Note: Descriptions are shown in the official language in which they were submitted.
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HYDROFOIL WITH RETRACTABLE PLATE
The present invention pertains generally to hydrofoils
imparting lift to a watercraft.
In the prior art are hydrofoils carried by small watercraft
with the primary ofjective being the reduction of the wetted
surface area of a hull to reduce drag. As disclosed in U. S.
Patent 4,487,152, a hydrofoil may be mounted on a cavitation
plate of an outboard motor or outdrive, in a modified version,
for the purpose of lifting and stabilizing a boat hull. U. S.
Patents 1,576,237; 2,654,336; 3,965,838 andl 4,048,940 all dis-
close trolling plates attached to the lower' unit of an outboard
motor.
On small fishing boats, it is common i:o utilize a plate
called a trolling plate located rearwardly adjacent the propeller
of an outboard motor to slow the craft to <~ desired trolling
speed. Trolling plates are often carried by a bracket mounted
on the motor cavitation plate and are retractable through ninety
degrees to an inoperable or streamlined position. When deployed,
a trolling plate reduces propeller efficiency to diminish boat
speed.
The present invention is embodied in ~~ hydrofoil for a water-
craft to impart lift to the craft hull with the hydrofoil addition-
ally serving to slow the craft when so desired.
The present hydrofoil includes a positionable plate member
which, upon deployment, decreases propeller deficiency in the
general manner of a trolling plate. For watercraft operations at
speeds above trolling speed the positionable member is retracted
whereafter the hydrofoil serves as a source of lift for the hull.
A lock mechanism maintains the plate member in the desired position
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with a control permitting remote positioning of the plate member.
The hydrofoil has a recessed wall surface to permit the plate
member to be retracted into a streamlined position.
Objectives of the present hydrofoil include the provision of
a single unit for watercraft for imparting lift to the craft and
hence a speed increase by a reduction wetted hull area with the
additional capability of slowing the craft by deploying a plate
member of the hydrofoil; the provision of a dual purpose hydrofoil
which may be conveniently attached to the lower unit of an outboard
engine or to the outdrive of an inboard-outboard propulsion unit.
In the accompanying drawings:
Figure 1 is a side elevational view of the present hydrofoil
located rearwardly of a boat transom;
Figure 2 is a top plan view of the hydrofoil removed from a
boat propulsion unit;
Figure 3 is a vertical sectional view taken along line 3-3 of
Figure 2; and
Figure 4 is a perspective view of a positionable plate member
of the hydrofoil.
With continuing attention to the drawings wherein applied re-
ference numerals indicate parts similarly hereinafter identified,
the reference numeral 1 indicates a portion of a boat hull below
the waterline.
Adjacent the hull is a propulsion unit 2 shown in fragmentary
form and may be the lower unit of an outboard motor or the outdrive
of an inboard-outboard. A cavitation plate at 3 serves to restrict
the formation of a partial void aft of a propeller 4. The foregoing
description is intended to be only general in nature as a wide range
of propulsion unit configurations exist.
The present hydrofoil is indicated generally at 6 and is of a
lengthwise section to induce lift with upper and lower surfaces 7
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and 8 being of different shapes with surface 7 having a camber
to provide a pressure difference thereon similar to an airfoil.
The leading edge 10 of the hydrofoil may be recessed at 11 to
receive a rearward portion of the propulsion unit while a planar
surface at 12 permits surfacial engagement of the hydrofoil with
the cavitation plate of the unit for mounting purposes as by
threaded fasteners 13 extending upwardly through the cavitation
plate into engagement with the hydrofoil. The hydrofoil may be of
generally delta shape in plan view with a trailing edge at 14 and
l.0 rearwardly diverging edges at 15 and sides at 16.
Swingably mounted on the underside or lower surface 8 is a
positionable plate structure 20 carried by a pivot shaft 21 jour-
nalled in inset bearings as at 22. The plate 20 may be termed a
trolling plate. As best viewed in Figure 4~, a pair of stops 23
and 24 are provided which project from the plate for cooperation
with later described locking means. Plate upper and lower surfaces
(when retracted) are at 20A and 20B with the plate upper surface
being received within a recessed area 8A in the hydrofoil lower
surface which terminates rearwardly proximate trailing edge 14
20 of the hydrofoil. Plate surface 20B serves, as a hydrofoil lower
surface when the plate is retracted. Located adjacent the lead-
ing edges of plate 20 is a bore 25 disposed transversely across the
plate to receive pivot shaft 21 journalled in bearings 22. A flange
26 on the plate defines an open area 29 through which shaft 21
passes to receive a spiral spring having spring arms 27-28 which
bias plate 20 toward a operative, extended position. Spring arm
27 bears against plate flange 26 while spring arm 28 bears against
an internal wall surface 30 of the hydrofoil. For retention of
plate 20 in place, the stops at 23 and 24 a.re shouldered at 30
30 and 31 for abutment with locking means 32 while an additional pair
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of shoulders at 33 and 34 on the stops cooperates with the locking
means to prevent upward retraction of the plate in response to
water impingement. Hydrofoil 6 is slotted at 6A and 6B to receive
stops 23-24 to permit same to swing through 90 degrees or so during
plate travel between deployed and retracted positions.
A control for the locking means may be embodied in a control
wire 35 attached by a fitting 36 to locking means 32 to enable
remote actuation of the locking means, for example, by a boat
operator seated at an operator's station. Locking means 32 may
I.O be a member formed from rod stock having reversed end segments
32A pivotally carried within pedestals 37-~~8 on upper surface 7
of the hydrofoil. For the prevention of d~~mage to plate 20 and
locking means 32 by water exerted forces at>ove trolling speeds,
the shoulders 33 and 34 may be formed with surfaces inclined some-
what rearwardly and upwardly to the vertic~~l to provide a caroming
action for upward displacement of the lockiing means permitting
plate 20 to retract automatically from heavy propellor wash with
the locking means subsequently engaging shoulders 30-31 for plate
retention.
20 In use, the plate 20 is deployed by sp ring action upon actua-
tion of remote control 35. The lowered plate inhibits water flow
past propeller 4 to reduce the speed of the watercraft. At the
cessation of slow speed operation of the w<~tercraft, actuation of
control 35 permits plate 20 to retract out of the propellor wash
to the streamlined or stowed position on tire underside of the
hydrofoil with latching of same in place b~y locking means 32.
A range of hydrofoil shapes and sizes may be utilized to
achieve desired hull lift and attitude.
While I have shown but one embodiment of the invention, it
30 will be apparent to those skilled in the art that the invention
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may be embodied still otherwise without departing from the spirit
and scope of the invention.
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