Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROU~D OF THE -~NVEN~ION
This invention relates to a steering aid for o~ltboard
motors and inboard/outboard drives wherein the slipstream of
the propeller acts to provide a steering effect on the boat.
It is well known that as long as the propeller runs
at a relatively high speed, a sufficient slipstream is provided
to give steerage to the boat. However, once the speed of the
motor is reduced, the slipstream is also reduced and
conse~uently the steering of the boat becomes less responsive
~ 10 and more difficult.
There is accordingly a need for a system which will
allow the operator of a boat to control and manoeuver the boat
safely at slow speeds and also to allow the user to keep the
- boat on a steady and positive course. There is a need to
15 provide boaters with positive and safe steering while trolling
or manoeuvering in and out of tight harbour areas at slow
speeds.
The prior art has provided various forms of fixed
rudder arrangements involving the use of a rudder plate located
20 rearwardly of the propeller in a position to react with the
- propel'er slipstream. The problem associated with the fixed
rudder construction is that the steering force becomes overly
large at high speeds. The fixed rudder usually causes the
- boat to oversteer at high speeds and in extreme cases the
25 boat could be made to capsize.
In an effort to overcome the disadvantage of the
fixed rudder blade arrangements, the prior art has provided
means for lifting the rudder vertically upwardly
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a predetermined speed thereby to achieve the advantage of theauxiliary rudder at iow sped while avoiding its disadvantage
at higher speeds. One such arrangement is shown in Canadian
patent number l,001,904 issued 76/12/~1 to Wasenius. In the
5 arrangement shown in this patent, a bracket is connected to
the anti-cavitation plate of an outboard motor, such bracket
including a pair of spaced parallel steering rods. A rudder
is mounted for vertical sliding motion along these parallel
rods and the lower end of the rudder is provided with adjustable
10 hGrizontally disposed fins which exert a lifting force on the
rudder as the speed of travel through the water increases. The
difficulty with this arrangement resides in its complexity and
attendant cost as well as its dependence on the abilit~ of
the rudder to slide freely along the vertically disposed rods.
15 Any obstruction preventing the free sliding movement of the
rudder in the vertical direction will impair or completely
destroy the capability of the device to function. In systems
of this general nature, marine deposits and/or corrosion
can pose a serious problem and hence there is a need to
20 provide an alternative form of system which avoids the
disadvantages of the apparatus briefly described above.
S~MMARY OF THE INVENTION
It is a general object of the present invention to
provide a very simple yet effective rudder arrangement for use
25 on boat drives of the outboard or inboard/outboard type,
which rudder arrangement is so arranged as to pivot upwardly
and be raised out of the water automatically to avoid over-
steering at higher speeds with such rudder automatically
; lowering downwardly toward its lower position as the boat
30 slows down thereby to provide for more positive steerlng at
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slow speeds.
It is a further object of the present irvention to
provide a rudder arrangement which li~ts upwardly at higher
speeds and which at the same time avoids the use of slidable
S mounting arran~ements for the rudder which could become
fouled by v~rious deposits, and which rudder arrangement is
extremely simple and thus relatively cheap to manufacture.
Accordingly, the present invention in one aspect
provides in combination, a drive for a boat of the outboard or
10 inboard/outboard type, said drive having a propulsion means
for producins a slipstream as it moves through the water;
the drive being turnable ahout a steering axis to prcvide a
steering effect on the boat, and a rudder to assist in steering
the boat at speeds below a selected speed. A mechanical
15 coupling connects said rudder directly to said drive so that
both the drive and the rudder turn together about said
steering axis as the boat is steered. The mechanical coupling
between said rudder and said drive includes means defining a
pivot axis generally transverse to said steering axis
20 permitting the rudder to pivot relative tc said drive between
a lowered position where the rudder can react to the slipstream
of the propulsion means and a raised position where said rudder
is substantially removed from the slipstream. The pivot axis
is located relative to the rudder such that forces acting on
' 25 said rudder in its lowered position by virtue of the motion of
water relative thereto provide a moment about said axis capable
of pivoting the rudder about said axis and moving same toward
the raised position as the relative speed between the water
and the rudder approaches a predetermined value to make -the
30 steerin~ of the boat substantially independent of the rudder.
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The rudder may cor.lprise a simple generally flat plate.
The above-noted mechanical coupling preferably includes arms
connected to the plate, with such arms having free end portions
remote from the plate with said means defining the pivot axis
5 being located at the free ends of the arms.
The arms are preferably connected adjacent an upper
end portion of the rudder plate, with such arms being made so
that they diverge away from one another toward thelr free
outer ends to e~brace a portion of the drive therebetween. The
10 pivot axis defining means may include brackets secured to the
drive above the propulsion means with the brac~ets being
pivotally secured to the free end portions of the ~rms. In
a typiczl embodiment these brackets are secured to the anti-
cavitation plate of the outboard drive.
15 BRIEF DESCRIPTION OF VIEWS OF DRAWI GS
In drawings which illustrate an embodiment of the
invention:
Fig. 1 is a side elevation view of a lower end portion
of an outboard drive showing a rudder arrangement according to
20 the invention connected thereto with raised positions of the
rudder being shown in phantom;
Fig. 2 is a rear end elevation view of the outboard
drive of Fig. 1 showing the rudder arrangement in its lowered
position;
Fig. 3 is a top plan view of the rudder arrangement
per se;and,
Fig. 4 is a ~rasmentary section view taken along line
4-4 of Fig. 1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
- 30 Referring now to the drawings, there is illustrated
a lower end ~ortion of a drive 10 of an outboard motor, it
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being realized that the drive can also be of the inboard/
outboard type. The outboard drive can be of any commercially
available type, such drive including a propeller 12 which
produces a slipstream during movement through the water in the
5 usual fashion. The drive unit 10 also includes the usual anti-
cavitation plate 14 disposed immediately above the propeller
12. The entire outboard drive 10 is turnable about a steering
axis S-S as illustrated in Fig. 1 to provide a steering effect
on the boat in the manner well known in the art.
