment. The rig, sails and
appendages were all kept constant for the various
historical hull designs.
5.2 RIG, SAILS AND APPENDAGES
A set of foils and spars were designed to be used in the
VPP. Each hull would be tested with these appendages
under the same wind speeds and directions, isolating the
hull shape as the only changing factor between each test.
The performances of each design could then be accurately
analysed and compared.
The largest allowable sail area written into the Rater
Association Rules was chosen and several existing sail
sets were compared to determine the best foresail area to
mainsail area ratio. The sizing of the spars and rigging was
determined using The Nordic Boat Standard [12].
The rudder and centreboard were designed with a straight
quarter-chord semi elliptical shape to encourage elliptical
spanwise loading, reducing the induced drag from the
appendages. Multiple symmetrical airfoil sections were
tested to determine the most efficient shape at the angles
of attack experienced when the vessel is underway.
Figure 10: Point cloud achieved from the table of offsets.
Figure 11: Surface Generated and fitted to point cloud
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
5.3 WEATHER CONDITIONS
The Thames A-Rater sails on the upper regions of the
River Thames throughout the year and , during this time
they experience a wide variety of conditions, with wind
speeds ranging from 0 to gusts in excess of 30 knots. In
order to better refine and target the VPP to the most typical
sailing conditions, a weather study was conducted looking
at the wind speeds experienced by the Raters during one
of their main racing events, namely Bourne End Week,
over the last 9 years. The results of the weather study are
summarised in Table 4.
Year
Day 1
Day 2
Day 3
Day 4
Day 5
Avg
2010
11.3
17.4
9.6
6.1
6.1
10.1
2011
14.8
13.0
10.4
9.6
9.6
11.5
2012
11.3
13.0
11.3
10.4
12.2
11.6
2013
9.6
7.8
16.5
6.1
7.8
9.6
2014
9.6
12.2
6.1
9.6
7.8
9.0
2015
9.6
8.7
8.7
9.6
10.4
9.4
2016
9.6
11.3
13.0
16.5
13.9
12.9
2017
14.8
4.3
6.1
13.9
4.3
8.7
2018
16.5
7.8
9.6
10.4
5.2
9.9
Table 4: Weather study for past Bourne End Weeks: maximum steady
wind speed (kts).
5.4 PERFORMANCE ASSESSMENT
All three boats were tested in the VPP under the same
conditions, particularly focussed between 8 to 12 knots,
however with light wind speeds as well for the purpose of
assessing the determining design factor affecting the
performance. Indeed, three main factors are at play:
A longer length on waterline implies a lower Froude
number for a given speed, thus contributing to a
reduction in the wave making drag.
A wider beam provides better stability, keeping the
spars and sails more upright, and offering the
maximum sail area to the wind, while reducing the
amount of wind spilling form the sails, thus
increasing the vessels performance in higher winds.
A reduced wetted surface area (WSA), i.e. the surface
of the hull that is in contact with the water, minimises
drag at low speeds.
The three boats used in the study were good examples of
how the combinations of the aforementioned attributes,
quantified in Table 5, can affect performance.
Yacht
Lwl
(m)
Bwl
(m)
Tc
(m)
WSA
(m2)
Disp.
(kg)
Scamp
5.15
1.66
0.16
7.13
650
Spindrift
5.76
1.85
0.15
7.70
650
Dainty Too
4.25
1.74
0.18
6.30
650
Table 5: Main hydrostatics comparison.
It is important to note that the results in Table 6 do not
represent a definite comparison of the various boats on the
water, as these vessels all have different rigs and crew,
both significantly altering the performance of a racing
dinghy. Instead, the intent is to assess, for a given rig and
appendages, the hull design that would theoretically
results in the optimum performance.
