Note: Descriptions are shown in the official language in which they were submitted.
37
Improvements in and relatinq to winqsail craft and
wingsails therefor
Field of the invention
This invention ooncerns wingsail craft and particularly
the mounting, construction and balancing of wingsails.
Background of_the invention
It is known to construct a cra~t, typically a ship, having
a so called win~sail in which the sail is formed as a more
or less rigid aerofoil section as in an aircraft wing. In
such arrangements it is usual to moun~ the sail on the
vessel about an approximately vertical pivot axis, This
pivot axis normally comprises a single lower bearing about
which the wingsail is rotated in order to adjust the trim
angle of the sail to the wind.
In both servomechanically rotateZ and tail trimmed
wingsails, it is desirable to minimise the trimming work
needed. For this reason the axis of the trim bearing is
usually arranged to pass through the narrow zone in which
the centre of pressure of the sail is found in the normal
working range. ~Iowever, for most cambered and high thrust
sections this zone will lie approximately 35~ back from
the leading edge, while even in symmetrical sections it
will be some 25% back from the leading edge. Its vertical
position is approximately at the half height for wingsails
of rectilinear design, while simple geometrical construc-
tions are commonly used to locate the zone ve~tically for
wingsails of tapered or elliptical shape.
s~
The strongest part of the wingsail, most suitable for mating
with the vertical bearins assembly, is usually a Dbox
leading edge section, which may occupy only the leading 20%
perhaps of the total wingsail chord.
In the case o~ a wingsail having two elements, it is
normally assumed that the leading element is the principle
strength member.
Many wingsail propulsion sets need to be carefully balanced
about their vertical or near vertical axes of rotation to
enable optimum control of angle of attack to be achieved,
and the invention is in part concerned with wingsail
balancing.
In complex wingsails, composed of two or more elements
hinged or otherwise connected, three distinct types of
conformation may be obtained:
These are:-
Symmetrical and all-in-line,
Cambered for port tack sailing, and
Cambered Eor starboard tack sailing.
Such a sailset may be balanced about a vertical or near
vertical axis by a mass mounted on a boom and pivoted to the
leading edge of the leading sailset section.
The actual construction of a wingsail or the various
elements of a multiple element wingsail is important, in
that weight and strength are o~ primary importance. The
~s~
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invention is therefore also concerned with the actual
construction of a wingsail and o the elements which make
up a multiple element wingsail.
According to one aspect of the invention there is provided
a wingsail assembly, comprising~ at least a first and
second wingsail, said first sail being mounted for
rotation about a first generally vertical axisr and said
second sail being mounted on said first sail for rotation
about a second generally vertical axis spaced from said
first axis, means interconnecting said second sail wi~h
said first sail; a boom supported on said first sail; a
balancing mass mounted at a remote end of said boom; and
control means disposed on opposite sides of said boom for
moving said balancing mass in an approximately horizontal
: plane as said first and second sails move about their
respective axis such that said balancing mass balances
said wingsail assembly.
According to another aspect of the invention there is
provided a sailing vessel, comprising; a craft; at least
a first and second wingsail, said first sail being mounted
for rotation about a first generally vertical axis, and
said second sail being mounted on said first sail for
rotation about a second generally vertical axis spaced
from said first axis; means interconnecting said second
sail with said first sail; a boom supported on said first
sail; a balancing mass mounted at a remote end of said
boom; and control means disposed on opposite sides of
said boom for moving said balancing mass in an approxi-
mately horizontal plane as said first and second sailsmove about their respective axis such that said balancing
mass balances said wingsail assembly.
s'~
The locating means may comprise a pair of wire stays,
a mechanical linkage using a pushpull rod, or hydraulic
means or the like, in which the final balance position
is assured by a fixed or manually adjustable ratio sys-
tem. Where a computer is incorporated the latter maybe supplied with information relating to the sailing
conditions and the craft to allow the computer to compute
the optimum balance position.
