Note: Descriptions are shown in the official language in which they were submitted.
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THIS INVENTION relates to undërwater appendages
particularly such appendages adapted to derive a lift
from forward passage through the water.
Many vessels of different types employ underwater
lift devices in various circumstances and generally in
the form of a fin. ~or example, most vessels are steered
by means of a rudder which provides selectively a lift ~-
to one side or the other to change the course of the
vessel. Other vessels, particularly large commercial
vessels, employ stabiliser fins at each side of the vessel,
each adapted to apply either for lift in a~ upward or
downward dire¢tio~, whichever is the reverse of the
op~osite stabiliser fin~ to reduce the rolling of the
vessel, and sailing vessels are provided with a keel
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~5 assembl~ to enable them to tack to wi~dward.
~he present invention aims to provide an improved
- underwater appendage which may be utilised in the above-
mentioned and other applications. ~or illustrative purposes,
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the present specification will hereinafter describe the
application of the invention to the fin keel assembly of
a sailing vessel.
As is well known, sailing boats advance to
windward in a zig-zag path because it is not possible
to sail directly into the wind. Thus, it is an advantage
for a sailing craft to be able to point high into the
wind inorder to minimise the distance sailéd to windward.
Apart from the effect of the sails, the ability of a
vessel to sail to windward is partly determined by the
hull shape and in particular by the shape of the ~eel
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assembly which acts to prevent sideway movement of the boat
relative to its straight-ahead direction.
As the vessel has to travel in a zig-zag direction,
it is of course necessary for the vessel to be able to point
high into the wind on both the port and starboard tack and
this condition has resulted in most sailing boats having a
centrally-disposed symmetrical fin keel. The section most
often chosen is a streamlined symmetrical hydrofoil section,
preferably with a high aspect ratio. `
While there have been attempts to provide vessels
with laterally spaced asymmetrical keels which may be lowered
independently according to the tack the vessel is on, such
attempts have not been particularly successful because of
their complexity and their need for constant tending and be-
cause on other points of sailing, they are not as efficient
as the central fin keel arrangement.
Accordingly, it is an object of the present invention
to provide a keel assembly which is adjustable according to
the course of the vessel to achieve optimum keel configuration
for efficient performance. Other objects and advantages of
the invention will become apparent from the following descrip-
tion.
The present invention provides a hydrofoil comprising
a rigid supporting body adapted to be fixed to a vessel to ex-
tend outwardly therefrom and said supporting body providing
forwardly converging abutment faces at opposite sides thereof,
a foil-shaped outer casing extending about said rigid support-
ing body in such manner that the incidence plane of the casing
when disposed symmetrically is substantially parallel to the
fore and aft axis of the vessel and the sides of said casing
are spaced equally from said abutment faces, said casing being
formed of flexible material and being supported at its leading
and trailing end portions by respective fore and aft pivot
blade assemblies connected to said supporting body for pivotal
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movement about respective outwardly extending axes adjacent the
leading and trailing edges of said supporting body and said axes
being disposed substantially parallel to said incidence plane,
said aft pivot blade assembly being pivotally connected adja-
cent its leading edge to said rigid supporting body to permit
the trailing edge of said aft pivot blade assembly to be dis-
placed laterally to either side of itssymmetrical position
whereby the casing at said either side may be formed to a con-
cave shape and be supported against the respective said abutment
face, and there being provided torque transferring means opera-
tively interconnecting said fore and aft pivot blade assemblies
to cause the latter to pivot oppositely to one another. ;
In order that the invention may be more readily under-
stood and put into practical effect, reference will now be made
to the accompanying drawings which illustrate one embodiment of
the invention as applied to keel assemblies of sailing vessels,
and wherein:-
Fig. 1 is a side view of a keel assembly fitted to the
underside of a sailing vessel;
Fig. 2 is a similar side elevational view showing only
the main suppo~t structure for the keel assembly;
Fig. 3 is a cross-sectional view along the line 3-3
of Fig. 1, and showing the keel assembly disposed in its normal
or downwind position;
Fig. 4 is a view similar to Fig. 3 showing the keel
assembly disposed in a tacking position; and
Fig. 5 is a cross-sectional view similar to that of
Fig. 4, but illustrating an alternate embodiment of the inven-
tion.
As shown in Figs. 1 to 4, the keel assembly 10 is fit-
ted to the underside of a vessel 11. The keel assembly in this
embodiment comprises a support structure 12 extending downwardly
from the bottom of the vessel and terminating in a lead bulb
arrangement 13. The support
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structure 12 provides a support for the movable keel
portion 14 which, in this embodiment, includes a rudder
blade 15 supported pivotally on the vertically extending
shaft 16 and a leading portion 17 supported pivotally on
the forward vertical shaft 18. The shafts 16 and 18 are
connected between the underside of the hull 11 and the
upper end portions of the bulb arrangement 13. As can be
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seen clearly from Fig. 2, the support strut 19 terminates
inwardly of the ends of the lead bulb 13 so that the
latter project outwardly therefrom and suitably reinforced
to provide a support for the shafts 16 and 18.