Fastest
Hull
True Wind Speed (kts)
TWA
2
4
6
8
10
12
32
Scp
Scp
Scp
Spdt
Spdt
Spdt
40
Scp
Scp
Scp
Scp
Spdt
Scp
45
Scp
Scp
Spdt
Scp
Spdt
Spdt
52
Scp
Scp
Spdt
Spdt
Spdt
Spdt
60
Scp
Scp
Spdt
Spdt
Spdt
Spdt
70
Scp
Scp
Spdt
Spdt
Spdt
Spdt
75
Scp
Scp
Spdt
Spdt
Scp
Spdt
80
Scp
Scp
Spdt
Spdt
Spdt
Spdt
90
Scp
Scp
Spdt
Spdt
Spdt
Spdt
100
Scp
Scp
Spdt
Spdt
Spdt
Spdt
110
Scp
Scp
Spdt
Spdt
Spdt
Spdt
120
Dto
Scp
Scp
Spdt
Spdt
Spdt
130
Dto
Scp
Scp
Spdt
Spdt
Spdt
135
Dto
Scp
Scp
Spdt
Spdt
Spdt
140
Dto
Scp
Scp
Scp
Spdt
Spdt
150
Dto
Scp
Scp
Scp
Spdt
Spdt
160
Dto
Scp
Scp
Scp
Scp
Spdt
165
Scp
Scp
Scp
Scp
Scp
Spdt
170
Scp
Scp
Scp
Scp
Scp
Spdt
180
Scp
Scp
Scp
Scp
Scp
Spdt
Table 6: Comparative VPP results for Scamp (Scp), Spindrift (Spdt)
and Dainty Too (Dto).
The results depict a near perfect divide between Scamp
and Spindrift. The former performs better in lighter winds
thanks to its lowered wetter surface area, and larger wind
angles where stability is not needed, as Scamp is narrower.
As the wind speed increases, the friction drags
contribution to the total resistance decreases, and stability
becomes more critical. Consequently, Spindrift would
perform better in these conditions.
As for Dainty Too, despite a much smaller wetted surface
area and reasonable beam, the boat suffers from too short
a waterline length, implying it will sail at a much higher
Froude number for a given boat speed. With the exception
of specific downwind angles in extremely light winds, this
design never outperforms the others.
Referring back to the weather study, wind speeds between
8 and 12 knots would be most common, and Spindrift has
been shown to perform much better in those conditions
achieving up to a knot of boat speed more than the next
best hull. It would therefore be the recommended hull to
be employed for the development and growth of the
Thames A Rater Class.
Nevertheless, there are elements, such as the three A Rater
crew hiking out to the full extent of their ability to keep
the vessel flat that cannot be replicated in a computer
programme such as a VPP.
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
6. CONCLUSIONS
Using different techniques, such as taking the lines off
existing original linesplans, or performing measurements
on existing hulls for the purpose of generating a point
cloud of 3D models, the linesplan of three Thames A Rater
have been conserved, namely Scamp, Spindrift and Dainty
Too.
Furthermore, the three hull designs were combined with a
standard rig and appendages to perform a velocity
prediction, and assess their comparative performance in a
range of conditions, representative of the typical racing
weather that Thames A Raters are subject too. This
demonstrated the importance of minimising the Froude
number thanks to an increased length on waterline, as well
as the better performance in light winds and downwind of
Scamp, due to its lower wetted surface area and narrow
beam. Conversely, upwind and as the true wind speed
increases, Spindrift’s larger waterline beam and inherent
stability led to a much faster yacht.
This study therefore provides ways of accurately
reproducing historical designs for the purpose of historical
conservation, as well as the application of modern naval
architecture techniques, in this instance velocity
prediction.
7. REFERENCES
[1] LAITY, M., ‘Thames Clubs’, Classic Boats,
2001.
[2] LAITY, M., ‘Bell Boy’, Classic Boats, 2007.
[3] FROUDE, W., ‘Experiments of the surface
friction experienced by a plane moving through
water’, Report to the British Association for the
Advancement of Science, 1872.