A rudder 16 is provided to assist in assist in
steering the boat at speeds below a selected speed. A
mechanical coupling broadly designated by reference numeral 18
connects rudder 16 directly to the drive 10 so that both the
drive 10 and the rudder 16 turn together about the steering
lS axis S-S as the boat ls steered. Mechanical coupling 18
between the rudder 16 and drive 10 includes means defining a
; pivot axis P-P generally transverse to the steering axis S-S
to permit the rudder 16 to pivot relative to the drive 10
between a lowered position (shown in full lines in Fig. 1)
20 where the rudder 16 can react to the slipstream of the propeller
12, and a raised position A (shown in phantom in Fig. 1)
wherein the rudder 16 is substantially removed from the
slipstream. This pivot axis P-P is located relative to the
rudder 16 s-uch that the forces acting on the rudder in its
25 lowered position by virtue of the motion of water relative
thereto provide a turning moment about axis P-P capable of
pivoting rudder 16 about such axis and moving same toward the
raised position A as the relative speed between the water and
the rudder approaches a predetermined value (e.g. about 10
30 knots) to make the steering of the boat substantially
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independent of the rudder and thus avoid problems of over-
steering etc.
It will be seen from Figs~ l and 2 that the rudder
comprises a simple flat plate while the mechanical coupling 18
5includes a pair of arms 20 which are connected to opposing
sides of the uppermost end of the rudder plate by rivets 22.
The arms 20 diverse away from each other toward their free
outer ends so as to embrace a portion of the drive 10 there-
between. The means defining the pivot axis P-P include angle
lObrackets 24 c3nnected by fasteners 26 to the cavitation plate
14. Machine bolts 28 serve to secure the free ends of arms
20 to the angle brackets 24 with suitable nylon inserts and
washers 30 being provided to reduce friction between arms 20
and angle brackets 24 thereby to ensure free pivotal movement
15Of rudder 16 about pivot axis P-P.
The rudder 16 is preferably made from a high tensile
strength aluminum having suitable corrosion resistant
properties with the entire rudder a~sembly including arms 2C
preferably being anodized ln a suitable colour, such as black
20 or silver, to further enhance the appearance and to protect
the assembly from corrosion. The rudder assembly may be
quickly and readily attached to an existing outboard drive
simply by drilling a pair of small holes in the anti-cavitation
plate thereby to allow for attachment of the above-noted angle
25 brackets 24.
~ he manner in which the rudder arrangement functions
will be readily apparent to those skilled in the art. At low
speeds, such as when one is trolling or moving into or out of
close harbour areas, the rudder 16 will be located in the
30 lower full line position shown in Fig. 1. In this condition,
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the rudder 16 exerts a very positive steering effect due to the
fact that it is in a position where it can react to the
propeller slipstream. As the propeller speeds up however, and
the force of the propeller slipstream becomes greater, the
5 relative speed between the water and the rudder increases thus
increasing the friction forces between the water and the rudder.
Due to the fact that the pivot a~is P-P is located generally at
the level of the uppermost end of the rudder 15, and well above
the center line of the propeller, these friction forces exerted
10 on the rudder tend to create a turning moment about pivot axis
P-~ thus tending to cause the rudder 16 to tilt or rotate
clockwise as shown in Fig. 1 toward the raised position A. Thus,
as the relative speed between the water and the rudder surfaces
~` increases, the rudder tends to be lifted higher and higher out
- 15 of the water until an equilibrium position is ~eached, i.e.
a position wherein ~he downwardly acting forces of gravity on
the rudder balance the oppositely directed turning moments of
force exerted by the water acting on the rudder surfaces. It is
believed that persons skilled in the art will have no d fficulty
20 in providing a rudder of a suitable size as to accomplish the
above effect.
Two basic rudder sizes will suffice for use with
motors in the 2 to 200 horsepower range, the smaller rudder
being used for the lower horsepower range and the larger rudder
for the upper half of the horsepower range. sy way of example
these two basic sizes had the following approximate dimensions,
reference being had to Fig. 1:
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Small Rudder Large Rudder
Rudder height 30 cm 45 cm
Rudder width 10 cm 10 cm
Arm length (~ 18.5 cm 18.5 cm
Thickness ~rudder plate)3.5 mm 3.5 mm
A typical rudder constructed as above will begin
to lift out of the water between 6 and 8 knots and at somewhere
between 10 and 15 knots the rudder will be substantially out of
the water. ~he rudder will never clear the water entirely
10 however and even at high speed as much as 10 to 1~ percent of
the rudder will be immersed.
It will be appreciated that the above dimensions
are not critical and that those skilled in the art will be able
to select other suitable combinatlons of dimensions to adapt
the tiltable rudder system to various types of outboard and
;~ inboard/outboard drives. In the example given above, the rudder
plate and the arms 20 were made of high tensile strength
- aluminum.
It will be appreciated that the foregoing
20 description is for illustrative purposes only and that various
changes and modifications can be made within the scope of the
invention. Accordingly, the present specification is not to
be limited by the foregoing illustrative example, but only by
the scope of the claims appended hereto.
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