According to a further aspect of the invention there is
provided a sailing vessel, comprising a craft; at least a
first and second wingsail, said first sail being mounted
for rotation about a first generally vertical axis, and
said second sail being mounted on said first sail for
rotation about a second generally vertical axis spaced
from said first axis; means interconnecting said second
sail with said first sail; a boom supported on said firs~
sail; a balancing mass mounted at a remote end of said
boom; and control means disposed on opposite sides of said
boom for moving said balancing mass in an approximately
horizontal plane as said first and second sails move
about their respective axis such that said balancing mass
balances said wingsail assembly; one of said first
and second sails having a region of principal strength
extending between the bottom and top portion of said
one sail and further comprising a bearing at said bottom
portion of said one sail by means of which said one sail
is mounted in said craft, said bearing also defining an
axis of pivoting of said one sail wherein the axis of
pivoting of said one sail passes through a zone in which
a centre of pressure of said one sail normally lies and
through said region of principal strength and wherein said
region of principal strength extends to said bearing.
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_ ief descri~ion_of the drawings
The invention will now be described by way of example with
reference to the accompanying drawings in which
Figure 1 illustrates a wingsail craft,
Figures 2 and 3 illustrate wingsail constructions
embodying the first aspect of the invention,
Figures 4, 5 and 6 illustrate a twin element sailset in
the three different modes,
Fi.gures 7 and 8 illustrate locating means according to the
second aspect of the invention applied to such a sailset,
Figure 9 illustrates this aspect of the invention applied
to a sailset in which the leading sailset section is
hinged to the trailing sailset section,
Figure lO is a perspective view of an open tray section
the sides of which form the flanges of a rib, for a
wingsail,
Figure ll is a detail of the side of the rib, oE
Figure lO,
Figures 12 and 13 show parallelogram shaped wings
employing the third aspect of the invention, and
Figure 14 is a cross section on the centre line of a
forwardly raked sail element, employing this aspect of
the invention.
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Description of the ~referred embodiments
Figure 1 shows a salling craft hull A having a wingsail
B pivotally mounted in a bearing assembly C for rotation
about an axis D.
In ~igure 2, two wingsail assemblies have been shown
superimposed, both having the same centre of pressure zone
2, in which one has been drawn in chain dotted outline as
a simple rectangle, and the outer in solid outline as a
parallelogram. The two sail assemblies have the same
height, area and centre o pressure position.
The strong leading edge member, 3, shown cross hatched,
is arranged, by correct choice of forward sweep angle, so
that its lower end is located exactly over the position of
the bearing assembly 4, whilst the axis 5 of the bearing 4
still passes through the centre of pressure zone 2. The
strong leading edge member is provided with a fla~ge or
other arrangement to mate with the shaft or other rotating
element of the bearing assembly.
In wingsails of multielement design, it may be preferred
that the second or other element of the aerofoil section
shall contain the strong spar member. Figure 3 shows a
double element of such a wingsail configuration~ Here
the leading element 100 is hinged to the trailing main
strength element 102 by hinge assemblies 103. The centre
of pressure zone of this complex assembly is at 104~ and
as before, to minimize trimming work, the approximately
vertical axis 105 of the bearing 106 is arranged to pass
through this zone.
In this case, the main strength member of the wingsail
` 30 is the leading edge 107 of the trailing element 102 shown
cross hatched. This is now arranged so that its lower end
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falls into the ~est relationship for strong and reliable
mating of the bearing assembly by raking the entire
assembly aft as shown.
The design is arrived at by starting with the rectilinear
design, positioning the centre of pressure zone on the
bearing axis and then replacing the rectangle with a
parallelogram of the same height and area, whose angle
brings the base of the main spar conveniently over the
bearing.
WhiLe this aspect of the invention has been described
for simplicity with reference to parallel, constant chord
wingsails, it is nonetheless applicable to wingsails of
tapering or curvilinear outlineO
Figures 4, 5 and 6 show a twin section sailset where 11 is
`~ 15 the leading sail section and 12 is the trailing section,
hinged to leading sail section 11 along an axis 13~ The
whole sailset is mounted to the vessel 10 in this case via
section 11 on a vertical or near vertical axis 14, about
which the sail is trimmed to the wind.