[4] FROUDE, W., ‘Report to the Lords
Commissioners of the Admiralty on experiments
for the determination of the frictional resistance
of the water on a surface under various
conditions’, Report to the British Association for
the Advancement of Science, 1874.
[5] UPPER THAMES SAILING CLUB, ‘Upper
Thames sailing club gallery’, Available online:
http://bew.utsc.org.uk/, 2015.
[6] PHILLIPS, M., ‘Ulva’, Available online:
http://www.tradboatrally.com, 2005.
[7] THAMES SAILING CLUB, ‘The Thames A
Rater Association Rules’, Thames Sailing Club,
2007.
[8] KEMP, D., ‘Dixon Kemp’s manual of yacht and
boat sailing and yacht architecture. New and
eleventh edition. Edited by B. Heckstall-Smith
and Linton Hope’, Horace Cox, London, 1913.
[9] SOUPPEZ, J. B. R. G., ‘On the applications of
modern naval architecture techniques to
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8. AUTHORS BIOGRAPHY
Joseph E Thomas is a graduate of the BEng (Hons) Yacht
and Powercraft Design at Solent University with a
particular focus on performance sailing craft. He is an
avide Thames A-Class Rater sailor. He has worked on
refurbishment work for two vintage Thames A-Class
Raters keeping them in a sailable seaworthy condition. His
previous work with the class includes a dissertation
designing a new Mahogany Thames A Rater and a
presentation on his work given at the British Conference
of undergraduate research.
Jean-Baptiste R. G. Souppez holds the position of Senior
Lecturer in Yacht Design and Composite Engineering at
Solent University, teaching on the prestigious BEng
(Hons) Yacht and Powercraft Design, BEng (Hons) Yacht
Design and Production and MSc Superyacht Design. He
contributes to the European Master in Integrated
Advanced Ship Design (EMship+) as a Visiting Professor
and Research Supervisor, and is also the UK Principal
Expert in Small Craft Structures, in charge of representing
the interests of the British Marine Industry in the
development of international structural regulations (BS
EN ISO 12215). His research in fluid dynamics features
twisted flow wind tunnel, towing tank, wave and current
flume, particle image velocimetry, laser doppler
anemometry, and full size instrumented testing, as well as
a range of numerical methods.
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
9. APPENDICES
Figure 12: Linesplan Replica for Scamp [13].
Figure 13: Linesplan Replica for Spindrift.
Historic Ships, 5th 6th December 2018, London, UK
© 2018: The Royal Institution of Naval Architects
Figure 14: Linesplan Replica for Dainty Too.
... The historical Thames A Rater class saw its birth in the late 19 th century [24], and while the vessels still feature the same original wooden hulls [25], significant technological advances have been made over the years to keep the class competitive [26]. This led to a number of recent studies [19,27,28] focussed on performance optimisation, as well as characterisation of original designs, such as Scamp, a 1902 Linton Hope design, reproduced from the original linesplan [29], and presented in Figure 1. [29]. ...
... Rig in 1907 (left) [28] and 2014 (right) [28]. ...
... Rig in 1907 (left) [28] and 2014 (right) [28]. ...
Article
Full-text available
The scantlings of traditional wooden crafts often originate from the extensive experience of designers and boatbuilders. With the contemporary regain of interest for historical replicas and timber construction, and the ever-critical necessity to minimise displacement, a compromise between the original scantlings and modern structural assessment must be struck. The latter heavily relies on rules-based design, driven by formal regulations, though a number of empirical methods also exist. Consequently, to assess the comparative structural requirements between traditional small crafts, empirical methods and regulatory requirements, case studies will be undertaken on small crafts. Ultimately, the results showcase the differences between original specifications, the recommendation of simplified methods, and modern rules, with the latter allowing for weight savings.
... The historical Thames A Rater class saw its birth in the late 19 th century [24], and while the vessels still feature the same original wooden hulls [25], significant technological advances have been made over the years to keep the class competitive [26]. This led to a number of recent studies [19,27,28] focussed on performance optimisation, as well as characterisation of original designs, such as Scamp, a 1902 Linton Hope design, reproduced from the original linesplan [29], and presented in Figure 1. [29]. ...