In this embodiment~ both the leading portion
17 and the trailing rudder blade 15 are freely pivotable
about thelr respective support shafts 18 and 16. The leading
portlon 17 comprlses a rigld nose portlon 20 with flexible
side plates 21 extending rearwardly therefrom to overlap
the trailing rudder blade at 22 as illustrated. The -~
side plates 21 are connected together at their trailing
ends by a transversely extending vertical bar 23
connected to the respective side plates 21 by hinge means
24. This bar 23 maintains the rear portions of the side
plates 21 in their correct distance apart so as to neatly
overlap the rudder blade 15 while the central portions 25
of the side plates 21 are maintained in spaced-apart
attitude by abutment against an internally disposed bar
26 which passes slidably through an aperture 27 in the
support strut 19. The latter is also provided with
additional through-passages 28 to enable flow therethrough
of water as the disposition of the keel assembly is varied.
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In this respect, it will be seen that the
vertical side faces 29 of the support strut 19 are - -
so shaped as to closely accommodate thereagainst in ` ~`
abutting relationship the face of the concave-shaped
windward side plate 21. Thus, the support strut 19 is
symmetrical about the centre line.
In operation, the keel assembly 10 according
to the present invention when fitted to a vessel<sailing ~- i
downwind, would be disposed in its symmetrical attitude c
as illustrated in Fig. 3 as the pressure against either
side plate 21 would be equal. However, if the vessel is
heated to windward~ say on a port tack~ the starboard side
plate 21s will be sub~ect to a positive water pressure
as indicated by the lines P which will cause the side
plate 21s to move laterally into abutting engagement with
the support strut 19 and force the port side plate 21p
outwardly by means of the rod 26 which will push against
the inside face of the port plate 21p. Furthermore, the i
vertical bar 23 connected by the hinges 24 to the side
plates 21s and 21p will cause pivoting of the h$nges 24
connecting the overlapping portions 22 of the side
plates. This action will pivot the trailing rudder blade
15 to its new position as illustrated in Fig. 4. It will
be seen that in this position, the hydrofoil shape of the -
fin 10 will provide a positive lift to windward due to the
positive pressure P at the leeward side and the negative
pressure indicated by the lines N on the windward side.
The reverse position of the rudder assembly 10 for the
starboard tack is shown superimposed in dotted outline.
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In this construction, it will be seen that
the rudder actuation is automatic and no through~hull
fittings are required to actuate the keel assembly.
In the embodiment illustrated in Fig. 5,
the side plates 121 of the keel assembly 110 extend
between a leading pivot assembly 120 and a trailing
rudder assembly 115. The side plates include a vertical
expansion ~oint, expandable in the fore and aft direction -
so that their longitudinal dimensions may be varied -
according to the disposition of the keel assembly. In
this embodiment, the pivoting of the leading pivot assembly
120 and the trailing rudder assembly 115 is positively ;
controlled by means of eccentric members 30 and 31 fitted
to centrally disposed vertical shafts 118 and 116~
respectively~ which pass sealably through fittings in the
bottom of the vessel to a station where their pivotal
movement may be selectively controlled. In this manner,
the dispositlon of the keel assembly may be accurately
controlled so that say the fullness of the effective keel
section may be selectively varied according to the speed
of the vessel and/or its angle of attack with respect
to the wind. Also, as shown in this embodiment~ there
may be provided an additional trim or rudder blade 32
fitted to a shaft 33 at the rear of the keel assembly
and actuable from within the vessel. It will be seen
that the leading pivot assembly 120 is located between
the front pivot bar 34 and the rear eccentric member 30
while the trailing rudder assembly is located between a
vee-portion 35 which engages in a Y-notch arrangement 36
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in the rear vertical face of the main support structure ~
119~ and the eccentric member 31. '!'~''',.': ',
Of course, it is not essential to provide
a keel assembly with two actuating shafts, more or less
may be used depending upon the particular application.
The keel assembly according to the present invention may
be also provided with locking devices to lock the keel ~
assembly in its selected position. Furthermore, the keel '-
according to the present invention may be retractable
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and ap~liet to unballasted vessels as desired. As
indicated at the beginning of the specification, such
assemblies could be used as rudders or as stabilising
fins for Yessels.
In 8 further variation, the fin keel assembly
comprises curved side plates fixed rigidly together along
their leading edges and provided with a slotted connection
at their trailing edges and there is provided within the
side plates actuating means such as a hydraulic ram to
vary the chord length of one side plate whereby the fin ;,`
keel assembly may be selectively disposed asymmetrically
to cause lift in either lateral direction resultant from
forward motion through the water.
However, while the above has been given by
way of illustrative example, it will be understood that
the many variations of constructional detail and design
that may be made to the described embodiments by persons
skilled in the art are deemed to fall within the broad
scope and ambit of the invention as is defined in the
appended claims.