In the all in line casel the sailset is balanced about the
axis 14 by a mass 15 mounted on a boom 16 pivoted to the
leading edge of the leading section 11 at a pivot 17.
In the port tack sailing case, illustrated in Figure 5 it
will be seen that a new balance may be achieved by moving
the weight around in a clockwise manner until equilibrium
is restored.
Figure 6 shows the opposite tack case~
The location of the balance weight in an approximately
horizontal plane is achieved by a pair of wire stays,
as shown in Figure 7.
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To this end a streamlined structure having two fins 18, 19
is rigidly fixed to the base of the leading section 11 of
the sailset. A pair of pulleys 20, 21 are carried by the
fins around which wires 23 and 24 pass. The wires are
connected to the trailing section 12 at lugs 25, 26 and to
the counterweight boom at lugs 27 and 28. Spring elements
29,30 in the wires maintain wire tension. Dotted lines 22
show the trailing section 12 fully deflected.
~hen the trailing section 12 is moved relative to the
leading section 11 in order to develop camber, say in the
clockweise direction in the plan view drawn, wire 23 pulls
the counterweight to the correct position to maintain
balance. In this case wire 24 maintains tension. The
opposite action will occur upon anticlockwise rotation.
Figure 8 shows alternative versions of the lugs 25, 26.
The alternative lugs shown at 31 and 32 are slotted to
allow fine adjustment of the balancing effect.
In some wingsail designs the trailing section 12 is
mounted on the vessel via the axis 14, and the leading
section 11 is then hinged to the trailing section 12.
Figure 9 shows such a case. Here an end plate structure
33 broadly similar in principle to the structure 18, 19
of Figure 7 carries the counterweight boom pivot 17.
The pivot 13 between sections 11 and 12 could also be
mounted on the end plate structure 33, but for reasons of
bending moment optimisation is more likely to be mounted
on separate hinge arms 34, working through clearance slots
in the section 11. Wires 35 and 36 are now connected at
one end via lugs 27, 28 to the counterweight boom and at
the other end to adjustable lugs 31, 32 on the leading
section 11. The wires adjust the position of the counter-
weight to maintain balance.
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While bracing wires such as 23, 24 and 35, 36 are
illustrated~ the same action of broadly horizontal
movement of the counterweight may also be achieved by:
A mechanical linkage using a pushpull rod, or
Hydraulic or other means in which the correct final
balance may be assured either by a fixed or manually
adjustable ratio system.
Figure 10 shows a simple form of moulding envisaged by
the third aspect of the invention, in the form of an open
tray section where the sides 39, 40 of the tray form the
flanges of the rib 44. For ease of release from a simple
one piece mould, such mouldings should preferably be
arranged with a draft angle greater ~ ~han 0 as shown in
Figure 11. Such an angle can make the fixing of the skin
of the aerofoil to the rib difficult to achieve. However,
if the wing is parallelogram shaped, as shown in Figure 12
and 13 the draft angle may be utilised.
Figure 14 is a centre line section through a raked forward
sail element such as is shown in Figure 12 where a leading
edge member 41, a main spar 42 and a trailing edge 43 are
connected by a typical leading edge rib 44 and a typical
trailing edge rib 45. Figure 14 shows the rib 44 as it
would appear along section line XIV-XIV from Figure 10.
It will be noted that, because this is a swept Eorward
design, the leading edge rib 44 is fitted with its flanges
39, 40 upwards, while the trailing edge rib 45 is fitted
with its flanges downwards~ The draft angle of the mould
is made equal to the desired forward rake angle at leading
edge and trailing edge, but is gradually reduced ~o zero
so that the flange of each rib is at 90~ to the web in the
immediate vicinity of the main spar 42.
By varying the draft angle in this way along each rib the
rib flanges will in general be coplanar with the skin for
ease of skin attachment, whilst ~he mould and moulding
techniques are kept simple and reliable.
In the case of raked back wingsails, as in Figure 13, then
the leading edge rib elements will be fitted flange down
and the trailing edge ribs will be fitted flange up.
In the case of multielement wings t where each element has
its own broadly aerofoil shaped section and main spar, the
ribs will be fitted as described above in each individual
element, as if it were a complete wing.