... Rig in 1907 (left) [28] and 2014 (right) [28]. ...
... Rig in 1907 (left) [28] and 2014 (right) [28]. ...
Conference Paper
Full-text available
The scantlings of traditional wooden crafts often originate from the extensive experience of designers and boatbuilders. With the contemporary regain of interest for historical replicas and timber construction, and the ever-critical necessity to minimise displacement, a compromise between the original scantlings and modern structural assessment must be struck. The latter heavily relies on rules-based design, driven by formal regulations, though a number of empirical methods also exist. Consequently, to assess the comparative structural requirements between traditional small crafts, empirical methods and regulatory requirements, case studies will be undertaken on small crafts. Ultimately, the results showcase the differences between original specifications, the recommendation of simplified methods, and modern rules, with the latter allowing for weight savings.
... The past decade has seen a regain of interest in historical wooden boats and their analysis using modern naval architecture techniques [11,12,13,14,15]. This is further evidenced in the development of modern replicas [16,17,18,19,20,21], new builds [22,23] and wooden cargo vessels [24,25,26]. ...
Article
The contemporary environmental challenges faced by the maritime industry have triggered a regain of interest in wood as a sustainable material. Modern classics and replicas of historical vessels have been increasingly popular. However, owing to their historical nature and small market share, wooden yachts and small ships do not benefit from a robust and detailed regulatory framework. Instead, their structural design remains driven by designer and builder experience, historical scantlings and rules of thumb. As such, the lack of detailed regulations for the scantlings of traditional timber vessels has been identified as a limitation to their wider implementation in the maritime industry. Consequently, this paper explores existing regulations and recent experimental research to provide novel insights in to wooden structures and their associated scantling rules. First, a classification of wooden boatbuilding techniques is offered. Then, the lower carbon footprint of traditional carvel construction compared to modern cold moulding, strip planking, and plywood construction is quantified. Finally, recommendations are provided regarding the remaining outstanding research questions that need to be addressed to ensure reliable traditional wooden boat scantlings in modern regulations. It is anticipated these findings will facilitate the wider adoption of wooden construction for small crafts, support the use of more sustainable materials, and may further contribute to the development of future regulations.
... The past decade has seen a regain of interest in historical wooden boats and their analysis using modern naval architecture techniques [11,12,13,14,15]. This is further evidenced in the development of modern replicas [16,17,18,19,20,21], new builds [22,23] and wooden cargo vessels [24,25,26]. ...
Conference Paper
Full-text available
The contemporary environmental challenges faced by the maritime industry have triggered a regain of interest in wood as a sustainable material. Modern classics and replicas of historical vessels have been increasingly popular. However, owing to their historical nature and small market share, wooden yachts and small ships do not benefit from a robust and detailed regulatory framework. Instead, their structural design remains driven by designer and builder experience, historical scantlings and rules of thumb. As such, the lack of detailed regulations for the scantlings of traditional timber vessels has been identified as a limitation to their wider implementation in the maritime industry. Consequently, this paper explores existing regulations and recent experimental research to provide novel insights into wooden structures and their associated scantling rules. First, a classification of wooden boatbuilding techniques is offered. Then, the lower carbon footprint of traditional carvel construction compared to modern cold moulding, strip planking, and plywood construction is quantified. Finally, recommendations are provided regarding the remaining outstanding research questions that need to be addressed to ensure reliable traditional wooden boat scantlings in modern regulations. It is anticipated these findings will facilitate the wider adoption of wooden construction for small crafts, support the use of more sustainable materials, and may further contribute to the development of future regulations.
... There has been a strong resurgence of interest for timber in construction due to its sustainability (Souppez, 2020a). This led to new considerations for regulatory compliance (Bucci et al., 2017;Souppez, 2020b), and is motivated by both the development of modern replicas (Alessio et al., 2016;Thomas & Souppez, 2018) as well as new designs (Linden & Souppez, 2018;Scekik, 2018). The literature reveals the high interest and potential of timber construction for lowemission vessels, with two major obstacles; the lack of reliable mechanical properties (which requires experimental testing to minimise safety margins and achieve a lighter structure), and the limited coverage of wooden structures in rules and regulations. ...
Conference Paper
Committee Mandate: Concern for structural challenges of non-conventional, special surface vessels, including uncertainties in established design methods and modelling techniques. Particular attention shall be given to mega yachts, naval craft, offshore service vessels and work boats, which can be characterized by particular structural configurations and materials (wide openings, large unsupported structures, unconventionally shaped superstructures, etc.) and/or are to sustain specific loading conditions (harsh environment, severe cyclic loads or extreme operational ones).
... Modern advances in structural engineering leading to progressively lighter boats, coupled with significant progress in adhesives (ISSC, 2009) and the contemporary interest for wood as an engineering material call for a new understanding of the mechanical properties and strength of timber. The research is further motivated by the regain of interest for wooden boats, evidenced in both modern replicas (Alessio et al., 2016;Alessio, 2017; Thomas & Souppez, 2018;Martus, 2018) and new builds (Souppez, 2015;Linden, 2018;Scekic, 2018), leading to new considerations for the regulatory implications of timber constructions (Souppez, 2016;Meulemeester, 2018). ...
Article
Full-text available
Timber construction has recently seen a significant regain of interest across a range of industries, owing to contemporary concerns for sustainability. In the marine industry, historic principles of traditional wooden boatbuilding remain present, with empirical rules still common practice, as is the case for scarf joints. Moreover, laminated wood is made more attractive and efficient thanks to modern adhesives. However, with the progress made in structural analysis, these assemblies can now be refined based on scientifically informed evidence. This paper employs destructive testing to tackle two distinct cases. On the one hand, the strength of plain scarf joints as a function of their slope is evaluated. On the other hand, the effectiveness of a range of adhesives is ascertained for the purpose of laminated manufacturing. The results are compared to both solid wood and the mechanical properties assumed by modern scantling regulations, revealing significant differences. The novel research findings provide a better understanding of these fundamental timber construction principles, supporting designers and builders alike in making informed choices while promoting safer regulatory compliance and enabling the future development of structural small craft standards. Applications beyond the structural design of wooden boats are also anticipated, for instance in sustainable buildings and architecture.
... At this stage, it is commonly acknowledged that the performance is not a fully accurate value. Yet, it is appropriate for the purpose of comparative performance prediction [61]. At a later stage of the design, a more advanced PPP may be developed [58], often relying on both hydrodynamic tank testing [57] and aerodynamic wind tunnel testing [24], or CFD [21,62]. ...
Conference Paper
Full-text available
With the current global warming crisis and contemporary concerns for sustainability, the transport industry is developing and implementing novel solutions to reduce greenhouse gases. With close to 90% of the world's goods relying on maritime transportation, responsible for 3% of global energy-related carbon dioxide (CO2) emissions in 2019, there is a vital emphasis on reducing emissions. The latest legislation from the International Maritime Organisation has imposed even tougher sulphur oxide targets. On the other hand, emission intensity for CO2 will need to be decreased by 70% in 2050, compared to 2008 figures. While operating measures and fuel alternatives are suitable in the short-term to meet these novel regulatory constraints, as the use of fossil fuels tapers off, the long-terms solution appears to reside in wind-assisted ships. Consequently, this study aims to identify viable solutions that could reduce emissions, focussing on three prominent technologies, namely sails, rotors and kites. Furthermore, this review provides guidance on the benefits and risks associated with each technology and recommends guidelines for performance prediction and associated constraints. Ultimately, future stakes in wind-assisted propulsion are highlighted, including the need for full-scale validation, the challenge in assessing environmental and economic impact, and the structural issues associated with wind-assisted propulsion systems.
... While the hydrodynamic and stability influence of the various foils have been quantified, the sailing speeds remain to be assessed. Velocity prediction programs have been successfully employed for the comparative performance of racing yachts (Thomas & Souppez, 2018) as well as cruising vessels (Guell & Souppez, 2018), but current commercial packages do no account for the effect of hydrofoils. Consequently, a dedicated VPP was developed (Borba Labi, 2019). ...
Conference Paper
Full-text available
Hydrofoil-assisted racing monohulls have undergone significant development phases in the past decade, yet very little scientific data has reached the public domain: an increasingly critical issue as the superyacht industry is now looking at the implementation of foils onto leisure vessels. Consequently, three contemporary configurations, namely a Dynamic Stability System, a Dali-Moustache and a Chistera have been towing tank tested to present the first complete characterisation of the hydrodynamic efficiency, quantification of the added dynamic stability and eventually the resulting impact on sailing performance. Furthermore, the considerations inherent to the design and installation of hydrofoils onto superyachts will be detailed. Building on extensive experimental work, this paper provides a comprehensive assessment of current design options with both technical and practical guidelines and recommendations to improve performance. DOI: 10.3940/rina.smy.2019.05
Article
Full-text available
Increasing regulatory pressures to reduce shipping emissions have led to the design of low-emission vessels. These may rely on more sustainable propulsion and/or resistance reduction to reduce fuel consumption. However, the structural implications of such design strategies remain to be fully ascertained. This paper presents a review of the recent literature to identify the structural challenges associated with the next generation of sustainable vessels and tackles a range of available design options intended to reduce emissions. The results suggest that structural design has a fundamental role to play in enabling the application of low-emission design strategies on both small crafts and ships, but further developments in rules and regulations are necessary. It is anticipated these findings may support future regulatory advancements and may contribute to improvements in the design of sustainable vessels.
Conference Paper
Full-text available
The Thames A Rater class had a predominant role in the popularisation of inland racing in the United Kingdom towards the end of the 19th century, and remains a historical racing class that owes its longevity to the progresses made in naval architecture and technology; the most emblematic example being the 43 feet tall carbon fibre rigs on the 27 feet centenary wooden hulls. Today, the class is a perfect illustration of the balance between historical conservation and modernisation. The design of a contemporary wooden Thames A Rater will be presented, aiming at retaining the spirit of tradition of the class, while incorporating the latest design evolutions, and complying with the current rules and regulations. Techniques such as computational fluid dynamics and parametric optimisation will be employed, leading to a significant increase in performance quantified thanks to a velocity prediction programme, thus demonstrating the applications of modern naval architecture techniques to historical crafts.
Thesis
Full-text available
To enhance the university experience of the Yacht Engineering Program students and the members of the Solent Sailing Club, the design of a racing yacht dedicated to Southampton Solent University has been undertaken. The 9.99m strip planked vessel is intended to be built as a one-off by students in Timsbury to then compete in the Solent and Channel races, as well as being a teaching support for both yacht engineering and sailing. The will to produce a complete project led to tackle both the design and the production aspects, using a combination of engineering skills, empirical methods, experience, practical considerations as well as the interaction with specialised manufacturers. Indeed, the project has been conducted to replicate the professional environment of a small company developing a project from the client requirements to the building. A wide range of professional skills have been implemented, such as developing a performance design in accordance with a design brief and the relevant bodies of regulation; ascertaining the most appropriate production method for the given work force; considering time and cost constraints to develop a building philosophy; establishing an accurate building schedule and cost estimate; time management between independent learning for the purpose of this dissertation and the design and production phases; and professional communication through a formal report and industry standard CAD drawings. The final proposed design appears to meet the regulations and satisfies the design brief, achieving a performance and safe boat. On the other hand, accurate cost estimation and planning have been developed so the boat can be built within the given time and for a lower cost than a similar vessel on the market, therefore making it an attractive investment for Southampton Solent University.
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